STABILITY OF TERRESTRIAL ECOSYSTEMS AS TO PEST...

G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I

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AXIOM 8(1) FACTORS of DISTURBANCE of ECOSYSTEM STABILITYto PLANT PESTS and their EFFECTS

To keep ESPPs in any ecosystem on the admissible level as long as possible, it should know the factors, which disturb it. A meaning of the term "disturbance" needs in some sidelight. It should pay attention on the difference between life strategy of biocenoses and destination of articenoses.

The life strategy of biocenoses is directed on keeping ESPPs biomass of the category D-I on the level 3.1. "Proper control." The decrease ESPPs in this category of biomass under diverse stressors to the level 3.2. "Lag control" endangers biocenoses by a change of composition of dominants. The decrease ESPPs of it on the level 3.3."Late control" results in destruction of biocenoses.

Contrary, on the biomass of the category D-II, a decrease ESPPs on the levels 3.2. and 3.3. has no a destructive character. In some environmental conditions, it takes place an often decrease ESPPs to the level 3.3. "Late control." The advanced Tolerance of dominants allows biocenoses to survive in spite of the common affection by herbivores. It is necessary, however, a periodic suppression of herbivores by CESPPs 2.5. "Effects of crowding", which provides a reprieve for restoring of vitality of dominants. Therefore, on biomass of the category D-I, a disturbance changes a character of an ecosystem, and it is undesirable, whereas on biomass of the category D-II due to advanced Tolerance the term a "disturbance" has no obligatory a negative sense.

The destination of articenoses, which is determined by people, is directed on keeping the level ESPPs 3.1. "Proper control" both in biomass of the categories D-I and D-II. When signs of a decrease of ESPPs from the level ESPPs 3.1. "Proper control" appear, CESPPs 2.6. "Human control measures" usually need to be entered in an operation. This is necessary in agricultural crops, where decrease of yielding and keeping of quality of production are the main concern of ecosystems. In ecosystems of other concern, the need of application CESPPs 2.6. "Human control measures" depends on local circumstances.

All the stressors, which decrease ESPPs from the level 3.1. "Proper control", will be referred to as factors disturbing ecosystem stability to plant pests (FDESPPs). Further, it will be considered the conditions, at which diverse FDESPPs are active, and their effects on dominants will be shown.

It has been declared the skepticism as to the durability (persistence) of plant resistance to PPs, which is implied as Antibiosis, due to arising of new pathotypes of phytopathogens and new biotypes of herbivores, which would capable to overcome the resistance.

Indeed, frequency of hereditary changes in PPs is much greater than that in their host-plants. The microevolutionary process that leads to a lost of the resistance in the system of interrelations " a host-plant - a consumer" has been considered by D. Pimental (1961 and other publications), and has got the special term the "genetic feed-back mechanism." Beside the mathematical proof, D. Pimental has given a number of examples, which illustrate the action of this mechanism in nature. It is known a row of cases, at which plant cultivars loss their resistance to PPs in innumerous years after wide-scale growing of these cultivars as field crops.

However, a lot of facts demonstrate the presence of an opposite trend. In this connection, it should mention the words by R.L. Gallun and G.S. Khush (1980, pp. 82-83), namely: "The breakdown of resistance may occur after few years although in some cultivars resistance remains for the last 50 years."

Consider prospects of keeping of plant resistance to PPs taking into account of FDESPPs and the circumstances, at which they are active, as well as the ways to counteract losses of the resistance.

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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH. PART II

8.1. Anthropic-18.1.1. Growing of cultivars in the range of exotic herbivores r-strategists

Breakage of the prerequisites:2.1.1.P.1. A hereditary ability of a plant taxon (species, subspecies, phenological forms,

varieties strains, hybrids, lines) to resist against a given taxon of PPs2.2.1.P.2. Adaptation of parasites and pathogens to overcome resistance of their hosts

2.2.1.P.9. Presence of effective vectors of pathogens8.1.1.1. CESPPs A.2.1.1.2.1. , 2.2.1., and 2.2.3. failed

8.1.1.1.1. Repeated arising of aggressive biotypes inducing outbreaks of the herbivores

As examples of this category, it can be used the cases offered by M.D. Pathak (1970). This is a list of pest insects, including the Hessian fly, Mayetiola destructor and five species of aphids, which overcome Antibiosis of their host-plants repeatedly by producing aggressive biotypes. They are the raspberry aphid, Amphoraphora rubi, the spotted alfalfa aphid, Theriophis maculata, the greenbug, Schizaphis graminum, the corn leaf aphid, Rhopalosiphum maidis, and the pea aphid, Acyrthosiphon pisum.

All the above species are r-strategists. The fly produces up to five generations per season, whereas the aphids have to ten ones or even more. The more number of generations of a herbivore per year, the more hereditary changes in its population, the more probability of arising of mutants with genes, which are able to overcome host-plant Antibiosis, rather that Antibiosis in host-plants to the above herbivores is not well-developed, if any.

These species feed on plant’s parts, which related to biomass of the category D- II. In native lands of the herbivores, these parts are protected by CESPPs A.2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of losses of host-plant tissues" in cooperation with CESPPs 2.2.1. "Natural enemies of invertebrate herbivores", A.2.1.2.1.1. "Superevasion from herbivores." or 2.1.1.4.1. "Evasion from herbivores." Being exotic species in North America, they hardly to suffer seriously on the part of natural enemies. At such circumstances, Tolerance is insufficient for self-protection of host-plants. If breeding of varieties having Antibiosis to the herbivores was conducted, the Antibiosis, however, occurred to be not potent, when to take into account specificity of tissues under the affection - young tillers, juvenile parts of stems, and foliage. There are the grounds, therefore, to consider the hereditary prerequisites of CESPPs Antibiosis in the given case as failed ones. In literature, such Antibiosis is characterized as monogenic one or the vertical resistance.

A combination of the above factors: advanced capacity of the herbivores - r-strategists to produce aggressive biotypes, low activity, if any, of resident natural enemies of these exotic herbivores, and weak expression of CESPPs A.2.1.1.2.1. "Antibiosis to herbivores" in the crops results in the loss of Antibiosis. Hereditary prerequisites of this Antibiosis in the above conditions failed.

In this context, it should paid attention that in exotic herbivores K-strategists, an arising of aggressive biotypes has not been traced. This fact was reported again by M.D. Pathnak (1970), in particular, in the wheat stem sawfly, Cephus cinctus and the European corn borer, Ostrinia nubilalis. Further, the plant’s parts, which are affected by these species, might by provided more developed Antibiosis than that in the above herbivore r-strategists. So that, hereditary prerequisites of CESPPs A.2.1.1.2.1. "Antibiosis to herbivores" in the K-strategists are rather durable ones.

Consider the ways to withstand an activity of FDESPPs 8.1.1. "Growing of cultivars in the range of exotic herbivores r-strategists." These ways are practicing of CESPPs A.2.1.2.1.1. "Superevasion from herbivores", A.2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of losses of host-plant tissues", and 2.2.1. "Natural enemies of invertebrate herbivores" by means of introducing of them.

The Hessian fly is known in North America from XVIII century, and it continues to be a serious pest mainly of the spring wheat until now. It has been bred a number of cultivars with Antibiosis to this pest, but duration of efficacy of this trait is limited due to arising of aggressive

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biotypes of the pest. The author has not found in literature reports about introducing of natural enemies of the Hessian fly. Probably, such attempts were been conducted, but they were not insistent.

The aggressiveness of the Hessian fly in America is more expressed than that in Europe. That fact might be explained by difference in activity of natural enemies of the Hessian fly in the compared continents.

Considering of the well-documented situation with the Hessian fly in Russia is able to bring clearness in the issue. This pest probably invaded in this country in the middle of XIX century or its aggressiveness was a result of mutation of a native species, as A.F. Kryshtal (1950) supposed. Over nearly a century, it was very dangerous, when its outbreaks arose with short intervals.

The first outbreak was recorded in Russia in 1847. Since the outbreaks were reported to be in 1879-1885, 1890, 1896-1898, 1906-1908, 1911-1913, 1923-1925, 1937-1938, 1948-1955, 1961-1963 (Pavlov, 1967, pp. 47-48). The level of affection becomes clear from the report by A.Ph. Kryshtal (1947, p. 12). According to this scholar, in 1938, the fly's outbreak was the most sever over 40-50 preceding years. On 1,621,731 hectares of the surveyed area in Ukraine, density of the fly (the number of larvae or pupae per square meter of the soil surface) reached in the spring wheat 300 individuals on 34.8% of the area and 1000 individuals on 8.6% of the area. In the winter wheat, the affection with the rate over 300 individuals was on 12.8% of the crop's area

Eventually, in USSR, the damage due to the Hessian fly has become less. After 1960-ies, outbreaks of the Hessian fly were recorded and forecasted in 1979-1980, 1991-1992 and in 2000-2001 (Biletsky, 1994). However, any general increase of density of this species in 1987-2001 in Ukraine was not recorded (G.A. Posylayeva, pers. comm. and author's observations). Over last decades, in the Forest-Steppe biome in Ukraine, it is known only one case of significant damage due to this species, namely: in 1972 several hectares of the winter wheat were damaged seriously by the fly in a breeding center (L.A. Burdenyuk, pers. comm.).

Even in the Steppe zone, where activity of the fly is usually more expressed, it has not been recorded over 1990-ies the decrease of grain yield in the winter wheat at the highest of the revealed values of the density - affection of 46% of tillers in fall and presence of cocoons in 14% in sheaths of stems in summer (Krut, 1992; 1998, pp. 51-52).

In the past, aggressiveness of the Hessian fly in the Steppe zone was higher. This problem was studied by P.I. Susidko (1969), who reported the following terms of Hessian fly outbreaks in the south of Ukraine (Ibid., pp. 19, 27): 1881, 1884-1885, 1890, 1892, 1896-1897, 1907-1908, 1910-1911, 1922-1924, 1930-1932, 1937-1938, 1947-1948, 1951-1952, 1959, 1966. In 1959, on irrigated wheat fields, the density of the Hessian fly exceeded 1000 larvae per square meter of the soil surface, so that one affected stem contained in average more than three larvae (Ibid.).

This species has developed SP – up to five generations per year that allows it to give a quick rise of density.

P.I. Susidko (1969, p. 19) stressed that outbreaks of the Hessian fly did not demonstrate any periodicity. Its High density continued one-two years. Since then, it took place a depression, which continued from one to ten years.

This view contradicts one keeping by Eu.S. Biletsky (1994), who attempts to connect arising of Hessian fly outbreaks with the periodicity of the solar activity.

As a cause of fluctuation of fly’s density, it might be diversity of weather situations. The role of weather has been stressed by A.F. Kryshtal (1972, pp. 504-506). He has noted that sharp change weather situation in spring from cold to continual warm one promotes to growth of the density. Contrary, a return of cold weather in spring after short warm weather induces mortality of the neonate larvae. The stable wet weather during summer does not promote an increase of the density, because the flies are active, but they unable find host-plants in the vulnerable stage – with young tillers, which are absent. On the other hand, at droughty summer, the flies stay in diapause. In fall, they become active and find abundant young tillers on winter wheat fields. In addition, wet weather over summer promotes activity of chalcidid parasites of the Hessian fly, whereas droughty summer suppresses them (Rubtsov, 1938).

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As an explanation of the trend to decrease of aggressiveness of the Hessian fly, it can be proposed an adaptation of resident natural enemies to use this species as a host. For substantiation of this proposition, it can serve the data offered by A.V. Znamensky (1926, p. 213). These data allow comparing mortality of a fall generation of the Hessian fly in Poltava (Ukraine) in 1923 at the early sowing date, and in Lafayette, Ind. (USA). The observations in Lafayette were conducted between September 11 and October 16, 1921. As to Poltava, the data are obviously original ones by A.V. Znamensky. A source of the data for Lafayette was not noted. In the Table 38, it is shown the comparative mortality of a fall generation of the Hessian fly in the stages of egg, larva, and pupa.

Table 38. The comparative mortality of the Hessian fly in Poltava (Ukraine) in 1923, and in Lafayette, Ind. (USA) in 1921

Location Crop

The number of studied objects Percentage of

plantlets with eggs

Percentage of objects with

larvae and pupaeThe

number of eggs

per plantlet

The overall

number of eggs

The overall

number of larvae

and pupae

Surv

ivors

hip,

pe

rcen

tage

Plantlets Tillers

The number of tillers per plantlet

Plantlets Tillers

1 2 3 4 5 6 7 8 9 10 11 12

PoltavaThe winter wheat 212 1695 8 100 44 52 56 11872 28 0.23

The winter rye 189 1701 9 87 7 6 19 3116 7 0.22

LafayetteThe winter wheat 50 135 2.7 100 69 44 36 1796 284 15.8

The winter rye 50 410 8 90 6 0.7 12 580 7 1.3

The Table 38 demonstrates the great difference in survivorship of the Hessian fly between the areas. In Lafayette, Ind. (USA), the survivorship was much higher than that in Poltava (Ukraine). The difference can be due to the better adaptation of natural enemies (probably parasites and pathogens) to this insect host in Poltava comparing with that in Lafayette.

Why does the activity of natural enemies of the Hessian fly in Poltava is greater than that in Lafayette? The answer is the rich fauna of relatives of the Hessian fly in Ukraine. In Europe, including Ukraine, it was recorded a number of species of the genus Mayetiola: M. avenae March., M. dactylidis Kieff., M. destructor Say, M. joannisi Kieff., M. schoberi Barnes, and M. poae Bosc. (Mamayeva and Mamayev, 1981).

In Ukraine, on the Hessian fly, it has been recorded twenty species of parasites (Bilanovs’ky, 1940, cited in A.F. Kryshtal, 1974, p. 505). From them, the most numerous are Eupteromalus micropterus, Merisus destructor, Platigaster minutula, and Eupelmella vesicularis.

As an example of potency of the parasites, it can serve the wasp Platygaster minutula Lind., Proctotrupidae, which oviposites in eggs of the Hessian fly, and the progeny finishes development in larvae or pupae; due to polyembriony, 15-20 larvae of the parasite develop from one of its egg (Shchegolev et al., 1949, p. 389).

An activity of the parasites is high in vicinity of forest plots and shelterbelts (Kryshtal, 1974, p. 505).

In wild vegetation, important role in SES is played by CESPPs 2.1.1.4.1. "Evasion from herbivores" operating on the level of separate plants. In crops, it is very effective of CESPPs A.2.1.2.1.1. "Superevasion from herbivores." Sowing of winter wheat in the optimal dates, which have been determined for diversity of States, prevents exposition of plants in vulnerable stage on the flies (Fernald, 1926, p. 316).

The Superevasion is prospective concerning the spring wheat. In fact, "In the spring-wheat section late seeding will not apply. It seems likely, on the contrary, that the earlier it is sown in spring the less it will suffer from the Hessian fly" (Fernald, 1926, p. 317).

The trait A.2.1.1.3.1.2. ''Tolerance to herbivores, Repair or compensation of losses of host-plant tissues'' allows the crops to survive in spite of significant activity of the Hessian fly.

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Turning to the Table 38, it is noticable high general tillering of the crops – eight tillers in the winter wheat and nine tillers in the winter rye. Abundant tillering allows to plants to tolerate losses of their tillers due to affection by the fly in fall, and to restore tillers in spring. To overwinter succesfully, a plant needs in only two tillers.

Nevertheless, CESPPs A.2.1.2.1.1. "Superevasion from herbivores" is insufficient for reliable protection of the spring wheat and in the winter wheat on condition that it grows in southern areas, where the fly can be active over winter. In such a situation, it is need cultivation of the varieties possessing the trait of expressed Antibiosis to the Hessian fly.

The Antibiosis is prospective, particularly in North Kazakhstan. Here, Mayetiola destructor is a tiresome pest (Yevdokimov et al., 1986). In these climatic conditions, it is possible to grow only the spring wheat, so that Superevasion is insufficient for the protection. Arid climate does not promote abundant general tillering, so that Tolerance is also insufficient. Further, areas of natural woody ecosystems and shelterbelts, where pest's parasites and predators find favorable conditions for overwintering and additional (imaginal) feeding, are actually absent. At last, here it is practiced the soil treatments without digging up. In this area, it is necessary the surface tillage - sharing for protection of the soil from wind erosion. That is why the fly overwinters successfully into shready stalks, whereas the wheat is grown as a monoculture.

At growing of wheat cultivars with Antibiosis to the Hessian fly, recurrence of outbreaks takes place at arising of aggressive biotypes of the pest. Contrary, growing of the winter wheat in the conditions, where Superevasion is effective, Tolerance is developed, and natural enemies of the fly are prosperous, results in unlimited keeping of its density on the Insignificant level.

Population dynamics of the exotic species of aphids is similar to that of the Hessian fly. This suggesion is concerned to the above-cited species Amphoraphora rubi on the raspberry, Theriophis maculata on the alfalfa, Schizaphis graminum on the wheat and the sorgum, Rhopalosiphum maidis on the sorgum and the corn, and Acyrthosiphon pisum on the pea, rather that Antibiosis against them is not expressed well. In their EEs in the native land, the role of Tolerance and activity of natural enemies is supposedly great one, so that there is no need in developed Antibiosis. A cooperation of all the above CESPPs provides admissible suppression of their density. Contrary, in the recently invaded area, low activity of natural enemies results in rather soon loss of Antibiosis. On the other hand, Tolerance is insufficient for self-protection in the conditions of high activity of herbivores – r-strategists.

Causes of outbreaks of the Russian wheat aphid, Diuraphis noxia Mordv. (in the contemporary Russian literature, this species is known as Brachycolus noxius Mordv.) can be included in this category of FDESPPs. In Russia, this species was described at the end of XIX century, when it occurred to be very abundant. In fact, N.A. Kholodkovsky (1912, p. 488) reported that this species (at that time, it was used the name the barley aphid, Brachycolus korotnevi Mordv.) was appeared sometimes in huge masses in south of Russia, and its imagoes composed vast clouds. Probably, this species penetrated into this country shortly before the outbreak. Eventually, density of this species has become Low although breeding of resistance cultivars has not been conducted.

Contemporary literature does not report about outbreaks of this species in the areas of its former abundance in East Europe. Diuraphis noxia is mentioned as a satellite of more important pest - Sitobion avenae in south Ukraine (Nikolenko and Omel'chenko, 1974). In the Forest-Steppe zone, the role of the aphid is considered as insignificant. In fact, the studies in 1976-1979 showed the presence of four species of aphids on the winter wheat, including Diuraphis noxia, however, the occurrence of Sitobion avenae equaled 92.4% (Dudnik, 1983, p. 6).

In East Germany, participation of Sitobion avenae in a total aphid stock on the winter wheat was about 90% (Assman and Wetzel, 1990) that also suggested the minor role of Diuraphis noxia.

It was reported that Diuraphis noxia is a species of the Central Asia origin (Schliephake et al., 1998). It spreads westward beginning with XIX century. The Low density of this species in Europe in nowadays might be explained by adaptation of resident natural enemies to suppress it.

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FDESPPs 8.1.1. cooperates with FDESPPs 8.6.1. "Invasion of exotic taxa of phytopathogens or herbivores, which are able to overcome 2.1.1.2."

8.1. Anthropic-18.1.2. Growing of a single cultivar on vast areas


varieties strains, hybrids, lines) to resist against a given taxon of PPs8.1.2.1. CESPPs A.2.1.1.2.2. failed

8.1.2.1.1. Arising of high virulent pathotypes in resident phytopathogens r-strategists inducing epiphytoties

The more an area of growing of a cultivar, the greater a probability of a contact of its plants with virulent pathotypes existing in nature, the more abundant agents of phytopathogens contact with these plants, the greater a danger of arising of new virulent pathotypes. That is why a trait of Antibiosis to phytopathogens can be lost over innumerous years after beginning of growing of a resistant cultivar on vast areas. This factor is of big importance in the present time. Modern agriculture practiced in developed countries is characterized by the growing of a few cultivars of a crop on vast area. This is a general trend of the progress, when the best cultivars quickly get recognition of numerous growers.

Resistant cultivars growing on minute areas, for examples in nurseries of breeding centers stay out of above threats. Here, a trait of the resistance remains much longer than that in the situation described above.

This FDESPPs is potent in phytopathogens r-strategists such as the rust and mildew species having numerous generations per year and high mobility of their spores. As consequencies of r-strategy, it is great hereditary variability. Within a species of the phytopathogens, there exist hundreds of pathotypes. In them, it lacks the stage of saprophy, which are characteristic for K-strategists, in particular for the root rots. A lack of saprophagy promotes a hereditary variability in a phytopathogen’s population.

The selection with the trend of an increase of virulence leads to extinction both of the pathotype and their host-plants as well as to defeat of a high-virulent pathotype in competition with pathotypes of less virulence. At this trend, the durability of host-plant Antibiosis is low, but this is a blind alley in microevolution of phytopathogens. This trend, which appears at growing of a single cultivar on vast areas, directs of a phytopathogen on the way of of high, but short-time virulence.

When growing a cultivar over vast areas, a loss of CESPPs A.2.1.1.2.2. "Antibiosis to phytopathogens" is influenced by diversity in virulence of subspecies taxa of a phytopathogen depended on a locality. M.P. Lesovoy (1977, and subsequent publications) stated that composition of races (and pathotypes) within a species is diverse even on rather small distance. Thus, in Ukraine, there are twenty Regions. M.P. Lesovoy and co-workers reported that among these Regions, there are significant differences, in particular as to virulence of pathotypes. The occurrence of them (eigtheen pathotypes of the race 77 of the leaf rust) on seven wild gremineous species in some localities is so significant that growing in them of certain varieties of the winter wheat is took the risk (Lesovoy, 1977, p. 24). Notably, that presence of high virulent pathotypes does no preclude thriving of wild plant species.

The diversity yielding of crops depending on a locality is known long ago. In Soviet Union, it was organized a service of the Seed Testing Stations – test plots, where newly bred varieties were proved on diverse agronomic traits. In Ukraine, in every Region, it has operated such a Station. The differences in yielding indeed were recorded in spite of varieties were grown in favorable for a given crop habitats, and differences in climatic conditions sometimes were little. After advantages of a variety are proved, a recommendation to grow a variety in a given Region is given.

It is accepted that at growing of a variety with monogenic (vertical) resistance on vast areas, it will be overcome by r-strategists during few years at least in some localities.

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When FDESPPs 8.1.2. "Growing of a single cultivar on vast areas" operates in a cooperation with FDESPPs 8.1.3. "Growing of cultivars in the conditions of a lack of operation of CESPPs A.2.1.2.4.1." loss of CESPPs A.2.1.1.2.2. "Antibiosis to phytopathogens" gets more probable.

In phytopathogens K-strategists, the situation is different one. The fact is the potato varieties resistant over many years to the wart (cancer) disease, Synchytrium endobioticum Schild., whereas in the case of the potato leaf blight, Phytophthora infestans (Ment.) De Bary the trait of resistance is of short duration. Yu.T. D’yakov (pers. comm.) explains these facts by different strategies of these phytopathogens: the category "K" in the case of the cancer, and "r" in the case of the blight.

8.1. Anthropic-18.1.3. Growing of cultivars in the conditions of a lack of operation of CESPPs A.2.1.2.4.1.


varieties strains, hybrids, lines) to resist against a given taxon of PPsA.2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or

special cultural practices with the aim of effective operation of CESPPs 2.1.2.8.1.3.1. CESPPs A.2.1.1.2.2. failed

8.1.3.1.1. Arising of high virulent pathotypes in resident phytopathogens r-strategists inducing epiphytoties

Host-plants select their phytopathogens on virulence. Only those pathotypes of them survive, which are able either to co-exist with host-plant Antibiosis or to overcome it. As to the latter, i.e. a loss of Antibiosis, the successful pathotypes produce agents, whose chance on survivorship is different depending on a character of a stock of host-plants within an ecosystem. If the stock consists of a single cultivar, its protective trait (Antibiosis) is the same in all the plants. Therefore, there are no obstacles for a successful pathotype to infest all the stock. Because the number of generations per year in r-strategists is numerous, an infection spreads quickly over a stock. This capacity is called a high aggressiveness of a pathotype.

Further, in this situation, it increases virulence of a phytopathogen species due to an increase of participation of the most virulent pathotype. This is so because in the conditions of an unlimited spread of infection, it arises an intensive competition among micelia. In the competition, it survives the micelia, which have better possibility to suppress Antibiosis of host-plant, so that they force out less virulent pathotypes. Therefore, at the monotonous hereditary composition of a stock of host-plants, it gives rise new pathotypes with ever-increasing virulence. This trend, however, takes place on susceptible cultivars. Contrary, on the cultivars with Tolerance, take place an opposite trend. Then, less-virulent pahotypes force out high-virulent pathotypes.

From ancient times, humans have known consequences of the above process. Therefore, they bred and used so called land races of crops. Now, it is known that a land race is composed by a number of hereditary very different entries, which, however, are identical in their agronomical, phenological, and morphological traits.

This problem was considered above in this text at characteristic of CESPPs of the category A.2.1.2.4.1. "Hereditary heterogeneity of a stock of host-plants." In the same Section, it mentioned the ways to counteract the process of increasing agressiveness and virulence of phytopathogens. The ways consist in development of methods as to increase of hereditary diversity in a stock of crops. In other words, this is the concept of intrafield diversification, which concerns growing of divers cultivars in mixture. In such conditions, both virulence and aggressiveness of phytopathogens are dumped; it survives the pathotypes, which are able to coexist with their host-plants, so that Tolerance thrives.

In the case of operation of CESPPs 2.1.1.3.2. "Tolerance to phytopathogens" and intrafield heterogeneity, the more virulent pathotypes have no advantages comparing with less virulent ones. Therefore, the above mentioned trend of forcing out of high-virulent cultivars by less-vitulent ones becomes especially expressed.

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The FDESPPs 8.1.3. operates usually jointly with FDESPPs 8.1.2. "Growing of a single cultivar on vast areas" that redouble the negative effect of such cultural practices.

8.1. Anthropic-18.1.4. Growing of cultivars in the conditions unfavorable for expression of

CESPPs A.2.1.1.2.Breakage of the prerequisites:

2.1.1.P.1. A hereditary ability of a plant taxon (species, subspecies, phenological forms, varieties strains, hybrids, lines) to resist against a given taxon of PPs

2.3.P.2. Limitation of aggressiveness of PPs8.1.4.1. CESPPs A.2.1.1.2.1. and A.2.1.1.2.2. failed8.1.4.1.1. Affection by phytopatogens and herbivores

It was recorded a phenomenon, which considering by scholars as an evidence of dependence of expression of Antibiosis genes on ambient temperatures. The case stories were considered above at characteristic of CESPPs 2.3. "Routine weather suppression."

In short words, affection of some wheat varieties by the Hessian fly occurred to be equals 3% at 15°C and 97% at 27°C (Painter, 1958). The similar results were obtained in another study (Sosa and Foster, 1976).

In phytopathogens, it was recorded a sudden loss of Antibiosis to the leaf rust on the winter wheat at a sharp skip of the weather situation from cold spring to hot summer (Gorlach, 1958, p. 147). The loss took place two seasons. At other weather situations, these varieties were resistant to the leaf rust over many years.

At last, significant fluctuations of Antibiosis depending on weather situation were recorded in species of the cabbage to Plasmodiophora brassicae Wor. (Tyuterev, 1981).

These cases show that Antibiosis to PPs can be lost in some seasons at specific weather situation or even continually if a variety is grown in the climatic conditions, where destructive weather situation is common.

8.1. Anthropic-18.1.5. Growing of cultivars in the conditions intensifying SP of PPs


varieties strains, hybrids, lines) to resist against a given taxon of PPs2.3.P.2. Limitation of aggressiveness of PPs

2.4.P.1. Keeping of severity of the season of an year when activity of PPs is suppressed8.1.5.1. CESPPs A.2.1.1.2.1., A.2.1.1.2.2., and A.2.1.2.1. failed

8.1.5.1.1. Affection by phytopathogens and herbivores

In tropical and subtropical climates, PPs are able do not stop their development over entire year. Application of irrigation leads to the same situation even if climate of an area includes a dry season. The factor of a seasonal limitation does not operate, when growing of agricultural crops in greenhouses independently to climate of an area, if summer interval in growing does not practiced. In such conditions, it increases both the number of generations of PPs and velocity of completion of life cycle. In so doing, an increase of populations becomes maximal.

Because CESPPs 2.4. "Periodic (bottle-neck) suppression" does not operate, CESPPs A.2.1.2.1. "Superevasion" does not operate also. Further, an amount of agents of phytopathogens becomes so large that they can overcome even advanced Antibiosis.

The same might be true for herbivores, especially sap-sucking ones. This is an increase of their aggressiveness.

A virulence of phytopathogens grows also. This is so because at competition of overcrowded micelia, the most virulent mutants obtain selective advantage. The stages of saprophagy and dormancy, which retard selection on the best parasitism, are absent. This is an additional factor of increase of virulence. Thus, CESPPs A.2.1.1.2. "Antibiosis" is ineffective.

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The above conditions are very valuable for estimation of CESPPs A.2.1. "Plant resistance to PPs." If an entry occurs to be resistant in such a severe pressing on the part PPs, its resistance would be durable in less severe conditions.

8.1. Anthropic-18.1.6. Growing of cultivars with spontaneous decrease of CESPPs A.2.1.1.2.2. especially at

specific weather situationsBreakage of the prerequisites:


2.3.P.2. Limitation of aggressiveness of PPs8.1.6.1. CESPPs A.2.1.1.2.2. failed

8.1.6.1.1. Affection by phytopathogens

This category of losses of CESPPs A.2.1.1.2.2. "Antibiosis to phytopathogens" has not been described in literature yet. Therefore, it deserves a consideration in detail, rather that the counteraction to this FDESPPs seems to be prospective to bring clearness in the principal issues of plant resistance to PPs.

The widely accepted concept assumes that plant resistance to PPs is durable if it has the polygenic character, whereas a durability of the monogenic resistance occurs is a rare event. However, it is not easily to gain an understanding, which kind of character (monogenic or polygenic) a resistance has in a concrete case.

To illustrate this statement, consider the case of a loss of resistance of the winter wheat varieties Avrora and Kavkaz to the leaf rust, Puccinia recondita Rob. ex Desm. f. sp. tritici Erikss.

In the North Caucasus Area of Russia after 1960, the winter wheat variety Bezostaya-1 got a wide spread ensuring highest grain yield for that time – 4-5 metric tons per hectare in the best environmental conditions. With the aim to shift this variety by more productive ones, in 1968, it was bred the varieties Avrora and Kavkaz, which produced 5-6 metric tons of grain per hectare. High resistance to the leaf rust, which was a serious disease in that region, was a valuable trait of these varieties.

M.P. Lisovyi (2001, p. 17) reported that "Any known in that time race of the leaf rust did not affect them. The author of these varieties Academician P.P. Luk’yanenko supposed that their resistance to the phytopathogen would be not never lost."

The valuable traits of these varieties resulted in the rush increase of areas of cultivation of them. In the North Caucasus and Ukraine, the areas reached such values: in 1971 – 19,000 ha, in 1972 – 337,000 ha, and in 1973 – 1,367,000 ha. In 1973, it came a crash. M.P. Lisovyi (2001, p. 18) wrote: "The fact of a loss of the resistance by the varieties so affected of health state of the breeder Academician P.P. Luk’yanenko that he died due to a heart infarction on a field of the wheat got brown in result of affection with the rust."

What is the cause of such sudden loss of the resistance? M.P. Lisovyi (1977) supposed that the cause consisted in an arising of new high virulent pathotypes of the race 77 of the leaf rust. They were marked 16, 20, 22, 23, 25, 26, and 28. Further, he considered this case as a didactic example of a failure of the monogenic (vertical) resistance (Lisovyi, 2001, p. 18).

But there exists a doubt as to validity of this statement. The resistance was considered as monogenic one, despite these varieties had been bred as resistant to all the races of the leaf rust as it was noted above. Further, it is rather strange that new-arisen high virulent pathotypes of the race 77 so quickly (during one growing season) spread over the vast areas. It needs an additional information to explain the above questions.

First of all, the studies in the North Caucasus in 1973 at the epiphytoty of the leaf rust did not find out any new high virulent pathotypes of the race 77 (Rudnev et al., 1975). The main pathotype that induced this epiphytoty was the well-known 103 of the race 77. Further, this pathotype affected not only the varieties Avrora and Kavkaz, but all the varieties grown in this region, including Bezostaya-1, as well as the wild gramineous species – Agropyrum dereshrum

9


Fisch., Aegilops sp., Bromus squarrosus L., B. arvensis L. ,and B. scoparius L. As to the wild species, it is difficult to suppose that they also have the monogenic type of the resistance.

The report by E.D. Rudnev et al (1975) suggests an impact of the factor unconnected with the increase of virulence of the phytopathogen, which has induced this general epiphytoty of cereals. As to the case of Avrora and Kavkaz, another line of reports indicates on operation of inapparent processes in heredity of these varieties.

In 1969-1970, resistance of these varieties to the leaf rust was studied by means of artificial inoculation by diverse pathotypes of the leaf rust (Shopina et al., 1972; Krayeva and Alekseyeva, 1972). These studies showed that most part of plants in Avrora and Kavkaz were resistant to all the rust pathotypes, but a few plants were susceptible to the race 143; some plants were susceptible to the races 77 and 122. In addition, the percentage of susceptible plants depended on a provenance of seeds ("lines" according to these scholars’ words). Those from the L’vov Region (Ukraine) were affected by the leaf rust on the level 60-80% –much more than the plants from seeds grown in other Regions.

The similar results were obtained in studies in Ukraine also before the epiphytoty (Lesovoy and Fyodorova, 1974). In that time, nearly 95% of plants within Avrora and Kavkaz were resistant to all the pathotypes of the leaf rust, whereas the rest were susceptible to a number pathotypes including the wide-spread races 21, 57, 77, 92, 130, 149, as well as the new, but unidentifined races marked X1, X3, X8, X9. The proportion of the unindentified races was only 2-8% in various experiments.

Further, the studies by V.F. Peressypkin et al. (1975) revealed a decrease of resistance of Avrora and Kavkaz over several years in succession, and an influence of ecological conditions on the rate of the resistance loss.

What is the factor, which has caused this epiphytoty? In literature, there is a legible answer to this question. Here are the words by P.S. Udintsov (1974, p. 39): "In last year (in 1973), in the period of vegetation in North Caucasus, in the Regions of the Center (the Forest-Steppe), the Central Chernozem Area, and the Volga River Basin, in many Regions of Ukraine, it occurred to be very favorable weather conditions for activity of the leaf rust on the wheat. The widest spread of this disease was recorded in the Krasnodar Region. Here, in the preceding fall, it was accumulated a great many infection on voluntary wheat. After a good overwintering and exclusively favorable conditions for the phytopathogen in spring and summer, it arose an epiphytoty of the disease. In some fields, the wheat varieties Avrora and Kavkaz, which formerly were considered as resistant to this phytopathogen, were affected on 80-95% especially on areas with early sowing dates and a high rate of fertilization by nitrogen comparing with the rate of fertilization by phosphorus and potassium."

E.D. Rudnev et al. (1975) also supposed that the epiphytoty was provoked by weather conditions favorable for activity of the leaf rust, rather than by arising of a high virulent pathotype.

The provocative role of weather situation favorable for the leaf rust was noted in the previous literature. Here is the report by M.V. Gorlenko (1973, p. 217): "According to the data by A.A. Gorlach (1954), a sharp change of outer conditions led to weakening and subsequent loss of wheat resistance to the leaf rust. In 1951 and 1953, in the Belaya Tserkov District (Ukrainian SSR) after prolonged cool in spring, it came suddenly hot weather. This led to serious affection of resistant varieties of the wheat by the leaf rust. Bad overwintering also can increase susceptibility of resistant varieties. Therefore, to be resistant to the leaf rust, varieties need to be provided by traits of winter-hardness and drought-hardness."

In The V.M. Remeslo Myronivka Institute of Wheat, in 1999 it was observed the mass affection by the leaf rust of all the wheat entries with the exception of the variety Kryzhynka. Here, in 2001 at uncommonly wet weather in spring and summer, nearly all the entries were affected by the root rots and the saprophagous fungi on spikes. The only exception was the variety Remeslivna.

Nevertheless, in above cases, a decrease of the resistance took place only over a season with the peculiar weather situation. On the other hand, the epiphytoty of 1973 showed the continual

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fail of the resistance in the Avrora and Kavkar. In a result, these varieties disappeared from grower’s fields.

An irrigation of wheat fields practiced in areas of arid (warm) climate enhances affection of the wheat with the leaf rust, so that a decrease of grain yield reaches 4-5% (Chumakov, 1963, cited in J. Lilley, 1976). This finding might be explained by setting up optimal conditions for vital activity of the leaf rust at combination of high humidity of air and favorable ambient temperatures. These data suggest heavy affection by the leaf rust, because irrigation increases grain yield if it does not accompanied by disease. This is another example of greater importance of weather situation than hereditary grounds of resistance to a phytopathogen.

The similarity of such effects might be seen at considering the data of laboratory studies, where the resistance was evaluated at optimum for vital activity of phytopathogen agents. In fact, the varieties of winter wheat Myronivs’ka-33 and Myronivs’ka-34 were nearly immune to the leaf rust at evaluating in conventional breeding nurseries. However, when they were evaluated being inoculated by this phytopathogen in the laboratory conditions, a significant part of their plants (32-67%) was susceptible or had low resistance (Rudenko, 1997).

In the environmental conditions favorable for a given phytopathogen species, it grows infectious loading by its agents and their vitality, i.e. its aggressiveness. This brings danger for any its host-plant. In addition, these conditions are able to decrease protective response of host-plants, because for expression of resistance trait, it needs staying of environmental factors in some range.

In fact, there are the data about the important role of air temperature for expression of resistance in the wheat against the stem rust. N.H. Luig and S. Rajaram (1972) showed that genes of resistance to the stem rust, Puccinia graminis Pers. f. tritici Erikss et Henn. are inactivated at temperatures 27-30°C. The same might be true for the resistance to the leaf rust in the varieties Avrora and Kavkaz. High percentage of susceptible plants in populations of them from the L’vov Region according to G.A. Krayeva and T.P. Alekseyeva (1972) suggests validity of this idea. The climate of the L’vov Region differs significantly from the above-mentioned territories (the Kiev Region, and especially the Krasnodar Region). This resistance can be fixed in heredity of the varieties being temperature-depended or moisture-depended.

Turning to the question of the character of rust resistance in the varieties Avrora and Kavkaz, it should note that the supposition as to the monogenic type is based on the only experiment. In the experiment, it was obtained F1B1 of the first backcross with Avrora and Kavkaz as donors of the resistance, and the variety Mironovskaya-808 as a recipient. In this generation, the number of plants resistant and susceptible to the race 77 corresponded the ratio 1:1 at rather low index of validity (P) – 0.95+/-0.25 (Lesovoy, 1977, p. 40).

The conclusion from this experiment that the resistance of Avrora and Kavkaz has a monogenic character is dubious, rather that exactly M.P. Lisovyi (2001, p. 17), has spoken the words: "Any known in that time race of the leaf rust did not affect them." This is charateristic just for polygenic resistance.

How do to explain above data from concepts of genetics? It has been known the patterns of gene activity within a taxon, which was defined by N.V. Timofeyeff-Ressovsky as the penentrance and the expressiveness of a gene (cited in M.E. Lobashov, 1967, pp. 567-568). The penentrance is determined by percentage of organisms with a certain trait, when the organisms stay in the same conditions. This index shows a uniformity of a taxon’s population. The expressiveness is determined by percentage of organisms with a certain trait, when they stay in diverse conditions. Thus, the latter shows the response of a gene on factors of the environment.

The varieties Avrora and Kavkaz had the high penentrance of gene resistance to the leaf rust in the conditions far from optimum for this phytopathogen, but their expressiveness occurred to be low, when the conditions become optimal. In subsequent years, this defect took place at any conditions, i.e. the trait of the high penentrance can be lost entirely.

The capacity of the variety Bezostaya-1 to produce good yielding in the conditions favorable for aggressiveness of the leaf rust implies advanced expressiveness of this variety.

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In the field evaluation of resistance of wheat varieties to the leaf rust, the Myronivs’ka-33 and Myronivs’ka-34 had high penentrance in the non-optimal conditions to the rust, and the low indices of expessiveness in the optimal for the rust conditions in a laboratory.

Above consideration allows drawing some conclusions as to causes of loss of resistance on the example of well-studies interrelations – the wheat and the leaf rust as follows:

i) The speculations as to resistance to the leaf rust is determined exceptionally by the number of relevant genes are not convincing.

ii) There exist the factors, which induce a progressive decrease of the resistance in successive generations with participation of destructive effect of some weather factors.

iii) The loss of resistance might be induced by an operation of FDESPPs 8.1.6. "Growing of cultivars with spontaneous decrease of CESPPs A.2.1.1.2.2. especially at specific weather situations."

iv) The loss of resistance might be induced by an operation of FDESPPs 8.1.4. "Growing of cultivars in the conditions unfavorable for expression of CESPPs A.2.1.1.2."

v) It might be the effect of FDESPPs 8.1.6. in successive generations proceeds as follows. The plants within a stem stock compete with each other. In so doing, they undergo natural selection on the part of diverse stressors (capacity to utilize resources, to withstand frost, resistance to other phytopathogens, etc.). Plants with the better capacity can have advantages comparing with plants having resistance to the leaf rust. Percentage of the latter decreases, i.e. penentrance of the gene of resistance in successive generations becomes lower.

DISCUSSION

The data on FDESPPs of the category 8.1. "Anthropic (hereditary imperfection of cultivars at certain circumstances") inspire to consider the issue of durability of plant resistance to PPs in the context of microevolutionary processes in the system "a host-plant – a consumer." In so doing, it will be used the data for both in agricultural crops and wild species, as to phytopathogens and herbivores.

The epiphytoty of 1973 allows understanding a sense of plant resistance to phytopathogens in crops. The sense consists in a holding of grain yield, rather than in low values of affection indices. This becomes clear, when comparing the yielding and affection of various wheat varieties.

In 1973 in North Caucasus, the losses of grain yield were the following: Avrora – 20%, Kavkaz – 16%, Bezostaya-1 – 9% (A.A. Morozova, 1974, cited in N.M. Stepanov et al., 1976). The less loss in Bezostaya-1 is of a special interest. The matter of fact that before the epiphytoty, this variety was known as susceptible to the leaf rust in contrast to the resistant Avrora and Kavkaz. All the plants of Bezostaya-1 were susceptible to most of pathotypes of the leaf rust (Krayeva and Alekseyeva, 1972).

In the the study by A.M. Dymchenko et al. (1990), it was evaluated of resistance of sixty-seven wheat varieties at heavy doses of inoculum by eight pathotypes of the leaf rust. In it, Bezostaya-1 occurred to be the first as to rate of affection (75-100% of a leaf surface) and the least as to yield loss – 0.6-0.8 metric tons per hectare.

The capacity of Bezostaya-1 to maintain high grain yielding at heavy loading of pathogen’s agents is a good example of supremacy of CESPPs A.2.1.1.3.2."Tolerance to phytopathogens" comparing with CESPPs A.2.1.1.2.2. "Antibiosis to phytopathogens" as a means of self-protection.

The data of studies cited above show that an inoculation by actually all the pathotypes including those known as high virulent on Bezostaya-1 occurs to be successful. Hence, this variety is able to enter in compatible interrelations with every of them. According to the classification of the present report, this is CESPPs A.2.1.1.3.2.2.1. "Tolerance to phytopathogens, Symbiosis with former parasites, Compatibility."

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The gene sources, which determine such traits of Bezostaya-1 are shown by M.E. Lobashov (1967, pp. 639-640). In this book, it is presented the pedigree of this variety. Among its ancestors, there are twenty-one varieties including well-known foreign and resident ones close to land races. The former includes Squarehead, Spyk, Lancaster, Fulz, Klein-33, Kanred, Rieti and others. The resident varieties are presented by Ukrainka, Krymka, Yefimovka, Mestnaya (this Russian word means "local"). One of the nearest ancestors is the variety Skorospelka-2. (this Russian word means an "early matured crop"). This implies that Bezostaya-1 has one more trait – CESPPs A.2.1.2.1.2. "Superevasion from phytopathogens."

In subsequent years, to replace Bezostaya-1, it has been growing the more productive varieties with significant A.2.1.1.3.2. "Tolerance to phytopathogens" to the leaf rust. One of them, it was the variety Myronivs’ka-61, which having a moderate numeric score of the resistance - 5 (the maximal score in the scale is 9), had been a leader in Ukraine as to grain yielding over 10 years until 2000.

In 1990, this variety was aworded with the Golden medal in All-Union Exhibition of Achievements of Soviet Economics in Moscow. Such an awordment occurred to be the last in history. In 1991, Soviet Union underwent a collaps.

Yu.T. D’yakov (1985, p. 168) has reported that the Tolerance is accepted as most prospective factor of resistance of the wheat and the oat against the mildew, Erysiphe graminis D.C., f. tritici March. At breeding on the resistance, it is practiced to cull both heavy affected plants and immune ones, whereas plants with the moderate level of the affection are selected. The mildew has exclusive capacity to produce new pathotypes, so that its capacity to overcome Antibiosis is well developed. The immune plants have less productivity than those with the moderate level of affection, because the former spend more resources for self-protection.

The heredity of wild plant species has not been changed by breeding. Therefore, it should suppose that the hereditary base of their resistance to phytopathogens is quite potent. That is why, it is interesting to consider these interrelations. The study have been conducted by M.P. Lesovoy (1977, p. 24) on seven species of wild cereal species showed that they year after year have signs of affection by eighteen biotypes of the 77 race of the leaf rust. The wild species are considered by this scholar as a source of high virulent infection for cultivated cereals, and as a cause of significant losses of grain yield.

The effect of the leaf rust on productivity or vitality of wild species has not been studied. But simple speculations suggest that the negative effect is negligible, if any. Otherwise, vitality of plants in these species would be suppressed, and they would be replaced by healthy competitors. Thus, the considered interrelations are concerned to the Tolerance. Most probably this is CESPPs 2.1.1.3.2.2.1. "Tolerance to phytopathogens, Symbiosis with former parasites, Compatibility" or CESPPs 2.1.1.2.3.2.2.2. "Tolerance to phytopathogens, Symbiosis with former parasites, Mutualism."

The durability of the CESPPs 2.1.1.3.2. "Tolerance to phytopathogens" has the theoretical grounds. In this case, microevolution of phytopathogens is directed on success in competition with pathotypes, which co-exist with their host-plants, rather than on growth of virulence. This fact has been noted by J.F. Schafer (1971, p. 248) in the following words: "The lack of selective pressure on the pathogen, making tolerance more stable than true resistance (M.D. Simons) is the one big advantage of tolerance over resistance which provides equal protection."

Further, low virulent pathotypes at an operation of Tolerance protect their host-plants from high virulent ones gaining a victory in competition, when infesting of host-plants.

In this context, it should quote D.R. Marshal (1977, p. 10): "…there is a strong negative correlation between the number of genes for virulence carried by a pathogen biotype and its fitness, it is by no means universally true."

Thus, the potent hereditary base of plants resistance in wild grassy plants to phytopathogens – r-strategists consists in operation CESPPs 2.1.1.3.2. "Tolerance to phytopathogens", and 2.1.1.4.2. "Evasion from phytopathogens." When cultivars have such traits, they are close in their self-protection to wild species that do not decrease agronomic traits of the former.

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There is the trend to consider the resistance to phytopathogens as Antibiosis, i.e. to record signs of the affection, and do not notice the traits of Tolerance and Evasion, which manifest themseves by capacity to keep productivity in time and space. For example, M.P. Lisovyi (2001, pp. 22-23) characterizes the variety Mironovskaya-808 as having no significant resistance to the leaf rust, because numeric score of affection by this phytopathogen is rather low. This variety, however, might be considered as having advanced Tolerance to the leaf rust, because it keeps productivity over a number of decades in diverse environmental conditions.

V.V. Shelepov et al. (2004, p. 432) characterize the variety Myronovs’ka 61 and Myronovs’ka 65 as ones, which “are affected by the diseases in medium level” (to the leaf rust and the mildue), although their grain yield is highest within a list of the shown varieties – 10. 24 and 10.30 metric tons per hectare correspondently. This is a case, when Tolerance is concidered as signs of affection. To the point, both the varieties were bred by V.V. Shelepov.

Wild woody plants also have their heredity untouched by humans. The prerequisite of their resistance to PPs 2.2.2.P.1. "A hereditary ability of a plant taxa (species, subspecies, phenological forms, varieties strains, hybrids, lines) to resist against a given taxon of PPs" is supposed to be proper. It is relevant to compare means of maintenance of their resistance to PPs with those in grassy plants.

In wild woody plants, the durability of resistance to phytopathogens is obviously the same as that in grassy species. In trees, it is known the cases of increase of damage on the part of resident species, and the cases of catastrophic mortality of trees on vast areas up to extinction. The causes of the mass mortality consist in penetrating into the range of a tree species the phytopathogens, which have not been factors of natural selection for this species. The same take place at growing of a tree species in an areas isolated from its natural range, where it is attacked by resident phytopathogens. The latter, again, have not been a factor of the selection.

The examples of such events are well known. The epiphytoties induced by species-invaders are those of the Dutch elm disease, Cerastocystis ulmi (Buismen) C. Moreau, the East American chestnut disease, Endotia parasitica (Murr.) A & A, and the European stem rust, Cronartium ribicola Diet.

Heavy epiphytoties in trees grown outside of their natural range in isolated areas are known for the rust fungus on the coffee tree in Ceylon, West Africa and Brazil, the virus disease on the cocoa-tree in Africa.

In nature, there exist, however, the obstacles to extinction under impact of the high virulent phytopathogens. First of all, this is CESPPs 2.1.2.4.1. "Hereditary heterogeneity of a stock of host-plants." The second obstacle is CESPPs 2.2.3. "Natural enemies of phytopathogens." They suppress virulence of phytopathogens, so that the diseases induced by them get a chronic character, rather than acute one.

Consider some facts, which might be supposed as an impact of indeed natural enemies of phytopathogens. The discourse is given according to Yu.T. D’yakov (1985, pp. 58-62 and 205-209).

The Dutch elm disease appeared in Europe in 1918, and over the period more that 30 years killed millions of elm trees. In 1950-ies, its virulence began to decrease. Newly affected trees ceased to appear, and formerly effected trees recovered. It seemed that the disease became similar to resident phytopathogens, which affected exclusively weakened trees. However, in 1967, it began the second epiphytoty of the disease the same as severe as the first one. The studies showed that this epiphytoty was caused by a new pathotype penetrated from Canada, whereas the first epiphytoty was induced by a pathotype penetrated from China.

What is the cause of the decrease of virulence in the first epiphytoty? The answer has not been found by the author in literature. Nevertheless, the explanation of this phenomenon might be inspired by studies of other diseases. The case is the East American chestnut disease. In these studies, it was found out pathotypes of the phytopathogen of low virulence. When they were inoculated on trees affected by common pathotypes, i.e. of high virulence, these trees began to recover. Further studies showed that the pathotypes of low virulence contained own parasites –

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virus-like particles, and the recovering of affected trees was a result of a spread of the virus-like infection on a micelium of the high virulent pathotype.

It is logical to suppose that if a hyperparasite appears in a population of phytopathogen, and spread within it, this leads to a decrease of its virulence. This is a hypothetical cause of the decrease of virulence at the first epiphytoty of the Dutch elm disease. The next step is to spread this hypothesis on other invading taxa of phytopathogens.

The chain composed by a phytopathogen (a rust fungus), its parasite (a bacterium) and hyperparasite (a bacteriophage) is known on the wheat and other cereal species (Klement and Kiraly, 1957).

G.E. Russel (1978) has paid attention on the fact that actually all the cases of losses of resistance to phytopathogens are concerned situation, when operate physiological (biochemical) mechanisms of this trait (in the present report, this is the CESPPs A.2.1.1.2.2.2.1.) Such a category of plant self-defense occurred to be less durable than other ones.

Contrary, the structural Antibiosis (in the present report, this is CESPPs A.2.1.1.2.2.1.1.) operates over unlimited time. Probably, the self-protection is especially durable if it consists of a combination of external structures and toxic factors. The protective means of such a principle has been developed by humans. This is the Beaurdeaux mixture consisting of solutions of cupric vitiriol and lime. It uses for spraying of plants before phytopathogen's agents come on plant surface. This preparation has been used over more one hundred years, but the resistance to it in phytopathogens has not been found out yet (Robinson, 1980). As to contemporary systemic fungicides, they become ineffective in not so many years after beginning of usage of them in a wide-scale due to acquired resistance of phytopathogens to the fungicides.

In a breeding process for selection the entries having the most expressed resistance to PPs, it has been used the method of evaluation of this trait in the conditions optimal for an affection. For example, it is practiced growing of wheat entries in areas of tropical climate optimal for activity of the rust phytopathogens. This allows selection of entries with the less affection. Naturally, they have the most potent hereditary base of resistance to these phytopathogens. These are the grounds to suppose that their resistance to them would be durable in less severe environmental conditions. Screening of crop’s entries on PPs resistance in the plots with increased loading by these organisms is bases on the same principle. These measures use the FDESPPs 8.1.5. "Growing of cultivars in the conditions enhancing of SP of PPs."

As to insect herbivores, the theoretical substantiation of durability of Tolerance also has been done. E. Horber (1974) has supposed that the Tolerance cannot be overcome by herbivores at all. This is so because the plants with this trait are not undergone selective pressure on the part of herbivores. The Tolerance neither kills herbivores, nor suppresses vitality of them. It allows to herbivores to reach significant density. In turn, it provokes an activity of their natural enemies, which suppress the hervivore hosts.

Insect defoliators and sap-sucking arthropods are exposed to suppressive effect of weather factors – CESPPs 2.3."Routine weather suppression." Therefore, the evolutionary evolving of herbivores in the case of operation of CESPPs 2.1.1.3.1."Tolerance to herbivores" moves in the direction to counteract these factors of mortality, and to decrease the negative effect on their host-plants. Further, presence of herbivores on plants in Moderate density exert even beneficial effect of these plants by means of enrichment of the soil. The sources of such enrichment are excrements of these herbivores and their predators, especially birds, and bodies of died herbivores. Honey dew of aphids enhances greatly activity of nitrogen-fixing organisms in the soil.

The durability of CESPPs A.2.1.2.1.1."Superevasion from herbivores" is based on the fact that vital activity of plants is possible at lower temperatures than that in arthropod herbivores. Moreover, they strengthen A.2.1.2.1.1. "Superevasion from herbivores" by culling the host-plants with less expression of this trait.

In this context, it should cite I.E. Pavlov (1967, pp. 170-171), who has reported that many varieties of the barley (Nutans-187, Europeum, Winner, Nossovsky, and others) have been bred many years ago. Nevertheless, their resistance to the flies Oscinella frit L. and O. pusilla Mg. not

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only remains until now, but even it is increasing. These varieties grow quickly in spring, so that before the beginning of the flight period of the flies, their tillers become hardened. Therefore, the flies’ larvae cannot feed in them. Thus, the flies exert selection of most fast-growing plants of the barley.

The Hessian fly, Mayetiola destructor is an interesting case of sudden appearing as a pest, probably being a native species in the range of its heavy damage in Russia. A.F. Kryshtal (1950) showed that close relatives of the Hessian fly feed on cereal species in humid habitats, whereas the fly feeds mainly in mesophytic habitats on various varieties and species of the wheat, Triticum spp., the rye, Secale spp., the barley, Hordeum spp. and on the couch-grass, Agropyrum spp., in particular Agropyrum repens (L.) P.B.

The change of habitats by the fly and growing of host-plants favorable for ancestors of the fly has been accompanied by forming of species traits and capacity to inflict heavy damage. A.F. Kryshtal (1950) supposes that the family Itonididae (Cecidomyiidae) in the present time is in a stage of abundant species forming.

Consider the issue: what is the cause of differencies in interelations of the Hessian fly with field crops, on the one hand, and the fly with the couch-grasses, on the other hand? In the European part of Russia, the Hessian fly was serious pest of cereal crops (mainly the wheat) over nearly a century. The couch-grasses are common host-plants for the fly. The couch-grasses are wide-spread and tiresome long-standing weeds. The question is why does being favorite host-plants of the fly, the couch-grasses have not been undergone a depression?

This fact implies that the couch-grasses has effective resistance probably of the categories of CESPPs 2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of losses of host-plant tissues" and/or 2.1.1.3.1.3. "Tolerance to herbivores, indifference to losses of host-plant tissues." The group of couch-grasses has the trait to store abundant resources in their root systems that allow it to produce seeds in spite of affection of some part of tillers, and to restore their tillers, when affection by grazing and insects colonization. In addition, it is probable the significant role of 2.1.1.4.1. "Evasion from herbivores."

In cereal cultivars, the traits serving as the above CESPPs are expressed less. Therefore, Mayetiola destructor endangers them more than the couch-grasses.

As an example of longevity of CESPPs A.2.1.2.1.1. "Superevasion from herbivores", it can serve the usage in North America until now the optimal (late) sowing dates of the winter wheat for protection against the Hessian fly. This measure is practiced over a hundred of years, but still is effective.

In woody plants, the CESPPs 2.1.1.2.1.2.1."Antibiosis to herbivores, Physiological (biochemical), Permanent" is quite durable. Long co-evolution of woody plants with their PPs has led to development of exclusively multilateral traits of self-protection of assimilative tissues in coniferous species and vascular tissues in all the woody species. The protective product of coniferous species – oleoresin consists of up to fifty toxic for PPs substances. Also eucalyptes are protected by great diversity of adequate substances. In volatiles of their foliage, it has been found out about 270 organic compounds probably of a protective concern (D’yakov, 1985, pp. 79-80).

Nevertheless, it is necessary for self-protection of coniferous tree species something more than only the presence of toxic substances in tissues. In fact, in tissues of weakened trees, the content of oleoresin is the same as that in healthy ones. This does not provide an obstacle for numerous species consuming coniferous species. The difference between healthy and weakened coniferous trees consists in a capacity of the former to convey oleoresin to attacking herbivores or to wounds that protects them against phytopathogens. In a result, attacking PPs occur inside a toxic and viscous product, whose amount is much greater than a mass of herbivore bodies or agents of phytopathogens. On the air, oleoresin becomes solid. Under such a complex effect, even rather large beetles die. Killing of bark beetles in oleoresin on a stem surface (in pitch tubes) or in bark of their host-trees is a common event. The same takes place at attacks of healthy treea by other stem borers, For example, A.S. Rozhkov (1982) reported about mortality in exuding oleoresin up to 70% larvae of the longhorned beetle, Xylotrechus altaicus Gebl.

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The great variety of protective substances in coniferous and eucalyptes species suggests that their resistance has indeed polygenic character. This is the case of the factor durability.

An additional obstacle for surviving of PPs in coniferous species consists in diversity of composition of turpentine within a species. Among samples of turpentine taken in trees a plot, there are no the trees having the same composition. Therefore, in such ecosystems, it operates CESPPs 2.1.2.4.1. "Hereditary heterogeneity of a stock of host-plants."

The complicated composition and peculiar physical properties of oleoresin hamper to consume this product. It is free of consumers with the exception of the little group of insects, which are called "resinocols" (Mamayev, 1971). They need to pay for feeding such an uncommon foodstuff by slow development and high mortality that result in Low density.

The ecosystems of coniferous tree species, where conductive and assimilative tissues concerned the biomass D-I, they are propected from PPs by CESPPs 2.1.1.2. "Antibiosis."

In woody deciduous tree species, CESPPs 2.1.1.2. "Antibiosis" operates only in conductive tissues. This is the biomass of the category D-I. In the biomass D-II of these species, it operates CESPPs 2.1.1.3."Tolerance" and being in a cooperation with CESPPs 2.2."Natural enemies", 2.3."Routine weather suppression", and 2.4. "Periodic (bottle-neck) suppression." These CESPPs provide durability of ESPPs on the level 3.1. "Proper control" that is demonstrated by flourishing of these ecosystems, if they have not been disturbed by humans or natural force-majeur impacts.

As to the defoliators, which inflict insignificant damage for host-trees, it is tolerable a decrease ESPPs to the level 3.2. "Lag control" by CESPPs 2.1.2.1. "Superevasion" or 2.1.1.4. "Evasion" in a cooperation with other CESPPs, so that these categories of host-plant to PPs also provide ESPPs with durability.

The hereditary prerequisite of all the subcategories of the in wild woody plant species retains in all the circumstances, except the cases of invasion of species-strangers and growing of tree species outside of their natural range.

To summing up. The durability of ESPPs is provided by diverse CESPPs on condition that their hereditary prerequisite is proper. Depending on the category of biomass, these CESPPs are the following:

i) On biomass of the category D-II (assimilative tissues, tillers), CESPPs 2.1.1.3. (A.2.1.1.3.) "Tolerance" (diverse subcategories) and CESPPs 2.1.2.1. (A.2.1.2.1.) "Superevasion" or 2.1.1.4. "Evasion."

ii) On biomass of the category D-I (vascular tissues, assimilative tissues in evergreen coniferous species and in the eucalyptes), 2.1.1.2. "Antibiosis", and 2.1.1.1. "Nonpreference."

These points correspond to understanding of the durability of plant resistance to PPs as having the polygenic (horizontal) character. The suggestion as to durability of monogenic (vertical) resistance needs to be proved. When operating with plant resistance to PPs, it should, however, follow the phenotypic display of this trait, rather than by speculations as to the number of the genes being engaged.

The practical implications from these speculations are the following:i) It needs to evaluate plant resistance to PPs (CESPPs A.2.1.) in the provocative for PPs

environmental (laboratory and field) conditions. Importantly, it should take into account not only numeric scores of affection, but also values of crop’s yielding, practicing the pesticidal check.

ii) It needs to maintain CESPPs A.2.1. of a cultivar by artificial selection of resistance plants in conditions of increased infectious loading at seed farming.

It should recall that CESPPs 2.1. (A.2.1.) “Plant resistance to PPs” is durable on condition that the presence of the following prerequisites:

2.1.1.P.1. (A.2.1.1.P.1.) A hereditary ability of a plant taxa (species, subspecies, phenological forms, varieties strains, hybrids, lines) to resist against a given taxon of PPs,

2.1.1.P.2.(A. 2.1.1.P.2.) Level of physiological state of a host-plant, which is close to proper one.

2.1.2.P.1. In biocenoses, forming of a dominant stock at the natural conditions. 17


A.2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or special cultural practices with the aim of effective operation of CESPPs A.2.1.2.

8.2. Anthropic-28.2.1. Cultural practices disturbing physiological state of dominants and obstacles for host-

plant superevasionBreakage of the prerequisites:

2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or special

cultural practices with the aim of effective operation of CESPPs A. 2.1.2.8.2.1.1. CESPPs 2.1.1.1.1.3, 2.1.1.2., A.2.1.1.2., 2.1.1.3.1.2., A.2.1.1.3.1.2., 2.1.2.1., and

A.2.1.2.1. failed8.2.1.1.1. Affection by phytopathogens and herbivores

R. Painter (1951) has considered the resistance of trees to pest insects as a special category of this trait – a physiological resistance. It might be this view is a reflection of the fact that the proper physiological state of trees as a prerequisite of resistance in forest trees occurs to be disturbed very often.

The causes, why silviculture concedes agriculture in maintenance of the proper physiological state of plants, consist in two realities. Firstly, it is difficult to control the state of perennual trees growing often in environmental conditions far from optimum for a given tree species. The second, in agriculture in field, defects of cultural practices become obvious in the same year or within few years. Therefore, the defects of cultural practices can be revealed easily.

Contrary, in silviculture, the improper cultural practices bring their fruits often through dozens of years. Obviously, it is difficult to reveal true causes of weakening of physiological state of these, if the grounds of that were laid many years ago. In this human activity, articenoses with improper composition of plants are often established, so that the prerequisites 2.1.2.P.. and 2.2.1.P. become disturbed that lays obstacles, in particular for operation of Superevasion and activity of natural enemies.

Due to above peculiarities of silviculture, the cultural practices in this province are characterized by the vast number of defects. It is necessary for growing of healthy forest to bring the defects on light. On the other hand, over centuries of its existence, forestry has developed measures, which allow establishing stable forest ecosystems even in severe environmental conditions. Unfortunately, the achievements of forestry often are not used in practice.

In silviculture, FDESPPs 8.2.1. "Cultural practices disturbing physiological state of dominants and obstacles for host-plant superevasion" includes a wide diversity of activities and operates in complexes with many other FDESPPs composing diverse combinations, in particular with 8.2.3., 8.2.4., 8.2.5., 8.2.6., 8.2.7., 8.3.1., 8.3.2., 8.3.3., 8.3.4., 8.3.5., 8.3.6., 8.4.1., 8.4.2. Therefore, later in this text, it will be numerous returns to this FDESPPs, when considering of a cooperation of FDESPPs and their complex effects.

Because the management in agriculture is controlled much better than that in silviculture, the cases of improper cultural practices in the former are rather rare. Nevertheless, the affection of the winter wheat by the frit fly, Oscinella frit due to improper cultural practices have been demonstrated by G.I. Vasechko (2001). In the one case, the winter wheat was grown in the special test with the diverse practices. In plots with surface tillage instead of digging up and absence of fertilization, value to tillering occurred to be low, percentage of tillers colonized by Oscinella frit was much greater than that at proper cultural practices (normal digging up and fertilization).

In the other case, the winter wheat was sown the large delay and on the exhausted soil (after harvesting of the sugar beet). These circumstances resulted in the same effect as that in above example. It had to re-sow this field.

These examples suggest that in agriculture, maintanance of the level ESPPs A.3.1."Proper control" needs in strict providing an operation of prerequisites of CESPPs A.2.1.1.3. and

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A.2.1.2.1. "Superevasion" both against herbivores and phytopathogens. The usage of optimal sowing dates of winter and spring crops allows decreasing of density of herbivores and affection by phytopathogens to the Insignificant values.

8.2. Anthropic-28.2.2. Changes in the soil conditions unfavorable for dominants

Breakage of the prerequisites:2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one

8.2.2.1. CESPPs 2.1.1.1.1.3., and 2.1.1.2.1.2. failed8.2.2.1.1. Outbreaks of stem borers

The disturbance of physiological state of plants is common at sharp change of water regime of the soil. The changes take place at building of large water reservoirs (storage lakes on rivers) and drainage of swamps. The reservoirs induce a lifting of the water table, which exerts destructive effects of forest sometimes on dozens kilometers outside of them. In a result, roots of the trees growing in depressions occur continually in the water and die off. The mortality of dominants takes place in riparian forest growing on banks above dams in river’s valleys. Below dams, riparian forest suffers due to cessation of flooding. Such causes of physiological state of trees operate, in particular in Ukraine in vicinity of the River Dnieper. On this river, it has been built several giants reservoirs, which established a number of problems of the above-mentioned character. After building of the grandiose Kakhovka storage lake on the River Dnieper, the water table on the level side of the Dnieper Valley rose on the distance thirty km for fifteen years (Skaballanovich et al., 1979, p. 163).

The dieback and decline of trees are common on edges of a forest with clear-cut areas in the humid habitats. Until integrity of a forest massif is not disturbed, the water table stays on admissible for tree vitality depth, because trees draw off water from the soil. Contrary, after clear cutting, a water table lifts on the soil surface, and a clear-cut area becomes a swamp. The latter spreads in a near by forest, and trees in the range of a swamp die off.

At drainage of territory, a water table brings down and stays continually on a low level. In Soviet Union, digging of trenches in swamps and humid forests was practiced often. The grounds of such activity consist in an intention of the powerful Ministry of Melioration to have objects, which prove necessity of existence of this monster.

At absence of drought over several years after digging of the trenches, the trees are able to spread their roots to the lowered level of the water table and to survive. Contrary, at drought in this period, the roots dry out and the trees die.

8.2. Anthropic-28.2.3. Damage of dominants by people or animals under human assistance


2.2.2.P.1. Proper activity of predators, which operates in cooperation with CESPPs of the category 2.4. Periodic (bottle-neck) suppression

2.2.2.P.2. A size of area of an ecosystem sufficient for providing of predators with vital requirements

8.2.3.1. CESPPs 2.1.1.2.2. ,2.1.1.1,1.3., 2.1.1.2.1.2. , and 2.2.2. failed8.2.3.1.1. Affection by phytopathogens and herbivores

A mechanical control of weeds, which is conducted in afforested areas annually until closing of their canopy, it is common damage of young stems. Again, these wounds serve as an entrance for infection. Therefore, application of herbicides is prospective for control of weeds.

The heavy techniques, which are used for withdrawal of cut trees, exerts damage of roots of reserved trees and wounds their stems. The damage is most destrictive, when tree cutting is conducted in warm period of year. In Tsarist Russia, it was conventional to conduct all kinds of wood cutting in winter. In Soviet Union and Former Soviet Union, all kinds of wood cutting are conducted the whole year round. In so doing, timber becomes endurable to rots.

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In forests, which are often visited by people, for example those of a recreative concern, it is common suppression of vitality of tree’s roots due to trampling down of the soil, that result in dieback or mortality of trees.

As to wild hoofed animals, a lack of their predators and insufficient hunting lead to heavy damage of young trees. In addition, the great damage is inflicted by cattle. Grazing of cattle in forest is practiced widely in this country. Protection of a young generation of forest from the grazing is limited by plantations until closing of their canopy. After that, cattle is able to penetrate into plantations freely. It is supposed to be this is the main cause of affection of oak stems with the stem cancer, which produces large tumors (Rudnev et al., 1975).

8.2. Anthropic-28.2.4. Affection by air pollutionBreakage of the prerequisites:

2.1.1.P.2. and A. 2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one

8.2.4.1. CESPPs 2.1.1.1.1.3., 2.1.1.2.1., A. 2.1.1.2.1., and A.2.1.1.2.2. failed8.2.4.1.1. Outbreaks of stem borers in forests and signs of diseases affecting agricultural

crops

Now, it is not popular to explain the forest decline by weakening of forest at improper silvicultural practices. The main cause of the decline is supposed to be air pollution. This idea may be seen in the quotation from W. Baltensweiler (1985, p. 77): "The risk of outbreaks of bark beetles and forest defoliators is enhanced in polluted ecosystems, either due to the reduced vigor of the trees and/or altered characteristics of the host-plants. The long lived trees are at a selective disadvantage, therefore air pollution must be stopped and any insect impact, which generally accelerates the "Waldsterben" should be avoided" (p. 77, Summary).

The role of air pollution comparing with other stressors is, however, unclear that may be seen in the following quotation: "Since World War II repeated outbreaks, snow breakage and air pollution combined caused the destruction of more than 100 000 ha (Wentzel, 1982)" (Ibid., p. 81). This phrase suggests that "repeated outbreaks, snow breakage and air pollution" are independent phenomena."

As to conversion of mixed beech-silver fir forest into overstocked spruce monocultures and exhaust of soil resources at withdrawal of wood biomass, when cutting mentioned in the cited paper, this is an obvious cause of repeated outbreaks and snow breakage in Middle Europe. Contrary, the role of air pollution in the wide-scale forest decline is not obvious.

It seems air pollution has become idèe fixe at explanation of the forest decline. It should stress that effect of air pollution is well detected by its location in vicinity of large industrial enterprises. Further, it is characteristic for countries of the Former Communist Block, where authority ignores protection of the environment.

As an example of such a situation, it can serve the report by V.V. Fomin and S.A. Shovnin (2001). The studies were conducted in a region of a copper-melting plant in the Sverdlovsk Region (Russia). It was shown that the heavy affection of forest spread eastward the plant - up to 20 km as an entire area. Farther, signs of the affection were recorded in separate plots of fewer areas. This disposition of the affected areas was due to the direction from the west of the prevailing winds in this area. Westward the plant, the affection spread only on 5 km.

This report is consistent with the view by W.H. Smith (1981). He has supposed that "Severe impact of air pollutants on forests are dramatic, but judged relatively unimportant because of their extremely localized nature" (cited in W. Baltensweiler, 1985, p. 77).

In the publication, which probably expresses the view of United Nations Organization, the pollution, although of another kind, is considered as the only cause of Waldsterben in the industrial countries (Horstkotte, 1995). This pollution is of the kinds of exhaust gases and spoiled subsoil waters. Such pollution is important as to human health, but its concern to Waldsterben is dubious. If this view would true, mortality of trees would affect first of all shade trees in settlements and road-side plantings. However, Waldsterben takes place just in exploiting

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forests, whose state is determined by silvicultural practices independently on distance from the exhaust gases and spoiled subsoil waters. The polluted subsoil waters cannot penetrate in mountain forest, which often undergoes the decline, in particular in Germany. The exhaust gases are hardly are able to kill the trees in remote mountain forest. Being such poisonous, the gases would depopulate all the settlements.

Again, the measures, which have been proposed in the above article to counteract the forest decline, are wrong. The measures are limited by a decrease of output of carbon dioxide (Ibid., p. 2). Firstly, the issue of carbon dioxide output is neither air pollution, nor subsoil water pollution. Secondly, the dependence of severity of droughts on output of carbon dioxide is very dubious. Here are examples of a lack of the dependence. In IX-XI centuries, the technology was too weak to effect on climate. Nevertheless, climate in the region of North Atlantic was warmer than that now. Contrary, XVI-XVIII centuries are known as the Little Ice Age. In the peak of the cold and wet period, when size of glaciers in Switzerland reached maximum, and the Rhone River is south France was caught many times by ice (1556-1595). In the same period, the western areas of North America suffered due to the severest drought. It continued over twenty years (1570-1590), and the values of precipitation composed over 20% of those typical for XX century (Le Roy Laburie, 1971, pp. 213-215). Notably, that the sequoia trees, which at present time are close to 1000 years old, have survived this stress, as well as the forest biome as a whole.

Further, air pollutants can serve as nutrients for plants. Here is the citation from D.P. Ormrod (1978, p. 22): "White pine seedling productivity increases with decrease in pH of simulated acid rain from 5.6 to 2.3. in spite of near depletion of available K, Mg and Ca ions in the soil at pH 2.3. (Wood and Bormann 1977). Additions of HNO3 to the simulated rain are associated with increased foliar N concentration."

Another report about beneficial effects of air pollutants is as follows (Ibid., p. 48): "Growth of white birch and pin oak seedlings responds to relatively high but subtoxic ambient SO2 air (Roberts 1975). Sulfur dioxide has a beneficial effect on white birch, a sensitive species, in that the over all growth is greater in the high S02 environment while the growth of pin oak, an insensitive species, is best at lower S02 concentration. White birch apparently is able to metabolize and utilize the S from the surrounding air, possibly because stomates are not closed by S02."

A. Ionescu and T. Moscalu (1973) reported that a decrease yielding of agricultural crops took place in the radius of two-three km from sources of air pollution. Outside of this area, yield losses were insignificant and episodic.

Surprisingly, although in 1990-ies in Europe, air pollution by sulfur dioxide decreased due to limitation of the emissions in the Western part of the continent, and due to the decline of industry in East Europe, it is reported to be these factors have led to a decrease of yielding of agricultural crops on 5%.

8.2. Anthropic-28.2.5. Affection of forest ecosystems by ground forest fires


2.2.1.P.5.1. Age and structural diversity of vegetation – a presence of several stories of woody vegetation, ground grass cover, and undergrowth

2.2.1.P.6. Undisturbed state of soil surface8.2.5.2.CESPPs CESPPs 2.1.1.1.1.3., 2.1.1.2.1.2.,and 2.2.1. failed

8.2.5.1.1. Outbreaks of defoliators and stem borers

Ground forest fires originated by people by chance or with the aim to promote grazing by cattle. This disturbance is supposed to be an important cause of outbreaks of Dendrolimus sibiricus on vast areas in Siberia. Negative effects of the disturbance depend on intensity of weakening of trees. In ecosystems, where dominands are matured trees with thick bark, groung

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forest fires decrease CESPPs 2.1.1.2.1.2. "Antibiosis to herbivores, Physiological (biochemical)" that spreads only on needles. If these fires takes place in early spring that is common in Siberia they kill parasites of the Siberian pine moth, Dendrolimus sibiricus overwintering in the soil, so that it failed CESPPs 2.2.1.Natural enemies of invertebrate herbivores, 2.2.1.1. Parasites.” When it takes place an addition to this complex of FDESPPs 8.3.1. "Disturbance of water balance in dominants of evergreen coniferous trees due to deficiency of precipitation", it arises outbreaks of Dendrolimus sibiricus.

Heavy weakening of evergreen coniferous trees by feeding of the moth results in failure of CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and 2.1.1.2.1.2. "Antibiosis to herbivores, Physiological (biochemical)" in their conductive tissues that leads to colonization by stem borers and arising of outbreaks of these insects.

In ecosystems with dominance of the larch, outbreaks of Dendrolimus sibiricus, outbreaks of the moth arise under effect the single FDESPPs - 8.2.5.

In ecosystems, where dominants do not reach the age of maturity having not so thich bark, ground forest fires usually decrease operation of CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and 2.1.1.2.1.2. "Antibiosis to herbivores, Physiological (biochemical)" in conductive tissues to the level, at which outbreaks of stem borers arise.

Because ground forest fires weaken host-trees, they lead to breakage of the prerequisite 2.1.1.P.2. Further, they kill natural enemies of invertebrate herbivores by destroying forest litter and an upper layer of the soil, grass cover and undergrowth, resulting in breakage of the prerequisites 2.2.1.P.5.1. and 2.2.1.P.6.

Control of forest fires is proceeded not only by organizational measures, but also by the practices aimed on isolation of forest plots by strips with the bare soil surface or strips planted by species, which are able to withstand forest fire.

The recommendations of such measures are numerous. As an example, it can serve the proposition by N.E. Zalensky (1940). He revealed that strips of the Siberian locust, Caragana arborescence Lamb. are able to stop ground forest fires. Its leaves, which fall in green state at the end of a season, are nonflammable. Its leaves are quickly mineralized, so that this brush does not accumulate forest litter. Under its canopy, it grows not too dense grass with juicy leaves, which stop fire. Further, this species fertilizes the soil by fixation of nitrogen from air. On slopes, beneficial effect of the fertilization spreads on the distance much more a width of the strips.

8.2. Anthropic-28.2.6. Establishing of forest ecosystems with acorns of diverse phenological forms

Breakage of the prerequisites:A.2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or

special cultural practices with the aim of effective operation of CESPPs A.2.1.2.8.2.6.1. CESPPs 2.1.2.1.1. and A.2.1.2.1.1. failed

8.2.6.1.1. Outbreaks of defoliators of the early-spring guild

A.I. Vorontsov (1978, pp. 137-138)) paid attention on the important cause of persistent outbreaks of the early-spring guild of oak defoliators. The cause on these outbreaks consists in ignorance of phenological forms of the oak at application of acorns for afforestation. The presence in a stand of trees with diverse terms of bud-bursting allows to neonate larvae of the defoliators to find every season the buds in the favorable phase for penetration into them. Therefore, in such stands, CESPPs 2.1.2.1.1."Superevasion from herbivores" does not operate. The situation becomes more worse at monocultural composition of a stand. In such case, activity of natural enemies of the defoliators is insignificant, so that this FDESPPs cooperates with the next one - 8.2.7. "Cultural practices inducing hostile environment for natural enemies and favorable microclimate for herbivores."

8.2. Anthropic-28.2.7. Cultural practices inducing hostile environment for natural enemies and favorable

microclimate for herbivores

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Breakage of the prerequisites:2.2.1.P.3. The diversity of species composition of vegetation within an ecosystem

2.2.1.P.4. Presence of microclimate appropriate for activity of parasites and pathogens,2.2.1.P.5. Abundance of ecological niches within ecosystems

2.2.1.P.5.1. Age and structural diversity of vegetation - a presence of several stories of woody vegetation, and undergrowth (in forest ecosystems)

2.2.1.P.5.2. The microrelief diversity within an ecosystem and the area-wide heterogeneity – a presence habitats necessary for temporary migrations of natural enemies of invertebrate

herbivores, which are located within a reach by these species2.2.1.P.6. Undisturbed state of the soil surface

2.2.1.P.7. A size of area of an ecosystem sufficient for providing of natural enemies of invertebrate herbivores with vital requirements

2.2.1.P.8. Presence of the annual stem fall (in woody ecosystems)2.2.1.P.9. Presence of effective vectors of pathogens

8.2.7.1. CESPPs 2.2.1. and 2.3. in forest and agricultural ecosystems failed8.2.7.1.1. Outbreaks of herbivores

This category embraces diverse conventional practices, which decrease activity of natural enemies of herbivores both in silviculture and agriculture. Consider some examples of such practices.

In silviculture, establishing of monocultures with high stocking density does not provide natural enemies of herbivores with prerequisites of their activity. In such articenoses, there are no undergrowth and old trees with stem holes, and a ground grass cover is very scarce. Neither bird predators, nor insect parasites are abundant in these stands.

Contrary, in oak forests of the sprout origin, stocking density is low. Open canopy causes intensive insolation of the soil surface. In a result, compositions of a ground grass cover changes. Then, it prevails more xerophytic cereals. Such plants are favorable as a forage for livestock. Therefore, these forests undergo heavy grazing. The hoofed animals usually destroy undergrowth nearly completely. An open canopy does not protect the natural enemies against destructive effects of weather extremes – high air temperatures, low humidity of air, and severe frost.

Thus, FDESPPs 8.2.7. cooperates with 8.3.3. "Appearing of hostile environment for natural enemies at weather extremes."

Withdrawal of the annual stem fall and large trees with holes wipes out from ecosystems the woodpeckers bereaving them by food (subcortial insects) and sites of nesting. Also, this practice is harmful for maintenance of general stability of forest ecosystems, because stem borers colonizing the annual stem fall provide the turnover of substances, whereas stem borers are absolutely safe for healthy dominants. On the other hand, weakened dominants in any case would die. Further, subcortial community is an important component of biodiversity. Every person, who likes nature should protest against this ignorance.

Grazing of cattle in forest destroys flowering species in the grass cover – a source of imaginal food for parasites of herbivores. The hoofed animals consume most part of brushy species, so that avian predators of herbivores disappear from such forests.

In agriculture, natural enemies are killed at digging up if they hibernate in the soil in the same ecosystems. At vast areas of fields, they lack of refuges for hibernation if they spend it in woody ecosystems. It is intolerable the destruction of hedges and road-site plantings – refuges for natural enemies of herbivores.

The usage of grassy ecosystems as a pasture change drastically composition and density of the vegetation suppressing natural enemies of herbivores. This leads to outbreaks of the locusts.

Here is the citation from S.P. Ivanov et al. (1938, p. 94). "In Angara River Basin (the Central Siberia, Russia), reservations of several species of locusts according to Rubtsov (1932-1935), are situated on long exploiting pastures. On them, in a result of trampling out and thinning out of grass by livestock, it has been formed more xeric and warmer plots, which are favorable for the locusts. Contrary, on meadows with dense vegetation having diverse species composition,

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especially as on glades in forest and forest edges, the locusts are innumerous. Although in the undisturbed by humans plots, species composition of the locusts is greater. Also, Bei-Bienko, who studied the locusts in the West Siberia concluded that outbreaks of the locusts were located on the pastures affected by heavy grazing with the exposed soil surface."

Further (Ibid., p. 94): "Predtechensky (1928, 1930) showed that the locust, Locusta migratoria L. in the central part of USSR, i.e. outside of its continuous range, occurs only in the most dry and warm locations on the sandy soils. The conditions for mass occurrence of the locust appeared in the second part of XVII century in a result of vast cutover of forests and development of agriculture. The locust found favorable conditions on bare fallow fields in a shift of crops system."

In should comment that the question is the middle-Russian locust, Locusta migratoria L., spp. rossica Uv. et Zol., - the subspecies, whose the range is limited by the central area of the European part of the country.

The best conditions for the locusts are arisen on abandoned fields, where digging up is absent, natural enemies are innumerous, and vegetation is scarce. This fact can explain the continuous outbreak of the complex of locust species, mainly Calliptamus italicus L., which took place in Ukraine and southern Regions of Russia, in 1920-ies. A.V. Znamensky (1926, p. 14) supposed that the outbreak in the beginning of 1920-ies was induced by appearing of vast areas of abandoned fields as a result of the Civil war. The role of FDESPPs 8.2.7. as to the locusts will be considered more detailed later at the point 8. (C-9) "The complex of FDESPPs."

The positive effect of thinning of grassy vegetation on growth of locust density is explained by the following data. The locust, in particular, Calliptamus italicus L. is susceptible to pathogens especially Empusa grylly Fres., so that in seasons with abundant precipitation outbreaks of diverse species locusts decline (Ivanov et al., 1938, p. 73). The decline begins in wet habitats. When grassy vegetation is dense, air in its low stage is saturated by humidity that creates favorable microclimate for thriving infection of diverse insect pathogens even in droughty periods. In particular, this fact was noted by E.G. Voronina (1971). Thinning of grassy cover changes the microclimate in the direction favorable for vitality of the locust.

"In Siberia and Kazakhstan, Calliptamus italicus L. and other locusts reach high density on old-field areas and overgrazing pastures… In North Caucasus, destruction of natural ecosystems by grazing leads to change as dominants Stipa spp. and Festuca sulcata Hack. on Poa bulbosa L. The latter species dries out to beginning of summer. Such a dominant is characteristic for southern part of the locust range, and it is optimal for locust reproduction. In the Middle Asia, Calliptamus italicus finds optimal conditions in abundoned fields of the alfalfa, dry hedges, waste lands and other items of improper cultural practices" (Shchegolev et al., 1949, p. 322).

The role of improper cultural practices might be traced of the situation with population dynamics of the locusts in Ukraine and Russia in 1920-ies described by A.V. Znamensky (1926, p. 14). The problem deserves the extensive citation of this scholar. Here it is. "At the end of XIX and in the beginning of XX centuries up to the period of World War I, in a result of development of our agriculture and expansion of arable areas, a significance of the locust insects was decreasing year after year, and their infestation spots moved in south-eastern direction - to flood plains and deserted steppes. People in Ukraine and in the middle Russia forgot completely an existence of these pests. Although in the past, the locusts bear significant damage in many Governorships of southern Ukraine and the Middle Chernozem Belt of Russia. The events after World War I induced heavy degradation and regress in agriculture. Cultural practices changed sharply in the direction of extensiveness; fields were abandoned, grown with weeds that favored to the locusts. Waves of locust pests in 1922-1925 overflowed the southeastern half of Ukraine ...and even in the central Russia (the Kursk, Voronezh, Tambov, Ryazan Regions). It was conducted a control these pests. In eastern and southeastern frontier Districts bordering with the continual reservations of these pests, the situation was much worse. The second example of dependence of pest status of an insect on agricultural conditions is an outbreak of the Noctuids moths, which were able to reach outbreak level on condition that fall digging up was not used, and sowing was conducted over shready stocks."

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In 1929 and beginning of 1930-ies, when Soviet Government waged the war against peasants, an outbreak of locusts arose again. It was impossible to report about this distress openly, because this outbreak implied a presence of some defects in the Soviet society. However, the following remark is rather expressive: "…heavy epizootics of the locust (Locusta migratoria rossica) took place in Ukraine in 1933, when during season, precipitation was exclusivelly abundant, and mists were frequent" (Kryshtal, 1973, p. 187). Indeed, in that time, it was appeared a lot of abandoned fields. Even heavy moisture did not interrupt the outbreak.

After World War II, mass outbreaks of these pest insects in agriculture in Ukraine were not been recorded. Only in 1946, their density was increased a little (Kryshtal, 1959, p. 138). Now in the beginning of XXI century, above-mentioned pest species threaten again. At the end of XX century and in the beginning of XXI one, as in 1920-ies, outbreaks of the locust insects are known on the vast area from Kazakhstan to the central part of Ukraine.

This fact might be considered as a result of the downfall of agriculture developing after the collapse of Soviet Union. It was supposed to be that the area of abandoned fields in Ukraine in 1990-ies reached six million hectares (M.P. Lisovyi, pers. comm.) or eight million hectares (V.M. Chaika, pers. comm.) of thirty-three million hectares of arable lands in this country. In Russia, in 1990-ies the area of abandoned fields reached thirty million hectares (V.F. Drozda, pers. comm.).

The prevailing in last years species Calliptamus italicus and close to it in ecological habits species of locusts reached High density on abandoned fields with abundance of the couch-grass (Kryshtal, 1959, p.257).

In Ukraine, the outbreak of the locusts took place in 1990-ies and 2000-ies. It is notably that this outbreak occurred to be more prolonged than that after the Civil war. The previous outbreak operated only within three years - 1923-1925 (Sekun and Lobko, 2004). Contrary, the new outbreak of the locusts, mainly Calliptamus italicus L. in south of Ukraine is durable. It started in 1994, continued to 1998, and began again in 2001 continuing to 2004. In 2005, the next decline took place (V.M. Lobko, pers. comm.). This scholar explains the causes of arising of the outbreaks and their decline as follows: appeasing of wide areas of abandoned fields after the collapse of Soviet Union in 1991. These fields have been grown by weeds, and the abandoned fields are free of natural enemies of the locusts.

The cause of the decline in 1998 and 2005 consisted in affection by the pathogen Entomophthorus (Empusa) grylli Fres. due to wet weather situation in the vulnerable stage of the locusts – the larvae of young instars.

It seems, the present depression in Ukrainian economics is more serious than that in a result of the terrible Civil war and World War II.

Population behavior of locusts in Steppe and Forest-Steppe biomes of West Siberia (the vast area from foothills of the Urals Mountains to foothills of the Altay Mountains) also shows a participation of diverse causes in arising of their outbreaks (Berezhkov, 1956). The fauna of locusts in this areas is rich – about eighty species (Ibid., p. 9), and outbreaks have been recorded long ego (Ibid., p. 49).

“Pallas …reported about damage of agrivultural crops by locusts in an areas between the Rivers Ob and Enisey in 70-ies of XVIII century. Gebler mentioned about an outbreak of locusts near by the Altay Mountains in 1812 and 1813… It is known outbreak of locusts in 1846 in West Siberia (Keppen, 1882) and in 1870 near by the Urals Mountains. In beginning of XIX century the vast outbreak spread on Steppe and Forest-Steppe zones of West Siberia…In 1911 and 1912, the outbreak took place in diverse places in West Siberia.”

Nevertheless, “The greatest outbreak took place in years of the Civil war (1918-1922), when many arable lands were abandoned, and cultural practices were poor, that occurred to be favorable for locusts…in 1919, in the Altay, Novosibirsk and Kemerovo Regions, more 220,000 hectares of agricultural crops were destroyed or heavy damaged. Detaled data about outbreaks of locusts in the same areas in 1920-ies were offered by Filip’yev (1925) and Predtechensky et al. (1935)”(Ibid., p. 49).

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In 1990-ies, the same areas in Russia and Kazakhstan again were seized by outbreaks of locusts.

Above discourse demonstrates the important role of improper cultural practices and weather situation on possibilities of the locusts to reproduce.

The above cases represent operation of FDESPPs 8.2.7. "Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores."

8.3. Weather disturbances8.3.1. Disturbance of water balance in dominants of forest ecosystems due to deficiency of

precipitationBreakage of the prerequisites:

2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one8.3.1.1. CESPPs 2.1.1.1.1.3, and 2.1.1.2.1.2.1.failed

8.3.1.1.1. Outbreaks of needle-eating defoliators and stem borers

Droughts decrease exudation of oleoresin and other protective substances that results in arising of outbreaks of stem borers and needle-eating defoliators. Again, the effect of drought takes place in separate locations within an area affected by it. That is, so because the outbreaks arise in forest plots growing in unfavorable environmental conditions, in particular the dry sandy soil or/and weakened by improper silvicultural practices, when droughts exert an additional stress.

If the deficiency of precipitation is not too heavy, it takes place a decrease of CESPPs 2.1.1.2.1.2.1. "Antibiosis to herbivores, Physiological (biochenical), Permanent" in needles, that induces outbreaks of needle-eating defoliators. If the deficiency is more serious, it takes place a decrease of CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and again CESPPs 2.1.1.2.1.2.1. in conductive tissues that induces outbreaks of stem borers.

8.3. Weather disturbances8.3.2. Mass coincidence of larval hatching or attacks of herbivores in older stages with

favorable phases of host-plant development in dominantsBreakage of the prerequisites:

2.3.P.4. Weather situation, which provides operation of CESPPs 2.1.2.1. Superevasion8.3.2.1. CESPPs 2.1.2.1.1. and A.2.1.2.1.1. failed

8.3.2.1.1. Outbreaks of defoliators of the early-spring guild of oak defoliators and the species with similar traits on coniferous trees

Survivorship of neonate larvae of the early-spring guild of oak defoliators depends on the following factors: composition of dominants as to diversity of the phenological forms of the oak and weather situation in the period of hatching of the insect, as well as on weather in preceding winter. The weather situations determines terms of bud-bursting of a given form of the oak. In the stands with dominance of a single oak form, the mass coincidence of larval hatching and bud-bursting is a matter of chance, because an onset of weather situation has such a character. Contrary, in the stands with dominance of wide diversity of oak trees as to the terms of bud-bursting, the mass coincidence usually takes place annually. This is so, because the neonate larvae are able to leave trees with closed buds and migrate on trees with buds in the phase favorable for penetration into them. So that, FDESPPs 8.3.2. cooperates with FDESPPs 8.2.6."Establishing of forest ecosystems with acorns of diverse phenological forms."

The weather factors, which cause the mass coincidence of larval hatching bud-bursting of host-trees, is the main FDESPPs determining arising of outbreaks of Zeiraphera diniana. They are important in the complex of FDESPPs, which cause outbreaks of Choristoneura fumiferana and Porthetria monacha.

In oak stands, FDESPPs 8.3.2. cooperates often with FDESPPs 8.2.6. "Establishing of forest ecosystems with acorns of diverse phenological forms."

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The effect of FDESPPs 8.3.2. is known in agricultural crops. "Decrease of air temperatures diminished activity of the large beet weevil, Bothynoderus punctiventris Germ., whereas a rain at amount of 20 mm in April 26 promoted good growth of the sugar beet, which evaded from damage due to the weevil… In 1954, at drought, synchronization of appearing of the sugar plantlets with mass emergence of the sugar flea resulted in heavy damage of the crop (Migulin, 1961, p. 4).

8.3. Weather disturbances8.3.3. Appearing of hostile environment for natural enemies at weather extremes

Breakage of the prerequisites:2.3.P.1. Temporal lasting of weather situations

2.3.P.3. Proper structure of ecosystems, which provides microclimate tolerable for natural enemies of invertebrate herbivores

8.3.3.1. CESPPs 2.3. failed8.3.3.1.1. Outbreaks of defoliators of diverse guilds

This FDESPPs concerns mainly defoliators of deciduous tree species of the spring-summer, summer-fall and fall-spring guilds in deciduous tree species. CESPPs operating against these insects are 2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation losses of host-plant tissues" and 2.2.1. "Natural enemies of invertebrate herbivores." Because prerequisites of CESPPs 2.3. (2.3.P.1., 2.3.P.2., and 2.3.P.3.) are absent, CESPPs 2.2.1. does not operate, it arises outbreaks of the above-mentioned guilds.

Droughts and severe winters with a lack of snow cover induce outbreaks of the defoliators that have been shown for a number of species. Such weather situations take place everywhere on vast areas. Nevertheless, within areas covered by such situations, outbreaks arise in certain spots. Other ecosystems with host-plants of a given species of defoliators as dominants occur to be unaffected. These ecosystems have structure and species composition, which keep activity of natural enemies of the above guilds of defoliators independently to weather situations. In them, the prerequisites of CESPPs 2.2.1. "Natural enemies of invertebrate herbivores" are in good state. Droughts and severe winters are unable to suppress natural enemies of defoliators in such ecosystems.

Contrary, at an operation of FDESPPs 8.2.7. "Cultural practices inducing hostile environment for natural enemies and favorable microclimate for herbivores", the prerequisites are destroyed that leads to disappearing of natural enemies, so that FDESPPs of the category 8.3.3. should be considered as secondary one, i.e. conditioned by human activity.

Some exclusion concerns ecosystems, which grow on the border of their range – forests in southern part of the Forest-Steppe biome, and extrazonal forests in the Steppe biome. In such conditions, activity of natural enemies of defoliators can be suppressed by weather factors independently on human interference. However, it is difficult to prove this statement, because in such areas human impacts on ecosystems are very potent.

It is probable a cooperation of FDESPPs 8.3.3. with 8.3.1. "Disturbance of water balance in dominants of forest ecosystems due to deficiency of precipitation", so that outbreaks of needle-eating defoliators are induced not only by decrease of CESPPs 2.1.1.2.1.2.1."Antibiosis to herbivores, Physiological (biochemical), Permanent", but also by disturbance of CESPPs 2.2.1. "Natural enemies of invertebrate herbivores."

8.3. Weather disturbances8.3.4. Increase of aggressiveness of phytopathogens and herbivores at favorable weather

in the period of their activityBreakage of the prerequisites:

2.3.P.2. Limitation of aggressiveness of PPs8.3.4.1. CESPPs 2.3. in ecosystems of diverse types failed

8.3.4.1.1. Arising of epiphytoties and outbreaks, increase of duration of outbreaks

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At breakage of the prerequisite 2.3.P.2., numerous subcategories of CESPPs 2.3. "Routine wreather suppression" do not operate. They are the following: 2.3.2., 2.3.3., 2.3.4., 2.3.5., 2.3.6., 2.3.7., 2.3.8., 2.3.9., 2.3.11., 2.3.12., 2.3.14. and 2.3.16. Such a diversity of stressors leads to diversity of the effects.

A weather situation in certain periods of a season determines the number of generations of phytopathogens and duration of their generations. When the situation is favorable, it arises epiphytoties, so that the cultivars known as resistant ones occur to be affected.

If expression of CESPPs 2.1.1.2.2. "Antibiosis to phytopathogens" or 2.1.1.2.1. "Antibiosis to herbivores" is temperature-dependent as to a given species, certain weather situations provokes an epiphytoty or an outbreak of this species.

The weather situation favorable for vital activity of insect herbivores in the period of their development maintain insect’s immune system is in the proper state, so that the herbivores become resistant to pathogens and parasites. In forest ecosystems, at cooperation with other FDESPPs, in particular 8.3.3. "Appearing of hostile environment for natural enemies at weather extremes" and 8.2.7. "Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores", this FDESPPs increases duration of outbreaks and the density.

For example, when drought takes place at the outbreak (erruptive) phase of population dynamics of Porthetria dispar, duration of the outbreak increases from six years to ten ones (Khanislamov et al., 1958).

In sap-sucking arthropods (aphids and mites), favorable ambient temperatures beside with positive effect on immune system, promote a growth of density by means of decrease of duration of their generations and increase of the number generations per season. When the temperatures cooperate with hostile conditions for their natural enemies, outbreaks of the arthropods become spectacular. Such a cooperation is common in fields of agricultural crops and in shade trees. Here, activity of parasites and predators is low. At an onset of drought, activity of their pathogens occurs insignificant.

Much more possibilities for their outbreaks take place in greenhouses. Here, if introducing of predators and parasites is not practiced, these organisms are absent completely. In addition, microclimates of greenhouses, where rain and dew are absent, suppress activity of pathogens. Therefore, in greenhouses, aphids and mites tend to reach High densities year after year.

Increase of aggressiveness of phytopathogens and herbivores at favorable for these PPs weather situation in the period of their activity is a common event. In so doing, as a means of self-protection of plants, it serves CESPPs 2.1.1.3. "Tolerance." Its efficacy is provided by a proper state of the prerequisite 2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one.

The role of FDESPPs 8.3.4. is of the crucial importance as to outbreaks of some taxa of the locusts. Here is the discourse about effect of weather on Locusta migratoria L. spp. rossica Uv. et Zol. in the period of its activity (Ivanov et al., 1938, pp. 144-145): "…in northern reservations of the locust, growth of its density begins in warm and dry seasons, because only at such weather, the egg production and oviposition proceed successfully (Predtechensky, 1928, 1939; Olsuf’yev, 1930). A decrease of locust density in these areas takes place usually in cold and wet seasons, when the eggs cannot reach maturity. Nevertheless, according to the studies by Zolotaryov (1936), other causes are able to decrease the density. Thus, in 1933, in spite of a cold beginning of summer, the eggs matured, but due to deficiency of warm and abundant precipitation in this season, the locust aggregated and oviposited in better warmed and xeric locations – on tops of sandy hillocks and hillsides exposed to south with scarce vegetation. Further, the eggs were placed closely to the soil surface in the most warm and xeric layer. In a result, a part of the eggs died occurring on the soil surface under effect of winds and rains in fall. Most of the rest eggs died in winter, because a snow cover was small, whereas frost reached 15°C below zero. In a result, in 1934, the locust was innumerous. In warmer seasons, oviposition takes place in locations situated lower especially on forest edges, where snow is accumulated, so that the winter mortality is low."

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In the Morocco locust, Dociostaurus maroccanus Thnbg., precipitation especially in spring is considered as the crucial factor of density (Shchegolev et al., 1949, p. 321). "The range of this species is located in the areas with amount of spring precipitation close to 100 mm; sharp increase or decrease of the amount exert a perish of the locust (Bey-Bienko, 1936). In the first case, the locust dies in the egg stage in their oothecae under effect of fungi (Fusarium sp. and others), which sometimes kill 50-100% of eggs. Contrary, sharp decrease of amount of spring precipitation promotes drying up of the eggs. Moreover, it can occur mortality of the neonate larvae due to food deficiency, because in droughty seasons, a plant’s cover of the soil dryes out quickly. The role of amount of precipitation is diverse one depending on local conditions and climate. In the North Caucasus closely to the north border of the species range, with amount of yearly precipitation 400-500 mm, its deficiency is favorable for the locust, whereas the normal amount is unfavorable. An increase of precipitation above the normal amount in spring and in previous fall decreases locust density dramatically…

In the Middle Asia, where the reservations situated in the conditions of deserts and semi-deserts, the sharp decrease of the density takes place in seasons with severe drought in spring, when the eggs and larvae die due to dessication, or in seasons with exclusively wet weather in spring, when the larvae die due to fungal deseases."

Arising of outbreaks of the desert locust, Schistocerca gregaria Forsk should be regarded as ones belonging to this category FDESPPs. In fact, according to N.S. Shcherbinovsky (1952), density of this species is determined by amount of rains that results in availability of its food - up to 400 plant species (Ibid., p. 19). The outbreaks arise in persistent infestation areas (tropical and subtropical savannas, brushy deserts and semideserts in Central Indostan, Arabia and East Africa), when monsoon rains are abundant and prolonged. Then, the solitaria phase transforms in the transiens and gregaria phases. The outbreaks begin nearly simultaneously in all the persistent infestation areas despite they are separated by large distance (Ibid., p. 32). Temporary infestation areas, known in southern Iran and Oman, arise at abundant winter rains characteristic for Mediterranean climate (Ibid., pp. 15 and 20). Good moistening of the soil provides florishing of host-plants of the locust in the period of its feeding.

A cyclicity of the outbreaks in the persistent infestation spots is surprisingly regular (Table 39).

Table 39. Indices of outbreaks of Schistocerca gregaria in India according the data of Indian Antilocust Organization published in 1942 and further observations (Shcherbinovsky, 1952, p. 31)

Years of the outbreaks

Duration of the outbreaks, years


Duration of the outbreaks, years

1800 - 1803 4 1876- 1881 61810 - 1813 4 1888 - 1892 41821 – 1826 6 1900 - 1907 81833 - 1834 2 1912 - 1919 81843 - 1845 3 1926 - 1931 61860 - 1866 7 1940- 1945 61869 - 1873 5 1949 – 1955* 6

*A forecast, which occurred to be true. A decline of the outbreaks is caused by solely deficiency of food at an onset of drought,

whereas pathogens and other natural enemies do not play noticeable role. This view is confirmed by cases of growth of the density at abundant rains in the innocuous period in 1935 and 1936, and at a decline of the outbreak in 1943 in Indostan. Because these rains took place during the limited period, they did not lead to the outbreaks (Ibid., pp. 25 and 272).

These data deserve a discussion. They show that vitality of the locust population is continually in a good state, so that the increase of its density takes place always, when food provided by rains is available. Therefore, fluctuations in affection of the population with pathogens are not a cause of increase and decrease of locust density.

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Hence, this case of FDESPPs can not be attributed to the category 8.4. “Endogenic disturbance”, 8.4.4. “Microevolutionary process in herbivore populations in the conditions with the weak operation of CESPPs of the Extrinsic class.” The fluctuations are determined only by a weather factor - an amount of rains. In the period of deficiency of rains, it operates CESPPs 2.3.11. “Drought devastating of food resource” with the effect 2.3.11.1. “Mortality due to starvation and at immigration.” This is the level ESPPs 3.1. “Proper control” to Sch. gregaria.

This conclusion is seemed surprising, because the fluctuations of locust density is strictly regular over one hundred and half century, although an amount of rains is known to be not a regular. Nevertheless, it has to admit that in the monsoon climate, there is a cyclicity of an amount of rains indeed with intervals in average 11.5 years, and common fluctuations 10-12 years. Just the same is cyclicity of Sch. gregaria outbreaks according to N.S. Shcherbinovsky (1952, p. 27).

The scales of the outbreaks are uneven. According the data about migrations of Sch. gregaria in Iran, Transcaucasus and Central Asia, the outbreaks in 1900-1907, and 1926-1931 were especially grandiose; the forecast on 1949-1955 promised the same (Ibid., p. 32). These fluctuations probably are determined by intensity and duration the rains.

8.3. Weather disturbances8.3.5. Increase of survivorship of PPs at favorable weather situation in the period of their

dormancyBreakage of the prerequisites:

2.3.P.2. Limitation of aggressiveness of PPs2.4.P.1. Keeping of severity of the season of a year, when activity of PPs is suppressed

8.3.5.1. CESPPs 2.4. failed8.3.5.1.1. Increase of density of herbivores and affection by phytopathogens

Moisture conditions of the upper layer of the soil, where the Asiatic locust, Locusta migratoria L. spends its preimagimal stages are vitally important for its survivorship. A decrease of precipitation in the sources of rivers diminishes longevity and scale of flooding in flood planes that is favorable for survivorship of the locusts overwintering in oothecae. In years with weather situation is close to the yearly average, noticeable density of the locust is limited by certain areas – reservations of the pest. Outside of them, the eggs die being under water due to flooding. This is an operation of CESPPs 2.4."Periodic (bottle-neck) suppression." When suppression by CESPPs 2.4. becomes lower, the areas of breeding ground, and the rate of increase of density grow. Thus, weakening of operation of CESPPs 2.4. is the impact, which disturbs ESPPs of the level 3.1. "Proper control" as to the Asiatic locust, Locusta migratoria L.

S.P. Ivanov et al. (1938, p. 145) has described the such a situation in flood plains of the rivers Kuban, Terek, Syr Darya and others in following words: "Olsuf’yev (1930) has found out that fluctuations of locust density in these areas depends on water regime of the flood planes. In the years with abundant and prolonged flooding, overwintering locust dies, so that its density decreases. Contrary, in the years with low flooding, the main amount of overwintering locust survives, and its density grows."

Therefore, the dependence in arising of outbreaks of the Asiatic locust on droughts, which decrease fooding, is very close. Here are the data of L.Z. Zakharov (1946) for the Astrakhan Region (Russia) situated in the low part of the River Volga Basin (Table 40).

Table 40. Dependence of outbreaks of Locusta migratoria on droughts (cited in N.S. Shcherbinovsky (1952, p. 33)

Years of the outbreaks in the Astrakhan Region, Russia

Years of big droughts in the River Volga Basin

1 21890 - 1891 1890 - 18921911 - 1912 1911 - 19121920 - 1923 1920 - 1921

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1 21927 - 1928 1927 - 19311935 - 1938 1936 - 19381943 - 1947 1944 - 1947

The data for vast areas demonstrate greater duration and frequency of outbreaks of the locust that can be explaned by uneven values of precipitation on such areas (Table 41).

Table 41. The indices of outbreaks of Locusta migratoria for all the south-east of the Russian federation, including the North Caucasus for 127 years (Zacharov, 1950, cited in N.S. Shcherbinovsky (1952, p. 33)


Continuation of the outbreaks, years


Continuation of the outbreaks, years

1822 - 1828 7 1905 - 1907 31830 - 1836 7 1912 - 1914 31841 - 1848 8 1917 - 1919 31855 - 1862 8 1921 - 1924 41872 - 1878 9 1927 - 1931 51879 - 1889 10 1936 - 1939 41892 - 1898 7 1943 - 1949 7

There exist a view that suggests importance of factors, which are unrelated with weather situation - it might be the notorious solar activity. Such view was expressed by E.P. Tsyplenkov (1968, p. 405) about the Asiatic locust, Locusta migratoria migratoria: "Synchronism of outbreaks of the Asia locust in diverse infestation spots often separated each other by big distance with different climate and regime of moistening indicates that these factors do not exert a crucial effect on population dynamics of this species." However, the Tables 40 and 41 do not agree with this view.

After mild winter, aggressiveness of phytopathogens increases. This fact is explained by survivorship of spores of a small size having less vitality. The greater amount of germinated spores in beginning of season, the higher values of a phytopathogen's population.

Mild winter supposedly promotes successful overwintering of herbivores with low body weight that leads to an increase of density of a herbivore species.

In Siberia, outbreaks of the Siberian pine moth. Dendrolimus sibiricus Tschetv. in the ecosystems with the larch as a dominant arise due to operation of this FDESPPs. In fact, severe droughts in August repeated several years in succession serve as releasers of outbreaks of this defoliator. It is so, because only in a dry media (forest litter) its overwintering caterpillars keep resistant to winter frost, and their survivorship becomes great. In southern areas on the larch range, where drought in August is common, density of the moth is suppressed periodically only by CESPPs of the Intrinsic class. This is the W.C. Cook’s zone (a) for the species.

In ecosystems with dominance of evergreen coniferous tree species, whose needles are protected by Antibiosis, FDESPPs 8.3.5.”Increase of survivorship of PPs at favorable weather situation in the period of their dormancy” operates in cooperation with FDESPPs 8.3.1. “Disturbance of water balance in dominants of forest ecosystems due to deficiency of precipitation.” These FDESPPs cause outbreaks of Dendrolimus sibiricus by means appearing of favorable conditions at feeding and overwintering of the larvae.

8.3. Weather disturbances8.3.6. Weakening of dominants by potent weather phenomena (the mighty winds, sun scold

or snow breakage)Breakage of the prerequisites:

2.3.P.1. Temporal lasting of weather situations

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2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one8.3.6.1. CESPPs 2.1.1.1.1.3. and 2.1.1.2.1.2.1., and 2.3. failed

8.3.6.1.1. Outbreaks of stem borers

This FDESPPs is important in cooperation with other FDESPPs, particularly 8.4.1. "Weakening of the main stock of dominants due to shallow effective depth of the soil", 8.4.2. "Weakening of the main stock of dominants due to aging of them", and 8.2.1. "Improper cultural practices."

Therefore, it is relevantly to consider this FDESPPs below as a complex effect of the factors - 8. (C-2) and (C-3) after description of the cooperators.

8.4. Endogenic disturbances8.4.1. Weakening of the main stock of dominants due to shallow effective depth of the soil


8.4.1.1. CESPPs 2.1.1.2.2., 2.1.1.1.1.3. and 2.1.1.2.1.2. failed8.4.1.1.1. Affection by phytopathogens, increase of density of defoliators and stem borers

The effective depth of the soil is "the depth of the portion of the soil that is either occupied or capable of being occupied by the roots of the tree" (Spurr and Burnes, 1973, p. 266). In habitats with the shallow effective depth of the soil, growth of trees is limited by small depth (often one-to-two feet) above a layer unpenetrable for their roots. This layer (the subsoil) is of diverse structures, namely: the rock, the permafrost bed, the hardpan in the soils of the podzol type, the water (phreatic) table, the salt bed, the continually dry space between upper wet layer and the water table. The latter type is characteristic for climate of the Steppe and Desert biomes and sandy dunes in diverse biomes.

The greater the effective depth of the soil, the better conditions for existence of trees, and vice versa. A value of the effective depth of the soil determines in a great extent the level ESPPs of forest ecosystems. FDESPPs 8.2.1. and 8.4.2. are the common as cooperators.

Again, this FDESPPs will be considered in the next complexes.

8.4. Endogenic disturbances8.4.2. Weakening of the main stock of dominants due to aging of them


8.4.2.1. CESPPs 2.1.1.1.1.3., 2.1.1.2.1.2., and 2.1.1.2.2. failed8.4.2.1.1. Affection by phytopathogens, an increase of density of defoliators and stem

borers

The longevity of tree species predetermines weakening of trees at senescence. An onset of senescence depends on environmental conditions and human interference.

In biocenoses, the better conditions for existence of a given species, particularly the effective depth of the soil, the more longevity of trees growing in them.

In articenoses, the longevity of dominants depends in a great extent on professional competency of silviculturists. Here is an example of the high competency. The forester Pluteau established in 1890-ies plantations of Pinus silvestris on the area of several square kilometers in the Fastiv forestry unit (Kyiv Region, Ukreaine). This plantation reached high productivity and survived until 1990-ies, when the decline of the plantation began. This plantation was a monoculture on an old-field area with low species diversity – absence of lower stages and undergrowth with ground grass cover suppressed by livestock’s grazing. Thus, when a deal is doing by competent persons, a monoculture occurs to be long-lived even on the soils far from optimal for tree growth.

This case can teach ecologists that species diversity in an articenosis is not necessary for providing it with both general stability and ESPPs up to age of maturity. Proper cultural practices result in good physiological state of dominants, so that they are self-protected well against all the

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PPs by Nonpreference and Antibiosis. Obviously, at the planting, it was used healthy seedling, and they were widely spaced.

The examples of opposite situations are much more numerous. Often, pine plantations begin to die in the stage of thicket (15-40 years old), when competition among trees in an overstocked monoculture at the shallow effective depth of the soil becomes mortal.

In some cases, it is unclear, what are favorable conditions for a species. For example, the rock pine, Pinus banksiana of the American origin being planted in Ukraine takes root well even in severe conditions (in dry sandy habitats) exceeding the resident species, Pinus silvestris. However, Pinus banksiana grows well up to aproximately. thirty years, when it dies off.

In old forest stands, high percentage of stems is affected by stem rots and stem borers. Further, old age of trees is one of causes of outbreaks of Dendrolimus sibiricus and Choristoneura fumiferana.

As cooperators of FDESPPs 8.4.2., it serves usually FDESPPs 8.2.1. and 8.4.1. It is advisable to consider this cooperation in the next complexes of FDESPPs.

8. (C-1). The complex of FDESPPs8.4.1. Weakening of the main stock of dominants due to the shallow effective depth of the

soil8.4.2. Weakening of the main stock of dominants due to aging of them,

8.3.1. Disturbance of water balance in plants due to deficiency of precipitation8.2.5. Affection of forest ecosystems by forest fires


2.3.P.1. Temporal lasting of weather situations8.(C-1). CESPPs 2.1.1.2.1.2.1., 2.1.1.1.1.3., and 2.3 failed

8.(C-1). Outbreaks of needle-eating defoliators and stem borers

The complex of these FDESPPs induces the phenomenon of the aged crash a forest -1. This phenomenon takes place in the environmental conditions, where weakening of dominants proceeds in the standing position of trees.

In the habitats with the shallow effective depth of the soil, dominants of forest ecosystems are predestinated on mortality long before of normal longevity of a given tree species. This is result of operation of FDESPPs 8.4.1. "Weakening of the main stock of dominants due to the shallow effective depth of the soil" and 8.4.2. "Weakening of the main stock of dominants due to aging of them." When combination of these FDESPPs is supplemented by an onset of heavy drought, i.e. FDESPPs 8.3.1. "Disturbance of water balance in plants due to deficiency of precipitation", it is possible two effects depending on severity of FDESPPs:

i) Dominants loss CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and 2.1.1.2.1.2.1. "Antibiosis to herbivores, Physiological (biochemical), Permanent" in stems and branches. State of CESPPs 2.1.1.2.1.2.1. in needles is unknown.

ii) At the beginning, they loss CESPPs 2.1.1.2.1.2.1. in needles; only after consumption of needle by defoliators, dominants loss of CESPPs 2.1.1.1.1.3. and CESPPs 2.1.1.2.1.2.1. in stems and branches.

The first effect (i) is characteristic for North America. The second (ii) is common in Siberia. This difference is determined by character of climates of these areas. In North America, it might be the aged crash-1 takes place in high-mountain conditions, where severe climate does not allow needle-eating defoliators to reach High density.

In distinctly continental climate with hot summer of Siberia, defoliators of coniferous tree species thrive. Here, the above complex of FDESPPs is often accompanied by FDESPPs 8.2.5. "Affection by forest fires." In Russian Far East, it prevails the situation of the effect “i”, when dominants are colonized straight away by stem borers. This is a result of a common onset of the cool and wet weather situation, which suppresses the defoliators.

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The effect of drought in August in Siberia consists in not only decrese of oleoresin exudation in even-green coniferous tree species (Abies spp., Pinus spp., and Picea spp.), when the larvae stay in vulnerable young instars, but also in drying of forest litter. The latter allows to caterpillars of Dendrolimus sibiricus Tschetv. to tolerate winter frost. In a result, CESPPs 2.1.1.2.1.2.1., 2.1.1.1.1.3., and 2.3. faled. These FDESPPs lead to arising of outbreaks of Dendrolimus sibiricus and its associates - Cosmotriche (Selenephera) lunigera Esp., Calliteara (Dasychira) abietis Den. et Schiff, Semiothisa signaria Hbn. and Deileptenia ribeata CI. (Boarmia abietaria Shiff.). A.S. Isaev et al. (2001, p. 295) have reported that the Siberian pine moth and the associates have a number of common habits, in particular owervintering in the larval stage.

This is a separate guild of defoliators giving vast and prolonged outbreaks as soon as it takes place the combination of such FDESPPs as the shallow effective depth of the soil, old age of host-trees, and heavy droughts in the vulneranle stage of their caterpillars.

As to this guild of defoliators, a surprizing is the difference in ability to reach of values of the density within their members. Therefore, it should study in detail the habits of above species. Such a study would show, why one of members of the guild is a forest pest №1 in the greatest country in the World, whereas others are insignificant associates. This knowledge is important for cognition of the nature of the phenomenon SP.

Outbreaks of both needle-eating defoliators and stem borers, which followed the former, endanger to neighboring ecosystems having the same tree species as dominants due to emigration of the herbivores. When density of these insects reaches a value close to High, they tenaciously emigrate from ecosystems, which undergo the aged crash of forest, affecting ecosystems even of the level ESPPs 3.1. "Proper control." One of the most spectacular example of such emigration is provided by the cerambicyd beetle, Monochamus urrusovi Fisch. in ecosystems with dominance of the fir. In the ecosystems affected due to the emigration, a cooperation of CESPPs of the Extrinsic class and CESPPs 2.5. "Effects of crowding" suppresses the invasion. Nevertheless, the suppression is accompanied by mortality of a part of the dominants.


soil8.4.2. Weakening of the main stock of dominants due to aging of them

8.3.6. Weakening of dominants by potent weather phenomena (the mighty winds)Breakage of the prerequisites:

2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one2.3.P.1. Temporal lasting of weather situations

8.(C-2). 2.1.1.2.1.2.1. and 2.1.1.1.1.3. failed8.(C-2). Outbreaks of stem borers

An operation of the complex effect of FDESPPs 8. (C-2) takes place at the aged crash of forest – 2. It is characteristic for climatic conditions, where droughts are too weak to disturb Nonpreference and Antibiosis of dominants. Therefore, the aged crash of forest proceeds without participation of FDESPPs 8.3.1. "Disturbance of water balance in plants due to deficiency of precipitation."

On the other hand, the environmental conditions predetermine weakening of dominants due to windfall and windbreak. Because physiological state of the damaged trees is disturbed, they loss CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and CESPPs 2.1.1.2.1.2.1. "Antibiosis to herbivores, Physiological (biochemical), Permanent." Therefore, on the blowdown wood, it arises outbreaks of stem borers. After exhaust of blowdown wood, stem borers colonize the trees staying in the standing position within the disturbed area, which, as a rule, also are weakened. Further, the borers emigrate into undisturbed ecosystems, where they are able to attack healthy host-trees and kill some of them.

The exist exist the trend of more probability of the aged crash of forest-2 with increase of age of a forest dominants. If fact, participation of matured and overmatured stands in value of

34


blowdown areas is greatest. Nevertheless, yonger stands also suffer due to the aged crash of forest-2. This is so because diverse factors effect on resistance of trees to the windblow.

These factors are the following: the value of effective depth of the soil, position of a stand as to direction of the mighty winds, structure of a stand, that determined by silvicultural practices. Overstocked monocultures are less resistant to the windblow than natural forest, where diverse trees species serve as dominant, whereas stocking density is less. The beach is more resistant to windblow than the spruce and the fir.



8.3.1. Disturbance of water balance in plants due to deficiency of precipitation,8.3.2. Mass coincidence of larval hatching or attacks of herbivores in older stages with

favorable phases of host-plant development in dominants8.2.1. Cultural practices disturbing physiological state of dominants and obstacles for host-

plant superevasionBreakage of the prerequisites:

2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one2.1.2.P.1. In biocenoses, forming of a dominant stock at the natural conditions

2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or special cultural practices with the aim of effective operation of CESPPs A.2.1.2.

2.3.P.4. Weather situation, which provides operation of CESPPs 2.1.2.1. Superevasion8.(C-3). 2.1.1.2.1.2., A.2.1.2.1., and 2.1.2.1. failed

8.(C-3). Outbreaks of the spruce budworm, Choristoneura fumiferana

This complex of FDESPPs results in arising of vast outbreaks of a single species - the spruce budworm. Its "Outbreaks have usually occurred in forested areas containing extensive stands of mature balsam fir. They have tender to follow periods of relatively dry weather during the larval stage, periods when mature trees flowered heavily and often (Wellington et al., 1950; Greenbank, 1956)" (Mott, 1963, p. 189).

This passage suggests an operation of several FDESPPs leading to the outbreaks. They are the following: 8.4.2. Weakening of the main stock of dominants due to aging of them", 8.3.1. "Disturbance of water balance in plants due to deficiency of precipitation", 8.3.2. "Mass coincidence of larval hatching with favorable phases of host-plant development in dominants."

Further, it should quote S.A. Graham (1939, pp. 172-174): "Forest fires, logging operations, and natural succession in the later part of the nineteenth century resulted in a decided change of forest type from pine and spruce to balsam fir, so that on vast areas, almost inconceivable in extent, balsam fir became the predominant tree. It was in these areas, predominantly pure fir, that the great outbreaks had their origin….It is probable that the forest containing a comparatively small proportion of balsam fir would have safe from attack had it not been for the adjacent areas of pure or nearly pure balsam fir…it has been shown that young stands and stands in which the balsam is overtopped for the most part by other trees are not favorable to building up budworm outbreaks (Graham and Orr, 1939), and also that general outbreaks are always associated with extensive areas of susceptible forests. Furthermore, within the areas where budworm outbreaks are likely to occur, there is a sufficient number of tree species and diversity of forest types, so that the silviculturist can produce a great variety of conditions by appropriate manipulations."

This passage suggests an activity of FDESPPs 8.2.1."Cultural practices disturbing physiological state of dominants and obstacles for host-plant superevasion."

The boreal forests of evergreen coniferous species on the plain grow on the soil of the podzol type, which is characterized by the shallow effective depth of the soil. This fact suggests an operation of FDESPPs 8.4.1. "Weakening of the main stock of dominants due to the shallow effective depth of the soil."

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Obviously, a cooperation of the above FDESPPs leads to breakage of prerequisites of CESPPs 2.1.1.2.1.2. "Antibiosis to herbivores, Physiological (biochemical)", and CESPPs 2.1.2.1.1. "Superevasion from herbivores." The trees defoliated heavily by the spruce budworm loss CESPPs 2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature", are colonized by stem borers.

The cooperation of FDESPPs of the complex 8.(C-3) makes up the phenomenon of the aged crash of forest – 3.

(C-4). The complex of FDESPPs8.2.1. Cultural practices disturbing physiological state of dominants and obstacles for host-

plant superevasion8.3.6. Weakening of dominants by potent weather phenomena (the mighty winds, sun scold

or snow breakage, etc.)8.4.1. Weakening of the main stock of dominants due to the shallow effective depth of the



8.(C-4). CESPPs 2.1.1.1.1.3. and 2.1.1.2.1.2. failed8.(C-4). Outbreaks of stem borers

The cooperation of the above FDESPPs is illustrated by the following examples. 8.2.1. "Cultural practices disturbing physiological state of dominants and obstacles for host-

plant superevasion." The clear cutting of forest, when extensive areas of untouched forest are subdivided on numerous forest strips, results in great increase of total length of forest edges. On them, the trees, which have grown in the state of a closed stand, occur suddenly on open air. They have thin bark, and therefore suffer due to sun scold. Further, the center of weight of their stems is situated on the height much more that that, when trees grow in a sparse state. Therefore, the formers suffer due to windfall, windbreak and damage of roots, when trees are swung by the wind. The latter continue to be in the standing position, but their roots are damaged by the wind. The degree of weakening due to above FDESPPs depends on weather situation.

When forest trees are grown in the conditions of an overstocked monoculture, they produce stems much more thiner and higher comparing the case, when they grow in mixed stands with less stocking density. Therefore, at abundant snowfall, overstocked forest monocultures suffer due to weight of a thick layer of snow on their crowns.

It is common a coopertion of FDESPPs 8.4.1. and 8.4.2. as follows.8.4.1. "Weakening of the main stock of dominants due to the shallow effective depth of the

soil." When forest trees grow in such environmental conditions, they are damaged by the mighty winds much more than those, which grow in the conditions of the deep effective depth of the soil.

8.4.2. "Weakening of the main stock of dominants due to aging of them." With increase of age of forest trees, the danger on the part of the above weather situation becomes higher, particularly at the combination with above FDESPPs. The stands in the age of overmaturity and maturity are endangered badly.

The cooperation of these FDESPPs results in outbreaks of stem borers. In turn, this complex of FDESPPs is a part of the more complicated phenomenon, which is known of the forest decline. It will be considered in the next complex of FDESPPs

8. (C-5). The complex of FDESPPs8.2.1. Cultural practices disturbing physiological state of dominants and obstacles of

superevasion8.2.2. Changes in the soil conditions unfavorable for dominants

8.2.3. Damage of dominants by people or animals under human assistance8.2.4. Affection by air pollution

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8.2.5. Affection of forest ecosystems by ground forest fires8.2.6. Establishing of forest ecosystems with acorns of diverse phenological forms

8.2.7. Cultural practices inducing hostile environment for natural enemies and favorablemicroclimate for herbivores

8.3.1. Disturbance of water balance in dominants of forest ecosystems due to deficiency of precipitation

8.3.2. Mass coincidence of larval hatching or attacks of herbivores in older stages with8.3.3. Appearing of hostile environment for natural enemies at weather extremes

8.3.4. Increase of aggressiveness of phytopathogens and herbivores at favorable weather in the period of their activity

8.3.6. Weakening of dominants by potent weather phenomena (the mighty winds, sun scold or snow breakage)

8.4.1. Weakening of the main stock of dominants due to shallow effective depth of the soil8.4.2. Weakening of the main stock of dominants due to aging of them


2.1.2.P.1. In biocenoses, forming of a dominant stock at the natural conditions.2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or special

cultural practices with the aim of effective operation of CESPPs A.2.1.2.2.2.1.P.3. The diversity of species composition of vegetation within an ecosystem

2.2.1.P.4. Presence of microclimate appropriate for activity of parasites and pathogens2.2.1.P.5. Abundance of ecological niches within ecosystems

2.2.1.P.5.1. Age and structural diversity of vegetation - a presence of several stories of woody vegetation, and undergrowth (in forest ecosystems)

2.2.1.P.5.2. The microrelief diversity within an ecosystem and the area-wide heterogeneity – a presence habitats necessary for temporary migrations of natural enemies of invertebrate

herbivores, which are located within a reach by these species2.2.1.P.6. Undisturbed state of the soil surface

2.2.1.P.7. A size of area of an ecosystem sufficient for providing of natural enemies of invertebrate herbivores with vital requirements

2.2.1.P.8. Presence of annual stem fall (in woody ecosystems)2.2.1.P.9. Presence of effective vectors of pathogens

2.2.2.P.1. Proper activity of predators, which operates in cooperation with CESPPs of the category 2.4. "Periodic (bottle-neck) suppression"

2.3.P.1. Temporal lasting of weather situation2.3.P.3. Proper structure of ecosystems, which provides microclimate tolerable for natural

enemies of invertebrate herbivores2.3.P.4. Weather situation, which provides operation of CESPPs 2.1.2.1. Superevasion

8.(C-5). CESPPs 2.1.1.1.1.3. and 2.1.1.2.1.2., 2.1.1.2.2.2., 2.1.2.1.1., 2.2.1., and 2.3. failed8.(C-5). Outbreaks of defoliators and stem borers, epithytoties

This complex unites diverse potent impacts that result in the forest decline = Waldsterben over vast areas. Here in lies the most urgent problem of forest pathology in Russia and its descendants continuing from XIX century. In some stands, mortality of dominants in values exceeding of the natural stem fall takes place annually. From time to time, it comes the periods of a number of years, when areas of dying forest plots increase significantly. Distinct droughts and/or severe winters precede the decline. The decline is accompanied by outbreaks and epiphytoties of PPs.

In the Russian and Ukrainian literature, there exist pluralism of views as to causes of the decline. The pluralism is determined first of all by complicated structure of this phenomenon, where it operates natural factors (the shallow effective depth of the soil, and weather stresses), and diverse anthropic impacts. An additional factor of the pluralism is a discrepancy in views of

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the persons engaged in these affairs, because they have own interests at explanation of the decline’s causes.

The officials, which rule by silviculture, tend to consider the decline as a natural hazard caused by uncommon weather situation and pest organisms, whereas the role of improper silviculture practices is not took into account. Indeed, the officials do not want to admit own incompetence.

The persons engaged in forest protection against PPs both entomologists and phytopathologists usually stress the role of PPs as a primary cause of the forest decline and call upon to apply pesticides as much as possible. In such a way, these persons rise their worth.

There exist, however, the view that severe weather situations and pest organisms exert their destructive effects only in the sites, where forest was weakened by improper silvicultural practices and/or by poor habitat conditions. Therefore, beside control of PPs with pesticides, it is need to apply practices of profilaxy to establish ecosystems, which are able to keep ESPPs on the level 3.1. "Proper control" at any weather situation even in poor habitat conditions.

Consider common improper silvicultural practices, which lead to loss of physiological prerequisites of CESPPs in forest ecosystems – articenoses established by people and biocenoses exploiting by them. It is convenient to use for this aim the rich experience of professional illiteracy characteristic for the planning economy of Soviet Union. The review of such practices are offered in the articles by D.F. Rudnev et al. (1975) and G.I. Vasechko (1983). An exposition of them is given below.

The problems begin with the quality of seeds used for afforestation. In the Steppe and Forest-Steppe biomes, it is difficult to provide afforestation by acorns of a local origin, because areas of matured forest plots, where harvesting of acorns is possible, are very limited in these biomes. Therefore, it is used mainly acorns from northern areas, where harvesting of them is possible yet. The trees growing from such acorns have no a sufficient hardiness to droughts, which are more common in areas situated southward, than that in their native land. The same is true for diverse forest tree species, whose seeds are brought from northern areas (Gursky, 1973).

Further, the presence of infection in acorns is not checked, although many oaks are affected by phytopathogens in vascular tissues, and this infection penetrates into their acorns. The problem of vectoring an infection through acorns collected on diseased trees was posed by A.L. Shcherbin-Parfenenko (1963).

An establishing of oak forests is possible by sowing of acorns or planting of seedlings. The latter is practiced in most cases. This operation makes afforestation easily. High yield of acorns takes place with intervals of several years. Therefore, to provide the annual need in acorns, they should be kept in appropriate conditions (in refrigerators) over this period that is connected with certain problems.

Further, the sown acorns are endangered on the part of consumers of them – mice and the wild bours. Therefore, it is a need in pre-sown treatment of acorns with repellents. Contrary, the seedlings can be planted in age of one-four years, so that they are available annually.

However, the planting of the oak complicates further existence of these stands. The matter of fact, oak seedlings produce in the first year the main root growing up to a meter in the soil depth. When planting, it has to retain only a section of this root of length about a foot. The rest of the main root needs to be choped off. Importantly, in the planted oak trees, the main (pivot) root is not restored. They are able to produce only a shallow root system –up to several meters in depth from the soil surface, whereas oak trees grown in suti spread root system on the depth 12 meters. Comparing with the trees grown from acorns in suti, the former are limited in soil resources, and, therefore, compete intensively for nutrients and moisture, being more endangered by drought and severe frost. In addition, the wound inflicted at cutting of the main root of an oak seedling is an entrance for infection. The latter defect of the oak planting method was noted again by A.L. Shcherbin-Parfenenko (1963).

In pines, an establishing of healthy forests by planting of seedlings is quite possible. However, a root system of pine seedlings is often turned up at planting. The trees with such

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defects are condemned to die in the following ten-twenty years. The lethal consequencies of this defect were shown by M.M. Padiy (1959, 1974).

The conventional density of seedlings on forest plantations is excessively high. Usually, it is practiced to plant ten thousand of seedlings per hectare in monocultured plantations independently to tree species. Moreover, the guide-book for foresters recommends: "…even initial density of seedlings per hectare in oak plantations 25-35 thousand, as well as 15-20 thousand in pine and spruce plantations is admissible" (Kovalin et al., 1961, p. 323). Such directions were not new ones. The same practices had been using in this country over decades before the above publication.

The main substantiation of the need in the high density of seedlings was to reach benefit by means of obtaining a mass of brushwood at thinning. It was supposed that people would buy the brushwood as fuel or for other needs (Ibid., p. 323). However, the benefit has not turned out. At the first, in the period approximately between 1960 – 1990, people were provided rather sufficiently by gas and charcoal as a fuel. The brushwood was not need for people. At the second, and this is the main cause, it was no possibility to practice widely thinning in young forest plantations. The forestry units obtained the state tasks to supply large timber wood for industry and export. They cannot pay a good salary to wood-cutters for thinning, and people were able to find a better job. Actually, thinning began in the plantations about thirty years. Even such a timber was often abandoned in forest having no pushing off.

The authorities in silviculture have not known that trees compete with each other, and that at an excessive stocking density of even-aged monocultured plantations, it arises the destructive competition especially in severe environmental conditions. Due to such an ignorance, it was proposed the following: "The worse area-wide and habitat conditions, the higher stocking density should be in forest plantations" (Ibid., p. 324).

By means of high density of seedlings, it intended to decrease payments on expensive control of weeds. It was supposed that overstocked seedlings would able to suppress weeds. Therefore, it was recommended; "The most part of plots is littered by weeds, therefore, the more is participation of tiresome weeds, the greater should be density of forest seedling on this plot to suppress the weeds" (Ibid., p. 324).

A validity of this directive is dubious, because planted seedlings are able to compete with weeds only after closing of their crowns, i.e. no less that through five years after planting. During this term, weeds would kill seedlings. To control weeds, it needs chemical or mechanical measures. Nevertheless, silviculturists are directed on less expenditure by means of establishing of overstocked plantations.

Further, it is adopted widely to plant on cut over areas the same tree species as those grown before the cutting. Therefore, roots of seedlings weakened by transplantation occurred in the media with abundant phytopathogens thriving on remnants of a foregoing generation of forest. The idea of shift of crops conventional in agriculture still has not been understood in silviculture.

If to gather above silvicultural practices in a whole, it might propose the following scenario of state of afforestation, which have practiced in Soviet Union over many decades and after its collapse.

In oak plantations, seedlings occur among oak stamps in the soil saturated with oak roots, i. e. in the media, where the honey mushroom, Armillariela mellea thrives. Due to open wound inflicted by cutting of the main root, the infection penetrates freely in the seedlings. In the stage of thicket, i.e. beginning approximately from fifteen years, the roots exhaust admissible volume of the soil and compete strenuously with each other, rather that their root systems having no the main root are limited within an outer layer of the soil. These defects are expressed especially in southern areas, where acorns inadequate to local conditions are often used, and where droughts are common.

On the soils of the podzol type, where the effective depth is close to two feet, the competion of the roots in such plantations is much greater, especially at droughts.

Cutting of oak stems produces sprouts from the stumps. In past times, these sprouts were often used as a means of restoration of a new generation, whereas on the cut areas, neither

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sowing of acorns, nor planting of oak seedlings were conducted, so that many oak stands are of the sprout (coppice) regeneration.

Because the coppice regeneration often (at summer cutting) leads to mortality of the main (pivot) root, which cannot be restored, such trees have root system limited by an upper layer of the soil. Thus, the trees occur in the conditions of the shallow effective depth of the soil. They suffer from deficiency of moisture and nutrients, they are exposed on negative impacts of drought and severe winters.

Therefore, such stands have low stocking density, and crowns of them are thinned. In the grass cover, it appears xerophytic cereals. Such ecosystems are convenient for grazing. The trees are affected by stem rots even in young age. With aging, their environment undergoes ever-increasing destruction. It is accepted to cut such stands in the age of sixty years. In the older age, in them, it takes place a "negative increment", i.e. an annual increase of volume of rotten wood exceeds the volume of healthy wood. When the sprout origin of the oak is practiced over a number of generations, state of a stand worsens with every generation. At onset of the weather stress, such stands undergo the aged crash of forest.

That is an impact of FDESPPs 8.4.1. “Weakening of the main stock of dominants due to shallow effective depth of the soil.”

The coppice regeneration always is worse for vitality of trees than the seed one. This is so, because dying tissues of stumps are affected by phytopathogens, which further spread on living parts of trees growing from the sprouts.

The defects of the coppice method of forest regeneration are greatest at cutting in summer. The sprouts appearing at summer cutting vegetate over short time, and, therefore, they are unable to provide their roots with a sufficient amount of assimilates in the same season. Due to deficiency of nutrients, the main (pivot) root dies off.

Contrary, at the main cutting of the oak in winter, the stump sprouts are able provide their roots with assimilates vegetating over all the season. Therefore, the main root can survive. The state of such a new generation is better than that at the summer cutting.

At the main (clear) cutting, it appears of forest edges composed by matured trees, which are exposed suddenly on sunlight. Because the tree crowns cover only a less part of stems close to tree-tops, and their bark is thin, the stems are unprotected from sun rays, and suffer due to sun scold, especially if the edges are exposed to the south. Further, it is important the factor of a lack of protection by opposed slopes from insolation and the wind. The edges are exposed to the wind being unadapted to their effect if they have grown at high stocking density. In them, the center of gravity is situated highly on stems. When the effective depth of the soil is shallow, trees on the edges in addition to sun scold suffer due to windfall and windbreak. The number of died trees is increased with year after year. The weakening of trees and mortality of them in result of colonization by stem borers spread on the distance fifty meters from the border with a clear-cut area. This is an operation of the complex of FDESPPs (C-4).

Contrary, natural forest edges are resistant to the above stressors even in the age of maturity. On the border with an open (meadow) area, the trees have thick bark, the long crowns, which protect from sun scold the stems up to their bases, and the low situated center of weight.

The destructive effect of clear-cutting on of forest edges bordering with clear-cut areas is shown in the Table 42. The values of thick of bark of spruce trees in the conditions concerned the issue under discussion are shown in the Table 43. These data are taken from the thesis by G.I. Vasechko (1967a, p. 124a and 128). Values of died trees and thickness of bark on forest edges were obtained three-fire years after cutting.

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Table 42. The effect of clear-cutting on the state of dominants of forest edges bordering with a clear-cut area. Exposition of the edges is southern or northern; the open edges are sutiated in upper parts of a valley being affected heavily by winds and sun scold, the closed edged are situated in lower parts of a slope being less affected

Position of a forest edge(southern or northern

exposition, open or closed)

The number of died trees of the spruce and the fir dependingon the distance in meters from a border with treeless area

three-five years after the cutting, percents0- 10 11 - 20 21 - 30 31 – 40 41 – 50 51 - 60 61 –70 71 - 80

1 2 3 4 5 6 7 8 9Southern, open 75-80 45-50 25-30 10-15 4-5 2-3 2-3 2-3Northern, open 40-50 25-40 10-20 5-10 2-3 2-3 2-3 2-3Southern, closed 30-40 5-10 2-3 2-3 2-3 2-3 2-3 2-3Northern, closed 5-10 2-3 2-3 2-3 2-3 2-3 2-3 2-3Natural forest edge bordering with a meadow, southern, open 2-3 2-3 2-3 2-3 2-3 2-3 2-3 2-3

Table 43. Values of bark (outer bark plus phloem) thickness in spruce stems on breast hight of living trees depending on the conditions of exposition in age of maturity

Position of trees

Sidesof stems

concerning insolation

The thickness of bark at diverse distance in metersfrom a treeless area, mm

0-10 11-20 21-30 31-40

1 2 3 4 5 6Forest edge at a clear-cut area, southern, open

On light 7.1+/-0.96 7.0+/-0.82 6.7+/-0.72 —In shade 6.7+/-1.13 7.2+/-0.82 6.3+/-0.84 —

Forest edge at a clear-cut area, northern, open

On light 6.9+/-0.75 5.8+/-0.66 — —In shade 6.9+/-0.78 6.0+/-0.76 — —

Natural forest edge, southern, open

On light 9.5+/-0.84 7.5+/-0.96 6.9+/-0.46 6.8+/-0.72In shade 8.0+/-0.70 6.8+/-0.66 6.7+/-0.42 6.5+/-0.66

Scattered trees growing on a meadow

Southern 12.6+/-1.32Northern 12.0+/-1.32

In the Table 43, the valid difference among the values of bark thickness equals 1.1.The weakening of trees on the forest edges is especially destructive due to adopted rules of

the main cutting. According to the rules, it should return with the main cutting of a strip of trees on the edges through four-five years. The substantiation of the term of a delay with the next main cutting of the exposed forest edges consists in a hope to achieve of natural regeneration of trees on cutover areas by dissemination from the edges. In reality, the aim of natural regeneration of the forest at the above method of the main cutting is not achieved. Therefore, silviculturists are forced to establish plantations on cutover areas.

The difference in state of the forest with prevalence of the spruce between an edge with a cutover area and a natural forest edge is shown in Figures 8 and 9 in this report.

The effects of the above method of the main cutting of the state of exposed forest edges were considered by D.F. Rudnyev (1928), D.F. Rudnev (1957) in oak stands and D.F. Rudnyev et al. (1962), Vasechko (1971) in spruce stands. The effects were destructive in the stands of both types. In the oak stands, it arose outbreaks of the large oak longhorned beetle, Cerambyx cerdo L., whereas in the spruce stands, it was recorded outbreaks of diverse species of stem borers. Among them, Ips typographus was most abundant. The mortality of trees with affection by stem borers spread on tens of meters from the edged in depth of a forest. Because the total length of the edged was large, areas of the outbreaks were too vast to practice sanitary cuttings in the time. Therefore, the quality of large amount of wood was lost.

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The above review of silvicultural practices was done in the context of explanation of causes of forest decline, which spread on vast areas in East Europe and concerned the main species used in silviculture – the pine, Pinus silvestris, the oak, Quercus robur, and the spruce, Picea excelsa (abies).

Summing up, the improper silvicultural practices are the initial causes of the forest decline, whereas affection by pest insects and phytopathogens is a consequence of a decrease of physiological state of host-trees or structure of ecosystems due to improper silvicultural practices.

The diagnosis as to causes of the forest decline allows to give recommendations of the treatment. The main propositions offered by M.M. Padiy (1959, 1974). D.F. Rudnev et al. (1975) and G.I. Vasechko (1983) are as follows.

The initial operation, which predetermines further state of forest, consists in getting over the shallow effective depth of the soil. On the plain terrain, the depth takes place in habitats with the soil of the podzol type, where a hardpan layer is situated on the depth approximately two feet; and on old-field lands, where the subsoil is condensed by digging up. This hindrance is withdrawn by mechanical means. Boring mechanisms punch orifices in the impenetrable for root layer. The number of such orifices should correspond to the number of planting seedlings or sowing seeds (acorns), which are distributed above them. The main roots of growing trees penetrate into deep layers of the soil that opens an access to greater resources of moisture and nutrients. Then, negative effects of drought and freezing of the soil at severe winters occur less. At abundant precipitation, water does not retained in an upper layer of the soil, so that destructive for tree roots excessive moistening is removed.

Oak ecosystems should be established by sowing of acorns. It needs to apply keeping of acorns gathered in years of abundant yield in refrigerators that conserves their vitality over several years. Acorns of the same phenological form of the oak should be used within a forest plot. It needs, application of repellents for protection of acorns against vertebrate herbivores.

The next operation is providing a cultivated forest with the optimal stocking density of the main species and useful composition of accompanying tree and brush species. The relevant recommendations were given by the classical forestry. In the age of maturity, the stocking density of dominants (the oak, the pine or the spruce) should be 400-500 trees of the main species per hectare. To reach this aim, it is sufficient to establish 1200-2500 trees per hectare at afforestation (Orlov, 1903, p.771). The satellite tree and brushy species should accompany the main (dominant) trees, so that the entire number of entries reaches 10,000 in the age of closing of cover (approx. five years after establishing of a stand). The satellite and brushy species, which should occupy lower stories in a stand, are able to play the useful role maintaining physiological state of the dominants, their productivity and good quality of production. They decrease competition among the dominants, promote the turnover of substances in an ecosystem, better a form of stems in dominants, and provide the soil with nitrogen by fixation of it from air. As to brushy species, the Siberian locust, Caragana arborescence Lam. is particularly useful. This species fixates nitrogen, its leaf fall is mineralized very quickly and induces the same process in forest litter; its spiny shoots protect young trees from damage on the part of hoofed animals. The undergrowth maintains natural enemies of invertebrate herbivores.

On mountain slopes with the low effective depth of the soil on rocky subsoil, establishing of overstocked monocultures leads to decline of forest in young age. If these soils are wet and rich, the conditions of overstocking provoke abnormal growth in height, whereas stem diameter occurs to be very thin. In age of thicket, such stands suffer due to snow breakage, and lately - due to windfall and windbreak. Therefore, participation of deciduous tree species and the optimal stocking density of dominants are of the crucial importance for good state of forest on mountain slopes.

Establishing of forest stands in the environmental conditions, where the shallow effective depth of the soil is determined by insufficient volume of precipitation, is much more complicated problem. This is pertinent for the Steppe biome. Water brought by precipitation penetrates into the soil on the depth up to a meter and half in the northern steppe and on the depth less than a

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meter in the southern steppe. Trees growing in such conditions are forced to spread their roots in an upper layer of the soil in the range of penetration of moisture. Here, competition for moisture is very severe. It increases with higher stocking density and aging of trees. At onset of drought, the roots are dryed out, and trees die.

On the other hand, there exist an urgent need in afforestation of arid areas. Here, there are vast sandy terrains, where forest is the only means, which precludes moving the sand dunes by the wind. Shelterbelts protecting fields of agricultural crops and railways, as well as other protective plantings have been established on large areas even in dry steppes.

Russian silviculturists, who have conducted afforestation in the steppe conditions from the middle of XIX century, accumulated the great experience, which can bring significant contribution in solving the global problem how to withstand the desertification. These activities should be considered as highest achievements of forestry in providing of articenoses with stability to all the stressors, i.e. the general stability, in the severe environmental conditions.

This experience has been presented in numberless publications. Here, it is possible to quote some classical reports, as follows: V. Bulatovich (1892), G.F. Morozov (1896), G.N. Vyssotsky (1905, 1912), Z.S. Golovyanko (1949, 1951), N.E. Kabanov et al. (1951), and A.G. Gael (1952).

In short words, the general stability of forest articenoses in the Steppe biome is provided by the following measures.

The sandy habitats

i) Deep loosing of the soil. The deeper is loosing, the deeper roots penetrate into the soil, the better survivorship of planted pine seedlings in the initial several years, the better growth of older trees.

ii) In some conditions, the entire loosing of the soil is impossible (on the ragged terrain) or it endangers wind erosion of the soil (on the sandy soils in southern steppe); in such conditions, instead of entire loosing it should apply mechanical boring of the soil to break hard layer, which lays obstacles for penetrating on tree’s roots in depth.

iii) On a plain terrain, forest plantings should have an island character being located in depressions of the terrain, and occupy a less part of an area. These circumstances provide plantings with better watering due to accumulation in them a snow blown from open areas, and better probability for their roots to reach the water (phreatic) table.

iv) With an exception of the black locust, Robinia pseudoacacia, on the ragged terrain, forest planting should occupy middle parts of hills and dunes, avoiding very dry tops and excessively moistened feet of them.

v) In northern and southeastern parts of the European steppes, as the main species, it should use the Scots pine, Pinus silvestris, on the rest part – the Crimean pine, Pinus pallasiana.

vi) The stocking density should be much less (one third) than that on the wet rich soils.vii) As accompanied species, it should use most drought-tolerant species, for example the

birch, Betula klokovi (the resident species on southern sands), the smoke tree, Cotinus coggygria (the sandy ecotype), the golden currant, Ribes aurum.

viii) The trees growing on the sandy soils are long-lived, if their roots penetrate to the level of the water table. The problem consists in a search for ways, how to stimulate roots to come through continually dry layer of the soil. It occurred to be, roots of deciduous tree species (the poplar, Populus niger, the aspen, Populus tremula, the birch, Betula spp.) penetrate deeper than roots of pines. The latter use old roots of the former spreading in wet layers of the soil. Therefore, it was proposed to begin afforestation with planting of the poplar or the aspen, and after cutting of them to plant the pine. This, however, is possible in northern steppe areas. It was explained the better state of mixed pine and birch plantings: pine roots wind round of birch roots and penetrate deeper than that in pure stands.

ix) The Crimean pine, Pinus pallasiana and the black locust, Robinia pseudoacacia have absolute superiority as dominants on the southern sandy soils. The traits of these species determine their uncommon drought-tolerance. Pinus pallasina is a champion as to retention of

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moisture in needles. In studies by G.N. Vyssotsky (1912, p. 91), needles of this species loss only 0.75% of moisture per hour, whereas needles of P. silvestris – 2.1%, leaves of Quercus robur – 9.6%. Robinia pseudoacacia spreads its roots on large areas in an upper layer of the soil and produces vertical roots penetrating into the soil depth. It was recorded penetration of such roots on the depth of seven meters reaching a layer moistened by phreatic waters (Gael, 1952, p. 81). In the Low-Dnieper sandy area (Ukraine), it occurs beautiful trees of Pinus pallasina and Robinia pseudoacacia in the age about 100 years with the higher class of growth on the soil, where native vegetation is presented by scattered grasses.

x) The black locust is the only tree species, which can be recommended for afforestation of hilltops and dune ridges on southern sands. The trees should be spaced widely. The distance among them on the dry soils should be no less than ten meters. The importance of wide spacing of black locust trees was proved as early as by V. Bulatovich (1892), who showed that trees of this species are long-lived on condition that their roots have possibility to spread on large distance. This species has valuable traits – fixation of air nitrogen, and its leaf fall is mineralized quickly. Therefore, Robinia pseudoacacia is a unique species as to its capacity to enrich the soil. During a few decades, under crowns of these trees, it develops a layer of the black soil with one-two feet in depth, and positive effect of enrichment of the soil spreads on the distance much more than a diameter of a tree crown. The trees growing on hilltops and dune ridges exert the beneficial and distant effect on water regime of the soil.

The chernozem habitats

For establishing of forest articenoses in steppes on the chernozem soils, it needs to solve two problems: to exterminate resident grassy vegetation, which is well-adapted to the local environment, and to increase the effective depth of the soil, which in steppes is insufficient for long-lived existence of a forest. In addition, the some kinds of chernozem soils are exclusivelly rich in salts that unfit for many tree species. Therefore, the following cultural practices should be used:

i) Digging up of the cultivated area; the better is cultivation of agricultural crops over several years that allows to some degree to clean the soil from seeds of grasses –weeds of seedlings of forest species.

ii) Sowing or planting of forest species on the deeply loosed soil. The oak should be sown. This is necessary for developing of the main root, which is able to penetrate in deep soil layers.

iii) To use most drought-tolerant woody and brushy species. As dominants, it is used the oak, Quercus spp. the black locust, Robinia pseudoacacia L., the honey locust, Gledischia triacantus L. It is prospective breeding of cultivars in the direction of better drought-tolerance. In fact, it was bred the hybrid of several species of the oak, which obtained the name "the oak of Vyssotsky" in honor of this prominent forester –a master of steppe afforestation.

iv) The oak should be cultivated in mixed stands. It is necessary a wide spacing of this species, which needs in large amount of soil space both in vertical and horizontal directions. The optimal stem density of this species in 1250 per hectare in the age of closing of cover (five- ten years). As accompanied species, it is used shade-tolerant and drought-tolerant species, for example Acer campestre L. and A. tataricum L. They make up the second stage, which provides a shade to counteract invasion of steppe grasses under canopy of forest stands and promotes better growth of the oak. Brush species are also necessary. They are additional lines in suppression of steppe grasses. Such species are numerous – Caragana arborescence, Cotinus coggygria, Sambucus nigra, Rhamnus cathartica, Rh. frangula, Evonimus europaeus, Crataegus spp. and others.

v) For steppe afforestation in distinct continental climate, the Siberian elm, Ulmus pumila is the best species.

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vi) Forest stands should have linear form (shelterbelts) or islands character with an area, which does not exceed of several hectares that allow them to accumulate snow.

vii) It needs chemical or mechanical control grassy vegetation over a number years after establishing of forest stands until the trees and brushes make up a canopy and get possible to compete with grasses.

viii) Robinia pseudoacacia, Gledischia triacantus and Caragana arborescence are most suitable for plantings having concern of protection against soil erosion – on slopes of ravines.

The further aspects of 8. (C-5). The complex of FDESPPs

To establish forest stands protected from complex of FDESPPs 8.(C-5), it needs to take into account an important capacity of forest or even single trees. This capacity was studied by Yu. Vyssots’ky (1929), who presented knowledge of this capacity as a special province of forestry –the science of forest pertinence. This is a sum of knowledge, how forest transforms environmental conditions. It occurred to be a forest is able to some degree to provide itself by moisture. This statement is based on the following facts. When a rain is accompanied by a wind, the direction of falling water deviates from a vertical to a horizontal one. When it encounters with trees, the water falls vertically under tree crowns. In a result, the value of precipitation within area of their rhizosphere increases greatly comparing with that calculated by the meteorological equipment.

In winter, forest trees accumulate on their branches the hoary-frost, which adds approximately 5% of moisture to yearly amount of precipitation. Weight of hoary-frost mass reaches two kg per meter of branch (Ibid., p. 20). At positive air temperatures, the dew sits on forest trees and then drops on the ground. The trees "comb over" moisture from air inducing the dew. An addition by the dew to the yearly average precipitation is surprising. It reaches 84% in heights exposed to wet winds (Ibid., p. 21).

Some traits of trees might be considered as those promoting the combing effect. They are retention of over fall and winter of foliage on twigs of the "winter" form of the English oak, Quercus robur L., var. tardiflora Chern., and pods on Robinia pseudoacacia.

Increased moisture of the soil surface under tree crowns leads to appearing of a brushy undergrowth. In turn, the undergrowth promotes accumulation of snow blown from open areas. Here, snow melts and water penetrates into the soil, so that the effective depth of the soil becomes greater. On open area, the significant part of snow precipitation evaporates and glides outside of an area, because water cannot pour in the frozen soil. The soil in a forest is much more penetrable for water than that in a field. Therefore, at showers, forest precludes flowing of water on surface of the soil outside of an area. The flowing is directed into depth of the soil increasing its effective depth.

The above phenomena obtained the name a "horizontal precipitation." The less area occupyed by trees, the more value of horizontal precipitation. Therefore, forest in arid areas has the very low stocking density (in the Savanna biome) or an island pattern (in the forest-steppe biome).

The effect of the "horizontal precipitation" tends to spread outside of forest ecosystems, so that on forest edges, it appears a brushy thicket. It forces out steppe grassy vegetation, but does not preclude regeneration of trees. In s result, forest ecosystems successfully keeps their position in competition with steppe vegetation if it is allowed by climate, and people do not lay obstacles.

Until now, this knowledge has been not realized in practice, as the following fact demonstrates. The scale of afforestation in the southern Ukraine (the Mykolayev and Kherson Regions) is great. Over 18 years before 1969, it was planted here fifty thousand hectares of pine stands (Tarasenko, 1969). The method of afforestation was the same as in the Forest biome – extensive areas of overstocked monocultures with the stocking density up to twenty thousand (!) seedlings per hectare. To decrease the density by thinning occurred to be impracticable. Such a situation is endangered by the forest decline and forest fires.

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Indeed, in August 2007, more than ten thousand hectares of pine plantations in south of Ukraine were burnt out. This was a striking example of sad consequences of silvicultural ignorance, so that immense efforts on the afforestation failed, and it arose necessity in heavy expenditures for utilization of burned wood and subsequent melioration of the affected areas.

It was practiced an alternative method of afforestation of these sandy areas proposed by P.S. Pogrebnyak (1954, pp. 160-161). Three pine seedlings were planted on 1 square meter plots situated on the distance of approximately five meters each other (a size of the plots, the distance between of the them, and the number of the seedlings is a subject of discussion). Because roots of such trees had the vast area for spreading, the trees were healthy. Sparse placing of the plots provided the plantations with impossibility of a forest fire. Nevertheless, officials from Ministry of Silviculture decided that these plantations were insufficiently productive and will not give valuable timber. Therefore, they were cut-out and shifted with conventional large tracts of overstocked plantations.

The complex FDESPPs 8. (C-5) results in outbreaks of all the guilds of arthropod herbivores. Character of these outbreaks is determined by composition of categories FDESPPs, severity of disturbance of ESPPs, and W.C. Cook’s zone, in which a given ecosystem is situated. The same is true for phytopathogens. It should stress the priority of FDESPPs 8.2.1. "Cultural practices disturbing physiological state of dominants and obstacles of superevasion." This category is the main one, which determine the level of ESPPs in articenoses.

As one may see, as early as in the first third of XX century, Russian forestry developed the system of silvicultural practices, which gave a possibility to establish long-lived forest stands in diverse habitats, in particular in the severe conditions of the Steppe biome. Unfortunately, realization of these scientific achievements in practice has been poor.

As to effects silvicultural practices on ESPPs in the countries outside of the Former Soviet Union, knowledge of the author is very limited. Nevertheless, some facts show that things are not well with the practices.

Here is the illustration in the book "The Face of Rural America, The 1976 Yearbook of Agriculture is a Visual Record of America’s Agriculture in the Bicentennial Year" (p. 27). On this illustration, one may see an overstocked monocultured pine plantation about 30 year old. The distances among trees are approximately eight feet between rows of the trees, and two feet in the rows. The signs of thinnings are unnoticeable, so that the level of silvicultural practices is no better than that in Soviet Union. Just in such conditions, it arises infestation spots of the southern pine beetle, Dendroctonus frontalis and its satellites, which kill thousands pine trees per infestation spot during a year.

The second case is concerned the state of silviculture in Central Europe. The author saw in 1988 a declined spruce stand, which stretched on the distance roughly a mile along the road leading from Weimar (East Germany) to the town Bozhy Dar (Czechoslovakia). This site was situated not far from the border of these countries, in the region of the Ore Mountains.

The decline of this plot might be explaned by operation of FDESPPs of the complex 8. (C-1) - the aged crash of forest - 1. The forest grew on the slope faced to the south. Its age was close to the stage of maturity, and its stocking density was high. The soil layer in this habitat was obviously shallow and exhausted. This is so, because over several centuries in this region, it was practiced intensive exploiting of forest. The short history of forest management in the Ore Mountains was offered by W. Baltensweiler (1985, p. 81). The cuttings were repeated many times, and in every case, nutrients were withdrown from the soil. In addition, it took place the effects of high stocking density, old age, and severe drought in 1986.

Surprisingly, in spite of obvious causes of a decline of this forest, it was adopted an explanation this case as a result of air pollution. It was not paid attention on beautiful state all the vegetation in this region with an exception of the strictly localized plot. It is strange that died trees were not salvaged immidiately at appearing of signs of the decline – change of tree crown color, and presence of bark beetle boring dust. Such a delay with salvage leads to loss of value of affected timber. This case demonstrates the most serious cause of the forest decline – the decline

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of professional competency, both in scientific (forestry) and practical (silviculture) domains. It is notably that the case took place in Central Europe, i.e. in a hotbed of forestry science.

The idea of disturbed physiological state of trees due to improper silvicultural practices as a crucial factor of the forest decline has not won wide recognition yet. It is common an explanation of this phenomenon by imperfect heredity of trees. As an example of such a suggestion, it can serve an explanation of low resistance to PPs of overstocked forest monocultures offered by W. E. Wallner (1987, p. 322) as a result of "…narrow genetic variability…"

8.4. Endogenic disturbance8.4.3. Saltations in populations of phytopathogens (increase of virulence) and herbivores

(increase of vitality)Breakage of the prerequisites:


2.2.3.P.4. Adaptation of superparasites to suppress their hosts2.2.1.P.2. Adaptation of parasites and pathogens to overcome resistance of their hosts

8.4.3.1. CESPPs 2.1.1.2., A.2.1.1.2., 2.2.3., and 2.2.1. failed8.4.3.1.1. Epiphytoties in certain populations of phytopathogens and herbivores with

weakly expressed periodicity

This category of FDESPPs is proposed to explain the cases of a sudden increase of virulence of phytopathogens r-strategists on wild plants with heredity unchanged by humans and having proper physiological state. In these cases, CESPPs 2.1.1.2.2. "Antibiosis to phytopathogens" does not operate. The affection leads to deformation of trees or complete mortality of them.

This phenomenon is called a saltation (Butler and Jones, 1949, p. 95). These scholars reported that even healthy host-trees can be affected by a phytopathogen.

As assuming cases of saltation, it can be considered the sudden mortality of perceptible percentage of shade trees in Kyiv (Ukraine) over a number of years. They are well-developed trees of the mountain ash, Sorbus aucuparia L., and the apricot, Prunus armeniaca L. Futher, numerous twigs of the cherry, Cerasus vulgaris L. are damaged often by an unknown disease. The birch, Betula verrucosa Ehrh. suffers due to dieback. These trees had signs of affection by phytopathogens. Exterior of the trees and conditions of their growth did not give the grounds to suppose that they were weakened before the affection.

Thus, a saltation in phytopathogens can operate at absence cooperator, i.e. it is possible on the level ESPPs 3.1. "Proper control", which decreases to the level ESPPs 3.3. "Late control." Saltations are absolutely unforeseen.

Operation of CESPPs 2.1.2.4.1. "Hereditary heterogeneity of a stock of host-plants" is seemed to be the only factor, which is able to save these species from extinction.

In nurseries of The V.M. Remeslo Myronivka Institute of Wheat (Ukraine) in 1977, in took place a sharp increase of density of the cereal leaf beetle, Oulema melanopus L. on all the cntries of the winter wheat including the varieties bred as having Antibiosis to this species (their leaves had dense trichomes). The most part of a flag leaf surface was consumed by larvae of the beetle. This was surprising, because before 1977 and after that, the damage was much less and steady year after year (10-20% of a flag leaf surface). The increase of damage by the beetle, might be suggested as a result of a saltation spreading on ability of the larvae to consume host-plant tissues with protective structures – dense trichomes on resistant varieties, and hardened tissues on all the entries. Nevertheless, it was unexplained, why increased damage took place during the only year, whereas the insignificant damage was in all the rest years.

8. (C-6) The complex of FDESPPs8.4.3. Saltations in populations of phytopathogens (increase of virulence) and herbivores

(increase of vitality)8.3.4. Increase of aggressiveness of phytopathogens and herbivores at favorable weather in

the period of their activity

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varieties strains, hybrids, lines) to resist against a given taxon of PPs2.2.3.P.4. Adaptation of superparasites to suppress their hosts

2.3.P.2. Limitation of aggressiveness of PPs.8.(C-6). CESPPs 2.1.1.2.2., 2.1.1.2.1.2., 2.2.3., and 2.2.1. failed

8.(C-6). Epiphytoties in certain populations with weakly expressed periodicity

Saltations seems to be characteristic for the rust fungi – distinct r-strategists having numerous generations per season. One of them is the stem rust cancer, Melampsora pinitorqua A. Braun, which induces bending of the May shoots in young trees of the Scots pine in Europe. S.I. Vanin (1948, p. 121) reported about mass affection of pine plantation by this species. In some seasons, signs of the affection appear on 50-80% young trees within a plot. In Europe, it is recorded mass affection of pine trees by the stem rust cancers, Cronartium flaccidum Wint., and Peridermium pini Kleb. The number of affected trees in some plots reached 30-50% (Vanin, 1948, p. 138).

Yu.A. Grafov (1973) studied affection by Melampsora pinitorqua of young pine trees sown or planted on cut over areas in the Vologda Region (Russia). He recorded that the trees were affected every year, but the initial affection fluctuated in diverse years from 30% to 100%. "In some years (1962-1963) was epiphytoty, and in young pines (sown in 1957) up to 40% of terminals completely died off" (Ibid., p. 58).

The epiphytoty was recorded in the seasons with very different weather situations – cool wet weather in 1962 and drought - in 1963. There are no the grounds, however, to deny the role weather factors at the affection. Appropriate weather situation can be necessary for successful inoculation, whereas subsequent proceeding of an epiphytoty is possible at any weather. An operation of FDESPPs 8.3.4. "Increase of aggressiveness of phytopathogens and herbivores at favorable weather in the period of their activity" is possible in this case.

The phytopathogen affected the best trees (Ibid., p. 59). It spoils a form of pine stems, but does not kill trees. Therefore, Antibiosis against this phytopathogen has not expressed well.

What is the cause of the saltation: a hereditary conditioned rise of virulence of a phytopathogen or growth of its aggressiveness under effect of environmental conditions? To answer is not simply. Here is the reflection of J.E. Van der Plank (1975, p. 117-120), who cites P.T. Bingham et al. (1971). In North America, the systemic disease of the oak, Ceratocystis fagacearum, and the fusiform rust of pine trees, Cronartium fusiforme and C. comandreae have the same pattern of population dynamics. Their epiphytoties arise and finish with the periods of several decades. It is unknown what is the cause of the fluctuations – virulence of the phytopathogens or environmental changes. Further, the resident American species Cronartium spp. and Peridermium spp. fluctuate. "The extent of the epidemics varies from few miles and more. These outbreaks often involve a burst of infection during a single season or even a single moist period, and often followed by years of tapering off as infection dies out. Longer epidemics also occur."

This passage contains a valuable information, which allows answering on above question. Indeed, the recurrence of epiphytoties with the periodicity close to several decades and the important role of weather situation give the grounds to suppose that it operates both a rise of virulence and growth of aggressiveness of the phytopathogens, i.e. FDESPPs 8.4.3."Increase of aggressiveness of phytopathogens and herbivores at favorable weather in the period of their activity." The aggressiveness is determined by weather.

What factors determine the fluctuations of virulence? It might be saltation (spontaneous increase of virulence of a phytopathogen’s population or increase of resistance of this population to natural enemies) resulting in epiphytoties. To the point, an increase of virulence can be a consequence of increased resistance of it to its natural enemies. Increase of virulence of a tolerable phytopathogen can be induced by affection of it with some viruses. A decline of a epiphytoty can be caused by adaptation of natural enemies to suppress virulent populations.

48


What are protective means of trees against these serious phytopathogens? The answer might be prompted by S.I. Vanin (1948, p.138), who reported that trees are able to live with signs of the stem rust cancer during 90 years. Here, it operates CESPPs 2.1.1.3.2.5. "Tolerance to phytopathogens, Permissible susceptibility." As one may see, this CESPPs is rather durable.

Here is a case story, which might be considered as an example of saltation in a herbivore species. In the Kyiv Region, Ukraine, in 1985-1986, it took place an outbreak of the cereal aphid, Sitobion avenae Rond. on the winter wheat, so that aphid’s density on fields reached several tens per wheat’s spike. Over the period 1987-2002 (in 2002, the observations were finished), density of this species did not exceed ten insects per wheat spike. The difference in aphid density between the above periods cannot be explained by effect of weather situation, because in 1987-2002 it occured more than once the situation close to that in 1985-1986. In these periods, other ecological factors were close also.

Contrary, in greenhouses, density of the aphid on the wheat annualy reached hundreds insects per spike, if insecticide control did not applyed. When wheat plants with the aphids were transferred from a greenhouse to a fileld, these insects died, so that an infestation spot in the field cannot be established. The mortality can be explained high susceptibility of greenhouse population of the aphid to pathogens under effects of common weather situation an outdoors. The field population of the aphid in 1987-2002 was also susceptible to pathogens. But in 1985-1986, it arose the population with advanced resistance to pathogens. In next year, pathogens acquired virulence to the aphid and kept it during subsequent years.

8. (C-7) The complex of FDESPPs8.4.3. Saltations in populations of phytopathogens (increase of virulence) and

herbivores (increase of vitality)8.2.1. Cultural practices disturbing physiological state of dominants and obstacles for host-

plant superevasion8.3.1. Disturbance of water balance in dominants of forest ecosystems at low precipitation

8.3.2. Mass coincidence of larval hatching or attacks of herbivores in older stages with favorable phases of host-plant development in dominants

8.2.7. Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores


varieties strains, hybrids, lines) to resist against a given taxon of PPs2.1.2.P.1. In biocenoses, forming of a dominant stock at the natural conditions

2.1.2.P.2. In articenoses, a resemblance of a dominant stock to that in biocenoses or special cultural practices with the aim of effective operation of CESPPs A.2.1.2.

2.3.P.3. Proper structure of ecosystems, which provides microclimate tolerable for natural enemies of invertebrate herbivores at weather extremes

2.3.P.4. Weather situation, which provides operation of CESPPs 2.1.2.1. Superevasion8.(C-7). CESPPs 2.1.1.2.2., 2.1.1.2.1.2., and 2.2.1. failed

8.(C-7). Outbreaks in certain populations of invertebrate herbivores with weakly expressed periodicity

Saltations in defoliators have not been noticed, but some peculiarities of affection in a number of species allow assuming that they indeed occur. This assumption concerns the species, which produce outbreaks with weakly expressed periodicity and prolonged intervals of duration at many decades between them. Such a species is the nun moth, Porthetria monacha L.

Characteristics of outbreaks of Porthetria monacha were descrided shortly by A.I. Il’insky and I.V. Tropin (1965, p. 239) as follows: "The largest and most prolonged outbreak of the nun moth was in the middle of XIX century, which embraced spruce forests of southern areas of the Baltic region and near by areas of Belorussia, Poland and East Germany. The large outbreak at the end of XIX century took place in pine forests of the eastern half of the European part of

49


USSR and West Siberia. Again, in West Siberia, it was observed large outbreak in the last decade."

In the Central Europe, the large outbreak of this species took place in 1920-ies.In Belorussia and north Ukraine, it was an outbreak of the Porthetria monacha in pine forests

at the end 1970-ies and in the beginning of 1980-ies. It is notable that the vast outbreaks of Porthetria monacha, if they affect the same areas,

beside the interval of about hundred years, embrace ecosystems with diverse host-trees as dominants.

Here are the data as to an operation in the complex 8.(C-7) FDESPPs 8.2.1."Cultural practices disturbing physiological state of dominants and obstacles of superevasion" and 8.2.7. "Cultural practices inducing hostile environment for natural enemies or favorable "microclimate for herbivores". At outbreak of Porthetria monacha at the end of 1970-ies and the beginning of 1980-ies, rich pine ecosystems were free from the affection in spite of they were situated in vicinity of affected pine forests, and pheromonal traps caught this species (M.M. Zavada, pers. comm.). In rich pine ecosystems, neither FDESPPs 8.2.1. nor FDESPPs 8.2.7. operate.

A.I. Il’insky and I.V. Tropin (1965, p. 239) found out in a Russian chronic for 1407 a report about mass appearing of "worms" in forests of the Tver Prinsdom (Moscovia, now the Tver Region, Russia). These scholars supposed that it was an outbreak of Porthetria monacha induced by heavy drought in 1403 reported also in this chronic. The usage of silvicultural practices in so ancient time is hardly to be probable. Nevertheless, it is possible an operation of FDESPPs 8.2.5. "Affection of forest ecosystems by ground forest fires."

Again, heavy droughts and coincidence of mass larval hatching with abundant staminate "flowering" in the pine and early appearing of young needles in the spruce are considered as necessary causes of outbreaks of this species (Ibid., p. 241-242).

This implies an operation of FDESPPs 8.3.1. "Disturbance of water balance in dominants of evergreen coniferous trees at low precipitation", 8.3.2. "Mass coincidence of larval hatching with favorable phases of host-plant development in dominants."

It is notable that Porthetria monacha needs the wet environment. But such conditions favorable for thriving of pathogens. To overcome infection, the larvae must possess advanced immunity. This is achieved due to severe selection, which gives the result in exceptional circumstances. That is why outbreaks of the species are rare. The following words of the above scholars show importance of increased immunity of the moth as a prerequisite of arising of outbreaks: "Color of the butterflies are very variable. In the period of the initial phases of an outbreak, it dominates dark-colored insects. Some of them have black color of wings." (Ibid., p. 239).

Outbreaks of Porthetria monacha arise in ecosystems affected by diverse FDESPPs. Nevertheless, the suggestions about the causes of outbreaks proposed by the literature seem to be insufficient for explanation of this phenomenon.

The rarity of the outbreaks and change in favorite host-tree (spruce, pine, beech), necessity to overcome affection on the part of pathogens in wet environmental conditions and counteract with residual Antibiosis of host-trees give the ground to assume an operation of an additional FDESPPs, namely: 8.4.3. "Saltations in populations of phytopathogens (increase of virulence) and herbivores (increase of vitality)." Here, the increase of vitality means the growth of resistance in populations of moths to pathogens and protective substances of host-trees.

The attempts to trace a dependence of outbreaks of from solar activity have not been successful. Such attempt was done by H.I. Eidmann (1931), who studied reports about population dynamics of Porthetria monacha in Germany operating the data from 1801 to 1928. In so doing, it was used the number of forestry units or districts, from which information about affection of forests by the moth was received. Because there exists a correlation between an area of affection by a pest and its density, one may draw a conclusion as to the level of density - High or Low. These values were considered in the context of years of minimum and maximum of solar activity. H.I. Eidmann supposed an existence of correlation between solar activity and

50


population behavior of the moth. It might be determined by effect of solar activity on weather situation.

These data have been considered critically by S.P. Ivanov et al. (1938, pp. 157-158) and arranged in the form of the table, which is quoted here with some modifications as the Table 44. The critical review by the above scholars has allowed drawing conclusions, which differ from those by H.I. Eidmann.Table 44. Analysis of population dynamics of Porthetria monacha in Germany with the aim to reveal periodicity in arising of affection by this species in the context with intensity of the solar activity (minimum or maximum of spots on the Sun)

YearsYears with

the values of solar activity

The number of years between

The number of years between affection and values solar

activity

Minimal occurrence

Maximal occurrence Min Max Next minim

of affectionNext maxim of affection

Minim of affection and solar activity

Maxim of affection and solar activity

1 2 3 4 5 6 7 81800 1807, 1808, 1809 1798 1804 12 6 - 10 2 3 - 51812 1815, 1816, 1817 1810 1816 13 5 - 8 2 0 - 11825 1822, 1823 1823 1829 6 4 - 7 2 6 - 71831 1827, 1828, 1829 1833 1837 17 7 - 11 2 8 - 101848 1836, 1837, 1838 1843 1848 11 17 - 20 5 10 - 121859 1855, 1856 1856 1860 14 12 - 15 3 4 - 51873 1868, 1869, 1870 1867 1870 12 13 - 21 6 0 - 21885 1883, 1889 1878 1883 14 3 - 12 7 0 - 61898 1892,1895 1890 1894 13 10 - 20 8 1 - 21911 1905, 1907, 1912 1900 1905 13 5 - 12 11 0 - 71921 1917 1913 1917 10 — 8 0— 1928 — 1926 — — — 2

The data of the Table 44 show the lack of both periodicity in affection of forest by the moth and coherence of the affection with intensity of solar activity.

In the cited article by H.I. Eidmann, it was reported that values of affection by Porthetria monacha coincided with those by Dendrolimus pini, Diprion pini, Panolis flammea, and Bupalus piniarius. This suggests the important role of weather situation as a releaser of outbreaks of all these species of defoliators. It seems, density of most of them increased in a result the only FDESPPs – favorable weather situation, whereas increase of Porthetria monacha density is a result not only this FDESPPs, but also a saltation.

In the posterior article (Eidmann, 1937), this scholar admitted that the periodicity of affection by Porthetria monacha in the area of entire Germany had not been proved. He supposed better prospects in a search for the periodicity in separate areas.

In Bashkiria (South Urals, Russia), Porthetria monacha is common actually annually. In such way, one may understand the words by N.K. Latyshev (1968, p. 64), namely: "…forming its reservations mainly in low-bonitet forests situated at the foots of slopes." Outbreaks of this species in this region are also probably common, because droughts induce them. Here, they occur often. The effect of drought is so stable that an onset of such a weather situation serves for forecast of the outbreaks (Ibid., p. 65). Notably, that the outbreaks arise in circumstances of expressed weakening of host-trees – Pinus silvestris. It might be that in the conditions of low level of ESPPs and a single species of host-trees, the saltation is not necessary for arising of outbreaks of Porthetria monacha.

8. (C-8) The complex of FDESPPs8.4.3. Saltations in populations of phytopathogens (increase of virulence) and

herbivores (increase of vitality)8.3.4. Increase of aggressiveness of phytopathogens and herbivores at favorable weather

in the period of their activity51


8.2.7. Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores

8.3.5. Increase of survivorship of PPs at favorable weather situation at dormancyBreakage of the prerequisites:

2.1.1.P.2. A level of physiological state of a host-plant, which is close to proper one2.3.P.3. Proper structure of ecosystems, which provides micloclimate tolerable for natural

enemies of invertebrate herbivores8.(C-8). CESPPs 2.2.1., 2.1.1.3.1.2., and A.2.1.1.3.1.2 failed

8.(C-8). Outbreaks in certain populations of invertebrate herbivores with weakly expressed periodicity

Another species, which produces outbreaks due to activity of FDESPPs 8.4.3. "Saltations in populations of phytopathogens (increase of virulence) and herbivores (increase of vitality)" as one of causes of outbreaks, is supposedly to be the beet web moth, Loxostega sticticalis L.

In East Europe, the wide-scale outbreak of Loxostega sticticalis was studied firstly in the beginning of XX century. The second outbreak took place in the 1929-31, and in less extend in 1932 and 1935. Over next forty years, density of this species stayed mainly on the Low level. It was some increases of the density that, however, did not endanger agricultural crops. In literature, it was suggested that outbreaks of the species are possible in the conditions of primitive agriculture with wide areas of bare fallow. Contrary, developed modern agriculture with high percentage of arable lands does not allow to this species to reach threatening density, because the digging up destroys its hibernating larvae.

Therefore, it was a great surprise the grandiose outbreak of Loxostega sticticalis on the same area in 1970-ies with the outbreak phase in 1975. Thereupon, over thirty years, outbreaks of this species were unknown in spite of after 1991, in the Former Soviet Union, it appeared great many of abandoned fields.

Causes of outbreaks of Loxostega sticticalis have been discussed intensively. Here are some suggestions as to the causes.

Contrary to most of insect herbivores, drought decreases density of Loxostega sticticalis. The review of abundant literature has been offered by S.P. Ivanov et al. (1938) as follows. "As early as in 1901, Pospelov has stated that at high air temperature and insignificant amount of precipitation in the period of mass flight of the moths, they are infertile...Ripening of the eggs begins at average air temperatures per 10-day period above 15°C-17°C at the flight period, but on condition that an amount of precipitation is not less than a half of sum of average temperature grades for the same time. It might be the effect of ambient temperature is not direct, i.e. it determines possibility of the feeding by nectar. For completion of egg development, the moths need in imaginal feeding. Only moths heavier than 40 mg lay the significant number of eggs, when consuming only water in the laboratory. The moths with less body weight lay eggs on condition that feeding by water solution of sugar" (Ibid., pp. 135-136). Moreover, if concentration of sugar exceeds 20%, the eggs cannot develop. Hence, at drought, when concentration of sugars in nectar is high, the fecundity drops. At relative humidity of air below 60%, the eggs do not ripe independently on quality of food (Ibid., p. 136).

Also, high air temperature at the egg stage of the moth is destructive. In 1932, in West Siberia, it took place at high temperature a complete unhatching of the eggs. Their density was so High that the substratum – the remnants of plants and the soil surface was of uncommon yellowish color due to the laid eggs (Ibid., p. 111). Although, in cool and rainy summer of 1933, density of the moth became low (Ibid., pp. 75-76).

On host-plants with high water content (87%), the larvae grow 2.5-3 times faster than on those with 70-67% of water content, so that abundant precipitation in the larval stage is favorable for increase of density (Ibid., p. 69). It is common a diapausation of the larvae in droughty summer.

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The above data suggest that an operation of FDESPPs 8.3.4 "Increase of aggressiveness of phytopathogens and vitality of herbivores at favorable weather in the period of their activity" takes place.

Although the role of weather situation is obvious, only this factor is insufficient to arising of the outbreaks. The matter of fact, the weather situation favorable for the Loxostega sticticalis in summer is common, but its outbreaks arise rarely, rather that the moths are very mobile. They are able to migrate to wet habitats, for example in river valleys, where environment favorable for them and to trace after rains (Ibid., p. 95). Drought in spring and summer occurs not so often to suppress this species over decades.

Composition of grassy vegetation does not limit the moth. The range of its host-plants is wide – thirty-five families (Shchegolev et al., 1949, p. 358)! In the laboratory, it developed well on such a diverse plants: Chaenopodium album, Beta sp., Trifolium spp., Polygonum avicularia, Artemisia austriaca, Cannabis sativa (Ivanov et al., 1938, pp. 68-69). This fact implies that CESPPs 2.1.1.2.1. “Antibiosis to herbivores” is absent in EE of this species.

High parasitization (50-70%) was recorded in years, when density of the moth was the least, whereas at High density, parasitization was in the range 20-40% (Ibid., pp.75-76). It seems CESPPs 2.2.1."Natural enemies of invertebrate herbivores, 2.2.1.1. Parasites" brings a low contribution in population dynamics of the moth.

Above review suggests that known FDESPPs cannot explain thoroughly an arising of outbreaks of Loxostega sticticalis. Therefore, the range of suggested FDESPPs should be wider.

The species spends its larval stage in a web net situated into the soil. A web net provides a good protection against parasites, but it brings danger on the part of pathogens thriving in a wet media. An increase of resistance of population to pathogens it seems to be a necessary FDESPPs, which would result in outbreaks of Loxostega sticticalis. The probability of such a hereditary change is a little one. Therefore, the intervals between outbreaks equal a number of decades.

It might be, suppression of vegetation in grassy ecosystems by humans is significant in the complex of causes of the outbreaks. In natural vegetation, the moth would be suppressed by wet microclimate in a dense grassy stand. In such a case, it operates FDESPPs 8.2.7. "Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores."

Due to increased vitality of a herbivore population, its density becomes so High that CESPPs 2.1.1.3.1.2. “Tolerance to herbivores, Repair or compensation of losses of host-plant tissues in host-plant tissues” does not operate although their physiological state is good, so that it takes place breakage of the prerequisite 2.1.1.P.2. “A level of physiological state of a host-plant, which is close to proper one.”

Probable participation FDESPPs 8.2.7. "Cultural practices inducing hostile environment for natural enemies or favorable microclimate for herbivores" implies breakage of the prerequisite 2.3.P.3. “Proper structure of ecosystems, which provides micloclimate tolerable for natural enemies of invertebrate herbivores.”

The next probable operating FDESPPs is 8.3.5. "Increase of survivorship of PPs at favorable weather situation at dormancy."

This complex needs in addition of an assumed participation of FDESPPs 8.4.3. "Saltations in populations of phytopathogens (increase of virulence) and herbivores (increase of vitality)."

The cases of increase of density of the Hessian fly in Ukraine in last two thirds of XX century might be concerned to this category of FDESPPs. The outbreaks are unnumerous, limited in area and short in duration – one or two seasons (Krishtal, 1974, p. 505). These situations can be explained at an arising of aggressive populations of the Hessian fly due to saltations. Such populations are resistant to pathogens or parasites. Nevertheless, local natural enemies soon adapte to affect these populations, and suppress them. This is possible in the conditions of rich fauna of natural enemies of the Hessian fly, which are able to suppress this species having advanced SP.

8.4. Endogenic disturbance53


8.4.4. Microevolutionary process in herbivore populations in the conditions with weak operation of CESPPs of the Extrinsic class

Breakage of the prerequisites:2.5.P.2. Temporal increase of resistance of herbivores to their pathogens (non-operation of

CESPPs 2.5.4.1.) due to microevolutionary process8.4.4.1. All the CESPPs, with exception of 2.1.1.3.1.2. Tolerance, 2.1.2.3.1. Supertolerance

and some 2.5., failed8.4.4.1.1. Outbreaks of herbivores with well-expressed periodicity

This category of FDESPPs operates in ecosystems, which are extremely poor as to CESPPs of the Extrinsic class. Only the well developed CESPPs 2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of losses of host-plant tissues" in a cooperation with some subcategories of CESPPs 2.5. "Effects of crowding" maintain such ecosystems. In insect herbivores, the best examples of this category are presented by population behavior of Zeiraphera diniana in the W.C. Cook’s zone (a), Porthetria dispar in the Chelyabinsk Region (Russia), i.e. again in the zone (a), and the cockchafer, Melolontha spp. in diverse areas.

In such conditions, the values of pest density are determined by vitality of a pest population. As soon as the population occurs to be free from the inapparent form of infection due to the sea-saw feed-back mechanism, it begins to growth until affection by the acute form of infection. In weather conditions, which preclude activation of the acute infection, mass mortality of the herbivores is induced by CESPPs 2.5.3.1.5. "Spontaneous or winter mortality of embryos" – an effect of the inapparent infection. The role of CESPPs 2.5.4.1. “Suppression of herbivores over the period, which provides a reprieve for restoring of vitality of dominants.”

Within the outbreaks, host-plants undergo heavy affection, but well-developed Tolerance allows them to survive. After a decline of the outbreak induced by CESPPs 2.5. "Effects of crowding", vitality of the host-plants restores during a number years. Operating in a pest population the sea-saw feed-back mechanism gives back vitality of this population. Therefore, the outbreak arises again.

Outbreaks of the cockchafer, Melolontha spp. demonstrate the rather expressed periodicity with intervals of several decades. The longer duration of the intervals comparing with the above-cited specie defoliators is determined by more prolonged term of generations of the cockchafer – up to four years.

W. Hase (1984) offered a review of the data on the cases of intensive flight of the cockchafer, Melolontha melolontha and M. hippocastani in Schleswig-Holstein (Germany) as well as the periods of heavy damage due to these pests in 1722-1982. The scholar has shown that population dynamics of the cockchafer has a wave-like character. The periods of their High density are interchanged by the periods of Low one. The longevity of both is almost several decades. The last period of Low density was recorded from the end of 1950-ies to 1981.

The same is true for neighboring Denmark. The coincidence might be spread on more significant area. Thus, in Ukraine, the cockchafer was a serious pest from 1920-ies to the middle of 1950-ies. The next surge of its density began in 1980-eis. Its infestation spots of limited areas were recorded until 2001 in rather uncommon habitats – a mountain meadow in the Carpathians Mountains, young birch trees in a shade planting in Kyiv, wheat and potato nurseries in breeding centers in the Kyiv Region.

Population dynamics the rodents in Tundra and Desert biomes has the same character. They are the lemmings, the hares in Tundra, the soil-dwelling rodends in Desert. Host-plants of these animals are not protected by CESPPs Nonpreference, Antibiosis, and Evasion. Although, an operation of Tolerance or Supertolerance is obvious, so that the biomass of the category D-II is affected. Variability of weather situation can effect on longevity of phases of population dynamics determining abundance of food, but weather cannot suppress the animals.

So that CESPPs 2.3. "Routine weather suppression" as well as CESPPs 2.4. "Periodic (bottle-neck) suppression" is not significant. Again, host-plants of the rodents survive due to their Tolerance or Supertolerance. The role of CESPPs 2.5. "Effects of crowding" is absolute as a

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regulator of density of the rodents. Because activity of vectors of an infection in the above biomes is great, affection of the rodent population by pathogens plays the primary role among the subcategories of CESPPs 2.5. "Effects of crowding."

In deserts, some species of soil-dwelling rodents destroy completely grassy vegetation in areas of their colonies [the Section 4(1)]. This is a rare case, when herbivores destroy an ecosystem completely. Nevertheless, this is not a progress of desertification. Contrary, grassy ecosystems are changed by more stable woody ecosystems with Haloxylon spp. as dominants, so that this is a kind of succession. The case should be considered as an operation of CESPPs 2.1.2.3.1. Supertolerance from herbivores.

In the above cases of Zeiraphera diniana in the W.C. Cook’s zone (a), Porthetria dispar in the Chelyabinsk Region (Russia), and the rodents in Tundra and Desert biomes, ecosystems continually stay on the level ESPPs 3.3. “Late control.” Nevertheless, due to well-expressed Tolerance of their foodstuff these ecosystems survive, whereas at operation of Supertolerance, it takes place a succession, when composition of dominants changes.

8.4. Endogenic disturbance8.4.5. Growing emaciation of progeny in the conditions of weak operation of CESPPs of

the Extrinsic and Intrinsic classesBreakage of the prerequisites:

2.5.P.1. Surpassing by PPs density some threshold8.4.5.1. All the CESPPs, with exception of 2.1.1.3.1.2. ,2.5.6.1., and 2.5.4.1. failed

8.4.5.1.1. Outbreaks of herbivores with well-expressed periodicity

This category of FDESPPs is based on the cases of mortality of young larvae of the Siberian pine moth, Dendrolimus sibiricus described by V.O. Boldaruev (1969) as the children’s mortality, The values of this mortality were "…in 1962, 49.0 - 57.4%, in 1963, 40.4 - 64.1%" (Ibid., p. 43). The analyses of died insects did not find any pathogens in them.

A.S. Rozhkov (1963) and N.V. Gorshkov (1971).) also noted significant values of the mortality. Although the latter two scholars do not use this tirm, and do not report about search for pathogens in the died larvae.

Decrease of the children’s mortality is an important cause of arising of the outbreaks. In fact, sets of droughts and ground fires suppress the parasites, decrease the children’s mortality nearly to zero and diminish duration of the generation to one year (V.O. Boldaruev (1969, pp. 29-57, 102-108),. The droughts are characterized by increase average air temperatures in August and in the next season in May on two centigrades or more comparing with yearly averages. In so doing, mortality of Dendrolimus sibiricus in the reservations decreases from more 99% to less than 10%. The decrease of the children’s mortality due to onset of the droughts was not explaned. Probably, the droughts increase content of nutrients in needles of the host-trees.

A decline of the outbreaks is caused by returning of the above suppressing factors to the level characteristic for the innocuous phase. An activity of the parasites spreads on entire area of infestation spots, and the children’s mortality becomes high again.

In addition, at decline of the outbreaks, it takes place mortality of 71.6% of the embryos due to an unexplained cause (Boldaruev, 1969, p. 67). This fact supposes an operation of CESPPs 2.5.3. "Increase of activity of pathogens and parasites in the specific conditions of high insect host density" with the effect 2.5.3.1.5. "Spontaneous or winter mortality of embryos." This fact gives grounds to suppose that the children’s mortality is induced by another CESPPs.

The report of N.V. Gorshkov (1971) allows to understand the essence of this phenomenon. In occurred to be the mortality is especially expressed in the enviromental conditions. where operation of CESPPs is extremelly limited. This is area on extreem south of the range of the larch – on the border of the Forest biome with the Steppe one. In such conditions, it absent conditions for accumulation even the inapparent forms of infection in a population of Dendrolimus sibiricus. Therefore, at decline of moth’s density, neither female weight, nor

55


fecundity decreased. Although, an average weight of eggs occurred to be less than common one. The larvae hatched from eggs of low weight underwent exactly children’s mortality.

This kind of mortality occurred to be actually the only factor, which suppresses the population of Dendrolimus sibiricus in larch ecosystems in the Chita Region (Russia).

Here, population dynamics of the moth had a pulsatory pattern, and “noticeable” defoliation of larch trees repeated every fourth year. Such a defoliation was observed in 1958, 1962, 1966, and forecasted on 1970. The children’s mortality began in young instars and continued up to entering of the larvae in middle instars. Activity of natural enemies of the moth was insignificant. Weather situation was steady, and, therefore, it cannot explain changing of the density.

A.S. Rozhkov (1965, pp. 66-68) observed mortality of moth’s larvae in first and second instars, which fed on secondary (repaired) needles in fall. This scholar explained the mortality by significant decrease of proteins and hydrocarbons in these needles. This scholar observed that they died at onset of first morning frost in fall and at hibernation. Studies of N.V. Gorshkov (1971) showed that the children’s mortality is common even at steady weather situation.

So, that FDESPPs 8.4.5. is characterized by lack of operation all the CESPPs with exception 2.1.1.3.1.2. “Tolerance to herbivores, Repair or compensation of losses of host-plant tissues” and 2.5.6.1.“Mortality due to starvation or inadequate food in the same generation or in the next one, decrease of fecundity”, and 2.5.4.1. “Suppression of herbivores over the period, which provides a reprieve for restoring of vitality of dominants.”

The children’s mortality operates widely in population dynamics of Dendrolimus sibiricus. In the situations, where numerous FDESPPs take part, its participation does not result in well-expressed periodicity of the outbreaks. However, if participation of FDESPPs is very limited, as it has been shown by N.V. Gorshkov (1971), the outbreaks become nearly continuous, so that an affected ecosystem stays on the level ESPPs 3.2. “Lag control.” In fact, because it was recorded only noticeable defoliation, ESPPs does not decrease to the level 3.3. “Late control.”

8.5. Force-majeure anthropic impacts8.5.1. Destruction of ESPPs at tree crown forest fires

Extermination of protective structures of dominants and natural enemies of PPs8.5.1.1. CESPPs 2.1. and 2.2. failed8.5.1.1.1. Outbreaks of stem borers

This category of FDESPPs concerns the foulest crime practicing in Russia in respect to forest. The question is an intentional arson of the forest stands of a protective function with the aim to kill them. Acccording to the law, forest of such a function can be cutover only by sanitary cutting, when being died off. That is why the mafias, which bosses the show in modern Russia, organizes arsons in the ever-increasing scales. In fact, the areas of burnt down forests are evaluated as equaled eight million ha in 2002 and thirteen million ha in 2003, whereas before 1991, i.e. in the Soviet period, the annual areas of forest affected heavily by fires was three million ha, although the total forest area in USSR was some larger in that time.

To kill forest entirely, it needs to cause tree crown fire. The ground forest fire in old age, when bark is thick, does not result in obligatory mortality of trees. The most dangerous terrain as to this plunder is streched from the Irkutsk Region to the Primor’ye (the Russian Far East), where from it takes place huge exportation of wood products abroad.

This sad facts were reported in the program Radio Liberty, Russian Service "The restricted area", September 16, 2003. The author and manager of the program Marina Kades spoke ironically as regard this: "If Russia would not sink, it would burn down."

8.5. Force-majeure anthropic impact CESPPs8.5.2. Total treatment by insecticides of non-selective action

Extermination of natural enemies of defoliators and sap-sucking arthropods8.5.2.1. CESPPs 2.2.1. failed

8.5.2.1.1. Outbreaks of defoliators and sap-sucking arthropods56


This is a wide-known negative effect of treatment by the insecticides with the wide range of toxicity, which fortunately is removed now by usage of less dangerous ones. Application of microbial or hormonal preparations for control of pest arthropods is an effective measure for saving natural enemies of these pests.

8.5. Force-majeure anthropic impacts8.5.3. Thinning of forest in the warm period of year

Destruction of significant part of natural enemies of defoliators8.5.3.1. CESPPs 2.2.1. failed

8.5.3.1.1. Outbreaks of defoliators

These operations exert destructive effect on avian predators and parasites of pest insects. Therefore, all kinds of cutting in forests should be conducted in the winter period of year.

8.6. Force-majeure natural impacts8.6.1. Invasions of exotic taxa of phytopathogens and herbivores, which are able to

overcome CESPPs 2.1.1.2.Breakage of the prerequisites:


8.6.1.1. CESPPs 2.1.1.2.2. and 2.1.1.2.1. failed8.6.1.1.1. Epiphytoties and outbreaks of PPs consuming biomass of the category D-I

The East-American chestnut disease, Endotia parasitica Mur A & A, which penetrated into America from Asia in the beginning of XX century, killed nearly completely trees of native chestnut species Castanea dentata within the new range of the phytopathogen. The affection is obviously is connected with absence of CESPPs 2.1.1.2.2."Antibiosis to phytopathogens" in Castanea dentata to this exotic species. This fact was substantiated by revealing in Asia the Chinese chestnut, Castanea mollissima, which had evolutionary experience interactions with the phytopathogen, and occurred to be highly resistant both in America and Asia to it (Elton, 1958, Ch. 1). Endotia parasitica penetrated also in Europe, where it endangered the native chestnut species Castanea sativa.

The case of the Dutch elm disease, Cerastocystis ulmi (Buismen) C.Moreau is similar to above one. This species penetrated to Europe and North America probably from Asia, because all the American and European elm species Ulmus spp. are affected heavily or significantly, whereas the Siberian elm, Ulmus pumila L. has advanced Antibiosis (CESPPs 2.1.1.2.2.).

There is the important difference between potency of Antibiosis of host-trees as to two above diseases. If Endotia parasitica kills host-trees indiscriminately, Cerastocystis ulmi kill less part of them. In fact, E.G. Brewer (1941, cited in Ch. Elton, 1958) reported that from 1933 to 1940 in USA in the course of sanitary cutting, it was chosen 4,250,000 of elms affected by the disease. Although this cipher is seemed as very high one, it regards to the survived trees as 1 : 8,000. The affection by the phytopathogen increases in a result of droughts.

This implies that at favorable weather situation, Antibiosis (CESPPs 2.1.1.2.2."Antibiosis to phytopathogens") occurs to be rather effective. Although, the effect of droughts can be caused by decrease of Antibiosis (CESPPs 2.1.1.2.1."Antibiosis to herbivores") to vectors of the phytopathogen – the engraver beetles, Scolytus spp. In result of drought, an amount of populations of these vectors increases greatly. Therefore, they inoculate the infection to the greater number of host-trees.

The false mildew of the cucumber, Pseudoperonospora cubensis (B. et Curt) Rostow. which exerted heavy damage to production of this crop in Europe in 1980-1990-ies, is an invader from Far East. This suggestion is based on absence of serious damage of cucumber varieties of the Far East origin. This fact implies an operation in these varieties CESPPs 2.1.1.2.2."Antibiosis to phytopathogens."

The European spruce beetle, Dendroctonus micans appeared in Georgia (the Former Soviet Union) in 1940-1950-ies and induced heavy damage of the Eastern spruce, Picea orientalis Link.

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growing in this area. The spruce stands occurred to be less resistant (CESPPs 2.1.1.2.1. "Antibiosis to herbivores") to this beetle, comparing to that as to resident species of bark beetles. In this region, before the outbreak of Dendroctonus micans, it took place a noticeable damage on the part of the resident species Ips sexdentatus Boern., but the latter induced mortality of the small number of the spruce trees.

Contrary, the former species colonized in some stand most part of trees and induced mortality of a significant part of them. The wide-spread pattern of affection by the beetle is presence of its colonies near by wounds in a base of spruce stems and on parts of roots situated above of a soil surface or in an upper layer of the soil. Such colonies are limited by weakened tissues, and in most cases do not endanger mortality of trees. Another pattern of affection by the beetle is colonization all the area of stems with thick layer of phloem. The thick phloem is necessary for successful development of the beetle having a body of a larger size than that in other bark beetles. Such colonization, which kills trees, is characteristic for the conditions, where the main stock of host-trees is weakened.

Their features are the following: situation near by borders of the forest mountain belt with the steppe one, disturbance by human interference, old age. The literature has shown that in other regions, outbreaks of the beetle arise also in the conditions, where the main stock of host-trees, the Norway spruce, Picea excelsa is weakened.

Importantly, climate of the area of the beetle’s outbreak in Georgia is much more arid comparing to that of the Carpathians Mountains, where the beetle inhabites also, but it continually stays at the Insignificant density (Vasetschko, 1968a). Thus, the level of expression of CESPPs 2.1.1.2.1. "Antibiosis to herbivores" in the Picea orientalis in Georgia was sufficient to withstand as a whole to resident species of bark beetles, but it was insufficient in a number of localities to withstand to the exotic bark beetle.

Notably, wet climate of the range of Picea excelsa in the Carpathians Mountains unfavorable to arising of outbreaks of Dendroctonus micans does not preclude heavy outbreaks of other species of bark beetles and stem borers as a whole, if spruce stands are weakened by improper silvicultural practices or by the aged crash of forest.

This difference can be explained by unequal demands of considering species to character weakening of host-trees. The duration of preimaginal stages of Dendroctonus micans is much larger than that in other bark beetle species. The development of the former is successful on condition that weakening proceeds slowly. The stressors in the Carpathians Mountains exert sharp decrease of vitality of host-trees. This is admissible for success in development of Ips typographus and its numerous associates - species of stem borers, but Dendroctonus micans stays here on the verge of extinction.

The above exotic herbivore and phytopathogen species are able to overcome host-plant Antibiosis (CESPPs 2.1.1.2.) in the vitally important (conductive) tissues. Therefore, affection by these pests endangers mortality of trees or heavy losses of yield in grassy crops, in particular the cucumber. If CESPPs 2.6. "Human control measures" are not practiced, and within an affected species (a variety) of host-plants are absent resistant individuals, the outbreaks would continue until extinction of a host-plant species or cessation to cultivate a susceptible variety.

In fact, extinction endangers to the American chestnut, Castanea dentata. In East Europe, it disappeared Ulmus foliacea Gilibert, which actually does not have Antibiosis to Cerastocystis ulmi on the species level. The variation Ulmus foliacea var, glabra Huds. occurred to be more resistant.

In colonies of bark beetles, both Scolytus spp. and, Dendroctonus micans, it operates a number of subcategories of CESPPs 2.5. "Effects of crowding." Nevertheless, they unable to suppress the pests until weakened host-trees are available.

A decline of the epiphytoties is achieved by cultivation of resistant species (varieties), breeding of resistant cultivars, grafting of attenuated strains of phytopathogens and control of vectors of infection. The usage of the Chinese chestnut, Castanea mollissima, the Siberian elm, Ulmus pumila and varieties of the cucumber of the Far East origin is an example of the simplest solution of the problem. Grafting of attenuated strains of phytopathogens allows infesting them

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with superparasites and gives a chance to save affected trees. Control of the vectors by sanitary cutting and usage of pheromonal traps to kill the vectors is prospective in suppression of Cerastocystis ulmi.

As to the Pseudoperonospora cubensis, decrease of virulence of this phytopathogen in late 1990-ies suggests that epiphytoties can decline due to natural causes – probably in a result of adaptation of their superparasites.

If bark beetles vectoring phytopathogens respond on attractive pheromones, control of them by traps promise significant decrease of the damage. This is the case of engraver bark beetles, Scolytus spp. affecting elm species both in America and Eurasia.

As to Dendroctonus micans, these beetles are not attracted by lures in nature. Danger due to this species would hardly finish until exhaust of susceptible trees. Nevertheless, the damage can be decreased significantly by control measures. They are a treatment of standing trees with insecticides or, if the colonized trees have no prospects to survive, practicing of sanitary cutting with debarking or application of insecticides.

8.6. Force-majeure natural impacts8.6.2. Invasion of exotic taxa of herbivores, which are able to overcome CESPPs 2.2.1.

Breakage of the prerequisites:2.2.1.P.2. Adaptation of parasites and pathogens to overcome resistance of their hosts

8.6.2.1. CESPPs 2.2.1. failed8.6.2.1.1. Outbreaks of defoliators and sap-sucking insects

This category includes the cases of invasion of herbivores, which are suppressed in their native lands by a cooperation of CESPPs 2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of losses of host-plant tissues" and 2.2.1. "Natural enemies of invertebrate herbivores." Therefore, for suppression of them at the invasion, it needs to introduce natural enemies of them from their natural range. Case stories concerned to this category are described in numerous publications. Some of them have been cited above.

Peculiarities of this category of FDESPPs become clear if to retell in brief the population behavior of gypsy moth, Porthetria dispar in America (the Section 5(1). The gypsy moth penetrated into America in 1868 or 1869, but until 1890, it was inappreciable. Beginning with 1890, it became a true distress for people in towns of New England States during a quarter of century. The gypsy moth devoured entire foliage of plants indiscriminately and brought public nuisance.

The parasites, which in that time were only resident species, exerted insignificant mortality. Both avian predators and ground (mammal) ones were impossible to suppress the pest. Activity of pathogens was innoticeable. Fecundity of the pest reached 1400 eggs, an uncommon value in the Old World. After complete defoliation of plants, it was observed mortality of the starving caterpillars. Such a population behavior gave the grounds to state that the gypsy moth stayed in the period of euphoria characteristic, according to K. Friederichs, for exotic herbivores during some time after their invasion.

The period of euphoria was finished soon after 1905, when in the first time, it was released parasites of the gypsy moth imported from the Old World. Then, the population was affected en masse by the "wilt" (probably the polyhedrosis) obviously inoculated by imported stinging parasites.

In a result of the affection, density of all the American population of the gypsy moth decreased dramatically, and stayed on the Low level until the middle of 1920-ies, when a new increase of the density began. This outbreak was provoked by exceedingly severe winters, which occurred in Northeast States. The obvious effect of the severe winters consisted in mass mortality of the parasites, imported from areas of mild climate (Southern Europe, Japan) and, therefore, unadapted to hard frost. The relief came at restoring of common weather situation, when the parasite-pathogen complex became to operate again.

Since then, in the generally infested area, population dynamics of the gypsy moth in North America has continued to be the same as that in the Old World. The outbreaks arise after drought

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in late spring – early summer and/or severe winters. The effect of the weather situation takes place in forest stands with hostile environment for natural enemies.

In the advancing front of the generally infested area and in the island infestations of the gypsy moth, where the parasite-pathogen complex has not formed yet, population dynamics of the pest has feature of the period of euphoria.

The performance of Porthetria dispar on a population level is a good example of efficacy of a multiple introduction of polyphagous parasites of an exotic pest. Over a century, they occurred to be effective suppressors of an insect host everywhere environmental conditions allow them to thrive.

The case of the larch sawfly, Pristiphora erichsonii Hart. demonstrates limitations of introducing of a single parasite, probably with the trait of monophagy. The larch sawfly penetrated into America from Europe at the end of XIX century, and caused heavy damage until in 1910-1913 it was introduced its parasite Mesoleius tenthredinis Morley. This species suppressed the pest effectively over thirty years. Outbreaks of the sawfly were not stopped, but they became rare that admissible for the larch having advanced Tolerance. In 1940-ies, its efficacy dropped due to encapsulation of parasite’s eggs in a host’s body. The problem was solved by introduction of a strain of the parasite resistant to encapsulation, and subsequent introduction the parasite Olesicampe benefactor Hinz.

The population behavior of the browntail moth, Euproctis chrysorrhoea L. in America is interesting as a case of greater efficacy of introducing parasites than that of resident ones in the native land of this defoliator. In fact, this exotic species was a serious pest "…throughout New England and into several of the Canadian Maritime Provinces in about 30 years… For reasons not completely understood, the range of the browntale moth began to recede in the 1920’s. Today, the insect is a maritime curiosity, with small colonies that persist on several islands in Casco Bay, off Portland, Me., and on coastal sand dunes of Cape Cod, Mass." (Leonard (1981, p. 10).

Although details of causes of the recede, indeed, are debatable, they are obviously the consequences of importation of pest’s parasites from Europe that has been described by L.O. Howard and W.F. Fiske (1911).

Quite another situation takes place in Russia – the native land of this species, where it is common of oak groves and fruit orchards in the Steppe biome and the southern part of the Forest-Steppe biome.

I. Yemel’yanov (1907, p. 5) offered the review of its outbreaks beginning with the first part of XIX century in diverse areas of Russia, namely: 1840, 1850-1851, 1855-1856, 1859 - in Bessarabia (now Moldova), 1841-42 - in Podol’ye (now southwest Ukraine), 1844 - in Saratov, 1848-1850 - in Kursk, 1848 - in Khar’kov, 1867-1869 - in Penza, 1862 - in the Crimea Peninsula.

After that, studies of the outbreaks were conducted by professional entomologists (Ibid., pp. 5-6): "…Rudzky supposes that this insect is most common pest in southern Russia; in 1863, he found out its caterpillars in the incredible numbers on vast areas on very diverse plants. At the end of 1890-ies, the mass outbreak was observed in the Governments Saratov, Simbirsk, Samara, Ural’sk (Schreiner), the Black Sea coast, Tavria, Cuban (Porchinsky) and Poltava (Shevyryov). At last, in 1905, and especially in 1906, it was observed its huge outbreaks over all the southern Russia from the southwest area to the Volga Governments. Thus, the browntale moth should be referred as a serious, common, and probably native pest insect in southern Russia."

Further, I. Yemel’yanov quoted a Russian Chronicle (the Ipat’yev Version), where at the year 1078, it mentioned the distress due to locusts, cockchafers and caterpillars. Among the latter, it supposed to be the browntale moth (Ibid., p. 6).

The winter web nets of this species is a well protective means against avian predators, but they do not able to provide the eggs and openly feeding young larvae by protection against parasites active in fall, when the larvae feed openly. In the Rostov Region (Russia), affection of the larvae in the nests by the parasite Eupteromalus nidulans Forst., family Pteromalidae reached 100% (Utchakina, 1968).

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Again I. Yemel’yanov (1907, pp. 15-31) reported about heavy mortality of eggs, caterpillars and pupae of this species under effect of numerous species of parasites and one species of bacterial pathogens. Pteromalus nidulans Thom. killed all the caterpillars in some nests. The pathogen is determined as Empusa aulicae Reich.

Contrary to Russia, on most part of the pest’s range in North America, the parasite-pathogen complex has lowered pest’s density to the Insignificant level continually. The success of control of the browntale moth in North America might be explained by climatic conditions of the East Coast of the continent. The climate is more humid than that in the Steppe biome in East Europe. Air humidity is favorable for activity both parasites and pathogens.

However, "on several islands in Casco Bay, off Portland, Me., and on coastal sand dunes of Cape Cod, Mass.", the imported parasites are unable to thrive (Leonard (1981, p. 10). It might be, they do not penetrated into these localities yet, or local environmental conditions are unfavorable for them.

The population dynamics of the winter moth, Operophthera brumata in Canada demonstrates the important role of natural enemies in suppression of this species (Embree, 1971). Accidentally introduction of the moth resulted in heavy damage of the oak stands over ten years. The deliberate introduction of two parasites Cyzenis albicans Fall., a tachinid fly, and Agrypon flaveolatum Grav., an ichneumonid wasp, resulted throw ten years in decrease of moth density in plots of evaluation to Zero level. Notably, that dramatic decrease of the density from the six pupae per meter of the soil surface took place next year after affection by the wasp reached high value – 40% of the pupae. In the following year, the density of the pupae dropped to Zero. Such events imply affection of a population by pathogens vectoring by stinging parasites.

Considering the prospects on values of pest’s density in future, this scholar supposes that it is possible its increase due to interference of such factors as affection by virus pathogens and synchronization between winter moth hatching and the bud-break of the oak (Ibid., p. 225). In fact, further observations have showed that the winter moth inhabited host-trees, but its negative effect on their vitality is close to that in Europe, i.e. it is as a whole insignificant one.

It should stress that introducing natural enemies should be adapted to climatic conditions of the recently invaded area.

8.6. Force-majeure natural impacts8.6.3. Invasion of exotic taxa of herbivores, which interact with host-plants protected by

CESPPs 2.1.2.3.The lack of operation of CESPPs 2.1.2.3.1. “Supertolerance to herbivores” due to human

demands8.6.3.1. CESPPs 2.1.2.3.1. failed

8.6.3.1.1. Affection of fruits by carpophagous insectsThe content of this category is considering on the example of the codling moth, Carpocapsa

pomonella L. At invasion of this species, any CESPPs of the Intrinsic or Extrinsic classes are not prospective for suppression of the pest to the Insignificant level of density, i.e. below a threshold of damage of apple yield. The damage of fruits by the moth does not exert a detrimental effect on vitality of host-trees. The consumption of fruits is not complete, and in affected fruits some seeds survive. That is why, neither CESPPs 2.1.1.1.1. "Nonpreference to herbivores" and 2.1.1.2.1. "Antibiosis to herbivores" nor operate in wild species of the apple-trees.

Although the varieties of apple-trees resistant to this pest are known, it is impracticable to recommend them as the main means of protection against the fly. The larvae of this species spend their development inside fruits, so that the larvae are well protected against natural enemies (CESPPs 2.2.1.) and suppressive weather factors (CESPPs 2.3.). An operation of these CESPPs takes place that is confirmed by the fact of uncompleted consumption of the fruits. Therefore, in biocenoses, CESPPs 2.1.2.3.1. "Supertolerance to herbivores", which operates in interrelations of the moth and its host-plants, is sufficient for co-existence of them.

But the level of damage of fruits is inadmissible for orchard management. That is why if an invasion of the codling moth has taken place, an extermination of the pest is urgently need. Such

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measures conducted in West Australia were described in detail by P.W. Geier (1970). If the codling moth has accustomed in a newly infested area, it needs to practice temporary suppressive measures conventional for its natural range.

These considerations might be relevant for the cases of invasion of other carpophagous species.

8.6. Force-majeure natural impacts8.6.4. Mass invasion of the locusts, stem borers and other herbivores, which are able to

overcome CESPPs 2.1. and 2.2.Inability of protective structures of dominants to counteract immigrants

Inability of resident natural enemies to suppress immigrants8.6.4.1. CESPPs 2.1. and 2.2. operating against a given immigrant failed

8.6.4.1.1. Destruction of plant tissues admissible for feeding by the immigrated insects

This category concerns invasions of voracious insects in the adult stage or late-instar larvae, which are able to consume green parts of plants nearly indiscriminately. CESPPs 2.1.1.1.1. "Nonpreference to herbivores" and 2.1.1.2.1. "Antibiosis to herbivores" are unable to protect plants. In a result, it arises a situation, which differs at some degree from typical outbreaks. In so doing, it is possible the following situations:

i) Ignorance of protective substances by starving pests ( the locusts, larvae of Porthetria dispar in late instars, the army worms (family Noctuidae also in late larval instars),

ii) Mass attack of bark beetles, which overcome Antibiosis.iii) Weakening of host-trees by parent beetles, which nibble of thin bark in tree crowns (in

some longhorned beetles, the family Cerambycidae). In addition, resident natural enemies are unable to suppress these immigrants, so that

temporary suppressive measures are necessary for saving the ecosystems.Invasions of defoliators in the adult stage have no character of a force-majeure impact. They

are able to lay their eggs in any ecosystems, but further destiny of this population is determined by potency of local ESPPs. If it is in the best state, the population is suppressed by local CESPPs. In the opposite situation, it arises an outbreak of defoliators.

8.6. Force-majeure natural impacts8.6.5. Destruction of ESPPs by tornado, tsunami, landslide, avalanche, etc.

Breakage of the prerequisites:8.6.5.1. CESPPs 2.1. and 2.2. failed

8.6.5.1.1. In woody ecosystems, arising of outbreaks of stem borers

These impacts kill trees, when falling and breaking of them. If the trees are left on an affected area being unprotected from stem borers by temporary suppressive measures, an arising of their outbreaks is very possible.

This category of FDESPPs results in the same process, as the complex of FDESPPs 8. (C-2) does, i.e. the aged crash of forest – 2. Unlikely to 8.(C-2), the affection at 8.6.5. takes place independently on character of a habitat and a forest stand. The destruction of dominants is determined exclusively by extrinsic force-majeure phenomena.

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