New I I I I I I 11 I I I I - Washington State...

INTENSIVE FIBER UTILIZATION AND PRESCRIBED FIRE:

EFFECTS r--- c--,OF ON THE F----- MICROBIAL m

m 3

A.E. Harvey, M.F. Jurgensen, M.J. Larsen

USDA Forest Service General Technical Report INT-28 I I I I I I 11 I I I I INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION

USDA Fores t Service General Technical Report INT-28

1976

INTENSIVE FIBER UTILIZATION

EFFECTS O N THE MICROBIAL ECOLOGY OF FORESTS

A.E. Harvey, M.F. Jurgensen, and M.J. Larsen

INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION Forest Service

U. S. Department of Agriculture Ogden, Utah 84401.

THE AUTHORS

A. E. Harvey, Plant Pathologist, i s responsible for research investigations on the microbiological impacts of intensive fiber utilization and prescr ibed f i re . He is stationed at the Fores t ry Sciences Laboratory, Missoula, Montana. Dr. Harvey received the B. S. degree in Biology (1960), the M. S. degree in Plant Pathology (1962), the Ph. D. degree in Plant Pathology (1968), and an academic year of postgraduate work in Plant Pathology (1972). He joincd the lnlermountain Station in 1965,

M. F. Jurgensen, Associate Professor of Soil Microbiology teaches and conducts research in Soil Microbiology. Dr. Jurgcnsen received the B. S. degree in Fores t ry (1961), the M. S. degrec in Silviculture (1965), and the Ph. D, degrec in Soil Science (1967). He has held the posilions of Research Associate (1966-1967) and Assistant Professor (1966) at North Carolina Stale University. His present position i s with the De- partment of Forestry, Michigan Technological University, Houghton, Michigan 49931.

M. J. Larsen, Mycologist, i s presently investigating the taxonomy and ccology of fores t fungi at the Center for Forest Mycology Research, Fores t Products Laboratory, Madison, Wisconsin 53705. Dr. Larsen received the B. S. degree in Botany (1960), M. S. cl~gree in Plant Prod- ucts Pathology (1963), and Ph. Tl . degree in E'oresl Mycology (1967). He held a position with the Canadian Forestry Service (19636-1970) and joined thc Center for Forest Mycology Research in 1971.

National projections show substantial increases in the dcrnantl for wood and wood fiber-based products, cspecially housing materials. Environmental considerations favor extending the use of wood, a renewable resource that canbe processed with less energy and less pollution than alternative materials. Present utilization standards and logging practices leave large amounts of residue-- small t rees, cull and broken logs, tops, and dead timber--on the ground following harvesting. These residues can contribute to the forest 's nutrient reservoir, reduce erosion, protect seedlings, improve soil quality (by either natural decay or as a fuel for natural wildfire) and provide wildlife cover. Rowever, in the quantities that frequently occur, residues can also create an unnaturally high fire hazard, inhibit regeneration, detract from esthetic values, ancl waste scarce fiber resourccs.

Interactions between logging systems, silvicultural treatments (such as prescribed firc) , and thcir respective residues will be manifested by changes in the soil microflora. These contributions a r e controlled by the basic physical and chemical aspects of the forest: environment that a r e influenced by man's activities in the forests. Results of thesc activities will affect the nature and function of both individual and collectivc microbial populations. Microbial activities will be mediated primarily through changes in the soil which may have a subsequent effect on site quality.

Prescntly, little is known about the optimum amount and kinds of residue needed to maintain or improve soil quality after timber i s harvested. This compendium was prepared as a basis for ini- tiating research into the microbiological effects of alternative rcsidues management procedures and to bring aboul an awareness of the potential problems and opportunities in this arena of environmental manipulation.

Past research reports many instances wherein management actions have had unforeseen effects on soil quality. This reflects a lack of knowledgc of many forest environments and emphasizes the need to examine each forest condition individually. Only by better understanding the net effects wrought by management prac- ticcs on each forest environment, can its soil be protected as a storehouse of essential microbial activity, mineral nutrients, and physical characteristics, which together comprise the substrate for growth of future forests,

Page

T H E E F F E C T S OF INTENSIVE UTIT,IZArITON AND FIRE: ON SITE QUALITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Intensive Ut i l iza t ion . . . . . . . . . . . . . . . . . . . . . . . F i r c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RET.,ATIONSHIF' O F UTFLIZATION INTENSI1:'Y AND FIRE T O MICROBIAI~ ECOIAXY . - . . , . - . . - - - . . . .

T e m p e r a t u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . Mois tu re . . . . . . . . . . . . . . . . .. . . . . . . . . .. . Aerat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrogen Ion Concentra t ion (pH) . . . . . . . . . . . . . . . . Nut r i cn t and Energy Supply . . . . . . . . . . . . . . . . . . . Avai lable Biota. . . . . . . . . . . . . . . . . . . . . . . . . .

IMPACT O F RESIDUE MANAGEMENT PRACTICES ON URI'I'JCA [,

MICROBlAL ACTIVITIES . . . . . . . . . . . . . . . . . . . . . Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mycor rh iza Format ion . . . . . . . . . . . , . . . . . . . . . . Soil Ni t rogen Fixat ion and Trans fo rmat ions . . . . . . . . . . Pathogen Activity . . . . . . . . . . . . . . . . . . . . . . . .

S U M M A R Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ABSTRACT

Reviews c u r r e n t knowledge of the e f fec t s of in tens ive wood uti l ization, p r e s c r i b e d burning, o r a combination of both t r e a t - m e n t s , on the m i c r o b i a l ecology of f o r e s t so i l s . Identif ies a d d i t i o n a l r e s e a r c h that mus t b e done to f i l l vo ids in knowledge.

Intensive Utilization

S o i l s a r e dcvcloped by t h e i n t eg ra t ed ac t i on of environmental f o r c e s upon paren t materials. The s o i l s produced have phys i ca l , chemical, and b i o l o g i c a l p r o p e r t i e s t h a t de r ive firom the r e l a t i v e i n f l uence of paren t m a t e r i a l s , c l imate , l i v i n g organisms, topograllhy , and t ime.

A s f o r e s t s o i l s mature, t h e i r p r o p e r t i e s become more d i s t i n c t and more s t a b l e . The h igh ly c h a r a c t c r i s t i . ~ p r o p e r t i e s of Eorest s o i l s a r e dependent on t he presence of o rganic ~n l a t e r i a l on t h e s o i l su r f ace , t h e continuous o r p e r i o d i c add i t i ons of f r e s h ma te r i a l a s l i t t e r f a l l , and decaying woody ma te r i a l s . To t h e ex t en t t h a t it changes t h e r a t e of depos i t ion and decay of organic ma te r i a l depos i ted on t h e f o r e s t f l o o r , u t i l i z a t i o n may a l t e r t h e r a t e o r d i r e c t i o n of s o i l formation processes.

Whon organic ma te r i a l s a r e removed from a s i t e , such a s by logging, t h e r e l e a s e of unava i lab le n u t r i e n t s i n s o i l i s acce l e r a t ed (Borman and o t h e r s 1968). Likcns and o t h e r s 61969) demonstrated t h a t severe t rea tments of watersheds r e s u l t i n t h e i nc r ea se of n i t r a t e s and o t h e r mineral anions i n streamflow. European ex e r i ence has a l s o shown t h a t continuous l i t t o r and r e s idue removal i n h i b i t s growthP (Krause and Har te l 1935; Waidemann 1934, 1935; Alber t 1924). Close u t i l i z a t i o n of r e s idues has no t been widespread i n North America. tiowever, i n c e r t a i n l o b l o l l y p ine s tands i n ea s t e rn Maryland where 1-eaf l i t t e r had been r e g u l a r l y removed a s a bedding ma te r i a l f o r animals , Cope (19251 rcported a decrease of both he ight growth and volume. I n Quebec, Weetman and Webbar (1972j i nd i ca t ed t h a t on d ry s i t e s with low organic r e se rves , whole t r e e logging may dep l e t e n u t r i e n t s dur ing the second r o t a t i o n . Zinke and Colwell (1972) agree , and i n d i c a t e t h a t on ly stems and t runks should be removed dur ing ha rves t i ng . Fol iage, branches, and r o o t s should be l e f t as an organic resource .

Decaying woody ma te r i a l s con t r i bu t e t o t h e d e s i r a b l e p r o p e r t i e s of f o r e s t s o i l s and p e r s i s t f o r decades (McFce and Stone 1966). Fur ther , decaying woody ma te r i a l cons t i t lu tes t h e primary food base f o r a myriad of decay fungi t h a t may se rve a s n u t r i - en t s i nks t h a t reduce Losses from leaching of mineral n u t r i e n t s (Stark 1972). Thus, removal of t h e organic ma te r i a l may rcduce s o i l n u t r i e n t s t h a t r e q u i r e many decades t o r e c o n s t i t u t e , n a t u r a l l y o r o therwise ,

Even on favorab le s i t e s wi th s t a b l e s o i l s , changes i n organic r e sou rce s could have shor t - te rm e f f e c t s . For i n s t ance , any t reatment t h a t a l t e r s t h e r e l a t i v e a b i l i t y o f c o n i f e r s and brush spec i e s t o compete dur ing recovery s t ages could a f f e c t e a r l y success iona l development. Whether o r n o t such changes are d e s i r a b l e depends on management o b j e c t i v e s .

C l ea rcu t t i ng has g r e a t impact on r e s idue reduc t ion and s o i l d i s turbance . Clear- c u t t i n g temporari ly i n t e r r u p t s t h e cyc l ing of n u t r i e n t s between t h e p l a n t s and t h e s o i l arid it inc rea se s both s o i l temperatures (Day and Duffy 1963) and moisture (Bethlahmy 1962). Those changes favor decomposition of r e s idues and o t h e r processes t h a t i nc r ea se n u t r i e n t r e l e a s e t o t h e s o i l (Likens and o t h e r s 1969). Removal of t h e p lant cover a l s o i n t e r r u p t s evapot ransp i ra t ion and i nc rea se s water movement through t h e s o i l system

' l e sn ik5 Prgce. 1933. Damages caused by removal of f o r e s t l i t t e r . Vol. 1 2 : 137-146,

(Bethlnlimy 1962; Co l t t l a rp 1960) , increasing t h c p r o l ~ a b i l i t y of n u t r i e n t l o s s through leaching. Ilowcvcr, nlost f o r e s t s o i l s have a h igh c a p a c i t y t o r e t a i n n u t r i e n t s a g a i n s t ground and s u r f a c e r u n o f f ( F r e d r i c k s o n 1972; Cole and Gesse l 1 9 4 5 ) . I f r e v c g e t a t i o n o c c u r s r a p i d l y , w i t h i n a few y e a r s systcrns c h a r a c t e r i s t i c of t h e a r e a a r e r e e s t a b l i s h e d (Marks and Rormari 1972) .

Thc amount and d i s t r i b u t i o n o f s l a s h and t h e e x t e n t o f d i s t u r b a n c e t o t h e f o r e s t f l o o r and s o i l sys tems a r e s t r o n g l y i n f l u c n c c d by t h e method of c l e a r c u t t i n g ( B e l l and o t -he r s 1974) . Under sonre c i r c u m s t a n c e s , even e x t e n s i v e t h i n n i n g can c a u s e s i t e damage ('l'amrn 1969) . S i m i l a r l y , whole t r e e u t i l i z a t i o n rnay cause smal l l o s s e s o f n u t r i e n t s t h a t cou ld b c s i g n i f i c a n t a f t e r many h a r v e s t removals (Boyle and o t h e r s 1973; White 7 4 'l'he n e e d l e s and t w i g s c o n t a i n a. l a r g c p r o p o r t i o n of t h e n u t r i e n t s o f t h e t r e e (Boyle and o t h e r s 1973; Keays 1970, 1971) . Thus, t h e combined e f f c c t o f c l e a r c u t t i n g , logg ing method, and i . n t c n s i v e o r whole t r c c u t i l i z a t i o n may have s j . g n i f i c a n t impacts on s i t c q u a l i t y . 'I'hese impac t s and t h e a b i l i t y o f s p e c i f i c s i t c s t o w i t h s t a n d them rernnin t o 11c de te rmined .

A 1 her ' t , A . 1924. Die aussc l l l aggc l~ende bedeuturrg d e s w a s s e r h a u s l ~ a l t e s f u r d i e e r t r a g s l i e s t u n g e n

u n s c r c r d i l u v i a l e n samdc, e r m i t t e l t du rch bodenuntcrsuchungen i n den1 wa ldgeb ie t d e r s t n n d e s h e r r s c h a f t l i c b e r o s c . N . - I,. Zei t s c h r . 1:;orest.-u. .Jagd. 56: 193-202.

Rcl l . , M . A . M., J . bl . Hccke t t , and W . F. I-lubbard. 1974. Impact o f h a r v e s t i n g on f o r e s t eriviroriments and r e s o u r c e s . Pac. For . Res. Cen. ,

Can. For . S e r v . , V i c t o r i a , B . C . Rethlnhmy, N .

1962. F i r s t y e a r e f f e c t s of t i rnbcr removal on s o i l m o i s t u r e . Bu l l . I n t . Assoc. S c i . Hydl-01. 7 : 31 -38.

Bor.rn:irr, F . t i . , I;. E . I , i kens , U . W . r i s h e r , a n d R . S. P i e r c e . 1.965. N u t r i e n t l o s s accelerated hy c l e a r c u t t i n g o f a f o r e s t sys tem. Sc ience 159:

882-884. Hoylc, J . K . , J . J . P h i l l i p s , and A . R . E k .

7 3 . "Whole t r e e " h a r v e s t i n g : n u t r i e n t budget e v a l u a t i o n . J . For . 71:760-762. Co le , C). W . , and S . F). Gessel .

1965. Movement: of e l ements th rough a f o r e s t s o i l a s i n f l u e n c e d by t r e e removal and f e r t i l i z e r a d d i t i o n s . I n : F o r e s t s o i l r c l a t i o n s h i p s :i,n North America., p . 95-104. C . T . Youngberg, c d . , Oreg. S t a t e Unjv. P r e s s , C o r v a l l i s .

Colt:harbl), G. D . 1960. Some e f f e c t s of a commercia l - typc c l c a r c u t on soj.1 and wa te r r e l a t i o n s on a

s n ~ a l l . wooded wa te r shed . Diss. A b s t r . 21: 12. C:ope , J . A .

1925. L o b l o l l y p i n e i n Maryland. IJniv. Maryland S t a t e Dep. For . 2nd c d . , 96 p . Day, K . . I . , and J . B . Duffy.

1963. Regenernt, ion a f t e r logg ing i n t h e Crowsnest F o r e s t . Can. Dep. For . Publ . 1007, 31 p .

F r c d r i c k s o n , R . C. 1972. N u t r i e n t budget. o f a D o u g l a s - f i r on an exper imen ta l wa te r shed i n wcs te rn

Oregon. I n : P r o c . , Research on c o n i f e r o u s f o r e s t ccosystems--a symposium, p . 115-131, . J . F. F r a n k l i n , L . J . Ucmster, and R . H . Waring, e d s . Pac.. Northwest For . and Range Exp. S t n . , P o r t l a n d , Oreg.

Kcays, . J . L . 1970, 1971. Comple te - t r ee u t i l i z a t i o n : an a n a l y s i s of t h e l i t e r a t u r e i n f i v e p a r t s .

For . Prod. Lab . , Can. For . S e r v . , Vancouver, B . C . Krauss , G . , and F. H a r t e l .

1935. Zur walsboden - un te r suchngen . S o i l Res. 4:207-216. L ikcns , C . E . , F. H . Borman, and N . M . .Johnson.

1969. N i t r i f i c a t i o n importance t o n u t r i e n t l o s s e s from a c u t o v e r f o r e s t e d ecosystem. S c i e n c e 163:1205-1206.

Marks, P . Id., and F . H . Bor~nan. 1972. Revegetation fol lowing f o r e s t c u t t i n g : mechanisms f o r r e t u r n t o s t e a d y - s t a t e

n u t r i e n t cyc l ing . Science 176:914-915. McFee, W . W . , and E . L . Stone. 1966. The p e r s i s t e n c e o f decaying wood i n t h e humus l aye r of nor thern f o r e s t s . Proc.

S o i l S c i . Soc. A m . 30:513-516. S t a rk , N .

1972. Nu t r i en t cyc l i ng pathways and l i t t e r fungi . Bioscience 22:355-360. Tamm, C . 0 .

1969. S i t e dalnage by th inn ing due t o removal of organic mat tc r and p l a n t n u t r i e n t s . Dep. P lan t Ecol . For . S o i l s Publ. 78. 6 p . Royal Co l l . Fo r . , Stockholm.

yeetman, G . F . , and B . Webbar. 1972. 'T'he in f luence of wood harves t ing on t he n u t r i e n t s t a t u s o f two spruce s t ands .

Can. J . Res. 2:351. We i dmann , E .

1934. Uber d i e beziehangen des f o r s t l i c h e n sandor tes zu dem wachstum und dem w i r t s c h a f t s e r f o l g i m walde. Deut. Forsch. 2 1 :5-106.

Weidmann, E . 1935. Die e rgebnisse 40- jahr igcr v o r r a t s p f l e g e i n den preussiscl len f o r s t l i c h e r ~

versuchsflachen. Fors ta rch ive 11 : 65-108. White, E . 11.

1974. Whole t r e e harves t ing dep l e t e s s o i l n u t r i e n t s . Can. J . For. Kcs. 4:530-535. Zinkc, P . J . , and W. L . Colwell, Jr.

1972. Nut r ien t cyc l ing i n f o r e s t s . Proc. 1 s t Annu. C a l i f . P l an t ancl S o i l Conf., p . 51. (Sacramento, C a l i f . , 1972).

The main eco log i ca l e f f e c t of f i r e i s t o compress t h e ox ida t i ve a c t i v i t i e s of decay i n t o a very s h o r t time span. Most of t h e products o f e i t h e r b i o l o g i c a l o r hea t ox ida t ion a r e s i m i l a r i n chemical composition and i n q u a n t i t y (Hall 1972; Komarek 1970). With t h e except ion o f charcoa l , f i r e r e s idues a r e even tua l l y consumed by microbes as they would be i n b i o l o g i c a l decomposition. Charcoal r e s i d u e s a r e not only h igh ly r e s i s t a n t t o decomposition, t hey a l s o change t h e s o i l environment (Tyron 1948). Charcoal has been known t o p e r s i s t i n s o i l s f o r s eve ra l hundred years (Soper 1919).

. Thus, f i r e o r t h e lack of f i r e can have longstanding e f f e c t s on f o r e s t s o i l s .

F i r e s i n heavy f u e l s can s t e r i l i z e and change t h e b i o l o g i c a l , physica1,and chemical c h a r a c t e r i s t i c s of t h e upper s o i l horizons (Neal and o t h e r s 1965). Changes inc lude i nc rea s ing s o i l pH from 0 .3 t o 1 . 2 u n i t s widening t h e C : N r a t i o s o f s o i l o rganic ma t t e r , and reducing s o i l pore s i z e , a e r a t i o n , water-holding capac i t y (Kalston and Hatchel 1971; Neal and o t h e r s 1965), and water i n f i l t r a t i o n r a t e s (DeBano and Rice 1973). These changes u s u a l l y reduce microbial a c t i v i t i e s f o r varying pe r iods a f t e r t h e burn (Ahlgren and Ahlgren 1965; Wright and Tar ran t 1957). Reinoculat ion occurs from windblown spores o r o t h e r d e b r i s , and through invas ion from subsur face l a y e r s . Because burning change-s t.he so i l ' * s phys i ca l and chemical p r o p e r t i e s and e l im ina t e s many.potential.competitors, microbes adapted t o t h e changed s o i l enuironment have an advantage i n t h e r eco lon i za t i on process .

When moisture i s s u f f i c i e n t , t h e microbia l populat ion i s quick ly r e c o n s t i t u t e d , p r imar i l y from organisms adapted t o t h e new s o i l environment. The r e c o n s t i t u t e d popula t ion may be g r e a t e r and more a c t i v e than t h e o r i g i n a l one (Ahlgren and Ahlgren 1965), perhaps because of t h e l a r g e q u a n t i t y of mineral n u t r i e n t s r e l ea sed from t h e ash and because of o t h e r s h i f t s i n s o i l chemistry. For example, spo re s o f t h e r o o t pathogen Rhiz ina undulata Fr. germinate only a f t e r exposure t o e l eva t ed temperatures (Gremmen 1971). I t thereby ga in s access t o s o i l s t h a t a r e r i c h i n n u t r i e n t s , t h a t are l i k e l y f o conta in young and s u s c e p t i b l e con i f e r r o o t s , t h a t harbor few competing -

'organisms, and t h a t have low concent ra t ions of h e a t - l a b i l e growth i n h i b i t o r s (Watson and Ford 1972). Increases i n o t h e r p o t e n t i a l c o n i f e r r oo t pathogens have a l s o been repor ted a f t e r burning (Wright and Bollen 1961; Tar ran t 1956).

Temporary r e d u c t i o n s i n c o n i f e r - f u n g a l mycor rh iza l c o n s o c i a t i o n s have been found a f t e r burn ing (Wright 1971, 1958; Mikola and o t h e r s 1964; Wright and T a r r a n t 1957; T a r r a n t 1956) . Exper imental h e a t s t e r i l i z a t i o n of s o i l s stimulates t h e p r o d u c t i o n o f b i o l o g i c a l l y d e g r a d a b l e p h y t o t o x i n s (Rovira and Howen 1966) . C r e a t i o n o f such t o x i n s by s u r f a c e f i r c s and t h e i r subsequen t m i c r o b i o l o g i c a l breakdown may r e p r e s e n t impor tan t processes in f o r e s t s o i l s . b lycorrhizal f u n g i have been r e p o r t e d t o n e u t r a l i z e t h e . e f f e c t s o f such t o x i n s (Zak 19711. These changcs w i l l v a r y i n degree and d u q a t i o n , depending on t h e i n t e n s i t y o f t h e burn, s o i l t y p e , c l i m a t i c c h a r a c t e r i s t i c s , and t h e t y p e of v e g e t a t i o n t h a t becomes e s t a b l i s h e d a f t e r t h e burn .

Most s o i l n i t r o g e n (N) i s p r e s e n t i n t h e form o f n i t r o g e n o u s compounds con ta ined i n l e a v e s , smal l t w i g s , and o t h e r m a t e r i a l s o f t h e decay ing d u f f . Both l a b o r a t o r y (Knight 1966) and f i e l d s t u d i e s (Metz and o t h e r s 1961) have e s t a b l i s h e d t h a t s u b s t a n - t i a l n e t l o s s e s o f N o c c u r clue t o b u r n i n g . However, N and o t h e r minera l n u t r i e n t s i n s p e c i f i c res ic lue m a t e r i a l s 'can i n c r e a s e . The apparen t - a c t i v i t y of micro-organisms a c t i v e i n t h e N c y c l e i s i n c r e a s e d in pos tburn s o i l s ( Jo rgensen and Wells 1971; Neal and o t h e r s 1965) . Although n e t l o s s e s o f N o c c u r th rough v o l a t i l i z a t i o n and l e a c h i n g , i n c r e a s e s i n N- f ix ing orga.nisms o f many s o i l s may r e c o n s t i t u t e a p o r t i o n o f t h i s l o s s (Metz and o t h c r s 1961; Wells 1971) . Thus, t h e e x t e n t o f N f i x a t i o n and subsequent s o i i N t r a n s f o r m a t i o n s o c c u r r i n ~ a f t e r f i r e a r e c r i t i c a l f a c t o r s i n e v a l u a t i n g t h e long- term c f f e c t s on s i t c q u a l i t y .

Although E i r c can have many d e t r i m e n t a l e f f e c t s on t h e s o i l environment , f r e q u e n t burn ing on s t a b l e s o i l s docs n o t s i g n i f i c a n t l y damage s i t e q u a l i t y (Stone 1971; Wells 1971) . F u r t h e r , most f o r e s t e d ecosystems i n North America have evolved under t h e d i r e c t i n f l u e n c e o f f i r e (I-iabeck and Mutch 1973; Komarek 1962; Ahlgren and Ahlgren 1960) . I n n o r t h t empera te f o r e s t s ene rgy i s s t o r e d a t r a t e s t h a t exceed n a t u r a l u t i l % - z a t i o n (Olsen 1963) . T h e r e f o r e , E i r c o r s i l v i c u l t u r a l a l t e r n a t i v e s may h e r e q u i r e d t o m a i n t a i n s i t e q u a l i t y by f r e e i n g energy and n u t r i e n t s bound i n f o r e s t r e s i d u e s . Not y e t clef ined a r c t h e l i m i t s and c o n d i t i o n s under which t h e r e j u v e n a t i v e (Lyons and Pcnge l ly 1970: Kamarek 1962) and p r o t e c t i v e s i l v i c u l t u r a l b e n e f i t s (Davis 1959) provided by f i r e exceed i t s p o t e r l t i a l f o r damage.

Li terature Cited

Ahlgren, .I. T . , and C. E . Ahlgren. 1960. E c o l o g i c a l e f f e c t s o f f o r e s t f i r e s . Rot. Rev. 26:483-533.

Ahlgren, J . K., and C . E . Ahlgren. 1965. I - f f cc t s o f p r e s c r i b e d b u r n i n g on s o i l microorganisms i n a Minnesota j ack p i n e

f o r e s t . Ecology 46:304-310. Davis , K . P.

1959. I :orest f i r e : c o n t r o l and u s e . 584 p. McGraw-llill, New York. DeBano, L . T . , and R . M . R ice .

1973. W a t e r - r e p e l l e n t s o i l s : t h e i r i m p l i c a t i o n s i n f o r e s t r y . J . For . 71:200-223. Gremmen , J .

1971. Rhizinn unduZata: a rev iew of r e s e a r c h i n t h e Ne the r l ands . Eur. J . For . Path . 1 : l - 6 .

Haheck, J . R . , and R . W . Mutch. 1973. F i r e dependent f o r e s t s i n t h e n o r t h e r n Rocky Mountains. Qua te rna ry Res.

3:408-424. H a l l , A. .J.

t

1972. F o r e s t f u e l s , p r e s c r i b e d f i r e , and a i r q u a l i t y . USDA For . S e r v . , Pac. North- west For . and Range Exp. S t n . , 44 p .

J o r g e n s e n , R . , J r . , and C . G . Wel ls . 1971. Apparent n i t r o g e n f i x a t i o n i n s o i l i n f l u e n c e d by p r e s c r i b e d burn ing . Proc.

S o i l S c i . SOC. Am. 35:806-810. Knight , H.

1966. Loss of n i t r o g e n from t h e f o r e s t f l o o r by burn ing . For . Chron. 42:149-152.

Komarek, E . V . 1962. F j r e eco logy . Proc. 'I 'all Timbers F i r e Ecol . Conf. 1:QS-107.

Lyons, J . I,. , and W . L . Penge l ly . 1970. Commentary on t h e n a t u r a l r o l e o f f i r e i n t h c Intermountain wcs t . I n t e r m t . F i r e

Rcs. Counc. P r o c . , Missou la , Mont. p . 81-84. Metz, L . J . , F. L o t t i , and R . A . Klawit t -er .

1961. Some e f f e c t s o f p r e s c r i b e d burn ing on c o a s t a l p l a i n f o r e s t s o i l . U.S. Dep. Agr ic . For . S e r v . , S o u t h e a s t . For . Exp. S t n . Pap. 133, 10 p .

Mikola, P . , 0 . Laiho, J . Er icka inen , and K. Kuvaja. ,1964. The e f f e c t o f s l a s h burn ing on t h e commencement o f mycor rh iza l a s s o c i a t i o n .

Acta . For . Fenn. 7 7 : l - 1 1 . Neal, J. L . , E . Wright, and W. B . Bo l len .

1965. Burning D o u g l a s - f i r s l a s h . P h y s i c a l , chcrni.ca1, and m i c r o b i a l e f f e c t s i n s o i l . Oreg. S t a t e Univ. For. Res. Lab. Kes. Pap. 1 , 32 p .

Olsen, J . S . 1963. Energy s t o r a g e and t h e ba lance o f p roducers and decomposers i n e c o l o g i c a l

sys tems . Ecology 44:322-331. Kals ton, G . W., and G . E . I l a t c h e l l .

1971. E f f e c t s o f p r e s c r i b e d burning on p h y s i c a l p r o p i e r t i e s o f s o i l . Proc. P r e s c r i b e d Burning Symp. , p . 68-84. 1ISI)A For . S e r v . , S o u t h e a s t . For. Exp. S t n .

Kovira, A . D., and G . D. Bowen. 1966. The e f f e c t s o f microorganisms upon p l a n t growth. 11. Detox ica t ion of h e a t -

s t e r i l i l z e d s o i l s by fung i and b a c t e r i a . P l a n t and Soi.1 25:129-142. Soper , E . K .

1919. The p e a t d e p o s i t s o f Minnesota. Minn. Geol. Surv . Bu l l . 16. Stone, E . L .

1971. E f f e c t s o f prescr i .bed burn ing on longLterm p r o d u c t i v i t y o f c o a s t a l p l a i n s o i l s . Proc. I- ' rescribed Burning Symp., 1). 115-127. I J . S . Dep. Agr ic . For. S e r v . S o u t h e a s t . For . Exp. S t n .

T a r r a n t , R . F. 1956. E f f e c t s o f s l a s h burn ing on some s o i l s o f t h e Douglas - f i r r e g i o n . Proc. S o i l

S c i . SOC. Am. 20:408-411. Tyron, E . J .

1948. E f f e c t s of c h a r c o a l on c e r t a i n p h y s i c a l , chemical , and b i o l o g i c a l p r o p e r t i e s o f Edres t s o i l s . Ecol . Monogr. 18:82-115.

Watson, A. G . , and E . J . Ford. 1972. S o i l f u n g i s t a s i s - - a r e a p p r a i s a l , Annu. Kev. Phytopath . 9:327-.348.

Wells, C... G . 1971. ' E f f e c t s o f p r e s c r i b e d burning on s o i l chemical p r o p e r t i e s and n u t r i e n t a v a i l a -

b i l i t y . P roc . P r e s c r i b e d Burning Symp., p . 86-97. U.S. Dep. A g r i c . , For . S e r v . , S o u t h e a s t For . Exp. S t n .

Wright, E . 1958. Occurrence o f mycorrhizac a f t e r logg ing and s l a s h burn ing i n t h e Douglas - f i r

f o r e s t t y p e . U.S. Dep. A g r i c . , For . S e r v . , Pac. Northwast For . and Range Exp. S t n . Pap. 160, 7 p .

Wright, E . 1971. Mycorrhizae on ponderosa p i n e s e e d l i n g s . Oreg. S t a t e Univ. B u l l . 13, 36 p .

Wright, E . , and W . B . Bol len . I 1961. M i c r o f l o r a o f D o u g l a s - f i r s o i l . Ecology 42:825-828.

Wright, E . , and R. F. T a r r a n t . - 1957. Microb io log ica l so i , l p r o p e r t i e s a f t e r logg ing and s l a s h burn ing . U.S. Dep.

Agr5c.,For S e r v . , Pac. Northwest For . and Range Exp. S t n . Pap. 157, 5 p. Zak, B.

1971. p e t o x i c a t i o n o f a u t o c l a v e d s o i l by a mycor rh iza l fungus. USDA For. Serv. Res. . ' Note PNW-159, 4 p . Pac. Northwest For . and Range Exp. Stn., P o r t l a n d , Oreg.

- RELATIONSHIP OF UTlLlZATlON INTENSITY AND FIRE TO MICROBIAL ECOLOGY

Thc major m i c r o b i a l f u n c t i o n s i n a f o r e s t ecosystem a r e c a r r i e d ou t i n t h e s o i l envixonmcnt. The ~ u r f a c e l a y e r s o f a f o r e s t s o i l may c o n t a i n 10 t o 100 m i l l i o n b a c t e r i a and I t o 100 thousand fungi p e r gram (0.035 0 2 ) . The m i c r o b i a l mass i n t h e t o p 6 inches (15 .2 cm) o f a n a c r e o f f e r t i l e a g r i c u l t u r a l s o i l has beer) es t i rnatcd a t 1,000 l b (450 k g ) of bacterial and 2,000 l h (900 kg) of funga l biomass, on a d r y weight h a s i s (Bol len 1959) . S o i l , l i t t e r , and woody r e s j d u c , l a r g e l y i n the form of c e l l u l o s e and l i g n i n , c o n s t i t u t e t h e energy base f o r t h i s i n t e n s e l y a c t i v e component of a f o r e s t . Thc mineral n u t r i e n t s r e q u l r e d t o m a i n t a i n a f o r e s t ecosystem a r e l a r g e l y d e r i v e d from such r e s i d u e and t h e m i c r o b i a l a c t i v i t y it s u p p o r t s .

P l a n t nutrients a r c d e r i v e d d i r e c t l y from t h e atmosphere o r s o i l p a r e n t m a t e r i a l s , rnainly th rough r n i c r n b i a l metabolism. 'The a c c u n ~ u l a t i o n o f o r g a n i c m a t e r i a l s i n o r on f o r e s t s o i l s p r o v i d c s n o t o n l y t h e energy source f o r mic rob ia l growth, b u t a l s o a r e s e r - v o i r f o r a v a i l a l j l c n u t r i e n t s . Thus, a f o r c s t e d ecosystem i c c h a r a c t e r i z e d by a l a r g e , h i g h l y e f f i c i e n t , i n t e r n a l c i r c u l a t i o n system t h a t t r a n s f e r s minera l n u t r i e n t s between t h e p l a n t cover and t h e s o i l . Prodrrction of l a r g e q u a n t i ~ i e s o f biomass from f o r e s t s o i l s i s t h e r e s u l t o f t h i s system (Oviiigton 1962) .

Ilow f o r e s t r e s i d u e s contribute t o t h e s o i l r e s o u r c e , through n a t u r a l decay o r p r e - s c r i b e d f i r e , must bc unders tood and managed if extreme changcs in s o i l p r o p e r t i e s a r e t o be avo ided . The s o i l i s a dynamic system t h a t i s main ta ined by an u n s t a b l e e q u i l - i b r j uni o f p h y s i c a l , chemical, and h i o l o g i c a l p r o c e s s e s . Residue e f f e c t s a r e mediated p r i m a r i l y through changes i n s o i l pa ramete r s , e . g . , t empera tu re , m o i s t u r e , a e r a t i o n , a c l d i t y , n u t r i e n t and energy supp ly , and a v a i l a b l e b i o t a (Bol len 1 9 7 4 ) . I t i s a p p r o p r i - a t e t o examine i n d e t a i l how c l o s e u t i l i z a t i o n o r burn ing of r e s i d u e s a f f e c t s t h e s i x f a c t o r s d i r e c t l y invo lved i n t h i s d e l i c a t e e q u i l i b r i u m .

Temperature

kach micro-organism has an o ~ ~ t i m u m tempera tu re bo th f o r growth and f o r each of Inany metabolic p r o c e s s e s t h a t c o n t r i b u t e t o i t s e c o l o g i c a l f u n c t i o n s . Outs ide t h e s e tempera- t u r c opt ima, growth o r f u n c t i o n c e a s e s o r changes (Raney 1965) . Within any given f o r e s t , micro-organism p o p u l a t i o n s a r e comprised p r i m a r i l y o f t h o s e we l l adapted t o t h c prevail- i n g t empera tu re regime. Radical changes i n s o i l t empera tu res , such a s t h o s e r e s u l t i n g from c l e a r c u t t i n g , p a r t i c u l a r l y when a s s o c i a t e d w i t h r c s i d u e removal o r burn ing , can cngcnder r a d i c a l changcs i n mic rob ia l populations ( P a r r 1968) . 'I'hese f l u c t u a t i o n s a r e most p r o n o ~ ~ n c e d i n t h e uppermost s o i l l a y c r s whcre t empera tu res a r c s t r o n g l y i n f l u e n c e d by r a d i a t i o n exchange o r s h o r t - t e r m c f f e c t s of burn ing . The s u c c c s s of t h e subsequent f o r e s t depends upon t h i s l a y e r .

Moisture

'I'lie optimum m o i s t u r e c o n t e n t of f o r e s t s o i l s f o r m i c r o b i a l a c t i v i t y i s n e a r SO p e r c e n t o f i t s wate r -ho ld ing c a p a c i t y (Bol lcn 1974) . A s m o i s t u r e d e c r e a s e s below t h a t l c v c l , growth and mctabolism of t h e s o i l m i c r o f l o r a a r e reduced . When s o i l becomes a i r - d r y , both p r o c e s s e s c s s e x ~ t i a l l y c e a s e . On t h c o t h e r hand, a s m o i s t u r e i n c r e a s e s , t h e a i r supp ly i s reduced ( d i s p l a c e d ) . A s a i r d i sp lacement i n c r e a s e s bcyond 50 p c r c c n t , m i c r o b i a l growth and lnetabolism a r e a g a i n reduced, u n t i l a l l a e r o b i c p r o c e s s e s come t o a n e a r s t a n d s t i l l ( S t o l z y and Van Gundy 1968) . Treatment o f f o r e s t r e s i d u e s profoundly

a f f e c t s bu f f e r i ng of s o i l moisture extremes, p a r t i c u l a r l y t he r a p i d i t y of drying of upper s o i l l a y e r s dur ing t h e summer (Day 196.7; Day and Duffy 1963). Drying r a t e i s a l s o s t rong ly a f f e c t e d by c l ima te and s i t e . For example, r e s idues i n wet spo t s ren~ain s a t u r a t e d f o r most of t h e year and decompose very slowly; and s o i l moistrrre l o s s i n t h e summer w i l l be morc c r i t i c a l t o t h e microbial a c t i v i t y of a southwest-facing s lopc than of a no r th - f ac ing s lope .

Aeration Gaseous oxygen (02 ) , carbon d ioxide (C02), and n i t rogen IN2) a r c components of

t h e atmosphere v i t a l t o microbial metabolism. Oxygen i q r equ i r ed f o r most processes t h a t decompose carbon compounds, t o produce energy f o r growth. Most micro-organisms r e q u i r e a t l e a s t a t r a c e of C02 t o i n i t i a t e growth. This conlpnund i s a l s o an end product o f energy- rc la tcd metabolism. Excessive amounts of C02 can r e t a r d microbial a c t i v i t y (Wimpenny 1969). Cer ta in N-fixing organisms incorpora te gaseous n i t rogen d i r e c t l y i n t o c e l l u l a r c o n s t i t u e n t s . Thus, movement of atmospheric gases i n t o t h c s o i l must be adequate f o r s a t i s f a c t o r y exchange. Any r e s idue t rea tments t h a t impede v e n t i l a t i o n w i l l p r ed i c t ab ly reduce microbia l a c t i v i t y j)y r e s t r i c t i n g O2 suppl ies o r by pe rmi t t i ng gases t o reach t o x i c concent ra t ions (Clark and Kemper 1967). Treatments t h a t encouragc compaction o r t h e formation of: impermeable s o i l l a y e r s can be exceed- ing ly de t r imen ta l . Accumulation of o rganic s o i l r e s idue docs no t adverse ly a f f e c t t he gas exchange process .

Hydrogen Ion Concentration [pH] Concentrat ion of hydrogen ions i n t h c s o i l s t r ong ly a f f e c t s microbial a c t i v i t y .

The observed e f f e c t s of s o i l a c i d i t y on micro-organisms may be a t t r i b u t e d t o (1) changes i n organic mat te r a v a i l a b i l i t y ; ( 2 ) pH-caused n u t r i e n t d e f i c i e n c i e s ; ( 3 ) t o x i c e f f e c t s of hydrogen or aluminum ions ; o r ( 4 ) a combination of t h e above f a c t o r s (Jurgensen 1973). Micro-organisms d i f f e r i n t h e i r degree of t o l e r ance t o ptl change. Some t h r i v c on ly i n a very narrow range and o t h e r s t o l e r a t e wide extremes (Davey and Danielson 1968) .

Radical changes i n s o i l pI1 r e s u l t from t h e e f f e c t s of r e s idue management, e s p e c i a l l y f i r e (Wells 1971). The presence of ash o r charcoal i nc r ea se s b a s i c i t y . When such a change occurs , organisms with e i t h e r a wide pH range o r a narrow pll range .

s u i t a b l e t o t h e new regime r e p l a c e t h e prev ious ly e x i s t i n g b i o t a . This e f f e c t i s p a r t i c u l a r l y pronounced a s s o i l pH nears n e u t r a l i t y and t he acid-base a c t i v i t i e s approach balanced l e v e l s . Thus, t h e microbio logica l a c t i v i t i e s of weakly ac id f o r e s t s o i l s are h ighly s u s c e p t i b l e t o d r a s t i c change.

Fores t s o i l s a r e t y p i c a l l y ac id . Leaching i nc rea se s a c i d i t y through l o s s of mineral elements. The ex t en t and r a t e of n u t r i e n t l o s s is a func t ion of ca t i on exchange capac i t y i n a r e a s of s u f f i c i e n t r a i n f a l l . P a r t i a l l y decomposed r e s idues provide an important source of exchange s i t e s , p a r t i c u l a r l y in coarse- tex tured s o i l s .

Nutrient and Energy Supply Because most s o i l organisms a r e he t e ro t roph i c , they r e q u i r e a source of energy i n

t h e form of carbon compounds. The e f f e c t of f o r e s t l i t t e r and woody r e s idues on s o i l microbial a c t i v i t y depends on t h e type of ma te r i a l , i t s n u t r i e n t conten t , and on t h e i n i t i a l f e r t i l i t y of t h e s o i l (Davey and Danielson 1968; Waksman and Tcnney 1928). A l ack of s u i t a b l e organic s u b s t r a t e s normally l i m i t s t h e growth of he t e ro t roph i c micro-orghnisms i n s o i l (Gray and Williams 1971).

Although an abundance of carbon (C] compounds i s d e s i r a b l e , excess ive amounts can produce marked expansion of microbia l popula t ions and excess ive competi t ion f o r mineral n u t r i e n t s . S o i l micro-organisms r e q u i r e many of t h e same n u t r i e n t elements a s do

h l g h e r p l a n t s and c a n , d t t l rnes , p r o v l d c i n t e n s e compet i t ior l t o p l a n t s f o r t h e s e nutrients. Because of t h e low N s u p p l y i n most woody r e s i d u e s and o t h e r s i m i l a r m a t e r i a l s , co rnpc t l t l on g e n e r a l l y r e s u l t s in s e v e r e N d e f i c i e n c i e s tcrmed "immohiliza- t l o n " ( Z o c t t l 1965) . The inimobilized N i s used i n t h e p r o d u c t i o n o f m i c r o b i a l c e l l s and , a l t h o u g h ~t i s n o t l o 5 t t o t h e ~ i t e , i t i s u n a v a i l a b l e t o h i g h e r p l a n t s u n t i l d e a t h and d e c o ~ n p o s i t l o n o f t h e mic robes exceed t h e i r p o p u l a t i o n growth (Mulder and

*

o t h e r s 1969) . For an optirnum r a t e o f t lccomposi t ion , t h e C t o N r a t i o shou ld Approxi- mate 2 5 : l . I n decay-resistant woody r e s ~ d u e s , t h c r a t l o 1s much widcr ( approx ima te ly 400: I ) , b u t much oE t h l s C i s I n t h e form ~f 1 i g n i n s , which b reak down s l o w l y ( A l l i s o n 2nd o t l l e r s 1963) . I l lus, l l g r i l c o l o u s m a t e r i a l 5 e x c r t low b u t long- t e rm N demands. Ilumus, and t h e r e f o r e mo5t s o i l s , ~ h o u l c l have a narrow C-to-N r a t i o ( approx ima te ly 2 0 : l )

Ilumus i s mos t ly made up of h i g h l y decomposed m a t e r i a l . l 'he m a t e r i a l t h a t i s n o t dccolnposed j s 11igl1 l y r e s j . s t a n t t o f u r t h e r breakdown. Humus a l s o c o n t a i n s a l a r g e quanti1.y o f t h e a v a i l a b l e c a t i o n exchange c a p a c i t y f o r n u t r i e n t s t o r a g e . M i n e r a l i z e d s o i l N ih e a s i l y y e l e a s e d from t h e s e c a t i o n exchange s i t e s and i s r e a d i l y a v a i l a b l e f o r p l a n t o.r m i c r o b i a l growth. N d c f i c i c n c i c s in humus nornia l ly o c c u r o n l y when hi.gh C-to-N r a t i o , r c a d i l y dcconiposihle r e s i d u e s become i n c o r p o r a t e d . T h i s b e g i n s a r a p i d decay p r o c e s s t h a t q u i c k l y immo1)ilizes much of t h e s o i l N s u p p l i e s (Ba.rtholomew 1965) . On t h e o t h e r hand, r e s i d u e s t h a t remain on but n o t i n t h e s o i l may, th rough l o w decay, a c t u a l l y i r i c r e a s c N s u p ] - ~ l i c s t o t h e s o i l under t h e r i g h t cond i t . i ons .

Available Biota

S o i l org;inisrns compete f o r m i n e r a l n u t r i e n t s , food s u p p l i e s , and p o s s i b l y oxygen (Clark 196!)), wh-ich lead:; t o I ~ i g h l y r e f i n e d c o m p e t i t i v e mechan,i.sms a d a p t e d f o r spec ia l ' - i zed n i c h e s . Prot11rct.ion o f a n t i h i o t i c s , and p a r a s i t i s r ~ i , p r e d a t i o n , and symbios i s s e r v e a s examples. Cornpet.-itior~ so~rletimcs l i m i t s t h e dcvclopment of c e r t a i n s p e c i e s and lcacis t o s u c c e s s i o n s o f orj ianisms a s decomposi t ion p roceeds (Alcxander 1964) .

Frcrlllent 1 y , t h e n a t u r e o f t h c microhi a1 s u c c e s s ions i s d i c t a t e d by t h c p i o n e e r organisnis p r e s c n t when a food s o u r c e 1)ecomes a v a i l a b l e . P i o n e e r organisms a r e l a r g e l y c o r l t ~ o l l e d by t l ,e p r e v i o u s l y d e s c r i b e d p h y s i c a l and chemical p a r a m e t e r s t h a t govern macr 'ohahi. tat . P i o n e c r s p e c i c s may imposc permanent changes on t h e subsequen t sucoes - s j o n s o f micro , -organisms u n t i l a s p e c i f i c food s o u r c e i s exhaus ted (Shigo and E l l i s 1973) . l<es iducs arld r e s i d u c t r e a t m e n t s d i r e c t 1 y i n f l u e n c e t h e s u c c e s s i o n a l p a t t e r n s . 'l 'hus, t h e p i o n e e r orga1.1isrns p r e v a l e n t d u r i n g t h e season i n which t h e r e s i d u e s a r e j icnernted may c o n t r o l subsequcrit m i c r o b i a l ~ ~ o p u l a t i o n s .

A s i n d i c a t e d p r t , v i o u s l y , a v a i l a b l e m o i s t u r e , t e m p e r a t u r e , and amount and k ind of o r g a n i c substrate d i c t a t e t h e t y p e o f organisms a c t i v e i n t h e s o i l a t any g iven t ime . B i o t i c h i s t o r y can a l s o in f lue r l ce s o i l rn i c ro f lo rn . For example, p r e v i o u s a c t i v i t y of s o i l p a t h o g e r ~ s o r s tem decays may a f f e c t r e f o r e s t a t i o n . Rcs idues i n d i r e c t l y a f f e c t s o i l a c t i v i t y j u s t a s t h e y a f f c c t t h e e s t ab l i sh rncn t o f h i g h e r p l a n t s on t h e s i t e , e . g . , t h e e s t a h l i s h ~ n e n t o f Alnus or C'eanothus s p e c i e s f o l l o w i n g b u r n i n g p r o v i d e s h o s t - roo t s f o r c e r t a i n s y m b i o t i c organisms (Youngberg and IVollum 1 9 7 0 ) . S i rn i la . r ly , s p e c i f i c c o n i f e r s a r c h o s t s f o r c e r t a i n ectonrycor-rhi z a l f u n g i .

Thc s o o t s o f p i o n e e r i n g p l a n t s d i r e c t l y i n f l u e n c e t h c s o i 1 . 'I'he s o i l a r e a s u r r o u n d i n g t h e r o o t s o f h i g h c r p l a n t s , termed t h e r h i z o s p h e r e , i s c h a r a c t e r i z e d by '

v e r y i n t e n s e nlicl 'ohial a c t i v i t y . T h i s a c t i v i t y i s based on l e a k a g e o r s l o u g h i n g o f food m a t e r i a l s , such a s c e r t a i n s u g a r s and amino a c i d s , from t h e ro0 t . s (Rov i ra 1969; S l a n k i s and o t h e r s 1964) . 'The e x t e n t and . inf luence o f such r o o t sys t ems i n s o i l s a r e l i t t l e a p p r e c i a t e d . A s i n g l e r y e p l a n t grown i n 2 f t 3 (0 .06 m3) o f s o i l had 13 ,800 ,000 r o o t s w i t h a t o t a l l e n g t h o f 387 m i ((319.2 kmj, and 14 by l o 9 r o o t h a i r s w i t h a t o t a l l e n g t h o f 6 ,600 m i ( lO,( i lS km), and p rov idcd a t o t a l s u r f a c e a r e a o f 6 ,874 f t 2 (638.6 m2). The t o t a l e x t e r n a l s u r f a c e o f t h e s h o o t s and l e a v e s of t h i s p l a n t p rov ided o n l y 51.38 f t 2 (4 .72 m7.) o f s u r f a c e a r e a (Ditmer 1937) . A 55-yea r -o ld D o u g l a s - f i r i s r e p o r t e d

t o havc 464 f t (141.4 m2) o f r o o t s g r e a t e r t h a n 1 cm i n d i a m e t e r (McMinn 1963) , b u t t h e g r e a t e s t l e n g t h and s u r f a c e a r e a would be c o n t r i b u t e d by s m a l l e r r o o t s . Dead r o o t s a r c a l s o impor tan t a s food s u p p l i e s f o r decay organisms -i.n deep s o i l s t r a t - a .

Alexander , M . 1964. Biochenljcal eco logy o f s o l 1 microorganisms. Annu. Rev. Micrnh lo l . 18:217-252.

A l l i s o n , F. E . , R . M . Murphy, and C. J . Kle in . 1963. Ni t rogen r e q u i r e m e n t s f o r t h c decomposl t lon o f v a r l o u s klrlds o f f i n e l y g r o ~ ~ n d

woods i n s o i l . S o i l S c l . Y6:187-190. Bartholomcw, W . V .

1965. M i n e r a l i z a t i o n and imn~obi l i z ; i t lon of n i t r o g e n i n t h e deconiposit ion of p l a n t and animal r e s i d u e s . I n : Sol1 Ni t rngcn , Agron. Monogr. 10 , p . 295-306. W . V . Bartholomew and F. E . C l a r k , e d s . Am. Soc. Agron., Madlson, Wisc.

Bo l l en , W . B . 1959. Microorganisms and s o i l f e r t i l i t y . Oregon ~ t z t e Monographs, S t u d i e s in B a c t c r i -

o logy , No, 1 , Oreg. S t a t c C o l l . , C o r v a l l i s . Bo l l en , W . R .

1974. I n t e r a c t i o n between s o i l mic robes , f o r e s t r e s i d u e s , and r e s l d u e t r e a t m e n t s . I n : Environmental e f f e c t s o f f o r e s t r e s i d u e s management i n t h e P a c i f i c N o r t h w c ~ t . 0 . P . Cran~er ( ed . ) llSDA For . S e r v . Gcn. Tech. Rep. PNW-24. Pac . tJorthwcst 1,or. and Range Exp. S t n . , P o r t l a n d , Orcg.

C l a r k , F . E . 1969. E c o l o g i c a l associations anlorig s o i l microorganisms. J n : S o i l b i o l o g y , revicws

of r e s e a r c h . N a t l . Kesour. Res. UNESCO 93125-161. C l a r k , F. E . , and W . D . Kernper.

1967. Mi rcob ia l a c t i v i t y i n r e l a t i n g t o s o i l wa te r and s o i l a c r a t l o n . I n : I r r i g a t i o n o f a g r i c u l t u r a l l a n d s , p . 472-480. 1-1. R. H a i ~ c and T . W . Edminster , e d s . Am. Soc. Agron.

Davey, C . R . , and R . FI. Danielsori . 1968. S o i l chemical f a c t o r s and biological a c t i v i t y . Phytopathology 59:900-908.

Day, K . J . 1963. Spruce s e e d l i n g m o r t a l i t y caused by microcl i rnate i n t h e Kocky Mountains. Can.

Dep. F o r . , Publ . 1003, 35 p. Day, K . J., and P . J . B . Duffy .

1963. Regeneration a f t e r logg ing i n t h e Crowsnest F o r e s t . Can. Dcp. For . Publ . 1007 31 p .

Ditmer, H . J . 1937. A compara t ive s t u d y of t h e s u b t e r r a n e a n members o f t h r e e f i c l d g r a s s e s .

S c i e n c e 88:2290. Gray, T . R . G . , and S . T . Williams.

1971. M i c r o b j a l a c t i v i t y i n s o i l . Tn: Microbes and b i o l o g i c a l p r o d u c t i v i t y , p . 255- 286. D . E . Hughes and A . H . Rose, e d s . , 2 1 s t Symp. Soc. Gen. Mic rob io l . Cambridge Univ. P r c s s .

Ju rgensen , M . 1:. 1973. R e l a t i o n s h i p between nonsymbiot ic n i t r o g e n f i x a t i o n and s o i l n u t r i e n t s t a t u s .

J . S o i l S c i . 24:SlZ-522. McMinn, R . G .

1963. C h a r a c t e r i s t i c s of D o u g l a s - f i r r o o t sys tems . Can. J . Bot. 41:105-122. Muldcr, E . G . , T. A. L ie , and J . W . Woldcndorp.

1969. ,Biology and s o i l f e r t i l i t y . I n : S o i l b i o l o g y , r ev iews o f r e s e a r c h . Nat. . Resour . Res. UNESCO 9:163-208. Ovington, J . D ,

1962. Q u a l i t a t i v e eco logy and t h e woodland ecosystem concep t . Adv. Eco l . Res. 1:103- 192 .

P a r r , , I . F . 1968. The s o i 1 rn ic roh io log i c a l e c p i l i b r ium: n a t u r e and d u r a t i o n o f changes induced by

c u l t u r a l p r a c t i c e s . I n : F o r e s t f e r t i l i z a t i o n - - t h e o r y and p r a c t i c e , 13. 28-37. Terin. Va1.ley A u t h . , Muscle S h o a l s .

Raney, W . A . 1965. P h y s i c a l f a c t o r s o f t h e s o i l a s t h e y a f f e c t s o i l m,icroorga.nisms. I n Ecology.of . s o i l - b o r n p l a n t p a t h o g e n s , p . 115-119. R. F . Baker and W . C . Snydcr , eds,,. Univ'.

C a l i f . P r c s s , Berke ley . Kovira , A . 11.

1969. P l a n t r o o t e x u d a t c s . Bot. Rev. 35:35-57. S h i g o , A . I . . , and W. E . E l l i s .

1973. Heartwood, d i s c o l o r e d wood, and microorganisms i n l i v i n g t r e e s . Annu. Rev. Phytopa th . 11:197-221.

S l n n k i s , V . , V. C . Kuneckles , and (;. Krotov. 1964. Metabol i t c s l i b e r a t e d by r o o t s of whi t.e p i n e [Pinus strobus L . ) s e e d l i n g s .

Ph;,siol . P l a n t . 17:.310-313. S t o l z y , L. I I . , and S . I). Van Gilndy.

1968. 'rhc s o i l a s an environment f o r ln i c ro f lo ra and mic ro fauna . ~ h ~ t o p a t h o l o g y 583889-899.

Waksmarl, S. A . , and F . E . 'renncy. 1928. Conlposit ion o f n a t u r a l or.gan i c rna t c r i a l s and t h e i r decomposi tiion i n t l lc s o i l :

111. 'The i n f l u e n c e and n a t u r e of p l a n t up011 t h e r a p i d i t y o f i t s decornyosi t ion . S o i l Sc i . 25: 155-1 71.

W c l l s , C. G . 1971. E f f e c t - s 6 f p r e s c r i b e d htrrning on s o i l chemical p r o p e r t i e s and n u t r i e n t a v a i l -

ability. Proc . P r e s c r i b e d Burning Symp., p . 86-97. U.S. Dep. A g r i c . For . S e r v . , Soutl- icnst . F o r . Exp. S t n .

Wirnpcnny, -1. W . T. 1969. Oxygen and carbon d i o x i d c a s r e g u l a t o r s o f m i c r o b i a l g r o ~ t . ~ ~ arid metabolism.

I n : M i c r o b i a l g rowth , p . 161-197. P . M . Meadow and S . J . P i r t , e d s . 1 9 t h S p p . Soc . Cen . b l i c rob io l .

Youngbcrg, C . T . , and A . C . Wol lun? 11. 1970. Nonleglrminous s y m b i o t i c n i t r o g e n f i x a t i o n . I n : T r e e growth and f o r e s t s o i l s ,

11. 385-395. C . T. Youngberg and C . B . Davcy, e d s . k e g . S t a t e Univ. P r e s s , Oorval 1 is .

Z o c t t l , 13. 1965. Accumulation an3 t r a n s f o r m a t i o n of n i t r o g e n i n f o r e s t s o i l s . Ber i ch . Deutsch.

Hot. G e s e l l . 78: 1.67-180.

IMPACT OF RESIDUE MANAGEMENT PRACTICES ON CRITICAL MICROBIAL ACTIVITIES

Of the lnariy important activities of soil micro-organisms likely to be influcnccd by residuc nlanagcmcnt practices, the following arc critical and are corisidercd priority items for research: (1) Recycling of rnatrrials bound in woody resjdues through decomposition and decay; (2) cstahlishmcnt and funct ion of n~ycorrhi zal activities; (3) acc~~mula- tion and retention of soil N in the forest ecosystem;rand (4) activities of indigenous plant pathogens.

Decay

For purposcs here, decomposition or dccay is defined as thc cnzyrnatic oxidation of chemically con~plcx woody plant materials by micro-organisms, prcdominar~tly fungi (Satchel1 1971) , to more sirnple compounds and nutrients that become part of the so i J . Thesc matcrials make up the nutritional organic basc of thc forest. Woody materials in the various stages of decay may be at the soil surface or be totally or partially imbedded in it. Tree residues, depending on size, persist up to 150 years or more (McFee and Stone 1966; Dimbclby 1953). In thc surface foot of soil, woody residue comprises a significant volume, up to 30 percent (McFee and Stone 19hh). Ilence decom- posing woody tissues are an important component of the organic-containing soil layers in temperate forests. As integral parts of the soil system and function, their impact is yet to be fully elucidated.

The Ko le o f Residue Ikcay i n the F'orest Ecosystem

Thc decay and decomposition of plant materials have long been the subject of papers and discussions in both forestry and agriculture. The Carbon Cycle is particularly important to both disciplines. This is the process by which C is photochemically fixed, assimilated by the plant and, aftcr its death, reduced to a variety of simple organic compounds and COP by the soil rnicroflora (fig. 1). The left side of figurc 1 enconlpasses the processes involved in Cop fixation by tree growth, the right side depicts C02 release through decomposition associatcd with fungi and other micro-organisms. The decomposition of plant materials in a forest is one of the more complex phenomena associatcd with this cycle.

In any ecosystem, there is a balance between fixed and decomposed carbon. The principal controlling factors in this cycle are:

1. Light 2. Tcmperature 3. Moisture and Moisture Rcgimes 4. Latitude, Slope, and Aspect (insolation)

I'

Restrictive limitations imposed by any one of these factors normally result in responses from thc plant community that are reflected in the rate of biomass production and its decomposition (Loman 1965, 1962; Olson 1963; Spaulding 1929a, 1929b).

Figwe 1. --Th@ r o l e of fungi i n cyn2-i-ng carbon within an ecosystem. O n $he l e f t i s the .symbiotic cycZe direct Ly using photosynthetic . products. The decompos i t ion cyc le i s shown on the right (uf ' ter H a r l ~ y 1971) .

When examining t h e C c y c l e s o f f o r e s t t r e c s and a g r i c u l t u r a l c r o p s , t h e major d i f f e r e n c e s hetween t h e two a r c r e a d i l y a p p a r e n t . A g r i c u l t u r a l p r a c t i c e u s u a l l y invo lves annual harve ' s t and si t c management ( w i t h , a p p r o p r i a t e m i n e r a l and o r g a n i c f e r t i l i z e r amer~ciments). Tn f o r e s t . p r a c t i c e , h a r v c s t o c c u r s between 80 t o 150 y e a r s (sawt imber) o r 15 t o 25 y e a r s (pulpwood) and s i t e management r e l a t e d t o f e r t i l i t y and p r o d u c t i o n of t h e new c r o p i s l e f t p r i m a r i l y t u n a t u r a l ~ ~ r o c c s s e s . Man's i n t e r f e r e n c e wi.th t h e s e . p r o c c s s c s h a s been r e s t r i c t e d t o (1) l i m i t e d f o r e s t f e r t i l i z a t i o n , ( 2 ) nursery-grown o u t p l a n t s , (3) b r o a d c a s t s e e d i n g ( o f t e n w i t h r o d e n t c o n t r o l ) , and (4) s i l v i c u l t u r a l p r a c t i c e t h a t rnay cha.nge f o r e s t . t y p e .

Man's most r ecen t . . i n t e r c e s s i o n i n t h e n a t u r a l e v e n t s of f o r e s t r e g e r i e r a t i o n and s t a n d developmcnt ( i n adcli t i or) t o p r e v i o u s and c x i s t : i n g t i m b e r h a r v e s t i n g and management pr 'ac. t . ices) 113s 1)eerl t h e removal o f b o t h n a t u r a l and manmade f o r e s t r e s i d u c s - - a p r a c t i c e s t j m u l a t c d by : increased needs f o r wood f i b e r (Fou lge r and Harris 1972; Gardner and Hann 1 9 7 2 ) . 'l 'hcsc p r a c t i c e s have g e n e r a t e d q u e s t i o n s regarding t h e e f f e c t s o f r e s i d u e removal on f u n g a l popu la t - ions a s t h e y r e l a t e t o ~ n y c o r r h i z a l and d i s e a s e a c t i v i t y , and n u t - r i e n t r e l e a s e th rough decompos j t i on. S u r v i v a l o f c o n i f e r s e e d l i n g s d u r i n g t h e i n i t i a l p e r i o d o f e s t ab l i shmer l t i s i n t i m a t e l y r e l a t c d t o t h e s e p o p u l a t i o n s and p r o c e s s e s . S u r v i v a l becomes e s p e c i a l 1 y c r i t i c a l on t h e d r i e r s i t e s (Day 1963; Day and 1)uffy 1963) .

The Nature o f Hesicluue Decay

The form and age o f r c s i d u e s i n f l u c n c e the r a p i d i t y of decay . Residues formed from young m a t e r i a l s have a f a s t t u r n o v c r r a t e , under optimum decay c o n d i t i o n s , due t o t h c l r h i g h c a r b o h l d r a t e c o n t e n t ( o r lower l i g n i n c o n t e n t s ) . Res idues formed from o l d - growth t i m b e r a r c more r e s i s t a n t t o decay (IVaksman arid Tcnncy 1928) . Po lyyheno l i c m a t e r i a l ( t a n n i n ) d e r i v e d from l i g n i n o r l i g n i n l i k e compounds a r e a component of f o r e s t

s o i l s i n t h c form o f r e s i d u c s a t v a r i o ~ ~ s s t a g e s of decay. They u l t i m a t e l y c o n t r o l t h e n a t u r c o f t h e o r g a n i c r e s o u r c e and t h e n u t r i t i o n a l , p h y s i c a l , and b i o l o g i c a l q u a l i t y o f t h e s o i l ([lavies 1971) . For example, Bol len and Lu (1969) r e p o r t e d t h a t t a n n i n s (polyphenols) i n bark o f D o u g l a s - f i r s t i m u l a t c c e r t a i n 111olds i n t h e s o i l .

S t u d i e s on t h e decomposi t ion of f o r e s t l i t t e r have been conducted by Adam and Cornfor th (1973) , Kowal (196Y), Daubenmire and Prusso (1963) , Witkamp (19661, and IIayes (1965a, b ) . These workers have d e a l t p r i m a r i l y wi th l e a v e s , smal l t w i g s , and b a r k . A l l i s o n arid Murphy (1963) and A1114011 (1961) s t u d i e d t h e decom~los i t ion of wood and bark p a r t i c l e s i n s o i l b u t d l d no t examine whole wood on b a r k . 111 most of t h e above work, t h e s p c c i f i c fungi a s s o c i a t e d with t h e decornposit lon p r o c e s s e s were not ~ n d i c d t e d . Agrawal (1971) , i n c o n t r a s t , d i d u t l l i z e s p e c i f i c l i t t e r fung i t o a s s a y t o r c e l l u l y t ~ c c a p a c i t y . IIis exper iments , however, were c o n f ~ n e d t o prepared c e l l u l o s e which does riot lend i t s e l f t o a c c u r a t e e c o l o g i c a l i n t e r p r e t a t i o n .

Wagener and Offord (1972) have p rescn tcd d a t a on t h e r e l a t i o n s h i p of t ime t o s l a s h dccay i n n o r t h e r n C a l i f o r n i a . A f t e r 34 y e a r s , 43 and 85 p e r c e n t volume r e d u c t i o n s o f p i l e d s l a s h were observed in two d i f f e r e n t experimental a r e a s . Es t imates of s l a s h volume decayed over p e r i o d s o f t ime have a l s o been p r ~ v i d e d by Toole (1965) , Koff and Eades (1959) , G i l and Aridrews (19.561, Kimmey (1(355), Spauldirlg and Han4hrough (1944a, b ) , Kimmcy and F u r n i s s 11 943) , C h i l d s (1939) , Spaulding (192Yn, b) , 1-lubert (192.0) , and Long (1917).

The Fun.ct~:on o f Residua Decay

Tn a d d i t i o n t o t h e f u n c t i o n o f decay a s a mineral r e c y c l i n g a g e n t , S e i d l c r ancl o t h e r s (1972) have r e c e n t l y sugges ted t h a t t h e decomposition o f woody t i s s u e s i n cor i i fer stems o f t h e P a c i f i c Northwest may prov ide a s i g n i f i c a n t e c o l o g i c a l n i c h e f o r N- f ix ing b a c t e r i a o f t h e genus Clnstridiwn. Cornaby and Waide (1973) r e p o r t e d t h e m i c r o b i a l f i x a - t i o n o f a tmospher ic n i t r o g e n i n decaying and dccaycd logs of C~istanecx dentatu- i n t h e s o u t h e a s t e r n Uni tcd S t a t e s arid p r e s e n t e d convincing evidence t o suppor t t h e h y p o t h e s i s a s s t a t e d by Cowling and M e r r i l l (1966): t h e p o s s i b l e dcpcndcncc on e x t e r n a l s o u r c e s of N t o suppor t decay f u n g i i n woody m a t e r i a l s . The : i s soc ia t ion of N-f ixing organisms with t h e decay p r o c e s s may be ex t remely impor tan t 411 two ways: (1) by a f f e c t i n g t h e r a t e s o f

d e c a y i n f o r e s t r e s i d u e s , and ( 2 ) by s i t e N-replenishment as a f f e c t e d by k inds and amounts o f woody r e s i d u e s .

Another impor tan t e f f e c t o f r c s i d u c s , b u r i e d o r o t h e r w i s e , i s t h e i r mois tu re - ho ld ing c a p a c i t y (Bar r , 1930) . Largc ( l o g - s i z e d ) r e s i d u e s a c t a s perched wate r t a b l e s t h a t may e v e n t u a l l y d r y o u t , bu t a t much s lower r a t e s than t h e a s s o c i a t e d s o i l o r smal l ( l i t t e r and branch) r e s i d u e s . Such r e s i d u e s p rov ide , i n many c a s c s , we l l -de f ined e c o l o g i c a l n i c h e s i n o r on which f u n g i s u r v i v e and f u n c t i o n i n an environment o t h e r w i s e unfavorab le t o thcm (Zak 1969) .

Decaying r e s i d u e s s t r o n g l y i n f l u e n c e n u t r i e n t accumulat ion through funga l a c t i v i t y and n u t r i e n t r e l e a s e ( S t a r k 1973) . S t a r k (1972) h a s p r e s e n t e d d a t a s u g g e s t i n g t h a t funga l hyphae a c t a s " n u t r i e n t s inks" by i n c o r p o r a t i n g and b ind ing ( c o n c e n t r a t i n g ? ) e s s e n t i a l n u t r i e n t s i n t o t h e i r s t r u c t u r c s . The funga l soma i s e v e n t u a l l y decomposed, r e s u l t i n g i n slow n u t r i e n t r e l e a s e . That fung i a r e accumulators o f s u b s t r a t e n u t r i e n t s has a l s o been p o i n t e d o u t by Harley (1971).

Z'he Fungi Associat~d With Residue Decay

Maqy s p e c i e s o f decay f u n g i have been c o l l e c t e d and s t u d i e d by mycolog i s t s and. . p a t h o l o g i , s t s . These f u n g i have been d e t a i l e d a s p a r t s o f c h e c k l i s t s i n monographs, o r no ted a s o c c u r r i n g i n r e s t r i c t i v e e c o l o g i c a l n iches (Richards 1970) . For t h e most p a r t t h e y have n o t been r e l a t e d a s p a r t i c u l a r s p e c i e s , o r even a s broad taxonomic groups, t o e c o l o g i c a l f u n c t i o n s (Hering 1972) . The f u n g i r e s p o n s i b l e f o r decomposi t ion a r e i n

themselves complex i n g e n e t i c a l , , p h y s i o l o g i c a l , and e c o l o g i c a l makeup. They c o n s t i t u t e a group of organisms t h a t a r c b o t h a d a p t a b l e and u n s t a b l e . T h e i r s u r v i v a l , growth, and reproduct- ion may f r e q u e n t l y be l i m i t e d by t h e i r c c o l o g i c a l r e q u i r e m e n t s . Only r e c e n t l y have i n v e s t i g a t o r s a t t e n ~ p t e c l t.o e s t a b l i s h more p r e c i s e l y t h e r o l e s o f decay f u n g i i n t h e f o r c s t environment (Aho 19711; Shea 1960) . I t i s n o t enough t o know t h e f11ng.i p r e s e n t ; knowing why t h e y a r c o r a r c n o t p r e s e n t under p a r t i c u l a r for .es t env i ronments , manmade - o r o t h e r w i s e , i s e q u a l l y i m p o r t a n t . I

P r o c e s s e s invo lved i n decompos i t ion a r e e s s e n t i a l a s p e c t s o f ca rbon , n i t r o g e n , and rrlineral c y c l i n g , a l l o f which a r e i n t i m a t e l y r e l a t e d . llowever, p r e s e n t knowledge i s ,,

f r agmenta ry , p a r t i c u l a r l y whcn e c o l o g i c n l l y L n t c r r c l a t e d p r o c e s s e s concerned w i t h r e s i d u e decay a r e examined. T e n t a t i v e c o n c l u s i o n s a r e t h a t con t jnuous c ropp ing and i n t e n s i v e u t i l i z a t . i o n d e c r e a s e s i t e p r o d u c t i v i t y ( P i e r o v i c h and Smith 1973; White 1974) . I n e c o l o g i c a l 1 y se11sit:ive a r e a s , r c s i d u e s , a s s u b s t r a t e s f o r s p e c i f i . c f u n g i , may have t o be managed a s i n t e n s i . v c l y a s t h e t r e e s themsclvcs i f p r o d u c t i v i t y i s t o be main ta ined .

Rs.sc?rzrch Needs

'I'he fol lowir lg questions remai.11 t o be answered.. How much h e t e r o - and a u t o t r o p h i c p l a n t biomass i s a p a r t i c u l a r s i t e p roduc ing? flow much docs t h e N econolliy o f a f o r e s t e d s i t . c dcpcnd on r c s i d u e decay and a s s o c i a . t e d micro-organisms? I n - t e r m s o f s i t e k a i n t e - Ilance, do more desi.:rable or. l e s s d e s i r a b l e p o p u l a t i o n s ant1 s p e c i e s o f f u n g i o c c u r ? How does onc manngc o r s e l e c t f o r f u n g a l p o p u l a t i o n s and s p e c i e s most b e n e f i c i a l f o r s i t e maintenance'? 'I'hese complex, i n t e r r e l a t e d q u e s t i o n s r e f l c c t t h e k i n d s o f r c s e a r c h t h a t musr he done.

Li terat.zi.7.e C i t e d

Adams, S . N., and 1. S . C o r n f o r t h . 1973. Sonl'e s h o r t - t e r m e f f e c t s o f l ime and f e r t i l i . z e r s on a S i t k a s p r u c e p l a n t - a t i o n .

11 . 1 ,aboratory s t u d i e s on l i t t e r decomposi t ion and ni t r o g c n m i n e r a l i z a t i o n . F o r c s t r y 46:39-47.

Agrawal, S . S . 1971. The c e l l u l o l y t i c c a p a c i t y of some f o r c s t l i t t e r f u n g i . Phyton 28:169-175.

Aho, P. E . 1974. Decay o f f o r e s t r c s i d u e s . I n : Environmental e f f e c t s o f f o r e s t r e s i d u e s manage-

ment i n t h c P a c i f i c Northwest- -a s t a t e -o f -knowledge compendium, p . 91-913. USDA For . S e r v . [.;en. Tech. Rep. PNW-24, Pac. Northwest. For . and Range Exp. S t n . P o r t l a n d , Orcg.

A l l i s o n , F . E. d

1961. Comparnt.ive r a t e s o f deconiposi t ion i n s o i l o f wood and ba rk p a r t i c l e s o f s e v e r a l softwood s p e c i e s . P roc . S o i l S c i . Soc. Am. 25:193-196.

A l l i s o n , F . E . , and K . M . Murphy. 1963. Conlparative r a t e s o f decomposj t ion o f wood and hark p a r t i c l e s of s e v e r a l

s p e c i e s o f p i n e s . P roc . S o i l S c i . Soc. A m . 27:309-312. R a r r , P. M.

1930. The e f f e c t of s o i l m o i s t u r e on t h e establishment of s p r u c e r e g e n e r a t i o n i n B r i t i s h Columbia. Yale Univ. Sch. For . Bull . . 26 , 45 p . 8 ),

Rol len , W . B . , and K . C . Lu. 1969. b o u g l a s - f i r ba rk t a n n i n d c c o m ~ . ) o s i t i o ~ ~ i n two f o r e s t s o i l s . USnA For . Se rv . Res.

P a p . PNW-85, 1 2 p . lla.c. Northwest For . and Range Exp. S t n . , P o r t l a n d , Oreg. C h i l d s , T. W .

1939. Decay of s l a s h on c l e a r - c u t a r e a s i n t h e D o u g l a s - f i r r e g i o n . J . For . 37:955- 959.

Cornaby, B . W . , and J . B . Waidc. 1973. Ni t rogen f i x a t i o n i n decay ing c h e s t n u t l o g s . P l a n t and S o i l 39:445-448.

Cowling, E. B., and W. Merrill. 1966. Nitrogen in wood and its role in wood deterioration. Can. J. Bot. 44:1539-1544

Daubenmire, R., and D. C. Prusso. 1963. Studies of the decomposition rates of trcc litter. Proc. Soil Sci. Soc. Am. 27:589-592.

Davis, K. I. 1971. Relation of polyphenols to decomposition of organic matter and to pedogenetic processes, Soil Sci. III:80-85.

Day, K. 3 . ,1963. Spruce seedling mortality caused by microclimate in t h c Rocky Mountains. Can.

Ilcp. For. Publ. 100.7, 35 p. Ilay, R . , I . , and P . J. B. Duffy.

1963. Regeneration after logging in the Crowsnest Forest. Can. Dep. For. Puhl. 1007, 51 p .

Dimbleby, G. W. 1953. Natural regeneration of pine and b i r c h on the heather moors of northeast York- shire. Forestry 26:41-52.

Foulger, A. N., and J. Harris. 1972. Wood, bark, and nccdle residue volumes in a w&st Wyoming lodgepolc pine stand. U.S. Dep. Agric. For. Prod. Lab., Madison, Wisc.

Gardner, K. H., and D. W. flann. 1972. Utilization of lodgepole pine logging residues in Wyoming increases fiber yield. USDA For. Serv. Res. Note INT-160, 6 p. Intermt. For. and Kange Exp. Stn., Ogden, Utah.

Gill, L. S., and S. R. Andrews. 1956. Decay of ponderosa pine slash in the southwest. USDA For. Scrv., Intermt. For. and Range Fxp. Stn. Notc 19, 2 p. Ogden, Utah.

IIarlcy, J. L. 1971. Fungi in ecosystems. J . Ecol. 59:653-668.

Hayes, A. J. 1965a. Studies on the decomposition of conifcrnus leaf litter. 1. Physical and chemical changes. J. Soil Sci. 16:121-140.

Hayes, A. J. 1965b. Studies on the decomposition of coniferous leaf litter. 11. Changes in external features and succession of microfungi. J. Soil Sci. 163242-257.

flering, T. F. 1972. Fungal associations in broad-leaved woodlands in northwest England. Mycopath. MYCO~. Appl. 48: 15-21.

Hubert, E. E . 1920. The disposal of infected slash on timber-sale areas in the northwest. J . For. 18:34-56.

Kimmey, J . W. 1955. Rate of deterioration of Eire-killed timber. U.S. Dep. Agric. Circ. 962:l-22.

Kimmey, J. W., and R. L. Furniss. 1943. Deterioration of fire-killed Douglas-fir. U.S. Dep. Agric. Tech. Bull. 851,

G 1 p. Washington, D. C. Kowal, N. E.

1969. Effects of leaching on pinc litter decomposition rate. Ecology 50:739-740. Loman, A. A . 1962. The influence of temperature on the location and development of decay fungi in lodgepole pine logging slash. Can. J. Bot. 40:1545-1559.

Loman, A. A. 1965. The lethal effects of periodic high temperatures on certain lodgepole pine slasp decaying basidiomycetes. Can. J. Bot. 43:334-338.

.Long, W. H. 1917. Investigations of the rotting slash in Arkansas. U.S. Dep. Agric. Tech. Bull. 496, 15 p. Washington, D.C.

McFee, W. W., and E. L. Stone. 1966. The persistence of decaying wood in humus layers of northern forests. Proc. Soil Sci. SOC. Am. JO:513-516.

Olson, .I. S . 1969. Encrgy s t o r a g e and t h e b a l a n c e o f producers and decomposers i n ecological

sys tems . I-cology 44:321-322. P i e r o v l c h , J . PI., and R. C . Smith.

1973. Choosing f o r e s t r e s l d u e s management a l t e r n a t i v e s . USDA For . S e r v . Cen. Tech. . Kep. PNW-7, 11 p . Pac . N o r t h ~ e s t l o r . and Range Exp. S t n . , P o r t l a n d , Oreg .#

Richards , M . - 7 . 1970. S t u d i e s on Russuln emet:ica and o t h c r a g a r i c s i n a S c o t s p i n e p l a n t a t i o n .

T r a n s . B r i t . Mycol. Soc. 55:217-229. Roff , J . W . , and H . W . bades .

1959. D e t e r i o r a t i o n o f logg ing r e s i d u e on t h e B r i t l s h Columbia c o a s t (wes te rn hemlock, a rnah i l i s f i r , and S l t k a s p r u c e ) . Can. Dep. North . A f f a i r s Nat. Kesour . , For . B r . , F o r e s t Prod. Lab., 11'1. Note 11 , 38 1).

S a t c h e l l , J . E . 1971. Feasibility s t u d y o f an cnergy budget f o r Mcthop Wood. I n : P r o d u c t i v i t y o f

f o r e s l ecosystems. P . Duvigncaud, cd . IINESCO. S e l d l e r , R. J . , P. E . Aho, P. N. Rahu, and H . J . Evans.

1972. Nl t rogcn f l x a t l o n by h n c t e r l a l ~ s o l a t e s from decay i n l i v i n g w h i t e f i r t r e e s (Abies roncolor (Gurd. tl Glcnd . ) Lindl . ) . J . Gen. Mic rob lo l . 73 :413-416.

Shca , K . R . 1960. Fungus s u c c c s ~ i o n and s l g n l f i c a r i c e o f environrnerlt i n t h e d e t e r i o r a t i o n o f l o g s .

Weyerhaeuscr (.o. ] * o r . ftes. Note 30, 7 p . Spau ld ing , K .

1929a. Thc decay o f hardwood s l a s h i n n o r t h e r n New England. J . For . 27:241-245. Spau ld lng , R .

19291). llccay o f s l a s h o f riortl-icrn whl te p i n e i n s o u t h e r n New England. U.S. Dcp. /\grit. Tcch. n u l l . 132, 20 11. Washington, 11.C.

Spau ld lng , K . , and J . I{. l lansljrougl~. 1944a. llccay o f logg ing s l a s h i n t h e n o r t h c a s t . I1.S. Dep. Agr ic . Tcch. Gul l . 876,

22 11. Washington, D . C . S l laulding, R . , and . I . R . Ilanshrough.

1944b. Decay In halsam f i r in Ncw England and N e w York. U.S. Dep. Agr lc . Tech. 13ull. 872, 30 p . Washington, D . C .

S t a r k , N. 1972. N u t r l e n t c y c l i n g pathways and l i t t e r f u n g i . R iosc ience 2 2 :355-360.

S t a r k , N . 1973. N u t r l e n t c y c l i n g i n a . J c f f r c y p i n e ccosystcm. Mont. For . Conserv. Exp. S t n . ,

389 p . ' l 'oole, E . R .

1965. D e t e r i o r a t i o n o f hardwood logg ing s l a s h i n t h e s o u t h . I1.S. Dep. Agr ic . Tech. Ki111. 1328, 27 p . Washir~gton, I1 .C.

IVagener-, W. W . , and I-I. I t . o f f o r d . " 1972. Logging s l a s h : i t s breakdown and decay a,t two f o r e s t s i n n o r t h e r n C a l i f o r n i a .

USDA For . S e r v . Res. Pap. PSW-83, 11 p - Pac. Southwest For . and Range Exp. S t n . , Berkeley, C a l j f .

Waksn~an, S . A . , and F . E . Tcnncy. 1928. Co~nposit-j.ol-1 o f na t -u ra l o r g a n i c m a t e r i a l s and t h e i r d e c o n ~ p o s i t i o n I.n t h c s o i l :

111. The ir lf l lrence o f n a t u r e o f p l a n t upon t h e r a p i d i t y of i t s decompos i t ion . S o i l S c i . 25: 155-171.

White, E . 1 1 . I

1974. Whole t r e e h a r v e s t i n g d e p l e t e s s o i l n u t r i e n t s . Can. . I . For . Res. 4:530-535. Witkamp, l i f .

1966. Deconiposition o f l e a f l i t t e r i n r e l a t i o n t o environment , m i c r o f l o r a , and m i c r o b i a l r e s p i r a t i o n . Ecology J7:194-201.

Zak , B . 1969. C h a r a c t e r j z a t i o n and c l a . s s i f i c a t i o n o f mycorrhizae o f D o u g l a s - f i r .

I . Pseudotsugrz menzies i i + Toria Lerres tr i s (Blue- and o r a n g e - s t a i n i n g s t r a i n s ) . Can. J . Bot. 47: 1833-1840.

Mycorrhiza Formation

Wit11i.n t h e zone in f lue r l ced by p l a n t r o o t s e x i s t s a wide v a r i e t y o f f u n c t i o n a l a s s o c i a t i o r i s between r o o t s and c e r t a i n micro-organi sms (I.ewis 1973) . Pcrhaps t h e most s p e c i a l i zed o f t h e s e a r e t h e m u t u a l i s t i c (syrrtbiotic) a s s o c i a t i o n s , termed rnycorrlli zae , t h a t o c c u r bctween t l le r o o t s o f most hi .gher p l a n t s and c e r t a i n f u n g i . Most p a r t i c i - p a t i n g f u n g i and t h e i r h o s t s have evolved a s t r o n g i n t e r d e p e n d e n c e f o r s u r v i v a l i n ~ l a t u r a l ecosystems (Har ley 1971, 1 9 6 9 ) . I n mycor rh iza l a s s o c i a t i o n s , each p a r t n e r b e n e f i t s from t h e o t h c r (Trappe and Fogel 1974) . T h i s i s i . l l u s t r a t e d by t h e cornplete f a i l u r e o f a f f o r e s t a t i o n from seed o r s e e d l i n g i n a r e a s whcre s o i l s l a c k t h e a p p r o p r i a t e m y c o r r ~ ~ i z a l - f o r m i n g f u n g i (Mikola 1!>73; Vozzo and IIacslcaylo 1971; '1'ra.ppe arid S t r a n d 1969) and by t h e d i f f i c u l t y i n c u l . t u r i n g t h e f u n g i in t h e absence o f t h e h o s t r o o t ( P a l n e r 1971; Gerdeinann 1968) . Many f u n g i form mycor-rh-izae on one , o r orlly a few s p e c i e s o r t y p e s , o f h o s t p l a n t (Gerdemann and Trnppe 1974; C h i l v e r s 19731, s o changes i n v e g e t a t i o n can r c s u l t i n d i r e c t a l t e r a t i o n s i n popula t i .ons o f mycor rh iza l f u n g i . 'I'hus, s i t e t r e a . t - rtlents t .ha t a f f e c t p o p u l a t i o n s o f mycor rh iza l fungi , c i t h e r d i r ' ec t l y o r through compcti - t i o n , o r t h e a b i l i t y o f tl-iesc f u n g i t o forrrr t h e r n u t u a l i s t i c a . s s o c i a t i o n , cou ld c r e a t e J l i g h l y s i g n i f i c a n t i ~ n p a c t s on growth o r r e g e n e r a t i o n o f t h e succeed ing s t a n d .

Mycorrhi,zal Anatomy and UeveZoprn~nt

Four rnajor t y p e s o f mycor rh izae a r e r e c o g n i z e d on t h e b a s i s o f i n t e r n a l and c x t e r - n a l anatomy. The o r c h i d a c e o u s and e r i c a c c o u s mycor rh izac a r c a d i v e r s e group o f fungi w i t h s e p t a t e hyphae, no rmal ly found on members o f t h e E r i c a c e a e and Orch idaceae . These a r e c h a r a c t e r i z e d by i n t r a c e l l u l a r penc t ra t i . on t h a t u l t i m a t e l y d i g e s t s t l ie h o s t c e l l s . Thc ves . i . cu1a r -a rbuscu la r mycor rh iza l f u n g i have n o n s e ~ t a t c hyphae and u s u a l l y o c c u r on members o f t h e Cupressaceae , Taxod iaccac , Accraccae , so~nc s p e c i e s of t:he E r i c a c e a c , most hert)accous s p e c i c s , and a l l woody p l a n t s n o t e c t o m y c o r r h i z a l . 'I'hese f u n g i occur on more p l a n t s p e c i e s t h a n any o t h e r t y p e . They p e n e t r a t e t h e r o o t h11t form s p o r e s e x t e r n a l t o t h e root. and c a u s e 1 i t t l e , -if any, cha.nge i n morphology. The ectomycor- r l i i z a l f u n g i a r e found on members o f t l ie P i n a c e a e , Fagaceac , B e t u l a c c a c , ' f i l i a c e a c , and s e v e r a l o t h e r minor p l a n t f a m i l j e s . Thc cc tomycor rh izae a r e c h a r a c t e r i z e d by a h i g h l y specialized morphology and a r c r e q u i r e d f o r t h e s u r v i v a l o f t h e P inaceae and s e v e r a l o t h e r woody p l a n t f a m i l i e s in t e m p e r a t e ecosystems (Trappe and Foge l , i n p r e s s ; Mcyer 1973) . 'The f u n g i invo lved a r c g e n e r a l l y h i g h e r bas id iomyce tes o r ascomycetes t -ha t form a c h a r a c t e r i s t i c man t l e o f f u n g a l t i s s u e comple te ly e n c l o s i n g t h e h o s t r o o t l e t . P e n e t r a - t i o n by t h e fungus i s l a r g e l y l i m i t e d t o t h e i n t e r c e l u l a r r e g i o n s and o n l y r a r e l y o c c u r s w i t h i n t h e c e l l . I n t e r c e l l u l a r r a m i f i c a t i o n by t h e f u n g i , w i t h t h e absence of c e l l u l a r d i g e s t i o n , r c s t u l t s i n t h e f o r m a t i o n o f a n e t l i k e s t r u c t u r e , termed t h e ItHar.tig n e t , " wherein funga l t i s s u e s c o m p l e t e l y su r round t h e c o r t i c a l c e l l s . I n v a s i o n d o e s n o t proceed beyond t h e endodermis (Har ley 1969) . 111 some i n s t a n c e s , i r ~ t e r m e d i a r y t y p e s (ec tendomycorrhizac) a r e formed and a r c c h a . r a c t e r i s t i c o f c e r t a i n s p e c i e s (Zak 1 9 7 1 ) . The f o l l o w i n g d i s c u s s i o n w i l l emphasize t h e e c o l o g i c a l l y o b l i g a t o r y a s s o c i a t i o n s hetween members of t h e P inaceae and t h e e c t o m y c o r r h i z a l f u n g i because of t-he d i r e c t r e l a t i o n - s h i p w i t h r e g e n e r a t i o n o f t h c impor tan t w e s t e r n t imber -p roduc ing s p e c i e s .

Normal ly , a young c o n i f e r s e e d l i n g i s i n f e c t e d d u r i n g t h e f i r s t growing s e a s o n (Robinson 1967) . The fungus s p r e a d s a s a wef t o f mycclium [ funga l s t r a n d s ) ove r t h e young r o o t s u n t i l t h e e n t i r e s u r f a c e o f t h e r o o t , i n c l u d i n g t h e apex , i s covered . U l t i m a t e l y , a t y p i c a l t h i c k man t l e o f f u n g a l t i s s u e i s formed. P e n e t r a t i o n i n t o t h e r o o t g e n e r a l l y c o i n c i d e s w i t h b u t can p r e c c d c t h e n la tu ra t ion o f t h e m a n t l e . A s r o o t sys tems e n l a r g e , each new c r o p o f r o o t s becomes i n f e c t e d . I n f e c t e d young r o o t l c t s , devoid of r o o t h a i r s , emerge from t h c l a t e r a l r o o t comple te ly enshea thed by t h e fungus and a r e g r a d u a l l y t r ans fo rmed i n t o a c h a r a c r e r i s t l c m y c o r r h i z a l s t r u c t u r e . Young l a t e r a l r o o t s become t r ans fo rmed i n t o an e a s i l y r e c o g n i z a b l e s e r i e s o f s h o r t , o f t e n much branched s e r i e s of c l u b l i k e r o o t t i p s . Branching p a t t e r n s , c o l o r s , and o t h e r c h a r a c - t e r i s t i c s a r e o f t e n a s s o c i a t e d w i t h p a r t i c u l a r hos t - fungus combina t ions (Zak 1971; wi lcox 1968) .

Mycorrhizae a r e s u b s t a n t i a l l y l o n g e r l i v e d t h a n nonmycorrhiza l r o o t s (Har l cy 1969; Or lov 1968) . In a d d i t i o n , t h e f u n g a l hyphae f u n c t i o n as e x t e n s i o n s of t h e r o o t sys t em, a b s o r b i n g and t r a n s l o c a t i n g s o i l n u t r i e n t s and wnte r t o t h e h o s t (Bowen 1973; Har l ey 1969) . They may a l s o a c t , i n c o n c e r t wi th o t h e r f u n g i , a s n u t r i e n t s i n k s f o r conse rva - t i o n o f n u t r i e n t s on t h e s i t c ( S t a r k 1972; H a r l e y 1971) .

The f u n g a l symbinr~t. i s n o t g e n e r a l 1 y c a p a b l e of u t i l i z i n g complex c a r b o h y d r a t e s a s an enc rgy s o u r c e and i s , t h c r e f o r c , l a r g e l y dependent on t h e h o s t f o r a supp ly o f s i m p l e s u g a r s (I-lacskaylo 1973; Har l ey 1969) . [ lu r ing t i m e s of ex t reme d r o u g h t , t h e s u r f a c e s o i l l a y e r s which normal ly c o n t a i n t h e mycor rh iza l f u n g i a r c most a f f e c t e d and t h e h o s t may supp ly b o t h w a t e r and n u t r i e n t s from deep s o i 1 h o r i z o n s ( i n a d d i t i o n t o t h e ene rgy s o u r c e ) and e n a b l e a m y c o r r h i z a l p a r t n e r t o s u r v i v e .

I l l t i rnn tc ly , m y c o r r h i z a l hyphae and s t r u c t u r c s deri .ved from them can f u s e , forming l a r g e networks o f i n t c r c o n n c c t e d furlgal b o d i e s , p e r m i t t i n g i n c r e a s e d a h s o r p t i o n and t . r a i ~ s l o c a t i o n of nu.tr i .ent .s betwccn l l o s t s s h a r i n g a common f u n g a l network [Furman and l ' rappe 1971; Reid and Woods 19691. Among t r e e s d i r e c t g r a f t i n g o f r o o t s a l s o o c c u r s (:Barman 1966; b!c.P.linn 1963) . Thus t h e f o r e s t s o i l c o r i s i s t s of' an i n t e r c o n n e c t e d s e r i e s of p i p e l i n e s t h a t a c q u i r e and s h a r e r e q u i r e d m a t e r i a l s th rough a h i g h l y s o p h i s t i c a t e d and d c l i c a t e b a l a n c e o f s t r u c t u r e s d e r i v e d from bot.11 h i g h e r p l a n t s and t h e i r f u n g a l symbion t s . P h o t o s y n t h a t c ( s u g a r s ) and minc ra l n u t r i e n t s can be t r a n s f e r r e d between p l a n t s th rough t h e v a r i o u s components o f t h i s sys tem (Kcid and Woods 1969; Borman 1946; Woods and B-rock 1 9 6 4 ) . Of ] - ) a r t i c u l a r s i g r l i f i c a n c c a r e t h e p o s s i b l e i n c r e a s e s i n u p t a k e and t r a r l s p o r t o f ammonium n i t r o g e n (Melvin and Ni l s son 1 9 5 2 ) , s y n t h e s i s o f amino a c i d s i n t h e m y c o r r h i z a l s t r u c t u r e s (Krupa and o t h e r s 1973) , and i n c r e a s e d a b s o r p t i o n o f phns- [ )hate (13i.eleski 1973; Bowcn 1!17.3-) .

'The advan tages oT an u r~derg round p l p c l i n e , p a r t i c u l a r l y t o p l a n t s growing i n a h a r s h and i n f e r t i l e f o r e s t s o l 1 environmcrlt , a r e r e a d i l y a p p a r e n t . Mine ra l n u t r i e n t s , wn te r , and even p h o t o s y n t h a t c may he s t ~ p l ) l i e d t o new s e e d l i n g s o r t o i n d i v i d u a l t r e e s occupying extremely h a r s h rnicrosi t e s . An e a r l y a c q u i s i t i o n o f t h e b e n e f i t s p r o v i d e d by t h i s s o i l p i p e l i n e i s p a r t i c u l a r l y c r i t i c a l t o sced l i r lg s u r v i v a l . I n t h e absence of mycorr l l izac , s e e d l i n g r o o t p e n e t r a t i o n helow t h e summer d r o u g h t zone and r o o t s u r f a c e a r e a a r e n o t a d e q u a t e t o p r o v i d e s u f f j c i e r l t n l lncra l n u t r i e n t s d u r i n g t h e E i s s t s e v e r a l s e a s o n s i n even t h e most rnodcratr f o r e s t s o i l c o n d i t i o n s . 'Thus. some o f t h e most s u c c e s s f u l p l a n t s t h a t o c c u l ~ y r l g o r o u s rloridesert s i t e s , such a s t i m b e r l i n e o r c o a l s p o i l banks , a r e e c t o m y c o r r h i z a l (Schramm 1 9 6 0 ) . Fungi a d a p t e d t o p a r t i c u l a r environments appea r t o have evo lved concomi tan t ly wi th t h e a b i l i t y o f c e r t a i n p l a n t s t o s u r v i v e i n cxt rcme erivirorllnents (Marx and 13ryall 1971; Moser 19581. Many s p e c i e s o f m y c o r r h i z a l f u n g i a s s o c i a t e w i t h o n l y a s i n g l e genus o r even subgenus o f h o s t , o t h e r s a r e a p p a r e n t l y n o n s p e c i f i c ( C h i l v c r s 1973; Smith 1971 ; 'I'rappe 1962, 1371 j .

The l a r g e a s semblage o f mycor rh iza l f u n g i encompasses a wide spec t rum o f phys io - l o g i c a l and e c o l o g i c a l c a p a b i l i t i e s . P o t e n t i a l f u n c t i o n a l d i f f e r e n c e s between s p e c i e s a r e e x p r e s s e d i n h a b i t a t p r e f e r e n c e s :inrl s u c c e s s i o n a l changes i n f u n g i w i t h t h e age o f h o s t and s e a s o n (Anderson 1966; Mikola 1965; Uominik 1961, 1958) . Fungal s p e c i e s have demons t ra t ed d i . f f e r c n c e s i n r e s i s t a n c e t o t e m p e r a t u r e o r n ~ o i s t u r e s t r e s s (Mexal and Reid 1973; t i acskay lo and o t h e r s 1965; Moser 1 9 5 8 ) , and n i t r o g e n u t i l i z a t i o n (Bowen 1973; L,undcberg 1970) . I l i f f e r e n t i a l growth r e s p o n s e s o f v a s c u l a r p l a n t s t o d i f f e r e n t mycor rh iza l f u n g i have f r e q u e n t l y been observed (Bowen 1973; Mikola 1973; Laiho 1970) . Mycorrhizac can i n some i n s t a r l c e s be p i v o t a l f a c t o r s c o n t r o l l i n g p lan t . s u c c e s s i o n (Robinson 1972; Handley 1963) . N i t r o g e n - f i x i n g organisms may be s t i m u l a t e d by mycorrhi zae (Rambcl l i 197.7; S i l v e s t e r and Rerinett 1973) .

Mycorrhizal s e e d l i n g s r e s i s t drought b e t t e r t h a n ~lontllycorrhizal s e e d l i n g s (Bowen 1973; Shemakhanova 1962) . I n one c a s c a severed sp ruce shoot su rv ived f o r 8 months a s a r e s u l t o f an i n t a c t connec t ion betwcen a rnycorrhizal r o o t and t h e rhizomory~h of a mycor rh iza l fungus emanating from t h e s o i l on which it l a y (Simonsberger and Kohcrg 1967) . S e e d l i n g l o s s e s r e l a t e d t o d e s i c c a t i o n a r e p a r t i c u l a r l y s e v e r e i n c l e a r c u t s where s o i l and p l a n t s u r f a c e t empera tu res can k i 11 t i s s u e s (Day 1963) . Limited wa te r s u p p l i e s make s e e d l i n g s even more s u s c e p t i b l e t o hea t i n j u ~ y , arid r e s u l t a n t l o s s e s impose long d e l a y s i n r e s t o c k i n g c u t u n i t s (bay 1963; Day and Duffy 1963) . Ear ly fo rmat ion o f mycorrhizal s t r u c t u r e s may be p a r t i c u l a r l y s i g n l f l c a n t i n reduc ing h e a t m o r t a l i t y by i n c r e a s i n g t h e s e e d l i n g s ' a c c e s s t o s o i l n lo i s tu res .

In summary, c o n t a c t wi th s p e c i f i c mycorrhizal networks and s o i l c o n d i t i o n s a p p r o p r i a t e f o r mycor rh iza l e s tab l i shment a r e e s s e n t i a l t o t h e s u r v i v a l and growth o f c o n i f e r r e g e n e r a t i o n ( Z e r l i n g 1960) .

Distr ibut ion o f Mycorrhizal Fungi

L i t t l e j s known about t h e d i s t r i b u t j o n and p e r s i s t e n c e of ectomycorrhiznl fungi a p a r t from t h e i r h o s t s . A s a r u l e , mycorrhizal f u n g i do riot produce f r u i t i n g bodies o r s p o r u l a t c i n t h e absence of l i v e h o s t r o o t s (Komcll 1938) . Surv iva l i n t h e form of s a p r o p h y t i c hyphae i n t h e s o i l i s probably l i m i t e d (Ilarley 1969; Gerderriann 1968) . Hyphal a g g r e g a t i o n s termed rhizomorphs may p c r s i s t f o r sorne t ime due t o t h e i r tough o u t e r l a y e r s and a b i l i t y t o t r a n s p o r t n u t r i e n t s , b u t t h e y a r e p robab ly l i m i t e d t o w i t h i n a few f e e t o f a c t i v e h o s t r o o t s . Mycorrhizal s h o r t r o o t s may s u r v l v e a s h o r t whi le a f t e r t r e e h a r v e s t due t o t h e tough o u t e r mant lc and p o s s i h l c s t o r a g e of food m a t c r i a l s . Howevcx, evidence t o suppor t any o f t h e l a t t e r c o n t e n t i o n s i s n o t a s y e t a v a i l a b l e .

A t p r c s e n t , i t i s g e n e r a l l y thought t h a t ~ n y c o r r h i z a l f u n g i do n o t s u r v i v e f o r extended p e r i o d s i n t h e absence o f h o s t r o o t s (IIacskaylo 1973) , and t h a t t h e y r e i n v a d e through a i r b o r n e s p o r e s (Lamb and Richards 1974) o n l y a f t e r t h e appearance of s u i t a b l e h o s t s on t h e s i t e . Thus, c l e a r c u t t i n g may drastically rcduce t h e p o p u l a t i o n s of rnycorrhizal f u n g i i n d i r e c t p r o p o r t i o n t o t h e removal o f t h e h o s t s , p a r t i c u l a r l y conifers. L i t t l e o r n o t h i n g d e f i n i t i v e i s known concern ing s p o r e d i s p e r s a l p a t t e r n s and t h e i r ge rmina t ion requ i rements , o r t h e i r c f f c c t i v c n e s s i n r e e s t a b l i s h i n g mycorrhizal f u n g i o t h e r than t h e y have been observed t o a c t i n some i n s t a n c e s a s e f f e c t i v e inoculum ('l'heodorou and Bowen 1973) .

Potential Impacts o f Residues Management on the Mycor~rhizaZ Associat ion

In a d d i t i o n t o t h e requ i rement f o r a s u i t a b l e h o s t and fungus, t h e environment i n which t h e two meet imposes a s t r o n g i n f l u e n c e on t h e i r a b i l i t y t o form a s u c c e s s f u l mycorrhizal a s s o c i a t i o n (BjBrkman 1970) . Thus, t h c s o i l f a c t o r s a f f e c t e d by c l e a r c u t - t i n g and burn ing cause s i t e changes t h a t could a l t e r mycorrhizal symbios i s .

Temperature d i r c c t l y a f f e c t s r o o t c o l o n i z a t i o n by mycor rh iza l fung i (Bowen and 'I'heodorou 1973; Theodorou and Bowen 1971) and t h e i r growth i n v i t r o ( l iar lcy 1969; Ilacskaylo and o t h e r s 1965) . 'The r e l a t e d f a c t o r o f s o i l m o i s t u r e can a l s o l i m i t growth o f mycor rh iza l f u n g i (Bowen and Theodorou 1973) , and i n some i n s t a n c e s low s o i l mois tu re may be r e s p o n s i b l e f o r t h e replacement o f somc mycor rh iza l f u n g i by o t h e r s (Worley and Hacskaylo 1959) . S i m i l a r l y , s o i l a e r a t i o n a s r e l a t e d t o s o i l wa te r c o n t e n t has been r e p o r t c d t o a f f e c t mycorrhiza format ion (Mikola 1973; Mikola and Laiho 1962; Hcikurainen 1955) . S o i l a c i d i t y appears p a r t i c u l a r l y c r i t i c a l i n s u c c e s s f u l l y c o n t r o l l i n g s p e c i e s o f mycor rh iza l f u n g i on t h e s i t e and i n t h e a b i l i t y o f t h e fungi t o form t h e mycorrhizae (Bowen and Theodorou 1973; Theodorou and Bowen 1969; Richards 1961) . 'She complex s e r i e s of p h y s i c a l , chemica l , and b i o t i c changes wrought by f o r e s t burn ing r e s u l t i n temporary r e d u c t i o n s i n mycor rh iza l r o o t s on c o n i f e r r e g e n e r a t i o n (Wright 1971; Mikola and o t h e r s 1964; Wright and T a r r a n t 1958; l ' a r r a n t 1956) .

Other rnore s u b t l e e f f e c t s o f rr~anagement on t h c q u a l i t y o f f o r e s t s o i l s may c o n t r o l t l ic a b i l i t y o f mycor rh izn l f u n g i and t h e i r h o s t s t o form t h e m y c o r r h i z a l a s s o c i a t i o n . A v a i l a b i l i t y of 11ut.r- jents, o r g a n i c m a t t e r , and a n ene rgy s u p p l y i n t h e form o f s imple s u g a r s a r e c r i t i c a l t o mycor rh iza l f u n g i . I n g e n e r a l , mycorrhi zn forrnati.on i s enhanced when t h c r c i s a m i l ( 1 deficiency o f nlirleral n u t r i e n t s ( t i e s t e r b e r g and .Turgensen 1972) . Hatch (1937) r c p o r t c d a d e f i c i c n c y o f n i t r o g e n , phosphorus , po tas s ium, o r ca lc iuni s t i m u l a t e d mycorr l i iza l devclnpmcnt . Bjorktnan (1942) found t h e amount. of s o i l n i t r o g e n and phosphorus t o be d e c i s i v e f a c t o r s i n t h e f-ormation o f t h e a s s o c i a t i o n . Ile a l s o fourld t h a t t h e a d d i t i o n of a s h t o c c r t a i n s o i l s i n c r e a s e s t h e nunil)ers o f mycorrhizne (Bjgrknia~l 1941) .

Ihough 111,111ts w l t h r r~ycorrhlzae can be c u l t i v a t c d i n s o i l s w i t h a low o r g a n i c c o n t e n t (Hjijrknlan 1956, 1954) , hlgli l e v c l s o f o r g a n i c m a t t c r a r c r c p o r t c d t o have favora1) le e f f e c t s on mycorr l l lza l developrnent (Ruhtov 1964; Rayrler 1936, 1 9 3 8 ) . As a s i n g l e arne~idrnent, o r l p n i c m a t t e r can promote for inat ion of ~ n y c o r r h i z a c i n d e f i c i c n t s o i l s (blikola 1973) . Fore5 t r e s i d u e l c v c l s would g r c a t l y a f f c c t t h c subsequent o r g a n l c m a t t c r c o n t e n t o t r 11e s o i l . S ~ m l l a r l y , t h e p resence o f decay ing r o o t s a p p e a r s t o promote mycor rh iza l orinat i on (McMinn 19h3) .

011e o f t l l c ~ n o ~ t n o t n b l c p h y s i o l o g i c c h a r a c t e r i s t i c 5 of most n i y c o r r h i ~ a l fung i i s t h c i r r.cttu i reliirrlt f o r s i r n ~ ~ l e s u g a r s :IS enc rgy s o u r c c s . Such s u b s t a n c e s a r e g e n e r a l l y though t t o bc sul )p l i ed th rough p l a n t r o o t e x u d a t i o n (Hacskaylo 1973) . Ihus , f a c t o r s t h a t i n f l u c i i c c s u g a r l e v e l s in t h c h o s t p l a n t and i t s t r a n s p o r t t o and l i b e r a t i o n from r o o t s , such J S s ~ ~ n l i g h t ~ n d mi i icra l n u t r i t i o n , may a f f e c t mycorrl-~i t a l d e v e l o ~ > m e r ~ t (Bj&rkm:rn 1370) .

Stand coinl~os i t ion , a t t h e t inic o f h ; ~ r v e s t i n g , rnay condj t i o n t h e s o i 1 e i t h e r f a v o r - a b l y o r u n f a v o r a b l y f o r t h e succeedir lg c r o p th rough t l ie i n f l u e n c e of r o o t s ancl t h c i r e x u d a t c s . Rlli zosphurc n i i c r o f l o r a t h a t compete f o r s i m p l e s u g a r s exuded from r o o t s may d i r e c t l y a f - f cc t i i iycorrl i izal fungi (Har l ey 1969) ; a n t a g o n i s t i c r h i z o s p h e r e f u n g i may have s1 .11)~ress- ive e f f e c t s (Lcvisohn 1 9 5 7 ) ; r o o t pa thogens may i n f l u e n c e development of mycor- r l i i z n c o r v j c e versa. (Marx 1'3733; and ccrtai .11 micro-organisnis comnion .in t h e v i c j n i . t y of r o o t s may be s y n e r g j st i c 1.0 t l ie f o r m a t i o n o f mycor rh iza l structures (Voznyakovskaya and Ryzllkova 1955) . I l igher p l a n t s o r l i c h e n s nlay r e l e a s e s o i l chem-icals t .ha t t r i g g e r a l l e l o p a t h i c responses anlong rnycorrhiza l f u n g i (Handlcy 1963; W i l d e 1954; Brown and Mi.kola 15374). E a r l y s u c c e s s i o n of s l l r l ~ h s p c c i e s , which a r e t y p i c a l 1 y v e s i c u l a r - a rh r r scu la r 1nyco1-rllizal, nlny a f f e c t t.lie es tabl ishrr icnt o f ec tornycorrhiza l . f u n g i arid t h e r e - f o r e t h e i r llo:;ts, such a s p i n e s ( ' l ' r ;~ppe , p e r s o n a l communication) .

Mdl~agemcnt o f temperntr, f o r e s t s f o r op t ima l t r e e growth an? l o f a v o r s e l e c t e d s p e c i e s will a l s o r ec lu l r e tlic r i ~ a n a g c ~ ~ ~ c n t o f t h e funga l ~ y m h l o n t s on which t l i c ~ c t r c c s d c p c r ~ d . P r e s e n t anti cotitcmplatccl f o r e s t r e s i d u e 1)rac t i c e s wi 11 d i r e c t l y i n f l u e n c e t h e ~ ) ~ ~ n l ) i o t I L r n y c ~ f l u r ~ i . F ~ ~ ~ ~ ~ i l ~ i a t l o ~ i o f t h e n c t e f f e c t s of t h e s e i n f l u e n c e ? w i l l p rov ide valu , lb lc ~ n f o r m a t i on r e g a r d I ng b i o l o g i c a l lmp,lcts o f mandgemelit d r~d may p r o v i d e d i r e c t i n p u t s l i l t o ~n,rnagerncnt t a c t l c s des lgncd t o a c h i e v e o p t i m a l growth o f p rnde i ermi ned s p e c l c s .

Befo re ~t I S p o s s l h l e t o a 5 s c s s t h e environmental impact5 o f t r e a t m e n t s on v a r i o u s s i t e s i n f o r c s l e d ccos)fsteiiis, t h e f o l l o w i n g q u e s t i o n s t h a t r e l a t e mycor rh iza l development t o i n t e n s i v r u t i l i z a t i o n and p r e s c r i h c d b u r n i n g , o r t o h o t h , must h e answered. Docs ex te r l s ivc rernoval o r bu rn lng o f h o s t t r e c s o r o r g a n l c m a t e r i a l r educe o r change ~ ) o p u l a t l o n s of rnycorrhizdl furlgi a t s p e c i f i c s i t c s ? I f s o , how q u i c k l y and by what means do t h e s e p o p u l a t i o n s r e c o n s t i t u t e thcrnselves? I f e f f e c t s a r c significant, do t h e y constitute a haza rd t n , o r d e l a y , t h e e s t a b l i s h m e n t and growth of t h e succeed ing s t and?

Literature C i t e d

Anderson, J. 1966. Indahini sulla micorrizia in alcurle specie di eucalitto nell Italia centsale. Publ. Cent. Agric. For. (Koma) 8:259-274.

Bieleski, R. L. 1973. Phosphate pools, phosphate rransport, and phosphate availability. Annu. Rev. Plant Physiol. 24:225-252.

Bjorkman, E. 1941. The devclopmcnt and incidence of mycorrhiza among forest trees on ash- fertilized and unfertilized sectors of drained marshes. Medd. Stat. Skogsforsanst. 32 : 255-296.

Bjorkman, E. 1942. Uber die bedingungen dcr mykorrhizdbildung bci kiefer and fichte. Symb. Bot . Upsal . VI (2) : 1-196.

Bjorkman, E. 1954. Betzdelsen av godsling i skogstradsplantskolar for plantornas forsta utveckling

i skogsmarken. Norrlands Skogsvnrdsf. Tldskr. 543. Bjorkman, E.

1956. llber die natur dcr mykorrhizablldur~g unter hesonderer berucksichtigung der waldbaume und die anwendung in der forstlichen praxis. 1:orslwiss. Zentralbl. 75:265-286.

~jorkman, E. 1970. Forest trcc mycorrhiza--the conditions for its formation and the significance for tree growth and afforestation. Plant and Soil 32:589-610.

Bormann, F. H. 1966. The structure, function, and ecological significance o f root grafts in Pinus

strobus 1,. Ecol. Monogr. 36:l-26. Bowen, G. D. 1973. Mineral nutrition of cctomycorrhizae. In: Cctomycorrhizae--their ecology and physiology, p. 151-206. G. C. Marks and T. T. Kozlowski, eds. Academic Press, New York.

Bowen, G. D., and C. Theodorou. 1973. Growth of ectomycorrhizal fungi around seeds and roots. In: Ecton~ycorrhizac-- their ecology and physiology, p. 107-150. G. C. Marks and T. T. Kozlowski, eds. Academic Press, New York.

Brown, R. T., and P. Mikola. 1974. The influence of fruticose soil lichens upon the mycorrhizae and seedling growth of forest trees. Acta For. Fenn. 141:l-22.

Chilvers, G. A . 1973. IIost range of some eucalypt nlycorrhizal fungi. Aust. J. Bot. 21:103-111.

Day, R. J. 1963. Spruce seedling mortality caused by microclimate in the Rocky Mountains. Can. Dep. For. Publ. 1003, 35 p.

Day, R. J., and P. J. B. Duffy. . ~

1963. Regeneration after logging in the Crowsnest Forest. Can. Dep. For. Publ. 1007, 31 a.

~ominik; T. 1958. Studium nad mikotrofizmcm rodzaju PopuZus. Inst. Badaw. Lesn. Pr. 181:117-172.

Dominik, T. 1961. Studies on mycorrhizae. 1J.S. Dep. Comm. Transl. TT 65-50333 (1966), from Polia For. Polon. A 5:3-160.

Furman, T. E., an3 J. M. Trappe. 1971. Phylogeny and ecology of mycotrophic achlorophyllous angiosperms. Quart. Rev. Biol. 46:219-225.

Gerdemann, J , W. 1968. Vesic~lar-arbuscu1ar mycorrhiza and plant growth. Annu. Rev. Phytopath. 6: 397-418.

Gerdemann, J . IV. , and ( J . M . ' r rappe. 1'374. 'l'he enclogonaccae i n t h e P a c i f i c Nor thwest . Mycol. Mem. 5 : 1-75.

Hacsknylo , E . 1973. Ucpenderice o f ~ n y c o r r h i z a l f u n g i on h o s t s . B u l l . l ' o r r ey Rot.. Club 100:217-223.

1-lacskaylo, E . , .I. G . Pa lmer , ant1 J . A . Vozzo. 1965. Ef fec t . o f t - empera tu re on growth and r e s p i r a t i o n o f e c t o t r o l ~ h i c m y c o r r h i z a l

f u n g i . Ilyco1og.i.n 57: 748. I landlcy, W . I < . C .

1963. Mycorrhi 7,al a s s o c i a t i o r ] and CcrZZunn h e a t h l a n d af fores ta t . . i .on . Tior. Cornrn. B u l l . 3 6 : 3.-70.

lI;l.rlcy, . J . I , . 6 The b i o l o g y o f mycorrhi zn . L,eona-rd I l i l l , lor id or^. 3.74 p .

l.I:irlcy, ,J . I,. 1971. Fungi i n ecosystems. .J. Appl. E c o l . S:h27-642.

I l a t ch , A R. 1937. Thc p h y s i c a l b a s i s o f mycotrophy i n Pinus. Black Rock For . B u l l . 6 , 168 p .

Ile i k u r a i n e n , I . . 1955. I lur wur7.elaufhau clcr k i c f c r n b c s t a n d e a u f r e i se rmoorboden und s e i n e

b e i n f l u s s u n g durcll d i e ent .wasserung. Acta F o r . Fenn. 65. No. 3 . I lcs tcr l )er f i , (.;. A , , and M . F . . Jurgensen.

1972. l'he r e l a t i o r ) o f f o r c s t f e r t i l i z a t i o n t o d i s e a s e i n c i d e n c e . For . Chron. 48 :92-96 .

Krupa, S . , A . I:orltar~a, and ? , I . I 'a lenzona. 1973. S t u d i c s on n i t r o g e n metabol js r r~ i n ec tomycor rh izae . I . S t a t u s o f f r e e and bound

alninu ncicls i r l m y c o r r h i z a l and nonrnycorrhizal r o o t sys tems o f Pinus nigr~a and Cory%us alicller'n. P h y s i o l . P l a r ~ t . . 215: 1-(11.

Lniho, 0 . 1'370. Pc~xiZZms <nz~nlm-tus. 3 5 a n i y c ~ ) ~ r l i i z i l l syr~lbiont o f f o r e s t t r c c s . Acta I-:or. 1:enn.

106: 1 - 7 2 . I2aml), 11. J . , anrl B . N . R i c h a r d s .

1974. Slsrvival p o t e n t i a l o f s e x u a l and a s e x u a l s p o r e s o f ec to rnycor rh iza l f u n g i . 'I 'rans. 13-rit. blycol. Soc . 6.3: 181-191.

I,cv i s n l ~ n , T . 1957. A n t a g o n i s t i c e f f e c t s o f AZternaricz t enu i s on ccrt .ai .n r o o t - f u n g i o f f o r e s t

t r e e s . Na tu re 179:1143-1141. I,cwis, I ) . 11.

197.1. (:orlcel)ts i n f u n g i n u t r i t i o n and t h c o r i g i n of b i o t r o p h y . B i o l . Rcv. 48:261- 278.

Lundebcrg, G . 1970. l f t i l i z n t i o n o f v a r i o u s ni t .rogen s o u r c e s , i n p a r t i c u l a r bnund s o i l n i t r o g e n , by

m y c o r r h i z a l f u n g i . S t u d . For . Suec . Skogshogsk. 79: 1-95. MRTX, n. 11.

1973. Mycorrhizae and f e e d e r r o o t d i s c n s e s . I n : Ectoinyco-rrl-1iza.e-their eco logy and p l lys io logy , p . 351 -382. i;. C . Marks and '1'. T . Kozlowski, e d s . Acadc~nic Press, Ncw York.

Marx, D. II . , and lrl. C . Bryan. 1971 . I r ~ f l u e n c c o f ec tomycnr rh i zae or] s u r v i v a l and p,:rohth u f a s e p t i c s e e d l i n g s o f

l o b l o l l y p i n e a t h igh ternlleratl lrcs. F o r . S c i . 1 7 : 37-41. McM:irlr~, R . G .

1963. C h a r a c t e r i s t i c s o f D o u g l a s - f i r roo t sys t ems . Can. J . Bot . 41 :105-122. Melvin , E . , and H , N i l s s o n .

1952. Trans fe r* o f l a l3e l l cd n i t r o g e n from arl arnrnoliiunl s o u r c e t o p i n c s e e d l i n g s th rough t h e myceli~*ni o f Voletus z~uu'iegcrtus F r . Svensk Bot . ' r i d s k r . 46 : 281-285.

Meyer, F . H . 1973. Mycor.rh:i zae i n n a t i v e and man-made f o r e s t s . I n : Ectomycorrhi z a e - - t h e i r

eco logy and p h y s i o l o g y , p . 79-106. G. C. Marks, and T . T . Kozlowski ( e d s . ) Academic P r e s s , JEW York.

Mexal, J . , and C . P . P . Reid . 1973. ' fhe growth o f s e l e c t e d mycorrhi.za1 f u n g i i n response t o induced wate r s t r e s s .

Can. J . Bot. 51:1579-1588. Mikola, P.

1965. S t u d i e s on t h e e c t e n d o t r o p h i c rnycorrhiza.1 of p i n e . Actn For . Fenn. 7 9 : l - 5 6 . Mikola, t'.

1973. Mycorrhizal symbiosis i n f o r e s t r y p r a c t i c e . I n : Ec tomycur rh izae - - the i r ecology and physi.ology, p . 388-412. G . C . Marks, and 'I'. T . Kozlowski ( e d s . ) Academic P r e s s , New York.

Mikola, P . , J . E r i c k a i n e n , and K . Kuvaja. 1964. The e f f e c t of s l a s h hurning on t h e corr~mencement o f myco-r'rhizal a s s o c i a t i o n .

Acta For . Penn. 7 7 : l - 1 1 . Mikola, P . , and 0. Laiho.

1962. E4ycorrhizal r c l n t i.ons i n t h e raw humus l a y e r o f n o r t h e r n sp ruce f o r e s t s . Cornmun. I n s t . For . Fenn. 5 5 : l - 1 3 .

Moser, M. 1958. Der e i n f l u s s t i e f e r temperturen auf das washsturn und d i e l c b c n s t a t i g h e i t

hohere r p i l z e r n i t s p c z i e l l e r be rucks ich t igung von mykor rh izap i l zen . Sydowia 12:386-399.

Orlov, A. J . 1968. Development and l i ,ve d u r a t i o n of t h e p i n e feed ing r o o t s . I n : Mcthods of

p r o d u c t i . v i t y s t u d i e s i n root: systerrls and r h i z o p h e r c organisms, M . S . Ghi l a r o v and o t h e r s , eds . Publ . House Nauka, Len i~ lg rad .

Palmer, J. G . 1971. Tcchnj-ques and p rocedures f o r c u l t u r i n g ectomycorrhi.za1 f u n g i . I n :

Mycorrhizae, p . 145-1511. F:. t lacskaylo, ed. U.S. Uep. Agr ic . For . S e w . Misc. Publ . 1189, Washington, D . C .

Rambel l i , A . 1973. The r h i z o s p h e r e of mycorrhizne. Tn: G c t o n ~ y c o r r h i z a e - - t h e i r ecology and phys i -

o logy , p . 299-350. G . C . Marks and 1'. T. Kozlowski, e d s . Academic P r e s s , New York. Kayner, M . C .

1936. The mycor r l~ izn l h a b i t i n r e l a t i o n t o f o r e s t r y . 11. Organic composts and prowth o f young t r e e s . F o r e s t r y 1 0 : l - 2 2 .

Rayner, M . C . 1938. The u s e of s o i l o r hurnus inocula i n n u r s e r i e s and p l a n t a t i o n s . Emp. For . J .

171236-243. Reid, C. P. P . , and F . W. Woods.

1969. l ' r a n s l o c a t i o n of c-14 l a b e l e d compounds i n mycorrhizac and i t s i ~ n p l i c a t i o n s i n i n t c r p l a n t n u t r i e n t c y c l i n g . Ecology 50:179-187.

R ichards , B . N . 9 6 1 . S o i l pH and mycorrhiza devel.opment i n I'inus. Nature 190:105-106.

Kobinson, R . K . 1967. Ecology o f f u n g i . Eng l i sh Univ. P r e s s L t d . , Idondon, 116 Q .

Robinson, K . K . 1972. The p roduc t ion by r o o t s of CaZZuna vulgaris of a f a c t o r i n h i b i t o r y t o growth

of some mycor rh iza l f u n g i . J . Eco l , 60:219-224. Komell, L . G .

1938. A t r e n c h i n g exper iment i n sp ruce f o r e s t and i t s b e a r i n g on problems o f myco- t r o p h y . Svensk Bot. T i d s k r . 32:89-99.

Rubtov, S. 1964. Humusul di. l a r i c e - s t i m u l a t o r p u t e r n i k a1 c r e s t e r i i p u i e l o r de l a r i c e i n

p e p i n i e r e . Rev. P a d u r i l o r 69:279. Schramm, J . R .

1966. Mycotrophy of Woody P l a n t s . Akad. Naul. S .S .S .R . , Moscow. U.S. Dep. Comm. T r a n s l . TT 66-51073, Washington, D . C .

Shemakhanova, N . M , 1962. Mycotrophy of woody p l a n t s . (Rus.) l z d a t e d . Akad. Nauk SSSR. Moscow. 375 p.

S i l v e s t e r , W . R . , and K . J . B e n n e t t . 1973. Ace ty lene r educ t lo r l by r o o t s and a s s o c i a t e d s o i l o f Ncw Zealand c o n i f e r s .

S o i l 13iol. Biochcm. 5: 171-179. S imonsherge r , P . , and 1 1 . Koherg.

1967, Dcr p i l z a l s lchensrette--mykorrhizapilz Thclephora terrestris bewahrt abgeschr i i t t enen f i c h t e n s a m p l i n g v o r dem v e r t r o c k n e n . Mlhrokosrnos 5:147-149.

Smith , A . 11. 1971. Taxonomy o f ec tomycor rh iza l - fo rming f u n g i . I n : Mycorrhlzae , p . 1 -8 . E .

t I acskay lo , ed . U.S. Dep. Agr ic . F o r . S e r v . Misc. Pub l . 1189. Washington, D . C . S t a r k , N .

1972. N u t r i e n t cyc l i r lg pathway5 and 1 i t t c r f u n g i . B iosc ience 22: 355-360. ' I ' a r r an t , R F .

1356. F f f e c t s o f s l a s h b u r n i n g on some s o l l s o f t h e D o u g l a s - f i r r e g i o n . P roc . S o i l S c l . Soc . A m . 20:408-411.

Theodorou, C . , a n d G . Rowcn. 1969. I'he i n f l l lenccs o f ptl and rl i t r a t P on mycor rh lza l a s s o c i a t i o n s o f Pinus yladiata

L). I h n . A u s t . . I . Rot. 17:SC)-67. Tlicndorou, C. , arid (;. R o w ~ r i .

1971. Jn f l r l e r~ce o f t empr ra tu r r3 on t h e mycor rh izn l a s s o c i a t i o n s o f Pinus radia ta D . Don. Aus t . . J . Bot . 19 :13-20 .

Theodornu, C . , and G . 13. Howcn. 1973. Inocu la t io r l o f s e e d s and s o i 1 wi th b a s i d i o s p o r c s o f m y c o r r h i ~ a l f u n g i . Soi 1

R i o l . Blochem. 5 :765-771. Trappe , . J . M .

1902. Fungus aqsoc ~ a t e s nf c c t o t r o p h i c n lycorrhi7ar . Bot . Itclv. 28:5.38-606, Trappe , , I . M .

1971. Mvt-orrhi za-forming ascomycc t f s . In: M y c o r r h ~ z a c , p . 19-37 T . Hacskay lo , ?d . I1.S. Dcp. Agr ic . Tor . Scrv . Misc. Puh l . 1189, Waqhington, D . C .

T r a p l x , J . M., and R . D . F o g c l . Ecosys temat i c f u n c t i o n s o f rnycorrhizae . In: Belowground ecosys tems . Academic

P r e s s , New York. ( T n p r e s s ) . T rappc , J . M . , and R . F. S t r a n d .

1969. Mycor rh lza l d e f i c i e n c y i n a 1 ) o u g l a s - f i r r e g i o n n u r s e r y . For . S c i . 15:381-389. Voznyakovskaya, M., and A . S. Ryzhkova.

1055. M i c r o f l o r a accnnq)anying mycorrh i z a s . I n : Mycotropliy i n p l a n t s . A. A . I m s h e n e t s k l i , e d . I'rograrn f o r Scientific T r a n s l a t i o n s , 1967.

Vozzo, J . A . , and C . l l acskay lo . 1971. l n o c u l s t i o n o f Pinus caribaea w i t h ec tomycor rh iza l f u n g i i n P u c r t o Rico. For .

S c i . 17:239-245. Wilcox, H . C .

1968. Morphological s t u d i e s of t h c r o o t s o f r c d p i n c , Pinus resinosa. 11. Fungal colonization o f r o o t s and t h e development o f mycor rh izae . Am. J . Bot. 55 : 686-700.

Wildc, S . A . 1954. Mycor rh izs l f u n g i : t h e i r d i s t r i b u t i o n and e f f e c t on t r e e growth. S o i l S c i .

78329-31. Woods, F . W . , and K . Brock.

1964. I n t e r s p e c i f i c t r a n s f e r o f ~a~~ and P3? by r o o t sys t ems . Ecology 45:886-889. Worley, .I. F . , and C . Hacskaylo .

1959. The e f f e c t o f a v a i l a b l e s o i l m o i s t u r e on t h e m y c o r r h i z a l a s s o c i a t i o n o f V i r g l n i a p i n e . F o r . S c i . 5 : 267-268.

Wr igh t , t. 1971. Mycorrhizac on ponderosa p i n e s e e d l i n g s . Oreg. S t a t e Univ. Res. B u l l . 13 ,

36 p . Wright , E . , and R . F . T a r r a n t .

1958. Occur rence o f mycor rh izac a f t e r logg ing and s l a s h h u r n i n g i n t h e D o u g l a s - f i r t y p e . U.S. nep. A g r i c . r o r . S c r v . , Pac. Northwest For . and Range Exp. S t n . Pap. 160, 7 p . P o r t l a n d , Oreg.

Zak, B . 1971. C h a r a c t e r i z a t i o n and i d e n t i f i c a t i o n of D o u g l a s - f i r mycorrhizae . In: Mycorrhizae,

p. 38-53. C . I lacskaylo, ctl. U . S . Dep. Agr ic . For . Se rv . Misc. l3ubl. 1189. Washing- t o n , D . C .

Z e r l i n g , G . I . 1960. Dic mykorrhizabj lclung h e i l a r c h e u n t e r d e r bedingungen des trarrswolga-

tschernosems und i h r e s t i m u l i e r u n g . Mikrohiologya 29:401.

Soil Nitrogen Fixation and Transformations

Of t h e many elements e s s e n t i a l f o r p l a n t growth, n i . t rogen (N) i s r e q u i r e d i n g r e a t e r amounts t h a n any o t h e r minera l n u t r i e n t and has been found t o be a l i m i t i n g f a c t o r f o r t r e e growth i n bo th e a s t e r n and wcsT.ern f o r e s t s o i l s (Stonc 1973; Heilrnarl 1961) . The amounts o f N p r e s e n t and i t s subsequent a v a i l a b i l i t y i n f o r e s t s o i l s depend on a v a r i c t y of chemica l , p h y s i c a l , and b i o l o g i c a l processes.

Nit rogcn v a l u c s v a r y from l e s s t h a n 0.02 p e r c e n t i n s u b s o i l s t o g r e a t e r t h a n 2 . 5 p e r c c n t i n o r g a n i c s o i l s . The average N c o n t e n t i n t h e s u r f a c e l a y e r o f most s o i l s r anges from 0 . 0 3 t o 0 . 4 p e r c e n t ; t h e amount d e c r e a s e s wi th s o i l dcp th (Kremner 1967) . S p a c i a l v a r i a t i o n s i n N d i s t r i b u t i o n a r e especially e v i d e n t i n f o r e s t s o i l s where c o n s i d e r a b l y g r e a t e r alnounts o f N a r c found i n t h e l i t t c r l a y e r t h a n i n t h e minera l s o i l (Gessel and. o t h e r s 1973) . Es t imates of N l e v e l s p r e s e n t i n t h c l i t t c r beneath wes te rn s t a n d s have ranged from 80 kg/ha f o r pinon p i n e - j u n i p e r t o over 1 ,300 kg/ha i n second-growth D o u g l a s - f i r (Zavi tkovski and Newton 1967; Youngberg 1966) .

Man, by h i s i n t e r v e n t i o n i n t h e f o r e s t ecosystem, can have a s i g n i f i c a n t impact on t h e N c y c l e and corlsequently on s i t e p r o d u c t i v i t y (Wollum and Davey 1975) . Nirsogcn i s un ique among t h e s o i l n u t r i e n t s because i t i s p r e s e n t i n t h c s o i l alnlost e n t i r e l y as o r g a n i c forms. No i n o r g a n j c r e s e r v e is normal ly p r e s e n t t o a l l e v i a t e s o i l N l o s t t o t r e e removal, t o v o l a t i l i z a t i o n , o r t o l c a c h i n g ( Z o e t t l 1965) . In ~ l a t u r a l ecosystems t h e atmospherc s u p p l i e s N t o t h e s o i l through t h e f i x a t i o n o f i n e r t N2 i n t o forms u s e f u l t o p l a n t s . ilowcver, t h e s e g a i n s i n t o t a l N can be balanced by l o s s c s through b i o l o g i c a l convers ion of n i t r a t c t o t h e gases N7 o r N20 ( d e n i t r i f i c a t i o n ) , rcmoval by t imber h a r v e s t i n g o r hurn ing , and by l e a c h i n g i n t o t h e s u b s o i l (Knight 1966; N o r r i s 1962) . Each p r o c e s s i n t h e N c y c l c i s r e l a t e d t o s i t e p r o d u c t i v i t y and would bc s t r o n g l y s u h j e c t t o change by f o r e s t management p r a c t i c e s .

Cons iderab le work h a s been done i n a t t e m p t i n g t o e v a l u a t e t h e r e l a t i o n s h i p o f N - f i x a t i o n ( d i n i t r o g e n f i x a t i o n ) t o t h e o v e r a l l s o i l N ba lance and t o i n c r e a s e t h e e x t e n t o f f i x a t i o n i n t h e s o i l . However, t h e s i g n i f i c a n c e and c o n t r i b u t i o n o f N - f i x a t i o n i n many ecosystems have s t i l l n o t bccn r e s o l v e d . G e n e r a l l y , smal l amounts o f N a r e added t o t h e s o i l by p r e c i p i t a t i o n ( A l l i s o n 1965) and a b s o r p t i o n o f NM3 from t h e a i r by s o i l and p l a n t s (Malo and P u r v i s 1964) . I t has been advocated t h a t t h e slow o x i d a t i o n of s o i l o r g a n i c m a t t e r couplcd wi th s u n l i g h t f i x e s s j z a b l e p o r t i o n s of N (Dhar 1960) . IIowevcr, few i f any o t h e r i n v e s t i g a t o r s suppor t t h e l a t t e r view. T h e r e f o r e , most o f t h e N added t o t h e s o i l i s cons ide red t o have come from b i o l o g i c a l f i x a t i o n .

Symbiot ic

Probably t h e b e s t known symbio t i c r e l a t i o n s h i p a s s o c i a t e d w i t h N f i x a t i o n i s t h e b a c t e r i a l genus Rhizobium and t h e r o o t nodule it forms on members of t h e legume f a m i l y Lcguminosae. Leguminous p l a n t s , such a s soybean, pea , and a l f a l f a , axe p a r t of food and f o r a g e p r o d u c t i o n and have been found t o add up t o 200 kg N/ha/yr t o t h e soil

under p r o p e r management (S tewar t 1 9 6 6 ) . Itowever, most work h a s c e n t e r e d on a g r i c u l t u r a l sys t cms a n d , w i t h t h e e x c e p t i o n o f b l a c k l o c u s t ( I k c and S t o n e 1958) , v e r y l i t t l e i s known r e g a r d i n g t h e e x t e n t and s i g n i f i c a n c e of t h c Rh izob iwn- l ike legume a s s o c i a t i o n i n f o r e s t ecosystems (Wollum and Davey 1975) . In fo rmat ion i s needed on t h e d i s t r i b u t i o n o f legurnes i n f o r e s t s t a n d s , and shou ld i n c l u d e t h e wide ly d i s t r i b u t e d he rbaceous and s11rut)by s p e c i e s .

P o s s i b l y of g r e a t e r impor tance t h a n legumes t o t h e f o r e s t ecosystem i s t h e o c c u r r e n c e o f nonlegutninous bu t r lodula ted p l a n t s . Morc than 113 s p e c i e s have been r e p o r t e d t o form n o d u l e s . Included a r e t h e common wcs te rn p l a n t s r e d a l d e r Alnus rubra and snowhush Crrnuthun ve lu t inus (Youngberg and Wollilm 1970) . The e x a c t n a t u r e o f t h e

,nodule-forming endophytc h a s n o t been det .ermined. Var ious i n v e s t i g a t o r s have i s o l a t e d Strepf;omyc~s from s u r f a c e s t e r i l i z e d r .oots o f s e v e r a l nodu le - fo rming g e n e r a ( e . g . , Wol lum and o t h e r s 1966) . However, t h e s e a c t i n o t ~ ~ y c e t e s d i d no t c a u s e n o d u l a t i o n when grown under s t e r i l e c u l t u r e c o n d i t i o n s .

Nonleguin~nous p l a n t s have heen found t o f i x t i p p r c c i a b l e amounts o f N . Lahora to ry s t u d i c s have r e p o r t e d f i x a t i o n r a t c s e q u i v a l e n t t o 56 kg/N/ha/yr f o r AZnus rugosa, 15 kg/N/haiyr f o r Hippophac rhunmoides, and 4 kg/N/ ha /y r f o r Myri:ca c e r ~ i f ~ r a (Akkermans 1971; S j l v e r and Mague 1 9 7 0 ) . Cor is iderahly h i g h c r v a l u e s have been r e p o r t e d from f i e l d s t u d i e s on snorvbush and r e d a l d e r [VanCleve and o t h e r s 1971; Youngherg and Wollum 1970; IVewton ant1 o t h e r s 1 9 6 8 ) .

C e r t a i n l i c l ~ e r i s a r e a n o t h e r example o f a. s y m b i o t i c N - f i x i n g r e l a t i o n s h i p ; i n t h i s c a s e , hetween b l u e - g r e e n a l g a e and f u n g i . A number of s p e c i e s have heen found t o f i x N hoth -in tile l a b o r a t o r y and .in t h e f i e l d (Henr iksson and Simu 1971; Vogg and S t e w a r t 1968) . The a . c t u a l c o i i t r i h u t i o n s o f l i c h e n s t o t h e s o i l N supp ly would depend on weather, s o i l p r o p e r t i e s , and ext -cnt o f 1.jchcn c o v e r . A s t u d y on v a r i o u s v o l c a n i c and a r i d s o i l s found 2 t o 4 t i m e s g r e a t e r amounts o f N a s s o c i a t e d w i t h l i c h e n c r u s t s t h a n w i t h t h e h a r e s o i l s u r f a c e ( S h i e l d s 1957) . F i x a t i o n r a t c s from 10 t o 100 kg/N/ha/yr havc hccn a t t r i h u t c d t o l i c h e n s i n d e s c r t s o i l s of Utah (Rhychc:rt and S k u j i n s 1974) . 'The o c c u r r e n c e and development o f l i c h e n s on c e r t a i n f o r e s t s i t e s have been i n v e s t i - g a t e d ( P i k e and o t h e r s 19721, but. t h e significance o f t h e s e o rgan i sms t o t h e f o r e s t N hn 1 ancc i s unknown.

In c o n t r a s t t o s y m b i o t i c N - f i x a t i o n , t l le irriportance o f f r e e - l i v i n g N- f ix ing mi.cro-organisms i n s o i l i s s t i .11 unccr t r - l in . Lt. i s g c n e r a l l y conceded t h a t t h c nonsym- b i o t i c N-f i x i n g m i c r o f l u r a contribute o n l y smal l amounts of N t o a r a b l e s o i l s (Jensen 1965; 1lenzcl:l and N o r r i s 1962) . Ilowevcr, i n n o n c u l t i v a t c d s o i l s such a s g r a s s l a n d s and f o r e s t s where o r g a n i c m a t t e r i s n o t removed from t h e s i t e , N ga ins may h e s i g n i f i c a n t (Moore 1,966). S t u d i e s on s o i l N accumuln t ion and c y c l i n g on f o r e s t e d s i t e s have - ind ica ted s u b s t a n t i a l g a i n s o f N . I n t empera te zones , annua l N a d d i t i o r i s havc been r e p o r t e d t o r ange fro111 4 kg /ha /y r i n young s t a n d s t o between 10 and 25 k g / h a / y r i i i lnaturc s t a n d s ( R i c h a r d s and Voig t 19h5) , a l t h o u g h c o n s i d c r a h l y h i g h e r v a l u e s may b e o b t a i n e d on c e r t a i n s i t e s (R icha rds 1 9 6 4 ) . T r o p i c a l r a i n f o r e s t s appea r t o have a much h i g h e r f i x a t i o n r a t e , l i k e l y a v e r a g i n g ovc r SO kg /ha /y r (Greenland and Kowal 1960) . Recent s o i l s t u d i e s u s i n g d i r e c t meas~xrement t e c h n i q u e s i n t h e f i e l d have i n d i c a t e d f a r lower f j x n t i o n r a t c s , a v e r a g i n g i n t h e o r d e r of 1 t o 10 k g / h a / y r (Hardy and o t h e r s 1973)

T h i s anomaly betwecn t h e e x t c n t o f N g a i n s on f o r e s t s i t e s and t h e measurement of nonsyrnhiot ic N f i x a t i o n i n soi.1 may h c i n p a r t e x p l a i n e d by t h e enhanced m i c r o b i a l a c t i v i t y i n t h e r h i z o s p h e r c . N - f i x i n g micro-organisms would bc s t i m u l a t e d by t h e g e n e r a l l y low N c o n t e n t o f o r g a n i c m a t e r i a l s s e c r e t e d and s loughed o f f by p l a n t r o o t s ( S t a r k e y 1958) . N i t rogcn g a i n s o c c u r r i n g i n t h i s narrow zone around t h e r o o t would n o t no rmal ly be measurccl i n s t u d i e s on s o i l N - f i x a t i o n . Recent i n v e s t . i g a t i o n s have shown considerably h i g h e r N f i x a t i o n r a t e s a s s o c i a t e d w i t h t h e r h i z o s p h e r e o f c o n i f e r r o o t s

than w i t h r o o t - f r e e s o i l (Richards 1973; S i l v c s t e r and Bennet t 197.71. S i m i l a r s t i rnula- Tion o f N- f ixa t ion has been r e p o r t e d i n t h e r h i z o s p h e r e o f v a r i o u 5 g r a s s e s , c o r n , and r l c c (ilommergues and o t h e r s 1973; Yoshida and Ancajas 1973) . Some i n v e s t i g a t o r s have i n d i c a t e d t h a t N- f ix ing mic ro-organ i sn~s a r c favored 111 t h e r h l z o s p h c r e o f mycorrhizae , a s cornpared t o nonmycorrhizal r o o t s (Rambelli 1973; S i l v e s t e r and Bennett 1973) . However, t h e reduced r h i z o s p h e r c f i x a t i o n r a t e s a s s o c i a t e d w i t h s l a s h p i n e mycorrhizae (Richards 1973) show t h a t t h i s a s p e c t of nonsymbiot ic N - f i x a t l o n must be s t u d i e d f u r t h e r

Another s o u r c c o f N i n f o r e s t systems may be t h e l c a f s u r f a c e o f p l a n t s o r u p h y l l o s p h e r e . " Ruinen (1956, 19h5) i s o l a t e d N- f ix ing organisnis from t h c l eaves o f numerous p l a n t s p e c i e s and showed t h a t l e a f exuda tes were s u i t a b l e s u b s t r h a t c s for' t h e i r development. Various s p e c i e s of Aznkobacter have been found i n t h e phy l losphere of over 50 s p e c i e s o f t r e e s , c r o p s , o rnamenta l s , and a q u a t i c p l a n t s (Iswaran and o t h c r s 19733. Vlassak and o t h e r s (1973) have i s o l a t e d bluc-green a l g a e from phy l l o s p h c r e samplcs o f Ceratodon purpureus. The a l g a e showed a p p r e c i a b l e N-f ixing c n p a b i l i t i c s . In s t u d i e s on t h e t r o p i c a l g r a s s Tripsacurn Luxurn, l e s s than 1 kg/N/ha t o 3 . 5 kg/N/ha havc been a t t r i b u t e d t o phy l losphere f i x a t i o n (Bessems 1973; Ruincn 1971)). In a s i m i l a r l a b o r a t o r y s t u d y , Jones (1970) a t tempted t o de te rmine t h e e x t e n t o f N- f ixa t ion o c c u r r i n g on t h e l e a v e s o f Douglas - f i r where he i s o l a t e d n i t r o g e n - f i x i n g b a c t e r i a . Jones con- c luded t h a t a s much a s 65 g/ha/day o f N could be f i x e d i n some Douglas - f i r s t a n d s . Although such N g a i n s under n a t u r a l c o n d i t i o n s would appear u n l i k e l y , t h i s s o u r c e o f addcd N t o f o r c s t s i t e s could be o f importance.

In t h e p a s t , t h e a b i l i t y of micro-organisms t o grow on s o - c a l l e d "N-free" media was cons ide red proof o f N-f ixing c a p a c i t y . However, growth on t h e s e nledia i s no t p o s i t i v e proof because smal l amounts o f f i x e d N a r e always p r e s e n t , arid anln~onia can be absorhed from t h e a i r . Although t h e i n c o r p o r a t i o n o f 1 5 ~ i s t h e most d e f i n i t i v e nlethod by which N- f ixa t ion i s e s t a b l i s h e d , t h e a c e t y l e n e r e d u c t i o n t e c h n i q u e is now normal ly used f o r f i e l d i n v e s t i g a t i o n s . Many s t u d i e s have shown t h a t micro-organisms a b l e t o fix N a l s o have t h e a b i l i t y t o reduce a c e t y l e n e t o e t h y l e n e ( e . g . , llardy and o t h e r s 1973) . Product ion o f e t h y l e n e from a c e t y l e n e is almost complete ly r e s t r i c t e d t o N- f ix ing organisms, and i s cons ide red presumptive ev idence f o r t h e occur rence o f N - f i x a t i o n . Because o f i t s s e n s i t i v i t y , c a s e i n measurement, and economy (Ilardy and o t h c r s 1968) , t h e a c e t y l e n e r e d u c t i o n t echn ique i s p r e f e r r e d over t h e 15 a n a l y s i s .

N

Numerous genera o f b a c t e r i a and b lue -green a l g a e have bcen found t o c o n t a i n s p e c i e s o r s t r a i n s having an N- f ix ing a b i l i t y . Var ious f u n g i and y e a s t s have a l s o becn r e p o r t e d t o f i x N , a l though more r e c e n t cv idcnce i n d i c a t e s t h a t N f i x a t i o n does n o t occur i n t h c s e groups ( P o s t g a t e 1971) . S e v e r a l o f t h e nonsymbiot ic N- f ix ing micro-organisms, such a s Azotobacter and t h e b luc -green a l g a e , a r e normal ly r e s t r i c t e d t o n e a r l y n e u t r a l o r a l k a l i n e s o i l s . However, many o t h e r s , p a r t i c u l a r l y t h e spore - forming anaerobes , a r e s o wide ly d i s t r i b u t e d t h a t a l a c k of N-f ixing rn ic ro f lo ra would n o t l i k e l y be a f a c t o r l i m i t i n g N- f ixa t ion i n f o r e s t s o i l s (Jurgensen and Davey 1970) .

Near ly a l l o f t h e N i n s o i l i s t i e d up a s o r g a n i c complexes which, wi th t h e pos- s i b l e excep t ion o f a few amino a c i d s , a r e n o t a v a i l a b l e f o r p l a n t up take . The N must f i r s t undergo b i o l o g i c a l t r a n s f o r m a t i o n by v a r i o u s components o f t h e s o i l m i c r o f l o r a t o be eventually r e l e a s e d a s ammonium, an h form r e a d i l y used by p l a n t s . Thi. r e l e a s e , o r " m i n e r a l i z a t i o n " o f o r g a n i c N , t o g e t h e r wi th N p r e s e n t i n p r e c i p i t a t i o n , f u l f i l l t h e N r equ i rements o f t h e p l a n t community (Wollum and Davey 1975) .

Ni t rogen m i n e r a l i z a t i o n i s g e n e r a l l y determined by t h e f a c t o r s t h a t i n f l u e n c e decomposi t ion o f o r g a n i c m a t t e r , such a s kind o f o r g a n i c m a t e r i a l , s o i l moisture, n u t r i e n t l e v e l s , and t h e s o i l macro- and m i c r o f l o r a (Bartholomew 1965; Witkamp and van d e r Drift 1961) . S p e c i e s v a r i a t i o n h a s been l i n k e d t o changes i n decomposi t ion r a t e s of f o r e s t t r e e l i t t e r (Witkamp 1966) . M i n e r a l i z a t i o n r a t e s g e n e r a l l y a r e t h e

h i g h e s t a t s o i l m o i s t u r e l c v e l s n e a r f i e l d c a p a c i t y ( S t a n f o r d and E p s t e i n 1974) . Ammonium p r o d u c t i o n d e c r e a s e s a t h i g h e r m o i s t u r c t e n s i o n s b u t s t i l l o c c u r s even when t h e s o i l s a r e helow t h e permanent w i l t i n g p o i n t ( M i l l e r and Johnson 1 9 6 4 ) . A s i m i l a r r e d u c t i o n i n N r e l c n s c i s observed i n wet and p o o r l y d r a i n e d s o i l s (T~rsncem and P a t r i c k 1971). S o i l chemical p r o p e r t i e s a r c s i g n i f i c a n t hecause t h c a p p l i c a t i o n o f f e r t i l i z e r and l ime can c a u s e l a r g e i n c r e a s e s i n n ~ j r ~ e r a l i z a t i o n r a t e s [Wil l iams 1972; Broadbent 1965) .

N i t r i f i c a t i o n , t l ie c o n v e r s i o n o f ammonium t o n i t r a t e by s o i l mic ro -o rgan i sms, h a s r e c e n t l y been r e c e i v i n g c o r l s i d e r a b l e a t t e n t - i o n 1)ccause of i n c r e a s e d awareness of t h e r o l e o f n i t r a t e s i n s t r eam, l a k e , and ground wa te r p o l l u t i o n . I n c o n t r a s t t o t h e p o s i t i v e l y cha-rged a~nnioniurrl i on , t h e n i t r a t e arl ion i s n o t t i g h t l y h e l d on soi l . exchange s i t e s and i s r e a d i l y l eached t h r o u g h t:he s o i l p r o f i l e . D i f f e r c n c e s i n t h e u p t a k e o r " p r e f e r e n c e " o f t r e c s f o r ilrnrnonium v s . n i t r a t e have a l s o been found ( K r a j i n a and o t l > c r s 1973; van den U r i e s s c h e 1971) , t1111s making s o i l n i t r i f i c a t i o n a f a c t o r i n deve lop ing a ~ ~ d e v a l u a t i n g f o r e s t f e r t i l i z a t i o n programs.

The b u l k of n i t r a t e producetl i n s o i l s i s g e n e r a l l y assumed t o come from t h e a c t i v i t y of a s e l c c t g roup o f a u t o t r o p h i c b a c t e r i a , p a r t i c u l a r l y Ni1:rosc~rnonne and Ni:trnhacber. Thcse organisms o b t a i n t l ~ c i r cne rgy s o l e l y from t h e o x i d a t i o n of N cornpo~rnds. Thc l e v e l s o f s o i l o r g a n i c m a t t e r have l i t t l e o r no d i r e c t c f f e c t on n i t r i f y i n g b a c t - e r i a because t h e y u s e ca rbon d i o x i d e a s a ca rbon s o u r c e (Wallace and Nicliolas 1869) . However, o r g a n i c matter . -indirectly a f f e c t s n i t r i f i c a t i o n by i n f l u - cnc ing s o i l mo. is ture l e v e l s , s o i l terrlperature, and c a t i o n exchange c a p a c i t y . N i t r i f y - i n g organisms a r e much more s e n s i t i v e t o v a r i a t i o n s in t h e s o i l environment than micro- organisms a c t i v e .in m i n e r a l i z a t i o n . N i t r i f i c a t i o n i s d r a s t i c a l l y reduced a t low soj.1 n ~ o j s t u r e l e v e l s and under a c i d s o i l cor ld i t ions ( S i e f e r t 1970; Mel'ri 1 1 and Dawson 1967; Re i chtnan and o t h e r s 1'366) .

The t y p e and l e v e l s o f wood r c s i d u c r -~ f fec te t l by v a r i o u s rnanajiemcnt p r a c t i c e s g r c a t l y i n f l u e n c e t h c development o f t h e s o i l m i c r o f l o r a , e s p e c i a l l y t h o s e a c t i v e i n t h e N-cycle . 1r.creast.d r c s idue u t i 1 i z a t i o n and p r e s c r i b e d burn ing would r educc t h e amount o f o r g a n ~ c m a t e r i a l incorporated i n t o t h e s o i l . Because many d i v e r s e micro- organisms f u n c t i o n il-1 t h e c y c l i n g of s o j l N , such r e d u c t - i o n s i n r e s i d u e cou ld havc many r a m i f i c a t i o n s . I n o r d c r t o f u l l y e v a l u a t e t h e p o s s i b l e s i g n i f i c a n c e o f res i .due p r a c - t i c e s on s o i l N t r a n s I o r m a t i o n , 2111 a s p e c t s of t h e N-cyclc must be c o n s i d c r c d .

Ni t rogen 1: ixat ion

The Impact o f f o r e s t nianagcment practices on t h e i n c l d c n c e and a c t i v i t y o f symbi- o t i c N- f ix ing a s s o c i a t i o n s d e s e r v e s s t u d y , particularly t h e l e s s consp icuous symbiotic p l a n t s . Opening o f t h e f o r e s t canopy, e l t h e r th rough harvesting o r f l r e , and t h e r e s u l t a n t change i n s o i 1 chcmlcal a r ~ d pllys i c a l p r o p e r t l e q cou ld f a v o r o r r e s t r i c t t h e clcvclopmcnt and e f f l c l e n c y o f an N - f l x l n g f l o r a (1.oneragan 1972; Nutman 1972) . In e i t h e r c a s e , t h e p o t e r ~ t i a l o f such changes shou ld LC c o n s i d e r e d .

Most o f t h e N- f ix ing mlcro-organlsrns, o t h e r t h a n t h e b lue -g reen a l g a e and t h c a n a e r o b i c p h o t o t r o p h l c bacteria, r e q u i r e a supp ly o f o r g a n i c ca rbon a s an ene rgy s o u r c e . Adeci~rate ene rgy s o u r c e s would seem p a r t i c u l a r l y impo-r.tant f o r t h e s e organisms because t h c y a r c i n c f f i c i c n t u s e r s o f carbohydrates (S tewar t 1 9 b 9 ) . The r e l a t i o n s h i p o f s o i l o r g a n i c m a t t e r t o N f l x a t i o n depends on t h e t y p e o f m a t e r i a l , i t s n u t r i c n t c o n t e n t , and on t h e i n l t l a l f e r t i l i t y of t h e s o i l (Ricc and o t h e r s 1967) . Thus, t h c removal of o r g a n i c m a t t e r from t h e s i t e by logg ing o r r c s i d u e u t l l i z a t l o n could a f f e c t t h e

a c t i v i t y of nonsymbiotic N-f ixers i n s o i l o r i n woody r e s idue . This nlay be accomplished by reducing t h e organic sources a v a i l a b l e t o t he se organisms o r by changing t he physi- c a l and chemical environmerit o f t h e s o i l (Jurgenscn 1973).

The breakdown and decay of woody t i s s u e could a l s o i n f luence t h e f o r e s t ecosystem by d i r e c t l y a f f e c t i n g N-f ixa t ion . The N conten t of wood/unit carbon i s lower than most o t h e r types of p l a n t t i s s u e . llowever, i n s p i t e o f t he se low l e v e l s of N, wood-destroying fungi a r c a b l c t o metabol ize t h e carbon-r ich s u b s t r a t e and produce sporocarps and l a r g e numbers of spores comparat ively r i c h in N (Mer r i l l and Cowling 1966). One pos s ib l e explana t ion f o r t h i s phenomenon i s fungal use of N produced hy N-fixing organisms presen t i n t h c wood. The N-fixing populat ion could use simplc sugars produccd by t h e fungal breakdown of wood and i n r e t u r n , supply N t o t he primary decomposers. The p o s s i b j l i t y of such a s y n e r g i s t i c r e l a t i o n s h i p was s t rengthened by t he r ecen t s tudy of Cornaby and Waide (1973) who showed low but s i g n i f i c a n t amounts of N were being f i xed i n decaying chestriut logs . S e i d l e r and o t h e r s (1972) and Aho and o the r s (1974) have found t h a t a s i z a b l e f r a c t i o n of b a c t e r i a i s o l a t e d from decay zones i n white f i r had an N-fixing c a p a b i l i t y . Knutson (1973) has observed t h a t b a c t e r i a i s o l a t e d from hea l t hy and water-soaked aspen were ab l e t o grow on N-free media.

Reductions in r e s idue l e v e l s by f i r e would have f a r d i f f e r e n t consequences on N - t r ansformat ions than wood removal through logging. As noted e a r l i e r , s t u d i e s conducted i n t h e Southeast over a 20-year per iod have shown no s i g n i f i c a n t l o s s of N from the s o i l due t o prescr ibed burning; i n f a c t , s o i l N i nc r ea se s of 23 kg/N/ha/yr a s soc i a t ed with annual burning on some s i t e s have been repor ted (Jorgensen and Wells 1971). Other i n v e s t i g a t i o n s have a l s o r epo r t ed i nc r ea se s i n t h e s o i l N conten t upon burning ( e . g . , Klemmedson and o t h e r s 1962). These N ga in s have been a t t r i b u t e d t o an increased legume component i n t h e ground vege t a t i on a f t e r f i r e (Stone 1971). Another p o s s i b i l j . t y i s t he g r e a t e r a c t i v i t y of nonsymbiotic N-f ixers , p a r t i c u l a r l y t h c au to t roph i c blue-grccn a lgae . Thc increased l i g h t and n u t r i e n t l e v e l s o f t h e s o i l su r f ace a s a r e s u l t of burning would favor t h e development of such organisms (Jurgensen and Lhvey 1968).

Minera l iza t ion

The mine ra l i z a t i on of N from s o i l o rganic mat te r can be a l t e r e d by f o r e s t management p r a c t i c e s . Harvest ing, f i r c , and s i t e p r epa ra t i on techniques have a l l been shown t o a c c e l e r a t e t h e r e l e a s e of o rganic N (DeBell and Ralston 1970; Likens and o t h c r s 1970; Neal and o t h e r s 1965). This i s due, a t l e a s t i n p a r t , t o t h e r e s u l t a n t changes of microclimate on t h e s o i l microf lora (Borman and o t h c r s 1968). The r e l e a s c of n u t r i e n t s and pll i nc r ea se a f t e r burning o r logging may a l s o favor t h e organisms r e spons ib l e f o r N m ine ra l i z a t i on . Much of t h e ammonium re l ea sed may be immobilized i n t h e breakdown of woody ma te r i a l s . Addit ional N w i l l e n t e r t he s o i l and become a v a i l a b l e f o r uptake by t r e e s . However, some may be leached below t h e r o o t zone o r l o s t through overland flow i f t h e topography i s s t e e p (DeByle and Packer 1972).

N i t r i f i c a t i o n

E f f e c t s of f o r e s t r y p r a c t i c e s on s o i l n i t r i f i c a t i o n r a t e s and t h e n i t r a t e conten t of water supp l i e s a r e now being quest ioned. Likens and o t h e r s (1970) showed t h a t c l e a r c u t t i n g and he rb i c id ing of nor thern hardwoods i n New Hampshire g r e a t l y increased t h e s o i l popula t ions of n i t r i f y i n g b a c t e r i a and, consequent ly, t h e l e v e l s of n i t r a t e i n neighboring watersheds. However, t h e l o s s of n i t r a t e a f t e r c l e a r c u t t i n g has been found t o be much lower i n o t h e r p a r t s o f t h e country (Reinhart 1973). These d i f f e r - ences seem t o be r e l a t e d t o s o i l type, with podzols being e s p e c i a l l y s u s c e p t i b l e t o n i t r a t e l o s s e s .

Burning of logging r e s idues has r e s u l t e d i n l a r g e i nc r ea se s i n s o i l ammonium l e v e l s (Chris tensen 1973; Neal and o t h e r s 1965), which may inc rea se s o i l n i t r i f i c a t i o n r a t e s . The r i s e i n s o i l pH a f t e r a f i r e would a l s o favor t h e n i t r i f y i n g b a c t e r i a .

Vegetational changes f o l l o w i n g h a r v e s t i n g o r f i r e may a f f e c t t h e l e v e l s o f s o i l n i t r a t e . The n i t r a t e c o n t e n t o f s o i l s s u p p o r t i n g r e d a l d e r is c o n s i d e r a b l y g r e a t e r t h a n s o i l under w e s t e r n c o n i f e r s (Trappe 1972) . T h i s s p e c i e s d i f f e r e n c e may be r e l a t e d t o t h e t a n n i n c o n t e n t s o f t r e e b a r k and i t s effect on n i t r i f i c a t i o n (Bollen and Lu 1969). P l a n t s p e c i e s i n v a d i n g a f o r e s t s i t e a f t c r d i s t u r b a n c e have been a s s o c i a t e d w i t h nitrification r a t e s h i g h e r t h a n r ;* tes i n c l imax e c o s y s t c ~ n s (R ice and Pancholy 1972) .

N i t r i f i c a t i o n i s a n i n e v i t a b l e p r o c e s s o c c u r r i n g i n m i l d l y a.cid t o a l k a l i n e s o i l s . Although t h e r e h a s been c o n s i d e r a b l e i n t e r e s t i n s u p p r e s s i n g t h e n i t r i f y i n g b a c t e r i a by a p p l y i n g chen l i ca l s ( P a r r 1 9 7 3 ) , t h e s e treatments, even i f s u c c c s s f u l , would l i k e l y be l i m i t e d t o r e l a t i v e l y s m a l l a r e a s o f p a r t i c u l a r env i ronmenta l c o n c e r n . Lncreases i n n i t r i f i c a t i o n w i l l g e n e r a l l y o c c u r a f t e r h a r v e s t i n g o r s i t e t r e a t m e n t o p e r a t i o n s , and due t o t h e n a t u r c o f t h e n i t r a t e i o n , w:il.l r e s u 1 t ' i . n i n c r e a s e d N l o s s from t h e s o i l . The e f f e c t o f N l o s s on s i t e p r o d u c t i v i t y depends on t h e amount o f N l o s t , i . n i t i a 1 s o i l f e r t i l i t y , and t h e e x t e n t of N g a i n s coming from N - f i x a t i o n .

Ni t rogen i s s u b j e c t t o v a r i o u s b i o l o g i c a l t r a n s f o r m a t i o n s , many o f which occur s i m u l t a n e o u s l y i n t h e s o i l . Any n a t u r a l o r man-induced charlges i n t h e p h y s i c a l and chemica l p r o p e r t i e s of a fo res t . s i t e w i l l g r e a t l y a f f e c t t h e a c t i v - i t y o f t h e r e s p o n s i b l e s o i l micro-organisms. I t i s i m p o r t a n t t o u n d e r s t a n d t h c impact f o r c s t management t -echniques and 0 t ) j e c t i v e s havc on t h e s e p r o c e s s e s . By i n v e s t i g a t i n g t h e N c y c l e and t h e organisms a c t i v e i n i t s f u n c t i o n i n g , problem a r e a s can be : i d e n t i f i e d and r e s o l v e d by a p p r o p r i a t e management and s i 3 . v i . c u l t u r a l a c t i o n .

liesearch Needs

Of p a r t i c u 1 . a ~ i n t e r e s t a r e t h e s o u r c e s o f N - f i x a t i o n i n fo res t - s o i l s and t h e i r c o n t r i b u t i o n t o t h e s o j l N s t a t u s . 'I'he impor tance o f t h , i s informat ior1 f o r e v a l u a t i n g t h e n u t r i e n t changes i n s o i l and w a t e r sys tcms h a s been s t r e s s e d (Rcinha-rt 1973) . Thc e f f e c t s of harvesting, f i r e , and r e s i d u e rcnloval on r a t e s o f N - f i x a t i o n , N - r e l e a s e from s o i l o r g a n i c m a t t e r , and n i t r i f i c a t i o n need t o be known. Also r e q u i r e d i s t h e e f f e c t o f t h e v e g e t a t i o n a l changes o c c u r r i n g a f t e r s i t e d i s t u r b a n c e on N t r a n s f o r m a t i o n s and i f i n c r e a s e d r e s i d u e removal w i l l s i g n i f i c a n t l y a l t e r t h e N b a l a n c e i n f o r e s t s o i l s , e s p e c i a l 1 y on s t e e p t c . r r a i n . Such i r ~ f o r m a t i o n wi.11 be r c y u i r e d t o c v a l u a t e t h e po tcn - t i a l long- term impact o f i n t e n s i v e f o r e s t r y o p e r a t i o n s on s i t - e p roduc t : i . v i ty .

Aho, P . E . , K. J . S e i d l e r , 11. J . Evans, and P . N . Raju. 1374. D i s t r i b u t i o n , enumera t ion , and i d e n t i f i c a t i o n of n i t r o g e n - f i x i n g b a c t e r i a

a s s o c i a t e d w i t h decay i n l i v i n g w h i t e f i r t r c e s . Phytopathology 64:1413-1420. Akkermans, A. I). L .

1971. N i t r o g e n f i x a t i o n and n o d u l a t i o n o f AZnus and Hippophue under n a t u r a l cond i - t i o n s . Ph.D. T h e s i s . I J n i v e r s i t y of Leiden, Hol land

A l l i s o n , F . E . 1965. E v a l u a t i o n of incoming and ou tgo ing p r o c e s s e s t h a t a f f e c t s o i l n i t r o g c n . I n :

S o i l n i t r o g c n , Agron. Monogr. 10 , p. 578-606. W . V . Bartholomew and F . E . C l a r k , eds. Am. Soc. Agron., Madison, Wisc.

Bartliolomcw, W . V . 1965. M i n e r a l i z a t i o n and i m m o b i l i z a t i o n of n i t r o g e n i n t h e decompos i t ion o f p l a n t

and an ima l residues. In: S o i l n i t r o g e n , Agron. Monogr. 10 , p . 285-306. W . V . Bartholomew and P . E . C l a r k , e d s . Am. Soc. Agron., Madison, Wisc.

Hessems, E . P. M . 1975. N i t r o g e n f i x a t i o n i n t h e p h y l l o s p h e r e o f Gramincae. Wagingen Agr ic . Res. Rep.

786, 68 p .

Bollcn, W . B . , and K . C . Lu. 1969. Douglas - f i r ba.rk t a n n i n decornpositi.on i n two f o r e s t s u i l s . I J . S . Dep. Agr ic .

For . S e r v . , Pac. Northwest For. and Kange Exp. S t n . Res. Pap. PNW-85, 12 p . Borrnann, F . H . , G . C . Likens, [I. W . F i s h e r , and R. S . F i c r c e .

1968. N u t r i c n t l o s s a c c e l e r a t e d by c l e a r c u t t i n g o f a forest - system. Sc icnce 159:882-884.

Bremner, J . M . 1967. Nitrogenous compounds. In: S o i l b iochemis t ry , p. 19-66. A . D . McLaren and

G . H . Pe te r son , eds . Marcel Dekkcr, New York. Broadbent, F . E .

1965. E f f e c t o f f e r t i l i z e r n i t r o g e n on s e l c a s e of s o i l n i t r o g e n . Proc. S o i l S c i . Soc. A m . 29:692-696.

C h r i s t e n s e n , N . L . 1973. F i r e and t h e n i t r o g e n c y c l c i n C a l i f o r n i a c h a p a r r a l . Sc ience 181;66-65.

Cornaby, B . W., and J . B . Waidc. 1973. Ni t rogen f i x a t i o n i n decaying c h e s t n u t l o g s . P l a n t and S o i l 39:445-448.

UeBell, D . S . , and C . W. R a l s t o n . 1970. Release of n i t r o g e n by burning l i g h t f o r e s t f u e l s . Proc. S o i l S c i . Soc. Am.

34:936-938. DeByle, N, V . , and P. E. Packer.

1972. P l a n t n u t r i c n t and s o i l l o s s e s i n over land f low from burned f o r c s t c l e a r c u t s . I n : Watersheds i n t r a n s i t i o n , p . 296-307, Sandor C . Csa l lany , Thad G . McLaughlin, and Williarn D. S t r i f f l e r , eds . Am. Water Resour. Assoc., l lrbana, I l l .

Dhar, N. R. 1960. Role of o r g a n i c m a t t e r i.n s o i l f e r t i l i t y . Trans . 7 t h I n t . Congr. S o i l S c i .

7 (4) :314-320. Dommergues, Y . , J . Balandreau, G . Rinaudo, and P. Weinhard.

1973. Nonsymbiotic n i t r o g e n f i x a t i o n i n t h e r h i z o s p h e r c s of r i c e , maize and d i f f e r - e n t t r o p i c a l g r a s s e s . S o i l B io l . Biochem. 5:83-89.

Dr iessche , R . van den. 1971. Response o f c o n i f e r s e e d l i n g s t o n i t r a t e and ammonium s o u r c e s o f n i t r o g e n .

P l a n t and S o i l 34:421-439. Fogg, G . E . , and W . D . P. S tewar t .

1968. I n s i t u d e t e r m i n a t i o n s of b i o l o g i c a l n i t r o g e n E i x a t i o n i n A n t a r t i c a . Bul l . Brit. A n t a r c t . Surv. 15:39-46.

G e s s e l l , S . P . , D. W. Cole, and E . C . S t e i n b r e n n e r , 1973. Ni t rogen ba lance i n f o r e s t ecosystems of t h e P a c i f i c Northwest. S o i l Ki.01.

Biochcm. 5:19-34. Greenland, D . J . , and J. M . L . Kowal.

1960. N u t r i e n t c o n t e n t o f t h e moist t r o p i c a l f o r e s t s of Ghana. P l a n t and S o i l 12~154-174 .

Hardy, R . W . F . , R . D . Burns, and R . D . Hols ten. 1973. Appl icat ior i o f t h e a c e t y l e n e - e t h y l e n e a s s a y f o r nleasusement o f n i t r o g e n

f i x a t i o n . S o i l B i o l . and Riochem. 5:47-81. Hardy, K. W . F . , R . D . Hols ten , E . K . Jackson, and R , C . Burns.

1968. The a c e t y l e n e - e t h y l e n e a s s a y f o r N2 f i x a t i . o n : l a b o r a t o r y and f i . e l d c v a l u a t i o n . P l a n t . Phys io l . 43:1185-1207.

Heilman, P . S . 1961. E f f e c t s of n i t r o g e n f e r t i l i z a t i o n on t h e growth and n i t r o g e n n u t r i t i o n of

low s i t e i ) o u g l a s - f i r s t a n d s . Ph.l). Thes i s . Univ. o f Washington, S e a t t l e . Henriksson, E . , and B . Simu.

1971. Ni t rogen f i x a t i o n by l i c h e n s . Oikos 22:119-121. Henze l l , E . F . , and D . 0 . N o r r i s .

1962. Processes by which n i t r o g e n i s added t o t h e s o i l / p l a n t system. I n : B u l l . Commonw. Bur. P a s t . F i e l d Crops 46: l -18.

I k e , A . F . , and E . L . S tone. 1958. S o i l n i t r o g e n accumulat ion under b lack l o c u s t . Proc. S o i l S c i . Soc. Am.

22:346-349.

I swaran , V . , A . S c r i , and R . Apte . 1973. Aaotobacter chroococc7nm i n t h e p h y l l o s p h c r e o f w a t c r h y a c i n t h (E7I.ckhorni.a crossipes (Most.) Io ln ia) . P l a n t and S o i l 39:461-463.

J e n s c n , H . I,. 1965. Nonsymbiotic n.i.trogen f i x a t i o n . I n : S o i l n i t r o g e n , Agron. Monogr. 10 , p .

436-480. W . V . Hartholomew and F. E . C l a r k , e d s . Am. Soc. Agron. , hladison, Wisc. *Jones , K .

1970. Ni t rogen f i x a t i o n i n t h e p h y l l o s p h e r e o f t h e 1 ) o u g l a s - f i r , Pseudotsuga doug%asii. Ann. Bot. 36 : 239-244.

J o r g e n s e n , * I . K . , and C. G . Wcl ls . 1971. Apparent n i t r o g e n f i x a t i o n i n s o i l i n f l u e n c e d by p r e s c r i b e d b u r n i n g . P roc .

S o i l S c i . Soc . Am. 35:80b-810. J u r g e n s e n , M. F .

1973. R e l a t i o n s h i p between r~onsymb-iotic n i t r o g e n f i x a t i o n and s o i l n u t r i e n t s t a t u s - - a r e v i c w . J . S o i l S c i . 24:512-522.

, Jurgcnsen, M . F . , srld C . H . Davcy. 1968. N i t r o g e n - f i x i n g b lue -g reen a l g a e i n a c i d f o r c s t and n u r s e r y s o i l s . Can. J .

M i c r n b i o l . 1 4 : 1179-1183. , Jurgensen, M . F . , and C . B . Davcy.

1970. Norisymbiotic n i t r o g e n - f i x i n g micro-organisms i n a c i d s o i l s and t h e r h i z o s p h e r e . S o i l s P e r t . 33:435-416.

K a r j i n a , V . J . , S . Madoc-.Jones, and G . M e l l o r . 1973. Ammoni~rm and n i t r a t e i n t h e n i t r o g e n cconomy o f some c o n i f e r s growing i n

D o u g l a s - f i r cornmunitics o f t h e Paci f i c Northwest o f Amcri.c,a. So i 1 Ri.01. Biochem. 5:143-147.

Klernmedson, J . (I., A. M . S c h u l t z , H . J e n n y , and t-1. 11. B i s w e l l . 1962. E f f e c t o f p r e s c r i b e d b u r n i n g on f o r e s t l i t t e r and t o t a l s o i l n i t r o g e n . P roc .

S o i l S c i . Soc . Am. 26:200-202. Knight , H .

1966. I.oss o f n i t r o g e n fro111 t h e f o r e s t . f l o o r by b u r n i n g . F o r . Chron. 42:149-152. Knutson, D . M.

1973. 'I'hc b a c t e r i a of sapwood, wetwood, and heartwood o f t r e m b l i n g a s p e n . Can. J . Bot. 51 :498-500.

I . jkens , (;. E . , F . tl. Borman~l, N . M . Johnson, D. W . F i s c h e r , and R . S . P i e r c e . 1970. E f f c c t s o f f o r e s t c u t t i n g and 11erh-ici.de t r e a t m e n t on n u t r i e n t budge t s i n t h c

I-lubbard Brook wa te r shed ecosystem. Ecol . Monogr. 40: 23-47. Loncragan, J . I:.

1972. Thc s o i 1 chcmical environment i n r e l a t i o n t o symb.i.otic n i t r o g e n f i x a t i o n . I n : IJse o f i s o t o p e s f o r s t u d y o f f e r t i l i z e r u t i l i z a t i o n by legume c r o p s . I n t . Atomic Energy Agency Tech. Rcp. 1.49: 17-54.

Malo, B. A . , and E . K . P u r v i s . 1964. S o i l a b s o r l ~ t i o n of a t n ~ o s p h e r - i c ammonia. S o i l S c i . 97 : 242-247.

M e r r i l l , L . G . , and . I . E . Dawson. 1967. P a t t e r n s obse rved f o r t h e o x i d a t i o n of ammonium t o n i t r a t e by s o i l o rgan i sms .

P r o c . S o i l S c i . Soc . Am. 31:757-760. M e r r i l l , W., and E . B . Cowling.

1966. Role o f n i t r o g e n i n wood d e t e r i o r a t i o n : amount. and d : i s t r i b u t i o n o f n i t r o g e n i n f u n g i . Phy topa tho logy 56: 1083-1090.

M i l l e r , K . D. , arid D. D . Johnson . 1961. The e f f e c t o f s o i l m o i s t u r e t e n s i o n on ca rbon d i o x i d e e v o l u t i o n , n i t r i f i c a t i - o n ,

and n i t r o g e n n ~ i n e r a l i z a t i o n . P r o c . S o i l S c i . Soc . Am. 28:644-647. Moore, A. W .

1966. Nonsyrnbi.otic n i t r o g e n f i x a t i o n i n s o i l and s o i l - p l a n t sys t ems . S o i l s F e r t . 291113-129.

Neal , .J. L., J r . , E . Wright , and W . B. Hol len . 1965. Burnirlg Douglas-f i s s l a s h . P h y s i c a l , chemica l , and m i c r o b i a l e f f e c t - s jn

s o i l . Oreg. S t a t e Llniv. 1:or. Res. Pap. 1 , 32 p .

Newton, M . , B . A . E l Hassan, and J. Zavi tkovsk i . 1968. Role of r e d a l d e r i n westcrn Oregon f o r e s t s u c c e s s i o n . I n : Biiology o f a l ,de r ,

1). 73-84. J . W . Trappe, J . F . F r a n k l i n , R . F. T a r r a n t , and G . M . Hanson, eds . U.S. Dep. Agr ic , For . S e r v . , Pac. Northwest F o r . and Range Exp. S t n .

N o r r i s , D . 0 . 1962. The b i o l o g y o f n i t r o g e n f i x a t i o n . Bul l . Commonw. Bur. P a s t . F i e l d Crops

46:1113-127. Nutman, P . S .

1972. The i n f l u e n c e o f p h y s i c a l environmental f a c t o r s on t h e a c t i v i t y of Hhizobium i n s o i l and i,n symbiosis . I n : Use o f i s o t o p e s f o r s t u d y of fertilizer u t i l i z a t i o n by legume c r o p s . I n t . Atomic Energy Agency Tech. Rep. 149:55-84.

P a r r , J . F . 1973. Chemi.ca.1 and biochemical c o n s i d e r a t i o n s f o r maximizing t h e e f f i c i e r l c y o f

f e r t i l i z e r n i t r o g e n . J . Rnviron. Qual. 2:75-84. P ike , I , . H . , D . M . T racy , M . A . Sherwood, and D . N i e l s e n .

1972. Es t imates o f biomass and f i x e d n i t r o g e n o f e p i p h y t e s from old-growth Douglas- f i r . I n : P roc . Research on c o n i f e r o u s f o r e s t ecosystems-.-a synlpos.i.urn, p . 177-187. U.S. Dep. Agr ic . For . S e r v . , Pac. Northwest For . and Range Exp. S t n . , P o r t l a n d , Oreg .

P o s t g a t e , J . R . 1971. Relevant a s p e c t s of t h e p h y s i o l o g i c a l chemis t ry o f n i t r o g e n f i x a t i o n . SYIIIP.

Soc. Gen. Microb io l . 21:287-307. Rambel l i , A.

1973. The r h i z o s p h e r e o f mycorrhizae . I n : Ectomycorrhizae: t h e i r ecology and phys io logy , p . 299-349. T . '1'. Kozlowski, e d . Academic P r e s s , N . Y .

Rcichman, G . A . , D . 1 , . Grunes, and F. G . V ie tx , J r . 1966. E f f e c t of s o i l m o i s t u r e on amrnonification and n i t r i f i c a t i o n i n two n o r t h e r n

p l a i n s s o i l s . Proc. S o i l Sci ."Soc. Am. 30:363-366. R e i n h a r t , K . G .

1973. Timber-harvest c l e a r c u t t i n g and n u t r i e n t s i n t h e n o r t h e a s t e r n Uni ted S t a t e s . IJSDA For. S e r v . NE-170, 5 p. Nor theas t For. Exp. S t n . Upper Darby, Pa.

Rhychert., R . C . , and . J . S k u j j n s . 1974. Ni t rogen f i x a t i o n by b lue -green a l g a e - l i c h e n c r u s t s i n t h e Great Basin d e s e r t .

P roc . S o i l S c i . Soc. Am. 38:768-771. Rice , E . L . , and S . K . Pancholy.

1972. I n h i b i t i o n o f n i t r i f i c a t i o n by c l imax ecosystems. A m . J . Bot. 59:1033-1040. Rice, W . A . , E . A . P a u l , and L . R . Wet ter .

1967. The r o l c o f anaer0b ios i . s i n asymbio t i c n i t r o g e n f i x a t i o n . Can. J . Microb io l . 13:829-836.

R ichards , B . N . 1964. F i x a t i o n o f a tmospher ic n i , t rogen i n c o n i f e r o u s f o r e s t s . Aus t . For . 28:68-74.

R ichards , B. N . 1973. Ni t rogen f i x a t i o n i n t h e r h i z o s p h e r e of c o n i f e r s . S o i l R i o l . Biochem.

5:149-152. Richards , B. N . , and G . K . Voigt .

1965. Ni t rogen a c c r e t i o n i n c o n i f e r o u s f o r e s t ecosystems. I n : F o r e s t s o i l r e l a t i o n - s h i p s i n North America, p . 105-116. C . T . Youngberg, e d . Oreg. S t a t e IJniv. P r e s s , C o r v a l l i s .

Ruincn, J . 1956. Occurrence of Be i j e r inckCa s p e c i e s i n t h e p h y l l o s p h e r e . Nature 177:220-221.

Ruinen, J . 1965. The phy l losphere . 111. Nitrogen f i x a t i o n i n t h e p h y l l o s n h e r e . P l a n t and

S o i l 22:375-394. Ruinen, J .

1970. The p h y l l o s p h e r e , V . The g r a s s s h e a t h , a h a b i t a t f o r n i t r o g e n - f i x i n g microorganistns. P l a n t and S o i l 33:661-671.

S e i d l e r , R . , J . , P . E . Aho, R . N . Ra ju , and 11. J . Evans . 1.972. N i t r o g e n f i x a t i o n by b a c t e r i a l i s o l a t e s from decay i n l i v i n g w h i t e f i r e t r e e s

(Abies concnZnr ((;ortl. and Glend . ) !,indl . ) . .J. Gen. Microbial . 73:413-416. S e i f e r t , J .

1970. 'I'he i n f l u e n c e o f m o i s t u r e on t h e d e g r e e o f n i t r i f i c a t i o n i n s o i l . h c t a IJniv. C a r o l . - R i o l . 19G9:353-360.

S l l i e l d s , I,. P.1. 1!)57. Algal and 1 i c h e n f l o r a s i n r c l a t i o n t o n i t r o g e n content . o f c e r t a i n v o l c a n i c

and a r i d r angc s o i l s . Ecology J8 :661-663 . S i l v c r , W . S . , and '1'. Maguc.

1970. Assessnicnt o f n i t - rogen f i x a t i o n i n t c r r e s t r i n l environments i n f i e l d cond i - t i o n s . Na tu re 227 :.378-379.

S i l v c s t e r , I Y . B., a n d K . J . R e n n e t t . 197.3. Acetylene rc r luc t ion by r o o t s ant1 a s s o c i a t e d s o i l o f New Zenland c o n i f e r s .

S o i l B i o l . Riochem. 5 :171-179. S t :~ l i fo rd , G. , nnd E . E p s t e i n .

1976. Ni t rogen ~ n i n e r a l i z a t ion-water r e l a t i o n s i n s o i l s . P r o c . S o i l Sc i . Soc. A m . 38 : 103-107.

S t a r k e y , It. 1.. 1958. l n t c r r c l a t i o r ~ s l l i ~ ) I ~ ~ t w e e r l microorganisms and p l a n t r o o t s i n t h e r l l i zosphere .

H a c t c r i o l . Rev. 2 2 : 1.52-172. Stcwnr't., 1V. D. P.

19hb. Ni t rogcn f i x a t inn i n p l a n t s . Atl l lone P r e s s , L,ondon, 168 p . Stcwnr ' t , W . D. P.

1969. B i o l o g i c a l and ecological a s p e c t s o f n i t r o g e n f i x a t i o n by f r e e - l i v i n g o rgan i sms . P r o c . Roy. Soc. 172B :3h7-388.

S t o n e , E . L . 7 E f f e c t s o f p r e s c r i b e d b u r n i n g on long- term*i>roduct . iv i ty o f c o a s t a l p l a i n

s o i l s . T r l : P r o c . P r e s c r i l ~ c d Burning Symp., p . 115-127. U.S. Dep. A g r i c . F o r . S e r v . , S o u t h e a s t For . Exp. S t n .

S t o n e . F.. I . . 1973. Regional o l ~ j e c t i v c s i n f o r c s t f e r t i . 1 i z a t i o n , c u r r e n t and p o t e n t i a l . In:

1,'orest fertilization, p . 10-18. 11,s. Uep. A g r i c . F o r . S c r v . , N o r t h e a s t . For . Exp. S t n .

T rappe , , J . M . 1972. Regrll n t ion o f s o i l o r ~ a n i s m s by red a l d e r : a p o t e n t - i a l b i o l o g i c a l sys t em f o r

c o n t r o l of Poria ~ ~ ~ i r ' i i . i n : Managing young f o r c s t s i n t h c Llouglas - f i r r e ~ g i o n , v o l . 3 , p . 35-51. A. B . Berg l e d . ) . Oreg. S t a t e Univ. P r e s s , Corvallis.

r , lusncern, M. E., and W . tl. P a t r i c k , J r . 7 N i t:rogerl t r a n s f o r m a t i o n s i n waterlogged s o i 1 . La. S t a t e Univ. A g r i c . t x p .

S t n . Bu1.l.. 657, 75 p . VanClevr, K., L . A. V i c r c c k , and R . I,. S c h l e n t n e r .

11171. Accumulation o f n i t r o g e n i l l a l d e r (ALnus) ecosystems near F a i r b a n k s , A l a s k a . ArcT. a n d Alp. l tcs . 3 :101-114.

V l a s s a k , K . , E. A . P a u l , and R. E . f - l a r r i s . 1973. Assessmerit. o f l ~ i o l o g i c a l n i t r o g e n f i x a t - i o n i n g r a s s l a n d and a s s o c i a t e d s i t e s .

P l a n t and S o i l 38:037-6/19, Wal l ace , W., and 0. J . D. N i c h o l a s .

1969. The b i o c h e m i s t r y o f n i t r i f y i n g microorganisms. Biol . Rev. 44:359-391. I U i l l i a ~ ~ i s , B . I.>.

1 9 7 2 . Ni-trogen m i n e r a l i z a t i o n and o r g a n i c m a t t e r d e c o m p o s i t i o r ~ i n S c o t s p i n e humus. F o r e s t r y 45 : 177-188.

Witknnip, M . 1966. Decomposit ion o f l e a f l i t t c r i n r e l a t i o n t o env i ronment , m i c r o f l o r a , and

m i c r o b i a l r e s p i r a t i o n . Ecology 47:194-201. Witkamp, M . , and J . van d e r D r i f t .

1961. Breakdown o f f o r e s t l i t t c r i n r e l a t i o n t o env i ronmenta l f a c t o r s . P l a n t and S o i l 15:295-311.

IVollum, A. G . 11, C . T. Youngberg, and C . M . Gilmour. 1966. C h a r a c t e r i z a t i o n o f a Straptomyeas s p . i s o l c i t e d from r o o t nodu les of

Ceanothus u e l u t i n u s Dougl. P roc . S o i l S c i . Soc. Am. JO:463-467 . Wollum, A . G . 1 1 , and C . B . Uavey.

1975. Ni t rogen accurnulatjon, t r ans for tna t ion , and t ransp0r . t i n f o r e s t s o i l s . In: Proc. 4 t h N , Am. l o r . S o i l s Conf . , Quebec, 197.3.

Yoshida, T . , and K . K. Anr,ijas. 1973. 'I'he f i x a t l o n o f a tmospher ic n i t r o g e n i n t h e r i c c r h i z o s p h c r e . Soi 1 B i o l .

Kiochern. 5 : 15.7-155. Youngberg, C . T .

1966. t o r e s t f l o o r s in 1 ) o u g l a s - f ~ r f o r e s t s : I . Dry weight and chemical p r o p e r t i e s . Proc. S o i l S c i . Soc. Am. 30:406-409.

Youngberg, C . T . , and A. G . Wollum 11 . 11170. Non-leguminous syrnbiotlc n i t r o g e t \ f i x a t i o n . in: I'rec growth and f o r e s t s o i l s ,

p . 383-395. C. T . Youngberg and C . B . Davcy, e d s . Oreg. S t a t e Univ. P r e s s , C o r v a l l i s .

Zavi t k o v s k i , .I. , and M. Newton. 1967. The r o l e of s~lowbrush (CeanoLhus z>~Lut inzls I)ougl.) 2nd r e d a l d e r (AZnus rubrn

Bong.) jn f o r e s t r e g e n e r a t i o n i n t h e P a c i f i c Northwest. Prnc. IIJFRO Congr . , Sec . 2 1 , p . 429-440.

Z o c t t l , H. 1965. Accumulation and transfox.nlat ion of n i t r o g e n i n f o r e s t \o i 1 s . Bcr. Dcutsche

Bot. C e s e l l . 78:167-180.

Pathogen Activity

F o r e s t d i s e a s e s have heen r e f e r r e d t o a s n e g a t i v e i ~ ~ f l u e n c e s i n t h e f o r e s t environment (Boyce 1961; l luher t 1931) . Ilowcver, i n tcrms of p roduc t - iv i ty and s t a h i l i z a - t i o n o v e r many generations, many d i s e a s e s nlay prove u s e f u l t o n a t u r a l f o r e s t ecosystems, p a r t i c u l a r l y i n n o r t h t empera te f o r e s t s where o r g a n i c m a t t e r i s g e n e r a l l y produced a t a h i g h e r r a t e t h a n i t can be r c c y c l e d t l ~ r o u g h t h e p r o c e s s o f decay (Olsen 1963) .

I t i s g e n e r a l l y thought t h a t overmature f o r e s t s a r e more p rone t o f i b e r - d e s t r o y i n g d i s e a s e , p a r t i c u l a r l y stem dccays , than young v igorous f o r e s t s (Koyce 1961) . As more and more o f a s i t e ' s raw m a t e r i a l s become t i e d up i n p l a n t b o d i e s , t h e p l a n t s occupying t h a t s i t e become l e s s t h r i f t y ancl more prone t o i n s e c t and d i s e a s e a t t a c k . Th i s condi- t i o n w i l l e v e n t u a l l y l e a d t o an ccosystem whose p r o d u c t i v i t y , i n tcrms o f u s a b l e f i b e r p roduc t ion and game h a b i t a t , may be ex t remely low. Other a s p e c t s of p r o d u c t i v i t y , f o r example, watershed p r o t e c t i o n , may n o t h e g r c a t l y impaired. As dead p l a n t b o d i e s ( f u e l ) accumulate , t h e y become s u b j e c t t o f i r e s d u r i n g d r y seasons . E v e n t u a l l y , i n s e c t and d i s e a s e a t t a c k s , in c o o r d i n a t i o n w i t h d r y seasons and l i g h t n i n g s t o r m s , p rov ide c o n d i t i o n s i n which w i l d f i r e s a r e t h c pr imary nlearis o f r e j u v e n a t i n g t h e system (Lyons and Penge l ly 1970; Komarek 1963) . Under n a t u r a l c o n d i t i o n s t h i s p r o c e s s ( c y c l e ) i s r e p e a t e d f r e q u e n t l y .

Disease l l l o s s o s , q q a s t r a d i t i o n a l l y viewed by f o r e s t e r s and p a t h o l o g i s t s , may be n a t u r a l s i t e c h a r a c t e r i s t i c s s i m i l a r t o s u n l i g h t , m o i s t u r e , and o t h e r f a c t o r s . In a t l e a s t one c a s e , a stem decay h a s been c i t e d a s an agcn t t h a t may h e l p t o p r e s e r v e a f o r e s t c l imax t imber t y p e , t h c C a l i f o r n i a redwood (Stone and o t h e r s 1972) . In t h i s c a s e , sten1 decay c o n t r i b u t e s t o stetn breakage d u r i n g h i g h winds which i n t u r n p r e v e n t s u p r o o t i n g , t h u s s t i m u l a t i n g r o o t s p r o u t r e g e n e r a t i o n . Fxcess l o s s e s , however, can be i n t e r p r e t e d a s a b i o t i c i n d i c a t o r t h a t s i t c r e j u v e n a t i o n i s r e q u i r e d o r an i n a p p r o p r i - a t e s t a n d compositiori must be changed i n o r d e r t o main ta in s t a b i l i t y .

I n t r o d u c e d pa thogens , such a s w h i t e p i n e b l i s t e r r u s t , a r e r io t ab le e x c e p t i o n s t o a sys tem w i t h i n \~iliich cndcmic d i s e a s e s nlay s e r v e a n a t u r a l f u n c t i o n . Imported d i s e a s e s i n t e r r u p t n a t u r a l f low o f enc rgy 1)y c r c a t ing f i r e - c o n d u c i v e c o n d i t i o n s i n u n n a t u r a l c i r c u m s t a n c e s . t - la rves t ing a c t i v i t i e s , when n o t conducted w i t h i n t h e framework o f t h e n a t u r a l ecosys tem, may a l s o s e r v e t o i n t e r f e r e w i t h n a t u r a l s i t e development t o c r e a t e b i o t i c p rob lems . Management s h o u l d complement t h e f low o f t h e ecosystem and c o u l d improve t l ~ e e f f i c i e n c y u f n a t u r a l p r o c e s s e s .

By removirlg rcs i . s t :ant h o s t s from t h e p r o x i m i t y of h c a v i l y i n f e c t e d s t a n d s , f i r e Inay have changed t h e g e n e t i c evol i l t . ion o f h o s t s and p a r a s i t e s i n f i r e - d o m i n a t e d f o r e s t s . The accumula t ion o f r c s i s t a n c c , no rmal ly a s s o c i a t e d w i t h d e l i c a t e l y ba lanccd h o s t - p a r a s i t e c o e v o l u t i o n , may have bcen p r e v e n t e d th rough elimination o f t h e h e s t s o u r c e o f genes t o p r o v i d e r c s i s t a n c e . 'l 'hus, r e s i s t a n t i n d i v i . d u a l s , due t o t h e i r c l o s e 1)roximity t ,o hcavy f u c l s jdcad o r ( lying n e i g h b o r s ] , have a h i g h 1i .keli l iood o f d t , s t ruc t i . on by w i l d f i r e . Such an e x p l a n a t i o n has been sugges ted f o r t h e l a c k o f r e s i s t a n c c t o certn.il.1 dwarf m i s t l e t o e s (Ruth 1966). C e r t a i n l y , t h e r e l a t i v c e f f i c i e r l c y of w i l d f i r e s a n i t a t i o l ~ h a s bcen a major f a c t o r i n l i m i t i n g dwarf l i i i s t l e t o e s i n some s i t u a t i o n s and c l i s p c r s i n g tllenl i n o t l l e r s (Alexander and tiawksworth 1975) . O the r d i s e a s e s , p a r t - i c u l a r l y o f t h e a e r i a l p a r t s of- f o r c s t t r e e s , have p r o b a b l y hecn cori- s t r a i n e d t o v a r y i n g d e g r e e s (Chapman 1 9 2 7 ) , dependi.ng on t h e i r dispersal c a p a b i l i t y . A s 2 r e c y c l i n g a g e n t i n t h e f o r e s t . ecosystem, d i s e a s e may h e s o impor tan t t h a t i . n t e rna1 mechanisms have deve loped t o d i s c o u r a g e t h e i n c o r p o r a t i o n o f r e s i s t a n c c genes i n h o s t ~ ~ o p u l a t . i o n s . 'T'his would a s s u r c a c o n t i n u i n g r o l e f o r pa thogcns . '.l31~e a l ~ p a r c ~ ~ t l a c k of e f f c c t i v c r c - s i s t a n c c t o rnnny f o r e s t . d i . s eases may, t h e r e f o r e , be a rli r c c t r c s u l t o r n a t u r a l w i l d f i r e .

A s martagenlent becolnes more i n t c n s i v c and u t . i l i z a t i o n r e p l a c e s o r moderates some o f (lie e f f e c t s of f i r e i n many a s p e c t s o f t h e ene rgy c y c l i n g o f f o r e s t s , pe rhaps t h e e r a d i c a t i v c e f f e c t of w i l d f i r e on r e s i s t a n t genotypes can be r e v e r s e d . C o n s i d e r a b l e b e n e f i t may h e a v a i l a b l e th rough p e r m i t t i n g resistance t o d i s e a s e s t o h e i n c o r p o r a t e d i n t o t he gene p o o l s o f f o r c s t p l a n t s . T h i s could be clonc th rough management o f f u c l s by p r e s c r i b e d f i r e and i n c r c a s c d u t i l i z a t i o n i n c o n c e r t w i t h selection o f l e a v e t r e e s , p l a n t i r ~ g s t o c k , o r botl-1.

Fire trs r l Dll.sljer::iq Agent

A1 though w i l d f i r e i s ~ n n i n l y an a g e n t of-: s a n i t - a t i on , i t s v a r y i n g i n t e n s i t i e s some- t i rnes c r e a t e s t l i s c o n t i n u o u s e f f e c t s . Seve ra l g e n e r a t i o n s ( c y c l e s ) of f i r e rrlay b e r e q u i r e d t o l u l l y covc!r a f o r e s t . ecosystem. On a more l o c a l i z e d and t i m e - l i m i t e d t ~ a s i s , p a r t . i c u l a r l y i n a r e a s w i t h I - c l a t - i v e l y low f i r e f r equency and d i s c o n t i n u o u s s p r e a d , i n c r e a s e s in t h e i n t c n s i t y and l o s s e s from d i s e a s e s can r e s u l t .

F i r e frequency v a r i e s w i t h s p e c i f i c c o n d i t i o n s and i s c h a r a c t e r i s t i c of t h e s i t e (Ilabeck and Mutch 197.3). Pres~irnably , s i t e , s p e c i e s , and f i r e f r e q u e n c i e s havc evolved s o a s t o ba lance t h e ccosystern a t t h e maximum p-roduct ion l e v e l c o n s i s t e n t w i t h s t a b i l i t y . Al though a s p e c i f i c s t a n d ma); riot. be o p t i m a l l y productive o r s t a b l e , t h e ecosystem i s . When f i r e o c c u r s , i t a c t s a s a n a t u r a l s a n i t i z i n g and r e j u v e n a t i n g a g e n t (T\luller 1'321); Wcir 19233, which s e r v c s t o b a l a n c e ene rgy f l o w . In t h e n a t u r a l s t a t e , t h i s sys tcm p r o v i d e s a hc te rogc~ncous f o r e s t of h i g h l y mixed a g e s and s p e c i e s (Ilabeck and Mutch 19731, a s i t u a t i o n t h a t can be c o n s i d e r e d i d e a l w i t h r e s p e c t t o minimizing triost d i s e a s e l o s s e s . Converse ly , f i r c e x c l u s i o n o v e r a. l ong p e r i o d , o r d e v a s t a t i n g f i r e s o v e r l a r g e a r c n s , produce a s i t u a t i o n :innlogous t o a g r i c u l t u r a l monocul ture : l a r g e expanscs o f f r e q u e n t l y ovc r s tocked s i n g l e - a g e f o r e s t s w i t h l i m i t e d numbers o f s p e c i e s . T h i s s i t u a t i o n i s i d e a l f o r max in~ iz ing s p r e a d and i n t e n s i t y o f most d i s e a s e s (Day 1 9 5 5 ) .

\:ire s c a r s r e p r e s e n t a major r ~ d t u r a l i n f e c t i o n c o u r t f o r marly r o o t and b u t t r o t f u n g l (Hepting and Shlgo 1972; Toolc 1959; Nordin 1958; tL~sham 1957; Toole and I:urnival 1957; Burns 1955; Gustafson 11146; Gxrren 1941; Hcptlng 1941; l l a r t 1938; S t i c k e l and Marco 1936; Hept ing and 1Iedgccock 1935; Kaufert 1933; Nclson and o t l ~ e r s 1933; McCarthy 1928; S c h n ~ i t z and Jacksoil 1927; Lachmund 1923, I t - ) t l ; Doyce 1921) , ancl a t l e a s t a s i g - r i l f i c d n t onc f o r s e v e r a l stem canker f u n g i (Ilaig 19.78; Dearness and Ilansbrough 1934) . Incomplete p o s t f i r e r e n ~ o v a l of dwarf m i s t l e t o e - i n f e c t e d o v e r s t o r y c r e a t e s a s i t u a t i o n i d e a l f o r t h e sp read and i n t e n s l f i c a t l o n o f damagc from t h e n ~ l s t l e t o e p a r a s i t e s (Alexander and Ilawkswortll 19753 . W i l d f i r e a l s o c o n t r i b u t e ? t o i n c r e a s e d d i s e a s e pro])- l e n ~ s by c r e a t i n g t h i c k s t a n d s 'In w h ~ c h I n t e n s e compet i t ion f u r s p a c e , m o i s t u r e , and ~ i u t r l e n t s wcakcns t r c e s . Such a s t a n d i s an i d e a l s u b s t r a t e f o r r o o t and stern decay fung I (Kaxter 19h7; Boyce 1961) .

D i s e a s e s , l i k c dwarf m i s t l e t o e , whosc d i s t ~ i b u t i o r l and i r ~ t e n s i t y arc d i r e c t l y dcpcndent on f i r c h i s t o r y (Alexandcr and HawkswortE~ 1975) , should g radua l 1 y he e l i l n i na ted through improved h a r v e s t i n g p r a c t i c e s . The e f f c c t s of rnost o t h e r endentic pathogens can he minimized by c o n t r o l l , ing s t a n d a g e , v i g o r , composi t ion, and inoculum. 'They probably have been reduced through t h e s a n i t i z i n g c f f c c t of r ~ a t u r a l w i l d f i r e (Ileinselnian 1971; Chaparan 1927) .

past GffirLs of Disease Conf~roL I h m i ~ g h Usa of' Fire

'The e f f e c t i v e n e s s o f p r e s c r i l ~ e d f i r c and rcmoval. of r e s i d u e s a s a s a n i t i z i n g t r e a t . - ment f o r d i s e a s e i s wide ly recogn ized and has provided t h e impctus f o r a number of bo th s u c c e s s f u l and u n s t ~ c c e s s f u l a t t e m p t s t o c o n t r o l fo res t : pa thogens . Tn Michigan, a t t e m p t s t o e r a d i c a t e t h e swec t fc rn b l i s t e r rus t . (Crlonarjtiwn cornpt;oniae) by burn ing t h e i n f c c t e d p i n e s and t h e a l t e r n a t e h o s t were unsuccess fu l [Baxter 1967) . In t h e l a t c 1940 '5 , p r e s c r i b e d burn ing t o c o n t r o l t h e f u s i f o r m r u s t (Cr~onnrl; im fusiforme) i.n t h e s o u t h e r n Uni ted S t a t e s f a i l e d (S iggers 1949) . I n t h e l a t t c r c a s e , inoculum was reduccd, b u t c o u n t c r l ~ a l a n c i n g ep idemio log ica l f a c t o r s were s u f f i c i e n t . t o o f f s e t t h e gai.n. Inoculum r e d u c t i o n and lowered d i s e a s e i n c i d e n c e were achicved by f i r e i n t h e sou th - e a s t , and i n I n d i a w i t h t h e brown-spot n c e d l e d i s e n s e (:;c~rrhia rzcic?ola) and S e p t o ~ ~ i a p i n i o f l o n g l c a f pi.ne (S iggers 1944, 1932; Gihson 1938; Chapman 1 9 2 7 ) .

111 many s e c t i o n s o f t h e coun t ry , f i r c i s a s s o c i a t e d wi th an i n c r e a s e i n Hibes p o p u l a t i o n s (Davis and Klehm 1939) t h a t suppor t whi te p i n c h l i s t e r r u s t , and an i n c r c a s c i n oaks t h a t s c r v c a s a1 t e r n a t e h o s t s f o r t h e f u s iforni r u s t i n t h e s o u t h e a s t . 'I'he sp read and i n t e n s i f i c a t i o n of Nectricr and C:jtospor>a cankcr (Haig 1938; Dearncss and ~Iansbrough 1934) and m o d i f i c a t i o n o f s e v e r a l o t h e r funga l d i s e a s e s have been associated wi th burn ing (Muller 1 9 2 9 ) . Thc u s e of p r c s c r i h e d f i r e appears wcl l s u i t e d a s an a g e n t u s e f u l f o r t h e c o n t r o l o f dwarf r r l i s t lc toc under c e r t a i n s i t c c o n d i t i o n s (Alexander and llawksworth 1975) . Weir (1923) observed t h a t b r o a d c a s t burn ing reduced growth and f r u i t i n g o f t h e most impor tan t c u l l - p r o d u c i n g fungi i n Idaho and Montana. He noted t h a t c h a r r e d stumps and l o g s a r c r a r e l y r e i n f e c t e d by t h e c u l l f u n g i o f t h c Living t r e e . Boyce (1961) observed t h a t c h a r r i n g o f stumps i n t h e Southwest c o n t r o l l e d f r u i t i n g o f c u l l - p r o d u c i n g f u n g i , and Koth (1956, 1943) r e p o r t e d r e d u c t i o n s i n d e f e c t of f i r e - t h i n n e d oak wheri compared t o normal ly h a r v e s t e d o r t h i n n e d s t a n d s . Many o f t h e above c i t e d e f f e c t s of f i r c could be d u p l i c a t e d by c l e a r c u t t i n g arid i n t e n s i v e u t i l i z a t i o n .

Residue a.s a ~ i s ~ e r s i n g Agent

Whether r e l a t e d t o b i o t i c f o r c e s , p h y s i c a l f o r c e s such a s h i g h winds and w k l d f i r c s , o r t o man's a c t i v i t i e s , p l a n t r c s i d u c s l e f t i n p l a c e can pose d i s e a s e problems. C u l l - caus ing decay f u n g i producc s p o r e s from f r u i t i n g s t r u c t u r e s that deve lop on stumps o f f a l l e n t r e e s and o t h e r woody r e s i d u e ( G i l l and Andrews 1956; S p a l ~ l d i n g 1934; Wright 1934; Hubert 1920) . Many r o o t d i s e a s e s a r c dcpcndent on stunlps and r o o t s i n t h e s o i l o r decay ing t r e e b u t t s i n c o n t a c t wi th t h e f o r e s t f l o o r (Boyce 1961; Kaarik and R e n n e r f e l t 1957). 'I'hese r e s i d u e s a c t a s a s u b s t r a t e f o r growth and s p o r u l a t i o n and p r o v i d e t h e inoculum f o r new i n f e c t i o n s .

No o t h e r c l a s s o f f o r e s t d i s e a s e s c a u s e s more t i m b e r damage t h a n r o o t decays (Nelson and l lnrvey 1 9 7 4 ) . The s a p r o p h y t i c s t a g e s o f t h e s e f u n g i a r e c o ~ n p l e t e l y depend- e n t on woody r e s i d u e t o s u r v i v e from onc g e n e r a t i o n o f h o s t p l a n t s t o t h e next. . Thus , r e s i d u e s may e n a b l e t h e i n t e n s i f i c a t i o n o f r o o t d i s e a s e i n p r o p o r t i o n t o t h e i r volume and s u i t a b i l i t y f o r c o l o n i z a t i o n by i n c r e a s i n g t h e p r o b a b i l i t y o f s u r v i v a l of t h e c a u s a l f u n g i (fludson 1968) . ArmiZZaria mellea, Poria weirii, and Fomes annosus a r e i m p o r t a n t examples of t h i s t y p e o f pa thogen . H e a r t - r o t t i n g f u n g i can a l s o h e p ropaga ted i n t h i s manner (Iiudson 1968; Meredi th 1 9 6 0 ) . However, s t a n d i n g dead o r l i v e d e f e c t - i v e t r e e s a r e proba.bly more i m p o r t a n t a s a s o u r c c of i.noculuni f o r h e a r t - : r o t f u n g i . D i s e a s e s t.ha.t a t t a c k f o l i a g e , and t h e n produce s p o r e s on dead and f a l l e n n c c d l e s , niay a l s o r e p r e s e n t r c s idue h a z a r d s . Lophodsrrniwn, Herpotrichiwn, and IVeopeckia a r e r e j ) r c s e n t a t j . v e g e n e r a ( l leptir lg 1971; [Iudson 1968; Boyce 1961) .

S u r v i v a l o f pa thogens on r e s i d u e depends or1 many f a c t o r s : ( I ) s i z e and s p e c i e s o f r e s i d u e ; ( 2 ) c h a r r i n g ; ( 3 ) s o i l phys ica l . and chemical ch : l . r ac t e r i s t i . c s ; (4) s i t e ; (5) h o s t t r e c s available; (6 ) r e l a t i v e l o c a t i o n o f r c s i d u e s t o t h e s o i l and h o s t p l a n t s ; (7) s p e c i e s of pathogenic . f u n g i p r e s e n t . ; (8) r e l a t i v e v i g o r of t h e h o s t s ; and (9 ) t h e a d a p t i v e c a p a c i t i e s o f t h e pa thogens and t h e i r p o t e n t i a l h o s t s . Through a d e q u a t e r e d u c t i o n o f f o r e s t r e s i d u e s , - i n t e n s i v e u t i 1 i z a t i o n and f i r e can s u p p r e s s many t y p e s o f d i s e a s e s . C o n v e r s e l y , a l l o w i n g r c s i d u e s t o accumulate can encourage t h e s c same d i s e a s e s .

Residual Ef'fect:; of Ffre and ilurziesling on Site Factors That InfZu~nce Disease Problems

In a d d i t i o n t o t h e s ; l r r i t a t ion i n f l u e n c e p rov ided hy p h y s i c a l removal of wood o r bu rn ing , t.he s i x macroenvironmenta l p a r a m e t e r s t h a t change a s a r e s u l t o f t h e s e t r e a t - ments ( t en lpe ra tu rc , m o i s t u r e , a e r a t i o n , a c i d i t y , n u t r i e n t arid cner f iy s u p p l y , and a v a i l a b l e b i o t a ) a l s o p r o v i d e d i r e c t in l ' lucnces on d i s c a s c organisms on , i n , o r a s s o c i a t e d w'ith s o i l comporler~ts. For example, s u r v i v a l and d i s t r i b u t i o n o f c u l l - p roduc ing f u n g i i n s l a s h can be d i r e c t l y in f luc r l ced by temperatures brough t abou t by exposure t o i n s o l a t i o n (Loman 1965, 1962) .

S o i l tcmpera7:ures o f 60' t o 70' C f o r 10 minu tes a r c normal ly s u f f i c - i e n t t o k i l l most root. pa thogens (.Johnson 1946) . S u r f a c e f i r e s may cause t e m p e r a t u r e s i n t h i s r ange wi th i r i t h e upper 4 i n c h e s o f f o r e s t s o i l s (Van Wagncr 1970; Beadle 1940; Raymond S h e a r e r , p e r s o n a l communicat ion) . T h e r e f o r e , s t r h s t a r i t i a l r e d u c t i o n s i n t h e numbers of c e r t a i n f e e d e r r o o t pathogens i n t h e s e shallorv s o i l l a y e r s ( 2 t o 4 i n c h c s ) rnay o c c u r . flowever, t h e reporTed r e d u c t i o n i n f'ungnl and batter-ial p o p u l a t i o n s -induced by s u r f a c e f i r e (Neal rid o t h e r s 1965:) and p o s s i b l e conco~n:i.tant h e a t o r n u t r i e n t - i n d u c e d e l i m i n a - t i o n o f s o i l f u n g i s t a s i s 7 (Watson and Ford 1972, Uobbs and o t h c r s 1!-)60) cou ld l e a d t o i n c r e a s e s i n any p a t h o g e n i c orgar~isrns su rv iv i r ig i n t h e s e s o i l l a y c r s . Pathogens c o u l d he i n t r o d u c e d on o r i n t h e s e e d (Bloomberg 1 9 6 6 ) . l n c r c a s e d n u t r i e n t a v a i l a b i l i t y and reduced cornpet i t ion can c o n t r i l m t e t.o s o i 1 c o l o n i z a t i o n advan tages by surv:i .ving f e e d e r r o o t pa thogens and may l e a d t o t h e f i r e r e l a t e d 1)ui ldup of t h e s e pa thogens ( H a r t l e y and I ) i c rcc 1917) . I n a d d i t i o n , t h e suppressive e f f e c t s o f h e a t arid f i r e g e n e r a t e d s o i l e x t r a c t s on s o i l f u n g i have been r e p o r t e d t o h e g r e a t e r on f u n g i norrnally a n t a g o n i s t i c t o f e e d e r r o o t p a t h o g e r ~ s t h a n on t h e pa thogens (Widden and Pa rk inson 1975; Bo l l en 1969)

'The p o t e n t i a l f o r f - i r e - i n d u c e d f e e d e r roo t d i s e a s e damage by R. undulata t o c o n i f e r r e g e n e r a t i or1 i n t h e Nor the rn Rocl<y Mauntains i s poor l y d e f i n e d . I t i s known, however, t o be p r e s e n t i n w e s t e r n Montana and n o r t h e r n Idaho (Weir 191.5). 'I'he l a c k o f r e c e n t r e p o r t s on t h e fungus i n t h i s a r e a may be due, a t l e a s t i n p a r t , t o c f f e c t . i v e f i r e e x c l u s i o n and l i m i t a t i o r i . T h i s p a r a s i t e h a s d e m o r ~ s t r a t e d i t s p o t e n t i a l t o c a u s e e x t e n s i v e damage t o c o n i f e r s e e d l i n g s and even mature t r e e s i n Grea t B r i t a i n and Ellrope (Gremmen 1971; . J a l a l l rdd in 1967; Murray and Young 1961) . I t h a s a l s o been r e p o r t e d t.o h e d e s t r u c t i v e t o c o n i f e r s e e d l i n g s i n wes te rn Washington (Morgan and

--- -

2 ~ ~ i i n h i b i t o r y f a c t o r t h a t l i n ~ i t s ge rmina t ion o f f u n g a l s l lo res i n s o i l s . Such 3

f a c t o r h a s been r e p o r t e d p r e s e n t i n f o r e s t s o i l s (1)obbs and Bywater 1959) .

Driver 1973, 1972) . One r e p o r t a s s o c i a t e d t h i s organism wi th a d i s e a s e d condition i n an 80-year-old s p r u c e i n Vermont (I'hompson and T a t t a r 1973) . Thus, a l though i t s ~ ~ o t e n t l a l i n t h e Intermountain r c g i o n i s unknown, ~ t s presence h e r e arid i t s c a p a b ~ l i t y t o i n f e c t c o n i f e r r e g e n e r a t i o n i n r e c e n t l y burrled a r e a s a r c recogn ized .

A f t e r t h e i n i t i a l s o i l n ~ i c r o f l o r a r e d u c t i o n s fo l lowing f i r e , m i c r o b i a l p o p u l a t i o n s g r e a t e r than t h e o r i g i n a l can occur (Kcnbuss and o t h c r s 1973; Ahlgrerl 1965). 'I'he p r e s - ence o f p o t e n t i a l l y damaging f e e d e r r o o t d i s e a s e s , i n c l u d i n g Phykophdhorn, P!jhhiwn, Fusariwn, and Hhizoctonia in n a t u r a l f o r e s t s o i l s , amd t h e i r s u r v i v a l a f t e r burns of v a r i o u s i n t e n s . i . t i c s has been docunlerlted (Wright and Kollen 1 9 6 1 ) . I n c r e a s e s i n damaging f e e d e r r o o t pathogens have been r e p o r t e d i n p o s t f i r e s o i l s ( H a r t l e y and P i c r c c 1917); Wright and Bol len 1961; T a r r a n t 1956) . Conversely , charcoa l has heen r e p o r t e d t o reduce damping-off o f c o n i f e r s e e d l i n g s (Beltrarn 1963; Radovanovi.~ 1962; Commonwealtl~ of Pennsy lvan ia 1930; Boyce 1925) . Very s h o r t exposures t o i r icreased s o i l t cmpcra tu rcs r e s u l t i - n g from p r e s c r i b e d f : i r e s o r w i l d f i r e s may cause s h i f t s i n s p e c i e s composi t ion and numbers o f s o i l f u n g i (Pe te r son 1970; Seaver and Cla rk 1910) . I n c r e a s e s i n t h e a c t i v i t y o f asconlycetes such a s t h e r o o t pathogen l?hisinu unduZata (Morgan and Dr iver 1972; Ginrls 1908; J a l a l u d d i n 1968) a f t e r burning p rov ide a s p e c i f i c example.

A l k a l i n e s h i f t s i n s o i l pll havc been w e l l clocunlented subsequent t o s i t e burning (Ncal arid o t h e r s 1965) and weakly a c i d , n e u t r a l , o r a l k a l i n e s o i l s a r e g e n e r a l l y f a v o r - a b l e t o s o i l f e e d e r - r o o t pathogens. Secd l ing damping-off has been c o r r e l a t e d d i r e c t l y t o r a i s i n g f o r e s t s o i l pH l e v e l s (Tar ran t 1956) . I n add i t io r i , h igh n ~ o i s t u r c and l a c k of a e r a t i o n may be caused by f i r e o r h a r v e s t i n g p r a c t i c e s (Ra l s ton ant1 I Ia tchc l l 1971; Rethlah~ny 1962) and axe g e n e r a l l y conclucivc t o s o i l - i n h a b i t i n g p l a n t d i s e a s e s (Kaney 1970) . The e f f e c t s o f f i r e and n i t r o g e n f e r t i l i z a t i o n a r e sin1.i l a r (Sagara 1973) and h igh n i t r o g e n l e v e l s c o n t r i l l u t e t o an i n c r e a s e d s u s c e p t i b i l i t y t o f e e d e r r o o t d i s e a s e s (Rowan 1971; F o s t c r 1968) . T h i s i n d i c a t e s a r e a l p o s s i b i l i t y of f e e d e r - r o o t pathogen problems, p a r t i c u l a r l y on r e g e n e r a t i o n e s t a b l i s h e d d u r i n g t h e c a r l y pos tburn p e r i o d . The p o t e n t i a l e f f e c t s o f t h e s e f a c t o r s on t h c es ta1) l ishmcnt o f mycor rh iza l a s s o c i a t i o n s (Bjorkman 1970) and t h e apparcn t r c s i s t a r i c c t o f e e d e r - r o o t pathogens provided by mycorrhizac (Marx 1973) p r o v i d e an a d d i t i o n a l and p o t e r ~ t i a l l y s i g n i f i c a n t f a c t o r .

C l e a r c u t t i n g o r burn ing may t h r e a t e n t h e subsequent t imber c rop through e x c e s s i v e r e l e a s e o f n u t r i e n t s . Changes i n s o i l n u t r i e n t s , p a r t i c u l a r l y n i t r o g e n , cm1 i n f l u e n c e d i s e a s e (Hes te rbcrg and Jurgensen 1972; F o s t e r 1968; Sadasivan 1965) . For i n s t a n c e , because t h e a d d l t i o n o f n i t r o g e n t o f o r e s t n u r s e r i e s i n c r c a s c s i n c i d e n c e o f darnping-off d i s e a s e s , a p p l i c a t i o n s a r e de layed u n t i l seccll ings havc grown beyond t h e s u s c e p t i b l e s t a g e (Rowan 1971; F o s t e r 1968) . Adclitions o f n i t r o g e n , phosphorus , and potass ium t o young s l a s h p i n c i n c r e a s e d i n c i d e n c e of f u s i f o r m r u s t ( B l a i r and Cowling 1974; H o l l i s and o t h e r s 1972; Gilmore and L iv ings ton 1958; Bogess and S t a h e l i n 1948) . Conversely , r e g u l a t i o n o f s o i l n u t r i e n t ba lance can reduce i n c i d e n c e of t h i s d e s t r u c t i v e pathogen ( H o l l j s, p e r s o n a l communication) .

Root d i s e a s e causcd by Fomes annosus decreased when po tass ium and magnesium were added t o t h e s o i l , b u t i n c r e a s e d wi th a d d i t i o n s of manganese and i n c r e a s i n g s o i l pH [Yde-Anderson 1970) . 1 ; roe l i ch and Nicholson (1973) r e p o r t e d a r e d u c t i o n o f F. annosus r o o t r o t a s l a r g c q u a n t i t i c s o f s u l f u r were added. T h i s may have been more t h e r e s u l t of a lowering i n s o i l pI-I t h a n t h e i n c r e a s e d l e v e l s of a v a i l a b l e s u l f u r i n t h e s o i l . Addi t ions o f n i t r o g e n a l l c v i a t e l i t t l e l e a f d i s c a s e (Roth and Copeland 1957; Roth and o t h e r s 1948) , V ~ r t i c i Z Z i w n w i l t o f maple ( C a r o s e l l i 1956) , and maple d e c l i n e (Mader and Thompson 1969) .

Addi t ion o f s o i l n u t r i e n t s p robab ly i n f l u e n c e s d i s e a s e through c o n t r o l o f p l a n t h e a l t h and v i g o r . However, n u t r i e n t s may a l s o d i r e c t l y a f f e c t t h e s u r v i v a l and growth of t h e s a p r o p h y t i c s t a g e o f many r o o t pathogens. Again, n i t r o g e n o r t h e form of n i t r o g e n can be s i g n i f i c a n t (Huber and Watson 1974) . Ni t rogen l e v e l a p p e a r s t o r e g u l a t e t h e formati.on and germina t ion o f Fusariwn chlamydospores ( G a r r e t t 1 9 7 0 ) .

N i t r a t e f a v o r s CurvuZarin d i s e a s e a s compared t o ammonium (Sadas ivan 1965) , and n i t r a t e i s a p o o r n i t r o g e n s o u r c e f o r Fomes annosus (Johanson 19701, P o r i a w e i r i i , and Armillaria rneZZea (Cowling 1970) .

Any sudden i n c r c a s e i n a v a i l a b l e n u t r i e n t s w i l l a l t e r t h e q u a n t i t y and q u a l i t y of r o o t e x u d a t i o n and therefore t h e r h i z o s p h e r e . Both f e r t i l i z a t i o n and l i m i n g have g r e a t e r i n f l u e n c e s on t h e r h i z o ~ p h e r e n i i c r o f l o r a t h a n on organisms i n t h e s u r r o u n d i n g s o i l (Voznyakovskaya and Avrovn 1968; Welte and T r o l l e n d e n i e r 1961) . Thus, r h i z o s p h e r e - dependent mic ro -o rgan i sms , such a s f e e d e r r o o t pathogens and mycor rh izae , shou ld b e t h e f i r s t a f f e c t e d .

Cone Zusions

Although t h e c f f e c t s o f i n t e n s i v e u t i l i z a t i o n and p r e s c r i b e d burn ing on d i s e a s e organisms axe l i k e l y t o bc complex, t r e a t m e n t s which d i r c c t t h e change i n d i s e a s e s t a t u s a r e p o s s i b l e i n managed f o r c s t s . P o r e n t i a l f o r damage and o p p o r t u n i t i e s f o r c o n t r o l can be a n t i c i p a t e d .

F o r e s t managers must bccomc acquainted w i t h t h e n a t u r a l r o l e s o f d i s e a s e s j n f i r e - dependent f o r e s t s . H a r v e s t i n g , u t i l i z a t i o n i n t c n s i t y , and p r e s c r i b e d f i r e s cou ld bc used it: c o n c e r t t o d i s c o u r a g e , emula te , o r supplement t h e s e f u n c t i o n s . Comparisons o f t h e e f f e c t s o f i n t e n s i v e u t i l i z a t i o n and p r e s c r i b e d E i r c on f o r e s t pa thogen a c t i v i t i e s shou ld p r o v i d e c o n s i d e r a b l e i n s i g h t i n t o t h e i r f u n c t i o n s and means t o c o n t r o l them.

~esenr'ch Needs

I n t h e I n t e r m o u n t a i n Wcst, f o r c s t o p e r a t i o n s u s i n g bo th p r e s c r i b e d b u r n i n g and c l c a r c u t t l n g i n conjunction w i t h i n t e n s i v e f i b e r u t i l i z a t i o n a r e l i k e l y t o depend on r i a t u r a l r e g e n e r a t i o n . T h e r e f o r o , assessment and d i a g n o s i s o f s e e d l i n g m o r t a l i t y a f t e r such t r c a t m e n t s a r e j m p e r a t i v e . Tf s e e d l i n g l o s s i s s i g n i f i c a n t , t h e c o n t r i b u t i n g f a c t o r s should be i n v e s t i g a t e d . I f d i s e a h e i s e v i d e n t , i t s s i g n i f i c a n c e t o t h e r e g e n e r a t i o n and growth o f t h e s u b s c q u e r ~ t croI> shou ld a l s o be a s s e s s e d . I l i s r a s e , a c t i v e o r p o t e n t i a l , w i l l l i k c l y l i m i t t h e management o p t i o n s For many s i t e s .

Ah lg rcn , 1 . F . 1965. E f f e c t s o f p r e s c r i h c d b u r n i n g on s o l 1 ~ i i i c roorgan i sms i n a Minnesota j a c k p i n e

f o r e s t . Ecology 46:304-310. Ahlgrcn, I . F . , and C . E . Ahlgrcn.

1960. E c o l o g i c a l c f f e c t s o f f o r e s t f i r e s . Bot . Rev. 26:483-533. Alexander , M . E . , and F . (;. Ilawksworth.

1975. Wildland f i r e s and dwarf m i s t l e t o e s : a l i t e r a t u r e revlcw o f eco logy and p r e s c r i b c d b u r n i n g . IJSDA For . S e r v . Gen. Tech. Rep. RM-14. Rocky M t . Fo r . and Range Exp. S t n . , F t . C o l l i n s , Colo .

Basham, . I . T. 1957. The d e t e r i o r a t i o n by f u n g i of j a c k , r e d , and w h i t e p i n e k i l l e d by f i r e i n

O n t a r i o . Can. J . n o t . 35:155-172. Rax tc r , D. V .

1967. D i s e a s e i n f o r e s t p l a n t a t i o n s : t h i e f of: t i m e . 250 p. Cranbroolc I n s t . S c i . , Bloonlfield Ili 115, blich.

Readlc , N . C . W. 1940. S o i l t e m p e r a t u r e s d u r i n g f o r e s t f i r e s and t h e i r c f f e c t on t h e s u r v i v a l of

v e g e t a t i o n . .J . E c o l . 28:180-192. Bel t rnm, V.

1963. Drvcrli v g a l s - s e l e k t i v n j s t e r l l i z a t o r - t r a j n o posrcdrla d u b r i v o . Sumarski l i s t . 87:175-185.

Bethlahmy, N . 1962. F i r s t y e a r e f f e c t s of t imber removal on s o i l m o i s t u r e . B u l l . I n s t . Assoc.

S c i . I lydrol . 7 : 34-38. BjDrkman, E .

1970. F o r e s t t r e e mycor rh iza - - the c o n d i t i o n s f o r i t s fo rmat ion and t h e s i g n i f i c a n c e f o r t r e e growth and a f f o r e s t a t i o n . P l a n t and S o i l 32 : 589-610.

B l a i r , R . L . , and C . K. Cowling. 1974. E f f e c t s of f e r t i l i z a t i o n , s i t e , and v e r t i c a l p o s i t i o n on t h e s u s c e p t i b i l i t y of

l o b l o l l y p i n e s e e d l i n g s t o fus i fo rme r u s t . Phytopathology 64:761-762. Kloomherg, W . J .

1966. The o c c u r r e n c e o f endophy t i c f u n g i i n D o u g l a s - f i r s e e d l i n g s and s e e d s . Can. J . Bot . 4 4 ~ 4 1 3 - 4 2 0 .

Bogess, W . R . , and R . S t a h e l i n . 1948. 'The i n c i d e n c e o f f u s i f o r m r u s t i n s l a s h p i n e p l a n t a t i o n s r e c e i v i n g c u l t u r a l

t r e a t m e n t s . J . For . 46:683-685. Bo l l en , G . J .

1969. The s e l e c t i v e e f f e c t of h e a t t r e a t m e n t on t h e m i c r o f l o r a o f a greenhouse s o i l . Neth. J . P l a n t Pdth . 75:157-163.

Boyce, J . S. 1921. F i r e s c a r s and decay. The Timberman 22:7 .

Royce, J . S . 1925. Report on f o r e s t t r e e d i s e a s e s observed i n Grea t B r i t a i n and Dcnmark. A

r e p o r t of t h e Of f i ce o f I n v e s t i g a t i o n s i n P l a n t Pa tho logy . Bur. P l a n t I n d . , Washington, D . C . 87 p .

Roycc, J . S . 1961. F o r e s t pa tho logy . T h i r d e d . 5 7 2 p . McCraw-Jlill, Ncli York.

Burns, P. Y . 1955. F i r e s c a r s and decay i n Missour i o a k s . Univ. Mo. C o l l . Agr ic . Bu l l . 642.

C a r o s c l l i , N . E . 1956. The e f f e c t o f v a r i o u s s o i l amendments on maple w i l t i n c i t e d by VcrticiZLiwn

51.'. ( a b s t r . ) . Phytopathology 46: 240. Chapman, H . H .

1927. Use o f f i r e i n r e g e n e r a t i o n o f c e r t a i n t y p e s o f f o r e s t s i n l n d i a . J . POT. 25:92-94.

Commonwealth o f Pennsy lvan ia . 1930. Mont Al to S t a t e F o r e s t Nursery . Dep. F o r . and Water B u l l . 49, 57 p .

Cowling, E . B . 1970. Physiology o f Fomes annosus. Jn: Proc. T h i r d I n t . Conf. b'omes annosus, P.192-

201. U.S. Dep. Agr ic . For . S e r v . , S o u t h e a s t For . Exp. S t n . , A s h e v i l l e , N.C. Dav i s , K . P . , and K . A . Klehm.

1939. C o n t r o l l e d burn ing i n t h e wes te rn w h i t e p i n e t y p e . J . For . 37:399-407. Day, W. R.

1955. F o r e s t hyg iene i n Grea t B r i t a i n . Univ. Toronto For . B u l l . 4, 26 p. Dearness , J . , and J . R . Hansbrough.

1934. Cykospora i n f e c t i o n s f o l l o w i n g f i r e i n j u r y i n wes te rn B r i t i s h Columbia. Can. J . Res. 10:125-128.

Dobbs, C . G . , and J . Bywater. 1959. S t u d i e s i n s o i l mycology. 11. G . B . Fo r . Conlm. Rep. For . Res. 1958, p . 98-104.

Dobbs, C . G . , W . N. Hinson, and J . Bywatcr. 1960. I n h i b i t i o n of fungal growth i n s o i l s . In: The eco logy o f s o i l f u n g i , p . 130-

147 . D. Park inson and J . S . Waide, e d s . L ive rpoo l Univ. P r e s s , L ive rpoo l . F o s t e r , A . A .

1968. Damage t o f o r e s t s by f u n g i and i n s e c t s as a f f e c t e d by f e r t i l i z e r s . In: F o r e s t f e r t i l i z a t i o n - - t h e o r y and y r a c t i c e , p . 42-46. Tenn. V a l l e y Auth . , Muscle S h o a l s , Ala .

F r o e l i c h , R . C . , and J . D. Nicholson. 1973. Spread of Fomes annosus reduced by heavy a p p l i c a t i o n of s u l f u r . For . S c i .

19 : 75-76.

Garren, K . H . 1941. F i r e wounds hy l o h l o l l y p i n e and t h e i r r e l a t i o n t o decay and o t h e r c u l l .

J . For . 39:16-22. G a r r e t t , S . I ) .

1970. Pa thogen ic root-infecting f u n g i , 1). 284. Cambridge Univ. P r e s s , Cambridge. Glhson, J . M .

1938. Comments. J . For . 36:1049-1051. G111, I , . S . , and S . R . Artdrews.

1956. Decay of ponderosa p i n e s l a s h i n t h e Southwest . US1)A For . S e r v . , Rocky M t . Fo r . and Rarlgc Cxp. Strl. Iles. Note 19, 2 12.

Gilrnore, A. K . , and K . W . 1 , iv ings ton . 1958. Cultivating and f e r t i l i z i n g a s l d s h p i n e p l a n t a t i o n : e f f e c t s on volume and

f u s i f o r m r u s t . . J . For . 56:481-483. Ginrts, .J. 11.

1968. liizi;:ina undulata [ ) a thogen ic on U o u g l a s - f i r seedlings i n wes te rn North America. P l a n t D i s . Rep. 52:579-580.

Gr emmen, .T . 1971. Rhiz ina undulatn: a revlew of r e s e a r c h i n t h e N e t h e r l a n d s . Cur. J . For .

P a t h . 1:l-6. G ~ l s t a f ~ 0 1 1 , R . 0 .

1946. b o r e s t f i r e s , I ~ a s a l wounds, and r e s u l t i n g damage t o t inrber i n an e a s t e r n Kentucky a r e a . Ky. Agr ic . Exp. S t n . B r r l l . 493, 15 p .

Ilabeck, J . R . , and R . W . Mutch. 1973. Flre-dependent f o r e s t s i n t h e n o r t h e r n Rocky Mountains. Q u a t e r n a r y Res.

.7:408-424. l l a ig , . J . R .

1938. I . l r e I n modern f o r e s t management. J . For . 1045-1051. Mart , A. C .

1938. I h e r c l a t l o n of E l r c s c a r s t o decay I n l l v l n g t r e e s . M.S. t h e s i s , Yale Univ. l l a r t l c y , C . , and K . G. P i e r c c .

1917. The c o n t r o l o f damplng-off of c o n i f e r o u s seedlings. p . 1-32. I1.S. Dep. A g r l c . B u l l . 453, Washington, D . C .

H e ~ n s e l m n n , M . L . 1971. Thc n a t u r a l r o l e o f f i r c i n n o r t h c r n c o n i f e r f o r e s t s . rn: Proc. F i r e i n t h e

Northern Environment: a summary. 275 p . C . W . S l a u g h t e r , R . J . Barney, and G . M . Hansen, c d s . U.S. Dcp. Agr ic . For . S e r v . Pac. Northwest For . and Range Exp. S t n . P o r t l a n d , Oreg.

Hep t ing , G . H 1941. Prediction o f decay f o l l o w i n g f i r c i n Appalachian o a k s . J . A g r i c . Res. 62:

109-120. Hept ing, G . H.

1971. Diseases o f f o r e s t and shade t r e e s o f t h e Uni ted S t a t e s . U.S. I k p . Agr ic . I-landh. 3 8 6 , 658 p . Washington, D . C .

kleptjng, G . I I . , and G . C . Iledgcock. 1035. R e l a t i o n between b u t t r o t and f i r e i n some e a s t e r n hardwoods. U.S. Dep. Agr ic .

For . S e r v . Tech. Note 14, 2 1). Washington, D . C . Hcp t ing , G . H . , and A . I . Shlgo .

1972. L) i f ference in dccny r a t c f o l l o w i n g f i r e between oaks i n North C a r o l i n a and Maine. P l a n t Dis . Rep. 56,:41)6-407.

H e s t e r b e r g , G . A . , arid bl . 1.. Ju rgcn5cn . 1972. The r c l a t i o n o f f o r e s t fertilization to d i s e a s e i n c i d e n c e . For . Chron.

48192-96. H o l l i s , C . A . , W . 1 1 . Smi th , R . A . Schmidt, and W . L . P r i t c h e t t .

1972. R e l a t i o n between n u t r i t i o n a l s t a t u s o f s l a s h p i n e and f u s i f o r m r u s t . Proc. 2nd North An). For . B i o l . Workshop, Oreg. S t a t e IJniv. 51 p.

Iluber, D . M . , and R . D. Watson. 1974. Ni t rogen form and p l a n t d i s c a s c . Annu. Rcv. Phy topa th . , p . 139-166.

Huber t , F . t. 1920. 7hc d ~ s p o s d l o f in fcc tec i s l a s h on t i m b e r s a l c a r e a s i n t h e Northweqt. J . For .

18:34-30. IIubert , E. C .

1931. An o u t l i n e of f o r e s t p a t h o l o g y . John Wiley F, S o n s , N . Y . 543 p . Hudson, H . J .

1968. The ecology o f f u n g i on p l a n t rcnlains above t h e s o i l . V e w I1hytol. 67:838-874. .7a la ludd in , M.

1967. S t u d i e s on Rh-izinrz undulata. 11. 0 l ) s c r v a t i o n s and e x l ~ e r i m e n t s i n E a s t Angl i an p l a n t a t i o n s . T r a n s . Brit. Mycol. Soc. 50:461-472.

J a l a l u d d l r i , M . 1968. F i r e a s an agen t i n t h e e s t a b l i s h m e n t o f a p l a n t d i s e a s e . P d k . , J . S c i . 21 : 4 2 - 4 4 .

.Jolianson , M. 1970. D i s c u s s i o n s on Fornes clnnosu:;. In: Proc . 3d I n t . Conf . Fome:: nnnnsu.7, 1). 62-

65 . L1.S'. Dep. A g r i c . For . S e r v . , S o u t h e a s t . For . Exp. S t n . , A s l ~ c v i l l c , N . C . Johnson, J .

1916. So i l - s t edming f o r d i s e a s e c o n t r o l . S o i l S c i . 61:83-91. Kaar ik , A . , and C . R e n n e r f c l t .

1957 I n v e s t i g a t i o n s on t h e funga l f l o r a o f s p r u c e and p i n c s tumps. S t a t e n s S k o g s f o r s k n i n g 5 i n s t . (Sweden), Mcdd. 4 7 : l - 8 8 .

K a u f e r t , k. ti. 1033. F i r e and decay i n t h e s o u t h e r n bottomlnrld hardwoods. . J . For . 31.64-67.

Komarck, C . V . 1963. F i re r e s e a r c h and education. Proc . Tall Timbers I : i rc Ecol . Conf. 2 :181-187.

Lachrnund, 11. G . 1921. Somc phases I n t h e format ion o f f i r c s c a r s . J . For . 19:638-640.

Lachmund , t l . G . 1923. Bole ~ n j u r y I n f o r e s t f i r e s . J . F o r . 21 :723-731.

Idoman, A . A . 1962. The l n f luence o f t e m p e r a t u r e on t h e l o c a t i o n and devclnpment o f decay f u n g i i n

lodgepo le p i n c logg lng s l a s h . Can. J . Bot. 40:1545-1559. Loman, A. A .

1965. Thc l e t h a l e f f e c t o f p e r l o d i c h i g h t e m p e r a t u r e s on c e r t a i n lodgepo le p i n e s l a s h decay jng bas id iomyce teq . Can. J . Bot . 43:334-338.

Lyons, J . L . , and W . L. P c n g e l l y . 1970. Commentary on t h e n a t u r a l r o l c o f E i r e . I n : Symposium on t h e r o l e o f f i r e i n

t h e In te rmounta in West, p . 81-84. I n t e r m t . F i r e Res. Counc. , Mlssou la , Mont. Madcr, D . L . , and B . W . Thompson.

19h9. F o l i a r and s o i l n u t r i e n t s i n r e l a t i o n t o s u g a r maple r l e c l i n c . P roc . S o i l Soc. Am. 33:794-800.

Marx, D . H . 1973. Mycorrhizae and f e e d e r r o o t d i s e a s e s . I n : Ec tomycor rh lzac - - the i r ecology and

phys io logy . 444 p . G . C . Marks and T . 1'. Kozlowski, cds . Academic P r e s s , N . Y . McCarthy, E . F.

1928. A n a l y s i s o f E i r e damage In s o u t h e r n Appalachian f o r e s t s . J . For . 26:57-68. Meredith, D . S .

1960. E u r t h c r o b s e r v a t i o n s on f u n g i i n h a b i t i n g p i n e stumps. Ann. Bot. 24363-78. Morgan, P . , and C . H . D r i v e r .

1972. R h i z i n a r o o t r o t o f D o u g l a s - f i r s e e d l i n g s p l a n t e d on burned s i t e s i n Washing- t o n . P l a n t D i s . Rep. 5b:402-409.

Morgan, P . , and C . H . D r i v e r . 1973. R h i z i n a r o o t r o t i n c o n i f e r p l a n t a t i o n s i n wes te rn Washington. P l a n t Dis.

Rep. 57:167-169. Mul le r , K . M .

1929. Aufbau, wuchs, und ver jungung de r s u d o s t e u r o p a i s c h e n u r w a l d e r . Reviewed by M . tianover and 11. Schaper . J . For . 28 : 744.

Murray, J . S . , and C . W . T . Young. 1961. Group d y i n g i n c o n i f e r s . For . Comm. F o r . Rec. 46 , 19 p .

Neal , .I. I , . , E . Wright , and W . B . Bo l l en . 1965. Burning D o u g l a s - f i r s l a s h : p h y ~ i c a l , chemical , and m i c r o b i a l e f f e c t s i n t h e

s o i l . Orcg. S t a t e I Jn iv . For . Res. Lab. Res. Pap. 132 p . Nelson, C . C. , and G . M . I larvcy.

1974. Residues and f o r e s t d i s e a s e . In. Environmental e f f e c t s o f f o r e s t r e s i d u e s management i n t h e P a c i f l c Northwest- -2 s t a t e -o f -knowledge compendium, p . 51-511. 11SI)A For . S e r v . , Gen. Tech. Rep. PNW-24. Pac. Northwest For . and Kange t x p . S t n . P o r t l a n d , Oreg.

Nclson, R . M., I . H. Sims, and El, S . A h e l l . 1933. Basal f j r e wounds on some s o u t h e r n Appalachj an hardwoods. J . For . 31 : 829-837.

Nordin, V . J . 1958. Basal f i r e s c a r s and t h e o c c u r r e n c e o f decay i r ~ l udgepo le p i n e . For . Chron.

341257-265. Olsen , J . S .

1963. Energy s t o r a g e and t h e balnncu o f procluccrs and decomposers I n e c o l o g i c a l sys tems . Ecology 44:322-331.

P e t e r s o n , P. M . 1970. Danish f l r c p l a c e f u n g i - - a n ecological i n v e s t i g a t i o n o f fungi on h u r n s . Darisk

Rot. Ark. 2 7 : l - 9 7 . Rddovanovic, Z .

1962. U t i c a j drvcnog u g l a ria r a z v l t a k bora smrcc i j c l c . Sumarstvn 15:113-129. R a l s t o n , C . W . , and G. E . I l a t c h e l l .

1971. E f f e c t s o f prescribed burn lng on p h > ~ s i c a l p r o p c r t i c s o f s n i 1 . I'roc. P r e s c r l h e d Burning Symp. IJSUA For . S c r v . , Sor r th ras t . 1,or.. k x p . S t n , , p . 68-84.

Raney, W . A . 1970. P h y s i c a l f a c t o r s o f t h e s o i l a s t h e y a f f e c t s o i l microorganisms. In: Ccology

o f s o i l bo rne p l a n t pa thogens , p . 115-119. K . F. Baker, W . C . Snyder , e d s . Univ. Cal i f . P r e s s , Berkeley.

Relibuss, M . , G . A . C h i l v c r s , and L. 1). P r y e r . 1973. Microbiology o f a n ashbed. I'roc. Llnn. Soc. N.S.W. 97:302-310.

Roth, C . R . 1956. Ilecay f o l l o w i n g th l r in lng o f s p r o u t oak clurnps. J . For . 5 4 2 6 - 3 0 .

Roth, E . R . , and 0 . L . Copeland. 1957. Uptake o f n i t r o g e n and ca lc ium t)y f e r t i l i z e d s h o r t l e a f p i n e . J . For .

55:281-284. Koth, !c. K . , and G. ti. Iicpt'ing.

1943. O r j g i l i arid development of oak sturnp s p r o u t s a s a f f e c t i n g t h e i r l i k e l i h o o d t o decay . J . For . 41:27-36.

Roth, C. R . , E . R . Too lc , and C;. H. Hept ing. 1948. N u t r i t i o n a l a s p e c t s o f t h e l i t t l e l e a f c l l sease o f p i n e . J . For . 46:578-587.

Roth, L . F. 1956. F o l l a r h a b i t o f pondcrosa p i n e a s a h e r i t a b l e b a s i s f o r r e s i s t a n c e t o dwarf

mistletoe. I n : Breedlng p e s t r e s i s t a n t t r e e s , H . D. Gerhold and o t h e r s , e d s , , [1. 221-227, Pcxgamon P r e s s , [.ondon.

Rowan, S . J . 1971. S o l 1 fertilization, fumlga t lon , and t empera tu re a f f e c t s e v e r i t y o f b l a c k r o o t

r o t of s l a s h p i n e . I1hytopathology 61: 184-387. Sadas ivan , T. S .

1965. k f f e c t o f m i n e r a l nutrients of s o i l microorganisms and p l a n t d i s e a s c . I n : Ccology o f s o i l 1)ornc p l a n t pa thogens , p . 460-468. K . I:. Baker and W. C . Snyder , e d s . IJniv. C a l i f . P r e s s , Rerkcley.

Sagara , N. 1973. P r o t c o p h i l o u s fung i and f i r c p l a c c f u n g i . Trans . Mycol. Soc. <Japan 14:41-46.

Schmitz , H . , and L . W . R . Jack5on. 1927. I-leart r o t o f aspen w i t h s p c c i a l r e f e r e n c e t o f o r e s r management i n Minnesota .

Minn. Agr ic . Cxp. S t n . Tech. B u l l . SO, 43 p. S e a v e r , F. J . , and E. D . C l a r k .

1910. S t u d i e s i n p y r o p h i l o u s f u n g i . 11. Changes brought abou t by h e a t i n g o f s o i l s and t h e i r r e l a t i o n t o t h e growtli of I)!lmnemnu arid o t h c r f u n g i . Mycologia 2:109-124.

S i g g e r s , P. V . 1932. The brown s p o t n e e d l e b l i g h t o f l o n g l e a f p i n e s e e d l i n g s . J . For . 30:579-593.

S i g g c r s , P . V . 1944. 'i'he brown ? p o t n e e d l e b l i g h t o f p i n e s e e d l i n g s . 1J.S. Dep. A g r i c . 'I'ech. B u l l .

870, 36 11. Washington, 1) . C . S i g g e r s , P. V .

1949. F i r e and t h c s o u t h e r n f u s i f o r m r u s t . U.S. Ilep. A g r i c . , For . P a t h o l . Spec. Rc lease 33, 4 v . Washingtori, D . C .

Spau ld ing , P . 1934. P e r s i s t a n c e o f h e a r t - r o t t i n g f u n g i i n g i r d l e d t r e e s . Phytopathology 24:17-18

(Abs tr . ) S t i c k e l , P . W . , and H . F . Marco.

1936. F o r e s t f i r e damage s t u d i e s i n t h e N o r t h e a s t . 111. R e l a t i o n between f i r e i n j u r y and funga l i n f e c t i o n . ,J. For . 3.1: 4 2 0 - 4 2 3 .

S tone , E. C . , R . F. Grah, and P. J . Zinke. 1972. P r e s e r v a t i o n o f t h e pr imeval redwoods i n t h e Redwood Na t iona l Park. Am. For .

78:48-59. ' I ' a r rant , R . F .

1956. E f f e c t s o f s l a s h burn ing on some s o i l s o f t h e D o ~ l g l a s - f i r r e g i o n . Proc . S o i l S c i . Soc. Am. 20:408-411.

Thompson, J . E . , and T . A. T a t t a r . 1973. Rhizina unduZata a s s o c i a t e d w i t h d i s e a s e o f 80-yea r -o ld r e d s p r u c e i n Vermont.

P l a n t Dis. Rep. 573394-396. Toolc , E . K .

1959. Dccay a f t e r f i r e i n j u r y t o s o u t h e r n bottomland hardwoods. U.S. Dep. Agr ic . Tech. B u l l . 1189. Washington, D . C .

Too le , E . R . , and G . M. F u r n i v a l . 1957. P r o g r e s s o f h e a r t r o t fo l lowing f i r e i n bot tomland r e d oaks . J . For . 55:20-24.

Van Wagner, C . E . 1970. Temperature g r a d i e n t s i n d u f f and s o i l d u r i n g p r e s c r i hed f i r e s . Can. 13in1on.

Rcs. Notes 26:42. Voznyakovskaya, Yu M . , and N . P. Avrova.

1968. E f f e c t o f f e r t i l i z e r s on microorganisms producing v i t a m i n s i n t h e rh izosp l l e re o f wheat . Mikrob io log iya 37: 110-114.

Watson, A. G . , and E . J . Ford. 1972. S o i l f u n g i s t a s i s - - a r e a p p r a i s a l . Annu. Rev. Phytopath . 9:327-348.

Weir, J . K . 1915. Obse rva t ions on Rhizina in fZata . J . Agr ic . Res. 4 :93-97.

Weir, J . K . 1923. The c f f e c t o f b r o a d c a s t h u r n i n g on s a l e a r e a s on t h e growth of c u l l - p r o d u c i n g

f u n g i . J . For . 21: 183-184. Wclte, E . , and G . T r o l l e n d e n i e r .

1961. The i n f l u e n c e s o f t h e hydrogen i o n c o n c e n t r a t i o n o f t h e s o i l on t h e s h i z o - s p h e r e e f f e c t . Na tu rwissenschaf ten 48:509.

Widden, P . , and D . Parkinson. 1975. The e f f e c t s of a f o r e s t f i r e on s o i l mic ro fung i . S o i l B i o l . Hiochem. 7:125-138.

Wright, E . 1934. S u r v i v a l o f h e a r t r o t s i n down t imber i n C a l i f o r r ~ i a . J , For . 32:752-753.

Wright, E , , and W . B . Bo l l en . 1961. M i c r o f l o r a o f D o u g l a s - f i r f o r e s t s o i l . Ecology 42:825-828.

Yde-Anderson, A . 1970. D i s c u s s i o n s on Fomes annosus. In: Proc. 3d I n t . Oonf. Fomes annosus, p. 137-

148. U.S. Dep. Agr ic . For . S e r v . , S o u t h e a s t . For . Exp. S t n . , A s h e v i l l e , N.C.

From t h e many p o t e n t i a l e f f e c t s on microbial ecology t h a t could r c s u l t from t h e p r a c t i c e s o f i n t e n s i v e f i b e r u t i l i z a t i o n o r p rescr ibed burning i n fo r e s t ed ecosystems, f ou r major func t i ona l a r e a s d i r e c t l y in f luence subsequent s i t e q u a l i t y . 'I'hese inc lude : (1) decay with i t s e f f c c t s on carbon t ransformat ions , carbon, and mineral cyc l i ng , and t h e a s soc i a t ed s o i l development; ( 2 ) t h e formation and func t i on of mycorrhizal r o o t s ; ( 3 ) f i x a t i o n o f N and i t s t ransformatior ls ; and (4 ) t h e development and damage caused by p l a n t d i s e a s e fung i . The e x i s t i n g l i t c r a t u r e on cach of t h e s e s u b j e c t s was i n t e n s i v e l y reviewed t o provide t h e b a s i s f o r t h e fol lowing t e n t a t i v e conc lus ions .

'The processes and organisms involved i n r e s idues decomposition a r e e s s e n t i a l t o s o i l development through carbon and mineral cyc l ing and conserva t ion , and may c o n t r i b u t e i n d i r e c t l y t o n i t r ogen acquis . i t ion . Therefore, t h e r a t e of t imber ha rves t i ng i n con- junct ion with p r e sc r ibed burning o r i n t e n s i v e f i l l e r u t i l i z a t i o n should he ad ju s t ed t o provide an adequatc organic mat te r base f o r t he se processes . F a i l u r e t o do so i n t h e pa s t has r e s u l t e d in decreased s i t e p roduc t iv i t y .

The o b l i g a t e a s soc i a t i on between most con i f e r s and t h e i r mycorrhizal p a r t n e r s emphasizes t h a t management o f f o r e s t ecosystenls f o r optimal growth of s e l ec t ed spec i e s w i l l r e q u i r e management of t h e fungal symbionts on which t h e t r e e s depend. In s eve ra l i n s t ances pos tha rves t s i t c t rea tments d i r e c t l y a f f e c t e d t h e a b i l i t y of c o n i f e r s eed l ings t o e s t a b l i s h mycorrhizal a s s o c i a t i o n s .

Nitrogen i s sub j ec t t o va r ious t ransformat ions hy s o i l micro-organisms. Any changes i n t h e phys i ca l and chemical p r o p e r t i e s of a f o r e s t s o i l w i l l a f f e c t t h e a c t i v i t y o f t h e s e organisms. The most important n i t r ogen - r e l a t ed microbia l a c t i v - i t i c s a r e t he f i x a t i o n o f atmospheric N i n t o a form usable by p l a n t s and t h e convcrsion o f o t h e r forms of N i n t o n i t r a t e t h a t i s sub j ec t t o leaching l o s s e s . These a r c d i r e c t l y r e spons ib l e f o r t h e input and outflow of n i t r ogen i n Eorcst s o i l s . Becausc of jts importance t o f o r e s t ecosystems, management a c t i v i t i e s should bc d i r e c t e d toward provid ing maxinlun~ inpu t and minimum outflow of n i t r ogen . Both burning and ex tens ive f i b c r reinoval a r e known t o inf luence n i t rogen t ransformat ion .

Disease problems a r c no t c u r r e n t l y known t o be g r e a t l y a f f e c t e d by res idues management. Prescr ibed burning may inc rea se t h e a c t i v i t i e s of t h e p o t e n t i a l l y damaging Rhizinu roo t r o t o r o t h e r f eede r roo t d i s ea se s on young con i f e r s eed l ings . Large buried r e s i d u e s , stumps, and r o o t s i n f ec t ed by o r sub j ec t t o i n f e c t i o n by s eve ra l r o o t pathogens a r e known t o pe rpe tua t e such pathogens. I n some circumstances proper manage- ~nent of such n ~ a t e r i a l s , o r a l ack t he reo f , could c r e a t e s i g n i f i c a n t impacts i n pos t - t reatment fo r e s t - s .

Harvey, A. E., M. F. Jurgensen, and M. J. Larsen 1976. Intensive fiber utilization and prescribed f ire: effects

on the microbial ecology of forests . USD.4 For. Serv. Gen. Tech. Rep. MT-28, 46 p. Intermountain Fores t L Range Experiment Station, Ogden, Utah 84401.

---

Reviews current knowledge of the effects of intensive wood utilization, prescribed burning, o r a combination of both treatments, on the microbial ecology of forest soils. Identifies additional r e sea rch that must be done to f i l l voids in knowledge.

OXFORD: 83/86; 436; 44. KEYWORDS: utilization, residue management, prescribed f i re , microbia l ecology, decay, mineral cycling, mycorrhizae, nitrogen fixation, nitrification, mineralization, pathogen, disease, regeneration, fores t ecology, s i te quality.

Harvey, A. E . , M. F. Jurgensen, and M. J. Larsen 1976. Intensive fiber utilization and prescribed f ire: effects

on the microbial ecology of forests . USDA For. Serv. Gen. Tech. Rep. INT-28, 46 p. Intermountain Fores t & Range Experiment Station, Ogden, Utah 84401.

Reviews current knowledge of the effects of intensive wood utilization, prescribed burning, o r a combination of both t9patment s , on the microbial ecology of forest soi ls . Identifies additional r e sea rch that must be done to fill voids in knowledge.

OXFORD: 83/86; 436; 44. KEYWORDS: utilization, residue management, prescribed f i re , microbial ecology, decay, mineral cycling, mycorrhizae, nitrogen fixation, nitrification, mineralization, pathogen, disease, regeneration, forest ecology, s i te quality.

Harvey, A. E., M. F. Jurgensen, and M. J. Larsen 1976. Intensive f iber utilization and prescribed f i r e : effects

on the microbial ecology of forests . USDA For . Serv. Gen. Tech. Rep. TNT-28, 46 p. Intermountain Fo res t & Range Experimect Station, Ogden, Utah 84401.

Reviews current knowledge of the effects of intensive wood utilization, prescribed burning, o r a combination of both treatments, on the microbial ecology of forest soi ls . Identifies additional research that must be done to f i l l voids i n knowledge.

OXFORD: 83/86; 436; 44. KEYWORDS: utilization, residue management, prescr ibed f ire, microbial ecology, decay, mineral cycling, mycorrhizae, nitrogen fixation, nitrification, mineralization, pathogen, disease, regeneration, fores t ecology, s i te quality.

Harvey, A. E . , A.I. F. Jurgensen, and M. J. Larsen 1976. Intensive fiber utilization and prescribed f i re : effects

on the microbial ecology of forests . USDA For . Serv. Gen. Tech. Rep. INT-28, 16 p. Intermountain Fores t & Range Experiment Station, Ogden, Utah 84401.

Reviews current knowledge of the effects of intensive wood utilization, prescribed burning, o r a conzbination of both treatments, on the microbial ecology of forest soi ls . Identifies additional research that must be done to fill voids in knowledge.

OXFORD: 83/86; 436; 44. KEYWORDS: utilization, residue management, prescribed f i re , microbial ecology, decay, mineral cycling, mycorrhizae, nitrogen fixation, nitrification, mineralization, pathogen, disease, regeneration, fores t ecology, s i te quality.

WIIEST mourn UTIWTIWI RESEARCH M I D DEYEU)PUENl H O W M

New I I I I I I 11 I I I I - Washington State...

Documents

Transcript of New I I I I I I 11 I I I I - Washington State...