Home - Credit Valley Conservation Credit Valley Conservation...effects of climate change on forests...

��

��

��

��

��

��

�� !��"�#��$#��%�#&��$�&��$

��

��'��(��(��$#��)��

��

"�#��(��$#��$��*�$#�#&#��+"(�*,"�#��$#��%�#&��$�&��$

-./0�1&��#��2��&�#��#��"%��3��.20��

��+450,�673!.68-��(�9��+450,�673!.5/52!��:��$;��)��

��

��

�� <&$�2��#��$

��

��

��

!��"�#��$�%&%'('%%)�*��%+&,#��#�-$�.(///)(/0))()

%��1��2��!��1��&�!��1��#��"�� ,�##��!��3��#��###��

�4&'.�/�00%+5�%'') 0//�&�/22�'./%& �')('5+.2&(6

7�%'')"�8��9��9��"��

��:��;�

��$��3��!��3��#��%2&0�8��<��"��95=�2<0

�� /.0,�'+5(2')%!�> � /.0,�'+5(2.&.<(�� ?��:��

��@��@��

��

��This report reviews literature concerning the effects of global climate change on forest plants

and communities and provides author’s opinions of the potential impacts climate change may haveon Ontario’s forests. There is growing evidence that environmental changes caused by elevatedatmospheric carbon dioxide (CO2) and its potential effects on global climate will alter forest ecosys-tems in Ontario. A doubling of CO2 from pre-industrial levels is expected to occur within 80 years.Increased CO2 may increase average summer temperatures in Ontario between 3°C and 6°C, with thelargest increases in northwestern and southern Ontario. Precipitation is predicted to increase innortheastern Ontario, but to decrease in southern and northwestern Ontario. An increase in summertemperatures with no or little increase in precipitation would increase the frequency and severity ofdrought by elevating evapotranspiration. In addition, the incidence of extreme weather events andvariation in weather are expected to increase.

The length of the forest fire season is expected to increase with longer growing seasons. Inaddition, increased moisture loss from forests due to elevated temperatures would increase forest firefrequency and severity. Forest plant diseases and insects attack plants that have been stressed: in-creases in drought could also increase the frequency of major insect and disease outbreaks. Anincrease in forest fires, insect outbreaks and diseases would, in turn, alter the age structure and plantspecies in forest ecosystems, with the greatest impacts expected in northwestern and southern On-tario. Extreme weather events, such as ice storms, floods, and very high or widely fluctuating tem-peratures could further damage or stress plants.

Increased CO2, drought, and temperature will affect the growth and survival of plants byaltering their physiological behaviour. The genetic structure of plant populations may be affected byaltered selection pressures resulting from a changed environment, and species with larger geneticvariability are likely more adaptable to a variety of climate conditions and as a result may be moresuccessful. Competitive abilities of plant species now present in Ontario’s forests may change, withsome species becoming more competitive and others less so (e.g., herbaceous plants are favoured byincreased CO2 compared to woody plants). Productivity and timber supply in northwestern andsouthern Ontario may decline due to increases in drought, forest fires, insects and disease. However,this could be partially offset by increases in growth rates accompanying higher CO2 levels, warmertemperatures, and a longer growing season. Increases in precipitation in northeastern Ontario alongwith higher CO2 levels, increased temperatures and longer growing season could significantly in-crease productivity and timber supply in that region. Over hundreds of years, plant species maymigrate northward. In one scenario, tolerant hardwood forests of central Ontario may migrate as farnorth as Kapuskasing. Species, such as those of the oak-hickory forests of the central U.S., mayeventually migrate into what is currently the Great Lakes-St. Lawrence forest. However, differingmigration rates and the reactions of individual species to new environmental conditions could resultin new plant species mixes for which we lack forest management experience.

Forest management offers some means of reducing negative impacts to forests if the anticipatedlevels of climate change occur. Thinning to reduce moisture stress and early harvesting of standsdeteriorating due to stress, followed by planting with more climatically adapted populations andspecies could help maintain higher levels of productivity. Climatic adaptation could be increasedthrough tree breeding aimed at increasing pest and stress tolerance. Forests are important for theirrole in absorbing and storing carbon from the atmosphere. Although not presently a stated goal,carbon sequestration (storage) could in the future become an objective of forest management. Carbonsequestration is maximized by silvicultural practices that increase tree growth rates but release littlecarbon through the burning of fossil fuels. Process-based models of specific elements of forest eco-systems will be needed to predict the effects of climate change and consequently to develop forestmanagement practices that will minimize negative effects on Ontario’s forests.

�� We are grateful to the following individuals for providing technical reviews of individual

sections of this report:2. Climate Mike Wotton, Canadian Forest Service (CFS)3. Hydrology Michael Ter-Mikaelian, OFRI, Ontario Ministry of Natural Re-

sources (OMNR)5. Fungi Mike Dumas, CFS

Tim Meyer, OFRI, OMNR6. Forest Fires Mike Wotton, CFS

Al Tithecott, Aviation, Flood and Fire Management Section,OMNR

7. Physiology Francine Bigras, CFS8. Genetics Cheng C. Ying, B.C. Ministry of Forests9. Succession Wayne Bell, OFRI, OMNR10. Modelling Art Groot, CFS

Rich Fleming, CFS11. Silviculture Luc Duchesne, CFS

Our appreciation is also extended to Lisa Buse for editing the document for style, TrudyVaittinen for desktop publishing and graphics, and Anne Rovansek for typing.

��

��

��

�� !��

��"�� #��

��$��%��&��'��(�� )�� !��

��#��%��&��'�� *�� "��#��

��+��+��&��(�,�� $��

��)�� &��'�� $��

�� -��.�� %��

��/��%��0��'�*� �� !�� #��

��*��&�� "/��%�� $�� !��

�� $/

��'�� $

��

��

Stephen J. Colombo, Celia Graham, andMichael T. Ter-Mikaelian, Ministry of NaturalResources

The accumulation of carbon dioxide(CO2) in the atmosphere and the changesthis may cause to climate have potentiallyimportant consequences for Ontario’sforested ecosystems. While forests tend tobe viewed as unchanging due to the longlife spans of trees compared to humans,forests in Ontario have been changing as aresult of human activity since the middleof the 19th century (Armson et al. 1998).Historically, harvesting has been the majorcontributor to changes in species composi-tion and distribution of forest types. How-ever, since about the middle of the 20th

century, forests in Ontario and elsewherein North America have also been affectedby other aspects of human activity: theacidification of forest soils and the deposi-tion of nitrogen as a by-product of indus-trial pollution have altered soil chemistrythroughout much of central and southernOntario; ground-level ozone pollution,primarily in southern and central Ontario,has direct damaging effects on forestvegetation; the reduction of ozone high inthe earth’s atmosphere has increasedultraviolet radiation reaching the earth,with potentially serious effects on someplant species. Each of these factors bythemselves is a contributor to changes inOntario’s forests. Climate change, resultingfrom increased atmospheric CO2, is ex-pected to interact with the above factors tosignificantly alter the composition andfunction of forest ecosystems in Ontario(Schindler 1998).

There is growing concern that theincrease in atmospheric CO2 (and othergases produced by human activity, such asmethane and chlorofluorocarbons) will

increase air temperatures as a result of the“greenhouse effect” (Kuo et al. 1990). Thetrapping of heat by greenhouse gases thatoccurs naturally is beneficial as it main-tains warm temperatures over most of theglobe at suitable levels for agriculture andforests. However, industrial pollution willresult in an approximate doubling ofatmospheric CO2 by the end of the nextcentury. Examination of very long timescale polar ice cores shows a strong corre-lation between temperature and the con-centration of CO2 in the atmosphere. Accu-mulating greenhouse gases such as CO2will trap an increasingly larger portion ofthe re-radiating solar energy in the atmos-phere, and this may warm the earth meas-urably above current levels (Kräuchi 1994).According to Kräuchi (1994), the warmingseen over the last century is almost cer-tainly (i.e., with greater than 99% probabil-ity) the result of a real warming trend, andthis warming is associated with an in-crease in atmospheric CO2. Precipitationpatterns are also likely to be altered in theevent of climate warming, with some areasbecoming wetter and others drier (Joyce etal. 1990). The frequency of extremeweather events is also expected to increase(Hengeveld 1995), with potential increasesin the occurrence of severe drought, veryhigh temperatures, ice storms, and rapidlyfluctuating temperatures.

Forest management practices mustchange to keep pace with climaticallyinduced changes in forest ecosystems.Models are required to predict thesechanges, since forests are complex ecosys-tems that often respond to climate inunexpected ways both structurally (i.e., thespecies and ages of plants and animals inthe ecosystem) and functionally (i.e.,physiological and biogeochemical proc-esses). Even our understanding of the

effects of the present climate on forestecosystems is incomplete and climatechange effects cannot be predicted solelyby interpolation from present day fieldconditions or from laboratory experiments.In the future, forest ecosystems will beaffected by climate change in ways thathave never been observed or for whichdata are unavailable, and predictionsbased on present forest conditions may notbe relevant. Models are also useful becauseforest ecosystems are hierarchical (i.e.,effects controlling ecosystem structure andfunction can occur at scales ranging fromregional to as small as an individual plantand soil microbial populations), and havemany components that may be affecteddifferently both in terms of the magnitudeand direction of change. Even if one knewthe separate effects of climate change oneach component, their interactions wouldprevent assembling these effects into anadequate description of complex ecosys-tem effects. Thus, models are the best toolwe have to predict the effects of climatechange on forest ecosystems.

Increasing recognition of climatechange has lead to an international agree-ment to reduce greenhouse gas emissionsthrough the United Nations FrameworkConvention for Climate Change in 1992 andthe Kyoto Protocol in December 1997. Therole of forests in sequestering and storingcarbon is established in this Conventionand Protocol. Countries that ratify theProtocol will report on the area of man-aged forests, reforestation (renewal ofharvested forests), afforestation (conver-sion of non-forested to forested land) and

deforestation (loss of forest). Forests estab-lished between 1990 and 2012 may becounted as contributions towards Cana-da’s emission reduction target of 6%, asdefined by the Kyoto Protocol.

Ontario needs to begin to formulatethe role of forest ecosystems and forestryas part of a broader response to the inter-national commitment to address climatechange. The sustainability, biodiversity,health, and economic benefits of forestsmay be affected to varying degrees byclimate change. The long-lived nature oftrees requires that we consider the effectsof practices for periods of at least onerotation but preferably for several rota-tions (e.g., 200-300 years). It is the respon-sibility of the Ontario Ministry of NaturalResources (OMNR) as the steward ofCrown forests to understand the potentialeffects of climate change on forests andbegin to incorporate these effects into itsplanning. The OMNR’s mandate to sustainthe health and integrity of natural re-sources will need to include policies andguidelines to manage for mitigation andadaptation to climate change. One of thefirst steps is to develop an understandingof the impacts of climate change on On-tario’s natural resources.

This discussion paper examines themultiple effects of climate change onOntario’s forest ecosystems. The co-au-thors of this report have prepared sectionsaddressing the key issues and impacts intheir respective disciplines. Some possibleactions to mitigate adverse effects of cli-mate change are addressed in the section“Forest Management Responses to ClimateChange.“

Mike D. Flannigan, Canadian ForestService

While we tend to think of climate asbeing constant, in fact it is always chang-ing. Some changes follow patterns withextremely long time scales, such as the21,000 year cycle of the precession of theearth’s axis about the pole. Weather, incomparison, is by definition variable, andis the short-term (hours to months) varia-tion of the atmosphere. Climate is theweather at some location averaged over aspecified time period (typically 30 years)plus information on the variability andweather extremes. Climate, and its associ-ated weather, influence the natural envi-ronment directly, through elements suchas temperature and precipitation, andindirectly, through its influence on distur-bance and permafrost. Any change invariability in climate could be criticalbecause many of the ecological impacts ofclimate are the result of extremes. At thelocal scale, climate is influenced by varia-tions in solar radiation due to latitude,distribution of continents and oceans,atmospheric pressure and wind systems,ocean currents, major terrain features,proximity to water bodies, and local fea-tures, such as exposure, local topography,and urbanization (see Trewartha and Horn1980).

The “greenhouse effect” is the influ-ence of gases such as carbon dioxide,water vapour and methane on the earth’sradiation budget. The greenhouse gases inour atmosphere allow the shorter wave-length radiation (incoming solar) to reachthe earth’s surface while absorbing thelonger wavelengths (outgoing terrestrial),which, in part, is re-radiated back to theearth. Human activities have increasedcarbon dioxide, methane and other natural

greenhouse gases, in the atmosphere, aswell as added human-made gases such aschlorofluorocarbons (CFCs) andhydroflurocarbons (HFCs). Increases ingreenhouse gas concentrations are respon-sible for enhancing the natural greenhouseeffect. Global mean surface air tempera-ture has increased by 0.3° to 0.6°C sincethe late 19th century (IntergovernmentalPanel on Climate Change (IPCC) 1996).For Ontario, surface air temperatures haverisen by 0.5° to 0.7°C since 1895 (Gullettand Skinner 1992). The IPCC (1996) statesthat “the balance of evidence suggests adiscernible human influence on globalclimate” and that the climate is expected tocontinue to change in the future. Incontro-vertible attribution of the long-term causeof current climate change is difficult due tothe natural short-term variability in theearth’s climate. Future predictions aredifficult because of the complex interac-tions in the climate system.

General Circulation Models (GCMs),sophisticated computer models, are theprimary tool used to estimate what thefuture climate will be. Numerous GCMsare used (Lau et al. 1996), including aCanadian GCM (Boer et al. 1992,McFarlane et al. 1992). Most GCMs haveoutputs for 1xCO2 and 2xCO2 scenarios,which roughly correspond to atmosphericCO2 conditions in the mid-20th centuryand the second half of the 21st century,respectively. GCMs suggest that the aver-age global surface air temperature willincrease by 1 to 3.5°C by 2100 (IPCC 1996).However, more pronounced changesshould occur at high latitudes and begreatest in winter. The spatial resolution ofthese models is often around 400 km.Regional Climate Models are now beingdeveloped to provide climate

��

��

estimates at finer spatial resolution (~40km). These will be more suitable for pre-dicting regional effects of climate change inOntario (Caya et al. 1995).

The present climate of Ontario is bestdescribed as continental, with cold wintersand warm to cool summers. The climatearound the Great Lakes tends to bewarmer and wetter in winter because ofthe heat and moisture available from thelarge bodies of water. Conditions rangefrom warm and moist in the south to coldand dry in the northwest (Table 2.1). Amore detailed discussion of the recentclimate of Ontario can be found in Hareand Thomas (1974).

Projected global warming of 1 to 3.5°Cover the next century means that the cli-mate would warm at a rate faster than atany time in the past. These increasedtemperatures could make the next centurythe warmest so far during this interglacialperiod. Ontario is a large and diversegeographical region with great variation inclimate. Figure 2.1 shows the predictedincrease in surface air temperature duringthe 1 May - 31 August period derived fromthe Canadian GCM, comparing a doubled(i.e., 2xCO2) to present (i.e., 1xCO2) CO2concentration. According to this scenerio,temperature increases of 3°C to over 5°C

are expected across Ontario. The largestincreases are expected over southwesternsections of northwestern Ontario, while thesmallest increases are anticipated over theextreme northwestern region of Ontarioalong Hudson’s Bay. If these predictionsare realized, the summer temperatureregime in Sudbury at the end of the nextcentury would be similar to the currentsummer temperature regime in Windsor(Table 2.1).

Figure 2.2 shows the predicted effectof a doubled CO2 environment on summerprecipitation across Ontario, according tothe Canadian GCM. Values over 1.0 indi-cate increases in precipitation whereasvalues less than 1.0 indicate decreases inprecipitation for the end of the next cen-tury. Precipitation ratios range from justunder 1.0 for much of northwestern On-tario and most of southern Ontario to over1.2 for northeastern Ontario. There isincreased potential for water stress overregions with decreased precipitation inconjunction with increased temperatures.Precipitation has been increasing since1910 over the continental United States andmost of this increase is due to increasedfrequency of extremely heavy precipitationevents (Karl and Knight 1998). An increasein the number and severity of extremeweather events also is predicted to resultfrom climate change.

The impacts of climate change havebroad and far reaching implications forOntario’s forests, ranging from distur-bances (insects, disease, fire and wind) andbiotic responses (physiology, genetics andplant succession) to how we manage our

Table 2.1. Selected climate data for selected sites across Ontario from 1961-90 (Environment Canada 1993).

��

��

��

��

��

��

��

��

forests within this new environment (Weberand Flannigan 1997). The continued devel-opment of regional circulation models withshorter time intervals will be important topredict and respond to the impacts of cli-mate change on Ontario’s forests.

��

��

��

��

��

��

Chris Papadopol, Ontario Forest ResearchInstitute, Ministry of Natural Resources

Water availability to forest plantsvaries with precipitation, evaporativedemand and the capacity of the soil to storewater. Climate warming may modify wateravailability by changing precipitation andevaporative demand. The soil water bal-ance of forested sites is important becausewater availability strongly affects forestproductivity; numerous studies show thatdrier than normal seasons reduce tree ringsize.

Forest ecosystems can also modify thelocal hydrology and environment. Forestsaffect the environment locally and season-ally through albedo (i.e., reflectivity ofsunlight), roughness (i.e., evenness of thecanopy) and transpiration. Under favour-able conditions, forests also have the poten-tial to mitigate some of the local effects ofclimate change expected in the next cen-tury, for example by acting as CO2 sinks(i.e., enhancing biomass and litter produc-tion) (see Section 11).

Climate warming will accelerate thecirculation of moisture in the global watercycle (Bolin 1986). Since regional precipita-tion depends on major air circulation pat-terns, climate change may either increase ordecrease the amount of precipitation in agiven area (see Section 2, Figure 2.2). An-ticipated increases in summer temperatureswill increase evapotranspiration fromforests. The increased Atmospheric De-mand for Evaporation, ADE, is an impor-tant way that climate warming may influ-ence vegetation. Where soil water storage ispoor (e.g., coarse textured and thin soils),an increase in ADE may reduce soil water

availability, and through this, graduallychange the productivity and survival offorest plants.

Models of forest water balance canprovide estimates of soil water availabilityon sites where soil texture and forest plantspecies are known. It may be possible to usesuch models to develop regional estimatesof forest water use where the spatial distri-bution of soil texture and plant species areknown. To show the influence of warmingon ADE, the Thornthwaite model forevapotranspiration, ETp (Thornthwaite1946), was run for three scenarios: (i) nothermal increase, recorded mean air tem-perature (ETpO), (ii) recorded mean airtemperature + 2oC (Etp2), and (iii) recordedmean air temperature + 4oC (Etp4), usinghistoric daily data from Blind River, On-tario, and soil hydraulic conductivity for atypical stand in the Kirkwood forest, nearThessalon, Ontario. A water balance modelwas then run to simulate water availabilityin past growing seasons.

Warming increases evapotranspirationwith every degree Celsius in temperaturecausing an additional 0.15 mm/day or 4.5mm/month ADE (Figure 3.1). This increaseshould be interpreted in the context of therange of daily ADE, which during thegrowing season in Ontario, roughly variesbetween 6 and 2 mm/day from south tonorth. This increase in evapotranspirationwill reduce soil moisture and, in my opin-ion, may limit the distribution of somespecies and reduce the productivity ofothers. In comparison with recent historical

��

��

conditions, the future soil water regime ofsome regionsof Ontario will be less favour-able, especially on soils with high hydrau-lic conductivity, which cover large areas ofOntario.

An example of the possible site effectsof increased evapotranspiration is given inFigure 3.2, for a forest stand located in theKirkwood forest. The soil on this site hasan unavailable water content (i.e., heldwith a tension greater than -1.5 Mpa) ofbetween 25 and 50 mm of water up to 1.0m soil depth (based on a column of soil).Soil water balances were reconstructedfrom weather data from Blind River for1970, a year with abundant precipitation.

Soil drainage has a great influence onthe available moisture (Figure 3.2). Forevery 10 mm of rain, more than 50% infil-trates the soil, the rest is lost to runoff andevaporation. As the amount of rain perrainfall increases, the proportion of infil-tration increases. Therefore, although thesoil is supplied abundantly with water, it

does not have the capacity to retain thiswater and supply it steadily to trees. Infact, after an abundant rain, water is easilyavailable for only two to three days. InOntario’s forests, except for the clay belt,available water varies, approximately,between the limits indicated by Figure 3.2.However, in large areas in northwesternOntario, where soils are shallow and stony,they are also more prone to water deficit.The expected increase in annual variabilityof rains (Bolin et al. 1986), may result inmore frequent and longer occurrences ofsoil water stress.

Soil hydraulic conductivity (the rate ofwater movement in a soil), which signifi-cantly affects soil water regime, dependsgreatly on soil texture — the coarser thesoil, the greater the conductivity. Whileorganic matter significantly improves soilwater retention by reducing hydraulicconductivity, unfortunately, the organiclayer of most soils in Ontario (with the

��!��"�##��#��!�$ �%�&��'� ��(�� )�� #� $�)��)��*+�),�"��-��#�� () �� *+�)

�,%��.��/��0�*+�)

�,��0�*+�)

�,�.��(��

exception of peatlands) is thin. Sitedisturbances, especially hot ground firesand some mechanical site preparationtechniques, can greatly reduce the thick-ness of the soil organic layer, leading toincreased soil water deficits. Sites withcoarse-textured soils overlain by thinorganic layers are most susceptible toproblems with water availability. Organicmatter can be enhanced silviculturally bypromoting hardwoods.

The forest species that grow in On-tario, and whose distribution and produc-tivity is going to be affected by climatewarming include the commercial speciesblack spruce, jack pine, and red pine.Typically, these are shallow-rooted species,which depend solely on moisture availablein the first metre of soil. At present, thesespecies are productive because rains arefrequent or humidity is high, which eitherre-supplies the soil with moisture at shortintervals or results in low ADE, respec-tively. In a progressively warmer scenario,

with increased evapotranspiration butsimilar soil water holding capacity, thesespecies are likely to suffer moisture stressmore frequently and for longer periods.The expected increase in climatic variabil-ity may make the situation worse, becauselarge rainfalls, likely to occur under thisscenario, do not greatly improve the waterregime due to the large amount of precipi-tation lost to infiltration. These stands willfirst be affected in terms of reduced pro-ductivity, and then, in the event of a pro-longed drought with high ADE, mortalitymay occur. Reduced stocking throughthinning is a potential means of redistrib-uting soil moisture to prolong the produc-tive life of such stands. In contrast withshallow rooted species, deep rooted oneshave the advantage of being able to absorbwater from greater soil depths. Deeplyrooted species are expected to be betteradapted to the increased ADE and soilmoisture deficits that may occur in someareas of Ontario.

��!��"�##��#��!�$ �%�&��%�� (�� "�#��#�.�� "��#��.��/��((�� $

Across Ontario, the influence ofclimate warming on the soil water balancewill be affected by (i) air circulation pat-terns, (ii) regional soil characteristics, and(iii) inherent natural variability. On typicalforest sites in the next century, in myopinion we might expect that in south-western Ontario existing forest ecosys-tems will experience moderately in-creased moisture stress. Over a 30- to 50-year time frame, soil moisture stressshould be controllable through thinning.In the clay belt, water availability is ex-pected to remain high (Section 2). Onsome low-lying peatland sites in north-eastern Ontario, where water tables arealready high and drainage impeded, the

forecasted 10 to 20% projected increases inprecipitation (Section 2, Figure 2.2) mayraise the water table enough to causeflooding in some stands. On these sites,drainage could be used to preserve exist-ing stands. In the boreal forests in north-western Ontario, where soils are shallowover shield or till deposits vegetation isexpected to experience high levels of soilmoisture stress as a result of climatechange. This area is already prone toforest fires, which are predicted to in-crease under a warming scenario (Section6). The establishment of mixed conifer-hardwood forests should be encouragedto promote the buildup of forest litter andhumus, which will improve soil moistureretention.

Taylor Scarr, Forest Management Branch,Ministry of Natural Resources

Insect outbreaks have substantialeffects on Ontario’s forests. Outbreakssuch as spruce budworm and gypsy mothoften occur over large areas and can causewidespread tree mortality (Hardy et al.1986). Together with fire they are themajor disturbance influencing the succes-sional patterns in both the Boreal andGreat Lakes–St. Lawrence forests(Fleming and Candau 1997). They furtheraffect the nutrient and biogeochemicalcycles of forests through the conversion oftree biomass to other trophic levels of theecosystem.

If the predicted changes in climateoccur, resulting in increases in meanannual temperature and more extremeweather, there will be direct effects oninsect population dynamics, which in turnwill affect forest stand structure, composi-tion, and function. The greatest effect ofthe predicted climate change is likely tobe on the insect disturbance regime; thatis, the frequency, duration, and severity ofpopulation outbreaks (Fleming 1996).Because fire regimes are often intricatelylinked with insect disturbance, changes ininsect outbreak patterns will causechanges in the fire regimes, which to-gether will affect the composition of theforests of Ontario (Fleming and Candau1997).

The challenge caused by climatechange for forest managers is that it willbe very difficult to predict which treespecies will form the future forest in aregion, and which insect species willbecome the major disturbance forces in

��

��

that new forest (Sandberg 1992). Each treeand insect species must be consideredindividually in terms of its response toclimate change (Logan et al. 1995), yet eachwill influence the other. The uncertaintyover future forest condition makes it diffi-cult to project sustainable timber suppliesand to determine how to mitigate the ef-fects of climate change to maintain ahealthy forest that can meet society’s de-mands (Fleming and Volney 1995).

Tree species will respond differently toclimate change (changes in the average andextremes in temperature, precipitation,weather events, CO2 concentration, fire,insect outbreaks, disease). In the southernpart of current ranges, tree regenerationrates are expected to decrease while senes-cence rates are likely to increase (Fleming1996). Local extinction may result if anoutbreak of an insect occurs that attacksolder trees, driving the tree populationbelow the threshold at which it can sustainitself. For northerly sites, tree regenerationrates should increase, while senescencerates should decrease. The result, again, isdestabilization of the ecosystem. As de-scribed by Fleming (1996), "chance, histori-cal factors, and threshold effects" willsignificantly affect the condition of theforest ecosystem as this destabilizationoccurs.

Climate change is expected to haveseveral effects on insect-tree interactions:• insects that are currently pests may no

longer remain so depending on theirresponse, as well that of their host trees,to climate change (Hedden 1988);

• tree growth rates may increase underwarmer temperature conditions, butpoikilothermic insects may respond more

efficiently, giving them a competitiveadvantage (Fleming and Tachell 1995);

• tree growing seasons may be extended,but insect species may increase theirnumber of populations per year;

• some insect species may become pests ifthe new temperature or moisture re-gimes are outside the optimum range fortheir parasites, predators, or pathogens,allowing the host species to escape thesenatural controls;

• some insect species will be adverselyaffected by effects of climate change ondiapause requirements;

• some insect pheromones may be lessstable at higher temperatures, reducingthe species' reproductive potential andcompetitiveness (Hedden 1988);

• the increased CO2 concentration mayenable trees to produce more carbon-based antifeedants, increasing the resist-ance of some tree species to some insects;

• increased CO2 concentration may in-crease the carbon to nitrogen ratio in treefoliage, resulting in increased feeding bydefoliators to obtain sufficient nitrogen;

• increased drought could increase sucroseconcentration in foliage, favouring in-sects;

• increased drought can lead to earlier leafstomatal closure, increasing temperatureand decreasing relative humidity of theleaf outer microclimate, resulting inincreased insect growth rates, decreased

mortality, increased fecundity, and de-creased effects of pathogens (Fleming1996).

These effects of climate change are notmutually exclusive, and will be influencedby effects of climate change on trees andtheir competitiveness with other trees andplants, other disturbance regimes such asfire and extreme weather, the speed atwhich climate change occurs, and chance.The result of these effects and thedestabilized ecosystem will be individual-istic movement of parts of the system inresponse to climate change. For forestmanagers, this inherent uncertainty pro-vides only generalizations (Hedden 1988):• shortening stand rotations to reduce the

period of vulnerability and increasevigour;

• aggressive tree breeding to increaseresistance to insect pests or to speedadaptation to the emerging climate (seeSection 8);

• controlling competing vegetation (e.g.,via thinning, weed control) to reducestress to regenerating trees and helpproduce desired species composition inthe future forest (see Section 9);

• sanitation cutting to encourage healthystands;

• minimizing adverse disturbances duringharvesting to reduce stress;

• using insecticides to control damaginginsects and reduce timber volume losses.

Sylvia Greifenhagen, Ontario ForestResearch Institute, Ministry of NaturalResources

Of the many predicted effects ofglobal warming, a rapid increase in aver-age temperatures (1 to 3.5°C over the nextcentury), combined with increaseddrought periods and increased frequencyof catastrophic weather events, will havethe most significant impact on fungalcommunities in Ontario’s forest ecosys-tems. Soil microbes, of which fungi are amajor component, are the drivers behindmany of the processes occurring below theforest floor. Ecosystems are regulated bythe rates at which soil processes occur.These below ground systems will be criti-cal determinants of ecosystem response toclimate change (O’Neill 1994). The func-tional biodiversity of an ecosystem, espe-cially of below-ground organisms, playsan important role in regulating the impactsof disease by causing disruptions in eco-logical continuums, thereby limiting dis-ease outbreaks. Climate-caused changes infunctional groups may substantially affectthis regulatory role. The effects of globalwarming on tree diseases and the entiresoil microbial population, includingmycorrhizae, will vary with fungal species,the biotic forest community, the abioticenvironment, and interactions and associa-tions between these components.

Forest Tree Diseases. Over 20 millioncubic metres of timber are annually de-pleted by diseases in Ontario’s forests(Gross et al. 1992). Increases in incidenceand severity of diseases because of globalwarming will substantially affect thetimber resource. Many of the most impor-

tant diseases in Ontario’s forests, such asroot diseases, stem decays, and declines,require a stressed host before infection ordisease expression occurs. When a tree isstressed, less energy is available to sustainthe physiological processes critical todisease resistance, as more energy isallocated to life-sustaining processes(Wargo and Harrington 1991). Diseasesrespond to stress in plants in variousways such as increased incidence orseverity. When stressed, a normallyresistant tree species may become suscep-tible to a certain disease, broadening thehost range of the pathogen. Stress causedby an increase in the number and severityof catastrophic weather events, especiallydrought, may increase disease susceptibil-ity, especially where plants are not physi-ologically adapted to a site or are near thelimits of their range (McDonald et al.1987). For example:• above average temperatures, possibly

associated with soil drying and fine rootdeath, have played an important role insugar maple decline (Cannell et al.1989);

• in one study, a 2°C increase in soil tem-perature above the optimal temperaturefor growth of white birch (i.e., 18.5°C)caused substantial fine root death(Redmond 1955);

• red spruce dieback may be associatedwith summer drought and a generalincrease in temperature since the 1800’s;

• parasitism by Armillaria root diseaseincreases during periods of drought,while wet periods favour its saprophytic(i.e., living on dead organic matter) role(Nechleba 1927);

��

��

• certain Armillaria species primarilyattack conifers, but will attackhardwoods weakened by ice damage tothe crowns (Dance and Lynn 1963).

Drought-induced stress will be mostsevere on the shallow soils of the borealforests of northwestern Ontario, and inci-dence and severity of Armillaria ostoyae, themost common root decay fungus in theboreal forest, may increase on these sites.An increase in the host range of this stress-induced disease may occur in the hard-wood and mixedwood forests of easternand northeastern Ontario.

Soil Microbes. Soil contains the largestterrestrial pool of organic carbon (Batjes1996). Changes in the abundance anddiversity of soil microbial communitiesand functional groups as a result of climatechange may have far-reaching impacts onmany ecosystem processes. For example,soil microbes, including fungi, are respon-sible for carbon and nutrient cycling andformation of soil structure in forest ecosys-tems. Climate change may affect the ratesof decomposition or organic residues insoil, which will influence the availability ofnutrients required for plant growth. Be-cause of the intricate relationships thatexist between above-ground plants andsoil biota, changes to any one componentcan have far-reaching effects throughoutthe ecosystem.

Although the effects of climate changeon soil microbes will vary substantiallywith site and microbial species, in general,drought and fire reduce soil microbialdiversity, at least in the short term. Re-duced diversity may have adverse effectson forests, because a highly diversemycoflora could be important to the abilityof plants to adjust to climate change(O’Neill 1994). Increased atmospheric CO2levels may also significantly affect soilmicrobial processes. Concentrations ofnitrogen and other nutrients in plants maydecrease as atmospheric CO2 levels in-

crease, resulting in a gradual decrease indegradability of plant residues by microbes(Couteaux et al. 1995) and an accumulation ofnutrient-poor organic matter (Lekkerkerk etal. 1990). Mycorrhizae are a highly specializedgroup of soil fungi that form symbiotic asso-ciations with plant roots, enhancing plantnutrition, water uptake, growth, and stressresistance (Molina et al. 1992). As with soilmicrobes generally, mycorrhizal associationsare affected by soil moisture and temperature;the effects of climate change may, therefore,vary with fungal and host plant species(Monz et al. 1994). Certainly the complexity ofplant-microbial-environment interactionsmake the prediction of climate change effectsextremely difficult! However, under theassumed climate change scenario, the follow-ing events may occur:• fungi that are favoured by disturbance will

become more prevalent (Miller and Lodge1997);

• the rate of litter decomposition may rise byup to one third its present rate if annualtemperatures rise by 3°C (Cannell et al.1989, Schimmel 1995). Marginal soils shouldbecome more productive, at least in theshort term, where drought is not a limitingfactor;

• long-term, repeated drought will causefluctuations in the microfungal biomass,reducing the availability of nutrients andthereby limiting plant growth (Lodge et al.1994). Drought effects may be mitigated bymycorrhizae, which enhance stress resist-ance and nutrient uptake in trees (Millerand Lodge 1997);

• the migration of many pioneering treespecies will depend on the successful migra-tion of their host-specific mycorrhizae(Meyer et al. 1982);

• the productivity of boreal forests in the claybelt of northeastern Ontario, where wateravailability should remain adequate (seeSection 2), could benefit from an increase in

the rate of litter decomposition caused byincreased temperatures.

Interactions between climate andbiotic systems are extremely complex(Ojima et al. 1991) and understanding thepotential impacts of climate change onfungi in forest ecosystems is a great chal-lenge. Information is needed on howspecific fungi and fungal communitiesinteract with each other, with the forestecosystem in general, and with the chang-ing global environment. Stress-host-pathogen relationships and interactionsneed to be identified (Wargo andHarrington 1991). A better understanding

of microbial processes, microbial diversity,and variations with site, forest composi-tion, temperature, and moisture in On-tario’s forest soils will provide informationneeded to predict microbial responses toaltered environmental conditions. Moreinformation is needed on the ecologicalspecificity of mycorrhizae and their suc-cessional variation (Molina et al. 1992).This knowledge will improve our under-standing of the roles fungi play in commu-nity development and ecosystem stability(Molina et al. 1992), and can be used todevelop sound forest management prac-tices for a period of rapid global change.

Robert S. McAlpine, Aviation, Flood and FireManagement Branch, Ministry of NaturalResources

There is strong consensus that climatechange will increase fire activity in Ontario(Simard 1997). This increase in fire activitycan be attributed to three of the implicationsof global climate change: (i) increased fre-quency and severity of drought years; (ii)increased climatic variability and incidenceof extreme climatic events, and (iii) increasedspring and fall temperatures.

The most influential implication ofclimate change for forest fire management isthe predicted increased frequency and sever-ity of drought years. Clearly, during years ofmuch lower than normal rainfall, fuel mois-ture levels decrease and the forest is predis-posed to fire. This is manifested as an in-crease in the forest fire weather severityrating (Williams 1959, Van Wagner 1970,1987)—an integration of weather factors(temperature, relative humidity, wind speedand precipitation) over periods of variouslengths (daily, monthly, seasonal, etc.). Fireweather severity is an objective yardstick forcomparing weather (and hence the risk offorest fires) from site to site and from year toyear (Van Wagner 1970). Flannigan and VanWagner (1991) estimated that climate changewould produce a 40% increase in fireweather severity in Canada, resulting in asimilar increase in area burned. Stocks et al.(1998) extended this with results from re-fined climate change models to predictaltered patterns of fire weather severity inCanada.

Figure 6.1 uses methods similar to thoseof Stocks et al. (1998) to show the impact of adoubling of atmospheric CO2 on the seasonal

fire weather severity in Ontario. The figureshows a general increase in severity acrossthe province, with some larger changes inthe extreme west (Kenora area) and south-east (Ottawa area) of the province. The mostpronounced changes will occur during Juneand July and to a slightly lesser extent, May(Figure 6.2). While August and Septemberalso show a predicted increase in fireweather severity, it is not as conspicuous.The area near Quetico Park (south west ofThunder Bay) changes very little in anymonth. In contrast, the fire weather severityaround Sudbury and for much of SouthernOntario is expected to increase to near prai-rie-like conditions (see Figure 1 in Stocks etal. 1998 for comparison).

A second major element of climatechange that will affect fire management isincreased variability of the climate andincreased incidence of extreme climaticevents. Fire “flaps” result from a short-termincrease in fire danger caused by two ormore weeks without appreciable rain cou-pled with an ignition source (CanadianForestry Service 1987). This kind of climaticevent could easily be offset by episodiccooler moist weather and would thereforenot appear in the monthly fire weatherseverity plots of Figures 6.1 and 6.2. Withincreased climatic variability, the incidenceof these short term peaks in fire danger willbecome more prevalent. In addition, Fosberget al. (1990) and Price and Rind (1994) pre-dict that climate change will be accompaniedby increases in lightning activity, the causeof 80% of the area burned in Ontario. Typi-cally, large fire runs (and hence area burned)are the result of a few days of extreme fireweather. With increases in these extremeevents along with an increase in lightningactivity, an increase in area burned can beexpected.

�� !��

��

A third element affecting forest fireactivity is the predicted increase in springand fall temperatures, which extends boththe growing and forest fire seasons. Wottonand Flannigan (1993) estimate that climatechange will extend fire season length inOntario by 25 days (a 16% increase). Figure6.2 shows a slight increase in fire weatherseverity in September, however the monthlyresolution of this map is too long to show thepredicted increase in fire season length. Inaddition, data for the month of April wereunavailable. April may show a larger in-crease in fire weather severity than Septem-ber, as the trend from Figure 6.1 shows largerchanges in fire weather severity early in theseason.

The increases in drought years, extremeclimatic events, and fire season length indi-cate that climate change will result in longerfire seasons, with greater fire load andgreater incidence of extreme fire load years.Trends since 1985 indicate increased forestfire activity in Ontario. Whether this is theresult of climate change, increased weathervariability, or some other factor is difficult toassess. In any case, if the current protectionlevels are to be maintained, and a increases inarea burned minimized, the changes in theenvironment brought on by climate changewill necessitate increases in fire managementexpenditures. How to best minimize the totalfire management investment and provide anacceptable level of fire protection will be thechallenge of the next few years.

Forest fires are a natural part of theglobal carbon cycle. Increased fire activitywill release more CO2 into the atmosphere,adding to the greenhouse effect. Table 6.1shows carbon emissions from forest fires inOntario based on estimates of fuel volumeand carbon emission factors published byStocks (1990, 1998, pers. comm.).

Values in Table 6.1 are presented by firemanagement zone. The intensive zone corre-sponds to those areas of central and NorthernOntario containing major population centers,

recreational areas, and forest industry. Firesin the intensive zone are aggressively de-tected and suppressed (note the smalleraverage fire size). The measured zone encom-passes a broad east-west band north of theintensive zone, and covers areas of moder-ate recreational use and future wood sup-ply. Most fires are aggressively detected andattacked, however if initial attack fails, thefire is assessed to determine if suppressionaction will continue as aggressive, moder-ate, or minimal. The extensive zone repre-sents the far north of Ontario where mostfires are allowed to burn unsuppressedunless specific resources are at risk. Esti-mates of carbon emissions from prescribedfire, largely from burning of logging debris,are also provided in Table 6.1.

The combined CO2 emissions fromwildfire and prescribed fire is in excess of3.5 Terragrams (Tg) of CO2 (3.5 milliontonnes). This constitutes about 2% of On-tario’s total CO2 emissions. Increases in thelevel of protection in the measured or exten-sive zones of Ontario (the primary CO2production zone on a per fire basis) wouldreduce these emissions. To demonstrate, ifthe entire area of the measured and exten-sive zones were converted to intensiveprotection, the average forest fire size inthese zones would perhaps be reduced tothat of the current intensive zone. Thiswould reduce carbon emission by 2.38 TgCO2. However, this quantity of sequesteredcarbon cannot be protected ad infinitum.The carbon will be eliminated from the siteeither by decomposition or large conflagra-tion type fires (due to excessive fuel loads)unless it is removed from the site and se-questered elsewhere (e.g., wood products).The change in level of protection to reducecarbon emissions from wildland fireswould change the fire return interval of alarge part of Ontario’s wilderness. Theecological ramifications and economic costsof this change in fire return interval must becarefully considered.

1�� $ ��%�� %�� %� �%�� %��

2 �� %�� %�� %�� %��

+3� ��$ ��%�� %��%� ��%�� %��

4� �-�� "�� *�#��/ ��))#�-��# ��%�� %��)�# � �%�� %�� %�� )�# �,

��

Table 6.1. Annual average greenhouse gas emissions from Ontario wildland forest fires and prescribed burning from1989 to 1996.

!��"��#�$�

!��"��

��

%��

#��&�'��

�(�

��

�(�

��

��

��$�

� ��(�� $ �� . ��/��"�.��) ��#��/�)�#

)��"��

��

"��"�� #��

��

Stephen J. Colombo, Ontario Forest ResearchInstitute, Ministry of Natural Resources

The physiological function of com-mercial tree species is the basis for theirproductivity and the wood-based eco-nomic benefits derived from Ontario’sforests. In addition, the diversity of forestplants depends on physiological attributesthat allow different species to survive andthrive despite environmental stresses. Ifclimate change alters the occurrence ofplant physiological stress then the com-mercial benefits derived from forests andthe biological diversity of forest ecosys-tems in Ontario will also be changed(Joyce et al. 1990).

Plant physiology is one means bywhich environment is translated intoeffects on forest ecosystems, at first byaction on the physiology of an individualplant, and as a consequence on plantpopulations and communities. Forestvegetation is directly affected by tempera-ture, the concentration of CO2 in the air,mineral nutrition, and water supply, all ofwhich are expected to change in Ontario incoming decades (Walker and Steffen 1997).In addition to such direct effects, climatealso affects forest plant communitiesindirectly through plant-to-plant competi-tion for site resources (e.g., water, light,nutrients). An understanding of the directand indirect effects of climate change onplant physiology is needed to predictclimatically induced changes in forestproductivity, forest health, andbiodiversity.

Table 7.1 summarizes some of theeffects of increased atmospheric CO2,temperature, and moisture stress due tomore frequent and prolonged droughts on

plant physiological processes andgrowth. Rates of photosynthesis areincreased by higher concentrations ofCO2 and warmer temperatures (Battagliaet al. 1996); however, the magnitude ofsuch increases is proportional to growthrate (Tissue et al. 1996) and nutrientsupply (Drake et al. 1997). Stomatalconductance (which is related to the rateof water loss from leaves by transpira-tion) is reduced by increased CO2 and asan aftermath of drought, but increasedby warmer temperatures. Water useefficiency (the ratio between the rate ofphotosynthesis and the loss of waterthrough transpiration) increases withelevated CO2 and drought, but decreasesif conditions are warm and very humid.Phenology (the timing of bud burst,flowering, and other growth processes)is increased by warmer temperatures butdelayed by drought and elevated atmos-pheric CO2 (Murray et al. 1994). Warmertemperatures in the spring lead to earlierbud burst, which potentially exposesnew growing shoots to freezing damage(Colombo 1998). Warmer temperaturesin the fall may delay frost hardening andwarmer winters could reduce theamount of chilling plants receive; insuffi-cient chilling may not completely over-come dormancy of some species insouthwestern Ontario, which woulddelay bud burst resulting in a shortenedgrowing season. Drought, in compari-son, can shorten the growing season bycausing plants to cease growth earlier inthe summer. While each climate changefactor has an independent effect on plant

physiology, in many cases there are poten-tial interactions that produce complicatedeffects and modified plant responses. Ingeneral, more information on such interac-tions will allow us to better predict theeffects of climate change on plant physiol-ogy.

Our understanding of plant responsesto the environment is largely based onshort-term experiments conducted incontrolled environments, in which onlyone or two factors were varied, and smallor young plants were used. While this is alogical first step in attempting to under-stand responses to climate change, cautionis required when extrapolating plant-scaleresults to ecosystems, because of the over-simplification these experiments entail.Scaling effects frequently alter the wayfiner scale events (e.g., leaf or plant levelresponses over short time spans) translateinto larger scale results (e.g., stand orcommunity function and structure overlong time spans) (Körner 1993). Directobservations of plant behaviour and inter-actions in forest plant communities arerequired to link physiological processes tolong-term reactions of forest ecosystems.

Information obtained from studies ofphysiological behaviour in a plant commu-nity is required to develop managementoptions to mitigate the negative effects ofclimate change. There is probably morevalue in controlled environment studiesthat are planned based on observations ofplant behaviour in a community; in thistop-down approach it is possible to targeta particular species and to dis-aggregatethe effects seen at higher levels of organi-zation in terms of species interactions andprimary physiological processes.

All areas of Ontario will experience adoubling of atmospheric CO2 in the latterhalf of the next century and this is ex-pected to increase temperatures, with thegreatest temperature increase predicted innorthwestern Ontario (see Section 2).Precipitation in Ontario is expected to

decrease in the northwest and south andincrease in the northeast (Section 2). Thewarmer and drier conditions expected innorthwestern and southern Ontario willfavour species that are more tolerant ofperiodic drought (Schindler 1998). Basedon their physiology, more frequent andsevere drought will affect the growth ofthe following tree species in northwesternOntario increasingly in the order: jack pine(least negatively affected), white spruce,aspen, and black spruce (most negativelyaffected).

Relative physiological responses ofcompeting forest plant species to climatechange can be as important as absolutespecies responses. “Response hierarchies”based on plant physiological responses toincreased CO2, have been developed byKörner (1993). In general, increased CO2will favour evergreen species less thandeciduous woody species, which will inturn be less favoured than perennial spe-cies (e.g., fireweed, raspberry, andgrasses). Annual herbaceous species willbe most favoured by increased CO2. El-evated CO2 will favour seedlings morethan young trees and young trees morethan old trees. Late successional species(e.g., maple, yellow birch, white spruce,white pine) will be less favoured thanearly successional species (e.g., aspen,poplar, oak, jack pine, black spruce). Spe-cies with small or infrequent seed and fruitcrops (e.g., black spruce, aspen) will beless favoured than species with largefrequent seed and fruit crops (e.g., oak,white pine). Nitrogen-fixing species will bemore responsive to elevated CO2 than non-nitrogen-fixing species, and mycorrhizalspecies more so than non-mycorrhizalspecies. In terms of forest sites, elevatedCO2 levels will favour plants growing onnon-nutrient deficient and warm soils overthose on nutrient deficient and cold soils.Similar response hierarchies are needed tounderstand the effects of increased tem-perature and drought on Ontario forestspecies.

The rise in winter temperatures acrossthe province should help to expand thepotential range of less frost hardy speciesfrom the Great Lakes-St. Lawrence forestregion into what is now the southernboreal forest (Reed and Danseker 1992). Innorthwestern Ontario, where drought willbe more common, drier conditions com-bined with warmer winter temperatureswould favour the northern expansion ofthe ranges of red oak and red pine, whilethe range of sugar maple could also movenorth but be limited to moister sites. In

northeastern Ontario, where warmerwinter temperatures may be accompaniedby increased summer precipitation, thesouthern range of the boreal forest and thenorthern range of the Great Lakes-St.Lawrence forest should move north.Within perhaps 100 to 200 years, increasedwinter temperatures in southern portionsof northeastern and northwestern Ontariomay create conditions favourable to oak-hickory forest species that are presentlyrestricted to Minnesota, Wisconsin, andsouthern Michigan.

4/��/ ��

1�-� �� %�.��/�)��# �" ��-�

1�-� �� .

��/�)��# �" ��-�

! ��- ��/��"��

� ��-��

��- �#�(��%

� ��-�� - �#�(

��

) ��"�##�.��/�� #� "

* � %�� ))#�,

4/�� )��

5 -� �� *�

��##�,

1�-� ��

1�-� ��

5�� )��

�#��/�#�� -� ��

1�-� ��

1�-� ��

��(

��#�-��-��-

! ��- �

1�-� �� () �� )��

� 0! ��- �

��/�� ""�-� �-�

1�-� ��

6��-/��

5 -� ��

�� ""�-� �-�

1�-� ��

! ��- ��.

��( �� () �� *�"

1�-� ��

$�)��)� �� "�-��-/�� ,

6�� ""�-� �-�

1�-� ��

6�� "" -�

2�� -� ��

4/ ��#��

�/��

� ��.

��

7+��#� ��

��

+��#� ��- ��"��/�� #��

� #�� / ��)��

7��

$ #�)( ��"�.

�� "��

��#� �� / �"�##

/��

74�� #�#�-��"�-/�##��"��

��(��-�

��/. �� &��

0��)��8

71�-� �� .

�/��

� �

71�-� �� .

�/��

� �

71�-� �� "#�.

��

)#��

-��

7! ��- ��(��#�� (��

7+��#� ��

��"#�.

��

)��-��

�) -� �

71�-� ��

��.�/8�

��- ��/��

71�-� �� .�/�*�) -� �

��.

�/� ) �� ,��

##�-��

7! ��- ��# �"��

�� (

.��$�#�(

��- )��#��

��1�-� �� /��# ��- ��

4�� ##��-� �� (�� "��

(1�-� �� - )��#��/ ��

��

��(

��#�-#��

�)��.�� "� 9��

* � %��-��)� -�)��%��9�� ,��

�� -��

Tab

le 7

.1.

The

effe

cts

of th

ree

aspe

cts

of c

limat

e ch

ange

(inc

reas

ed a

tmos

pher

ic C

O2 c

once

ntra

tion

, war

mer

tem

pera

ture

, and

dro

ught

) on

sele

cted

impo

rtan

t pla

nt p

hysi

-ol

ogic

al p

roce

sses

.

�)$��*�!��(�

��&��

��+��$��!��

"��,"��

��"�-��

��

��

Marilyn L. Cherry, Ontario Forest ResearchInstitute, Ministry of Natural Resources

The genetic makeup of plant andanimal species in Ontario will be affectedby the consequences of climate change,including increased temperatures and CO2levels, changes in moisture patterns,higher occurrence of extreme weatherevents and forest fires, changes in growingseason length, and changes in insect anddisease occurrences, due to the selectionpressure exerted by these effects. It isgenerally believed (e.g., Peters 1990) thatspecies which are presently widespreadwill experience drastic shifts in rangeboundaries and undergo certain losses ofgenetic variation and some populationextirpation, while smaller, localized spe-cies may undergo severe reductions in sizeor possibly extinction. Effects of climatechange are not expected to be smooth andgradual; instead, they will involve thresh-olds to limits of tolerance (Vitousek 1994).Predictions as dire as a 37% decrease in theextent of the boreal forest with a 3°C globaltemperature increase have been made(Peters 1990). However, as the extent anddistribution of genetic variability is poorlyknown for most forest species, it is difficultto predict how populations will change inrelation to the uncertainties surroundingglobal warming.

General plant and animal responses tochanges in the environment includephenotypic plasticity, migration, andevolutionary change (Stettler andBradshaw 1994). Generalist species arethose in which a typical genotype is able toflourish under a wide range of environ-mental conditions. Phenotypic plasticity,the ability to acclimate in response toenvironmental cues, is a trait of generalist

species, and may itself differ betweengenotypes of a species. Phenotypic plastic-ity will allow for survival of individualsthat may not be the most genetically fit in aparticular environment (Eriksson et al.1995).

Migration rates following climatechange will differ for every species, de-pending on how efficiently they are able todisperse and whether migration corridorsexist between favourable environments(Peters 1990). Species assemblages willdissociate due to differing rates of migra-tion, and new species combinations willform (Peters 1990; Stettler and Bradshaw1994; Walker and Steffen 1997). Physicalbarriers to dispersal, such as the GreatLakes, will impede migration. Dispersal insome animal species will be affected bysocial requirements (such as territorialityand annual bird migration) (Harris et al.1984). Migration in plant species will beaffected by seed and pollen quantities,dispersal rates (Table 8.1), and whetherconditions are favourable for fertilization,seed production, or vegetative propaga-tion.

Evolutionary adaptation to newclimate conditions can only occur wheresufficient genetic variation exists to allowselective forces to discriminate betweenadaptive and maladaptive traits (Harris etal. 1984). Once an allele (one form of agiven gene) is fixed (only that one form ofthe gene is present in a population) or lost,only mutation or immigration can restoregenetic variability. Adaptation may occurmore rapidly in species with shorter lifecycles, as long as conditions are favourablefor reproduction, than in longlived speciessuch as trees which will undergo a timelag response to changing conditions(Brubaker 1986). Responses within

a species’ natural range may not be uni-form, but might vary from region to region(Rehfeldt et al. 1998). Due to genetic con-straints to adaptation and time lags inadapting, local populations are not alwaysthe fittest (Matyas 1994). Certain speciesunable to acclimate or adapt to changingclimatic conditions may not be able todisperse rapidly enough to avoid extinc-tion without human intervention.

Species most susceptible to changesin climate are those that are localized,highly specialized, or poor dispersers(Peters and Lovejoy 1992). Populationsmost at risk are isolated or peripheralcommunities at the edge of a species’range, and those that occupy montane,alpine, arctic, or coastal sites (Peters andLovejoy 1992). Species considered mostsensitive to past climate change showedevidence of latitudinal and elevationalshifts in response to changing conditions(Nowak et al. 1994).

An increase in atmospheric CO2 willincrease growth of some species at theexpense of others (Peters 1990). Underconditions of increased CO2, selection may

favour genotypes with an ability to com-pete for limiting resources other than CO2(Bazzaz et al. 1995).

Population reductions are expectedalong the southern edges of a speciesrange and inland, away from the moderat-ing effects of large bodies of water, as aresult of increasing temperatures andmoisture stress (Peters 1990; Nowak et al.1994). The latter is expected in northwest-ern Ontario, where drought is expected tobecome more frequent and severe (seeSection 2). Population reductions will alsooccur if populations shift upwards inelevation; however, this is unlikely to havea major effect in Ontario. Plants subjectedto high stress, such as those at the edge ofa range, will be more susceptible to insectsand pathogens (Ledig and Kitzmiller1992), which have the advantage of beingable to adapt to changing conditions morerapidly because of their much shorter lifecycles.

With range reductions, populationfragmentation will occur, and inbreeding,with its inherent loss of genetic variation,will increase as population size decreases.If selection due to climate change operates

:�-��)�� #�� )��

� ��)�� (�## � � ��

�� ./�� )�� ( ��( � � ( ��(

�#�-��)��- #�� %�$ � ��$ ( ��(

� ��)��- #�� %�$ � ��$ ( ��(

./�� )��- #�� %�$ � ��$ ��

��#��(�"�� #�� ( ��(

��(�)# ( ��( � �%�$ � ��$ ��

� ��(�)# ( ��( � �%�$ � ��$ ��

� �� ( ��( � �%�$ � ��$ )��

�� (�#��) � #�� %�$ � ��$ $ ��

Table 8.1. Relative range size and seed dispersal of some Ontario tree species.

�� .��# ��"��

differentially on subdivided populations,then the variation between thesubpopulations will increase, and discreteecotypes may be formed (Harris et al.1984). The length of time that a populationremains at reduced numbers will have agreater impact on reduction in geneticvariability than the actual number ofindividuals in the isolated population(Harris et al. 1984). Whereas highly hetero-zygous individuals (those with differentalleles in a given gene pair over many ofthe gene pairs) can generally tolerate abroader range of environmental condi-tions, perhaps due to the differing allelesbeing advantageous under differing condi-tions (Harris et al. 1984, Ledig andKitzmiller 1992), favourable complexes ofgenes that have adapted together will bereduced with inbreeding.

The ability of a species to withstandinbreeding and selfing is important inisolated populations (Peters 1990).Populations with reduced reproductivepotential or under low levels of selectivepressure will carry deleterious, potentiallyharmful genes for a longer period; with ahigh reproductive rate and intense selec-tion, fewer adverse effects of inbreedingwill occur (Harris et al. 1984). If dramaticclimate change occurs over a short timespan, selective pressures will be intense,and hence high reproductive rates will beadvantageous in isolated populations.Populations in which inbreeding hasoccurred prior to fragmentation are ex-pected to carry fewer deleterious genesand will not be as adversely affected bysubsequent inbreeding (Harris et al. 1984).Species that reproduce both by both sexualand asexual means will be less sensitive toclimatic change (Brubaker 1986), whereasspecies that rely on asexual reproductionwill be less likely to adapt (Table 8.1)(Harris et al. 1984).

Forest tree species generally have highlevels of genetic variability and gene dis-persal rates (Brubaker 1986; Stettler andBradshaw 1994). An exception is red pinewhich demonstrates low levels of geneticdiversity, probably because populations

were severely reduced during the lastglaciation. Trees also carry a high numberof deleterious genes (Stettler andBradshaw 1994). Due to their longevity,trees withstand a broad range of climaticvariation per generation, and some specieshave demonstrated phenotypically plasticresponses to environmental change.

The boreal forest of northern Ontariohas lower levels of biodiversity, with fewerplant and animal species, than the decidu-ous forests of southern Ontario (Dudley etal. 1996). Rare, threatened, and endan-gered species are often found onnonforested sites (Harris et al. 1984), andmay be especially dependent on habitatcharacteristics (Eriksson et al. 1995). Pre-dictions for the effects of climate changeon forest habitat in Ontario are varied andsometimes conflicting. However, mostmodels of tree migration predict a north-ward movement of coniferous species,particularly spruce, and a correspondingreplacement by hardwood tree speciessuch as maples and oaks (Joyce et al. 1990;Slocum 1995).

A climate change model based onprovenance trial data (Matyas 1994) pre-dicts a decline in the growth and competi-tive ability of jack pine at the southernlimits of its distribution. Under controlledclimate experiments, some generalistgenotypes for growth traits were identifiedfor seedlings of this species (Cantin et al.1997). Carter (1996) predicts a decrease ingrowth due to warmer growing conditionsin white ash, yellow birch, black cherry,balsam fir, tamarack, white spruce, jackpine, and eastern white pine, and in-creased growth in red maple and greenash. Other models predict a loss of balsamfir, eastern hemlock, and sugar maple fromthe Great Lakes region (Joyce et al. 1990).

It is undoubtedly premature to pre-scribe a northward transfer of species untilthe extent of climate-induced changes canbe more accurately predicted. However, itwould be wise to revisit old provenancetests to determine current limits to trans-ferability.

Better estimates of the amount and distri-bution of genetic variation within speciesare needed before the guiding principlesdiscussed above can be applied to eachspecies. Selection for pest resistance is alsorecommended, as pest infestations arelikely to worsen (see Section 4). Conserva-tion plans for rare, threatened, and endan-gered species should be developed andimplemented before population levels ofthese species decrease irreversibly. Suchplans should include development of

dynamic appraoches that will promoteincreases in genetic variance and futureadaptation, such as the multiple popula-tion breeding system proposed byNamkoong (1984). Genetic implications ofglobal warming cannot be consideredalone; changes in gene frequencies willdepend on many factors, some of whichare the intensity of selection pressures,responses of physiological processes, andchanges to forest succession, competition,and pest incidence.

�� $��%��

��

William C. Parker, Ontario Forest ResearchInstitute, Ministry of Natural Resources

Forest succession may be viewed asthe recovery of forest ecosystems followingany disturbance. Succession is dependenton the physiological, population, andcommunity ecology of the resident floraand fauna, as well as site and disturbancecharacteristics (Bazzaz 1996). A distur-bance is a natural or anthropogenic eventthat destroys biomass and alters ecosystemstructure and resource availability (Pickettet al. 1987, Attiwill 1994). Forest fires,insect outbreaks, windthrow, ice damageand harvesting are examples of distur-bances. The size, frequency, intensity andseasonality of disturbances influencesuccessional pathways through effects onresource availability and sources of vegeta-tion (seed, seed bank, vegetative reproduc-tion, advance reproduction) available forthe colonization of the new growing space(Oliver 1980, Petersen and Carson 1996).

The Boreal and Great Lakes-St. Law-rence (GLSL) Forest Regions of Ontariodiffer in their natural disturbance regimes.Boreal forest ecosystem dynamics aredriven by disturbance such as wildfire andinsects. Large, stand replacing crown firesat 70- to 100-year intervals were the pri-mary natural disturbance in the BorealForest Region of Ontario, and favoured theestablishment of forests dominated byearly successional, fire adapted jack pine,black spruce and poplar (Johnson 1992).Defoliating insects also play a major role inboreal forests. Spruce budworm outbreakslasting 5 to 15 years occur at 40-year inter-vals, affect large areas and predisposeinfested areas to wildfire 5 to 8 years after

stand mortality (Stocks 1987).Catastrophic fire is less frequent in the

GLSL Forest Region. In drier portions ofthe GLSL Region, crown fires occur atcomparatively longer intervals (ca. 150 to250 yr.). Frequent (20 to 40 yr.), low inten-sity, surface fires reduce the numbers offire-sensitive, shade tolerant species, in-crease understory light levels, and favoursub-climax forests dominated by whitepine, red pine and red oak (Heinselman1973, Whitney 1986). In more mesic habi-tats of the GLSL Forest Region, forests aredominated by late successional, toleranthardwood species and eastern hemlock, aslarge scale disturbances by fire and cata-strophic windstorms (e.g., tornadoes) arerare, with a return interval >1200 years(Canham and Loucks 1984, Whitney 1986).Comparatively frequent, low intensitywind storms (thunderstorms and periodichigh winds) are the primary natural distur-bance in these forests, affect a small per-centage (<1.0%) of a given area annually,and form canopy gaps (100 to 400 m2)through windthrow of single or smallgroups of trees. Smaller canopy gaps formafter the death of single trees, with returnintervals of 120 to 190 years (Dahir andLorimer 1996). These small gaps favouradvance reproduction of shade tolerantoverstory species.

Climate change can be viewed as aprogressive, anthropogenic disturbancewith an unusually long time frame relativeto natural disturbances. Altered tempera-ture and precipitation regimes and el-evated CO2 will have a direct impact onforest structure through their effects

on the physiology and population ecologyof plant species, as well as ecosystemprocesses such as decomposition, nutrientcycling, and plant interactions with otherorganisms (see Sections 4, 5 and 7). How-ever, the increased frequency of distur-bances due to fire, insects and extremeweather expected to accompany climatechange will likely exert a stronger effect onforest vegetation than the effects of modi-fied climate alone, by increasing the rate atwhich an equilibrium between vegetationand climate is attained (Davis and Botkin1985, Overpeck et al. 1990, Bazzaz 1996).In Ontario, regional differences in vegeta-tion response to climate change will de-pend on the plant species present, sitequality, and relative change in the currentclimatic and disturbance regimes (Davisand Botkin 1985, Grime 1993).

Changes in temperature and precipi-tation associated with a doubling of at-mospheric CO2 could increase the forestarea burned annually in Canada by almost50% (Flannigan and van Wagner 1991,Wotton and Flanningan 1993). In Ontario,increased frequency of wildfire is pre-dicted for the boreal forests in the north-west, and GLSL forests of the central andsouthern regions of the province (seeSection 6). If the warmer climate results inhigher incidence of insect outbreaks, therisk of fire could be further increased(Fleming 1996). In the boreal forest region,more frequent wildfires will increase thenumber of young, early successionalecosystems dominated by fire-adaptedshade intolerant species (Grime 1993,Bazzaz 1996), while in northwest Ontario,boreal forests may be replaced bygrasslands and aspen parklands (Hoggand Hurdle 1995).

A preview of the potential conse-quences of climate change in the BorealForest Region is illustrated in the Experi-mental Lakes Area in northwestern On-tario (Schindler 1998). The period 1970 to1990 was abnormally warm and dry.Several, large lightning-ignited forest fires

occurred, followed by revegetation ofburned areas by fire-adapted jack pineand black spruce. Because of the hot, drygrowing seasons that followed, mortalityof conifer regeneration was high. Some ofthese areas burned a second time, result-ing in the replacement of conifers bytrembling aspen and balsam poplar, whilesome sites remained barren of vegetation17 years after the second fire.

In the GLSL Forest Region, the pre-dicted 4 to 6oC increase in growing seasontemperature with little change in precipi-tation (see Section 2) will increase distur-bance by climatic stress events and fire(see Section 6) (Overpeck et al. 1990).Periodic drought may weaken foreststands and initiate “growth decline”,mortality and the formation of canopygaps (Millers et al. 1989, LeBlanc andFoster 1992, Reed and Desanker 1992).Overstory individuals suffering declinewill be vulnerable to secondary attack byinsects and diseases, further acceleratingstand senescence. Lower quality sites willbe affected first, as will species with nar-row ecological amplitude (e.g., red pine,hemlock) (Solomon 1986). Canopy gapswill initiate release of the understory, thespecies composition of which will dependon climate and past management effectson regeneration (Davis and Botkin 1985).Increased frequency of surface fires, re-lated in part to the higher fuel loading indeclining stands, could slow the currentsuccessional displacement of fire-depend-ent white pine and red oak by fire-sensi-tive sugar maple and balsam fir.

Models predict dramatic changes inforest composition and cover in Ontariobased on changes in temperature andprecipitation (Solomon 1986, Pastor andPost 1988, Sargent 1988, Solomon andBartlein 1992, Lenihan and Neilson 1993,Mackey and Sims 1993). These modelspredict the Boreal Forest Region will movenorthward, displaced by the northwardexpansion of temperate conifer and hard-wood species of the GLSL Forest Region

(maple, basswood, oak, white pine). How-ever, these models likely overestimate theimpact of changing climate on forest veg-etation dynamics, as they do not ad-equately account for the effects of CO2enrichment, barriers to migration, compe-tition, soil characteristics, physiologicaltolerance and acclimation, genetic varia-tion, disturbance regime, etc. (see Section11) (Lenihan and Neilson 1993, Loehle andLeBlanc 1996). More accurate model pre-dictions must await a better understanding

of the long-term effects of the interactionof climate change, CO2 and other environ-mental factors on forest ecosystem struc-ture and function. Despite this currentuncertainty, more frequent wildfire andforest decline will likely increase the areaoccupied by early successional ecosystemsat the expense of mid- and late succes-sional ecosystems. In the near term, tech-niques are needed to identify vulnerable,declining stands requiring silviculturalintervention to minimize potential effectsof climate change on Ontario’s forests.

Michael T. Ter-Mikaelian, Ontario ForestResearch Institute, Ministry of NaturalResources

Models are commonly used to predictthe effects of climate change on forest eco-systems. Models are popular because: (i)predictions are necessary either forsituation(s) that have not yet occurred or forwhich data are not available; (ii) forestecosystems develop and change over longperiods — studying the effects of potentialclimate change would require decades,which unfortunately also corresponds to thedesired prediction time; and (iii) forestecosystems are hierarchical multi-compo-nent systems — climate change may affectthese components differently both in termsof direction and magnitude. Even if theseparate effects of climate change on eachcomponent were known, their interactionsmake assembling a complete description ofecosystem effects difficult. Models providean indirect method of predicting attributesof forest ecosystems and how they changeover time.

Unfortunately, there is no existingmodel comprehensive enough to predict theresponse of forest ecosystems in Ontario toclimate change. In order to save time andresources, a model predicting climatechange effects on forests should be devel-oped using existing blocks (or modules)from other models. Table 10.1 presentsexamples of potential modules for some keyareas of forest ecology and management.The following criteria were used to selectthese examples: (i) the model includedclimatic variables that can be manipulatedto predict the effects of climate change onthe forest; (ii) the temporal resolution ofthese variables should match the long-termresolution of the climatic models generating

future climate scenarios (e.g., a modelrequiring daily values of some meteorologi-cal variable was considered impractical);(iii) preference was given to models thatdeal with a single process. For comprehen-sive reviews of climate change-relatedmodels the reader is referred to Goudriaanet al. (1998), Loehle and LeBlanc (1996), andUrban and Shugart (1992).

Some of the models in Table 11.1 can beapplied to climate change predictions forOntario immediately. Most of the modelscan be used independently to describe aspecific process or assembled into a morecomplex model addressing several proc-esses simultaneously. In both situations,there are several guidelines to follow whenmodelling the effects of climate change onforest ecosystems:

Spatial scale. Although many processesoperate at a number of scales, direct effectscan usually be associated with one particu-lar scale. For example, wildfires operate attree—stand—landscape scales (they burnindividual trees and stands, and changelandscape structure); however, the effectsare most pronounced at the landscape scale.Therefore, when simulating a process, onehas to identify the scale at which the effectsare most pronounced (target scale); otherrelevant scales can be included if the modelis multi-scaled.

Spatial hierarchy. Some processes maybe adversely influenced by climate changeat scales other than the target scale. Con-sider the task of estimating the effects of airtemperature increases on forest productiv-ity at the stand level. At the tree level,increased temperature increases individualtree biomass; at the stand level, it decreasesstand density since trees compete moreintensively as their size increases. Thus,elevated temperature may either increase

��& ��!�� '��

��

or decrease productivity at the stand level;the effect cannot be estimated without moreaccurate quantification of both processes.Similarly, if we were interested in effects atthe landscape level, we would have to ac-count for the effect on productivity at thestand level, as well as increased fire fre-quency which decreases the mean forest age.Therefore, models should include effects atthe target scale and one step below thetarget scale to ensure accuracy.

Temporal scale: Equilibrium state vs.transition state. "Transition state” predic-tions are given for periods when the climateis actually changing. Transition state modelsaccount for transition processes (e.g., rates ofspecies migration to new geographic areas);these models are time-specific, i.e., a timecan be specified for each prediction. “Equi-librium state” predictions assume that theclimate will change and then remain stablefor a period sufficient for ecological proc-esses to come to an equilibrium. Equilibriummodels are simpler because they ignoresome of the processes considered in transi-tion state models. Their predictions, how-ever, are not time-specific since it is impossi-ble to know when an equilibrium state isreached. Thus, when building a model it isnecessary to decide which type of predictionshould be made. The majority of existingmodels are equilibrium models.

Temporal scale: Short-term vs. long-termpredictions. If a transition state model ischosen, the length of projection needs to bespecified. Rates of climate-induced changewill differ for different processes; therefore,depending on the prediction time, someprocesses may be considered ”stable” andtherefore omitted from the model, whileothers have to be modelled. For example, fora 5-year prediction it is reasonable to assumethat the current geographic distribution ofspecies will not change, while in a 50-yearprediction possible shifts in species zonesmust be accounted for.

Temporal resolution. It is important toselect appropriate temporal resolution (timesteps) for modelling climate change effects.Large time steps can inadequately representa process because (a) the mean of the proc-

ess may be roughly the same but the varia-tion may change dramatically, and (b) somesub-periods within a selected time step maybe more important than others. For example,warmer winters may have unique effectsdepending on tree species: (a) evergreenspecies will be affected by increasedevapotranspiration more than deciduousspecies, (b) warmer winters and earliersprings may adversely influence some treespecies if they interfere with chilling require-ments for bud break phenology. At present,time steps should not be shorter than amonth, because climatic models are notaccurate at shorter intervals.

Climatic variables. It is important toidentify the variables affecting the targetecological process. Most climate changepredictions are given in terms of increasingair temperature, which does not necessarilytranslate into a change of the same magni-tude for some ecological variables. For exam-ple, Street (1989) demonstrated how trends intwo variables (temperature and precipita-tion) compensate for each other’s effect onforest fires, resulting in more moderatepredictions than those based on a singlevariable trend.

There will be few chances to validate a“climate change” model in the traditionalsense. For this reason, indirect testing of theaccuracy of climate change models will beneeded. Such testing can be done by inde-pendently testing modules of the largermodel. One means of testing the accuracy ofa climate change model is to determinewhether the model is able to predict pasteffects of climate on vegetation or ecologicalprocesses. Another way to test a climatechange model is to evaluate the survival andgrowth of species planted outside theirnative ranges (Loehle and Leblanc 1996). Inthis context, process models (i.e., those basedon measurable ecological processes that arecausally related to climate) may have advan-tages over statistical models (i.e., modelsbased on correlations between climate and anecological process that may not have a causalrelationship) for indirect testing of the accu-racy of climate change models (seeKorzukhin et al. 1996).

;��#��

<�)��=��

��)� ��-��(�:��.��

�� / �8

2��/#��(

��

0�#��

6��(��"�-��

"#�3 ��/��/��)#��

��

� () �� '

"��

�.�� / ��

� >��

"�� "��

(�-�(

(��#�

(��/#�

*� �� /�,

�$��#��# �(��/#�

)� -�)��'

� �� '

-#�(�� -��

(��/#��(

��

&��

� �-��)��$ ��

��.

�"��-��"

��"��(

��

)� -�)��

1�� -��

0�12+?8

��(�#�� )/�-

�� -�#

� �#��( ��

;�� ))#� ��

! >�� -�#��"��

��/ ��

��#

��"�� -��

*-�� ,8

� () �� '

)� ��-��/ ��

&��

��- ��/

(�� #

��

��-#�(��-�$��# �

��-

�. �#�

�"�0�#�� # ��

��( ��/

�� )/�-

��) -� ��)/ ��#��

)� -�)��

6��/�<( ��-�%��

��"��) -� �

#�$ ��-��-��+��)

�� "�� )��(

��#�

��-#�(

�� %

��(��

�))#�-��#

��- ��) -� �

* � %�@�)��(

��/,

5��

@��

�� "��./�� )��

�� -�#

2 ��(��(�(

;��

6 ��"�

��/ ��#��-�#

�#��

*)��$��- ,8

A�#��

() �� '

�� "��/�9��

� $ #�)(

��'�� #��

*��

��

��

��

��-

( ��#��A�#�

9�� *#�.%

�� *�

��,�"��

�A 0 �B

��-/ ,�/�9��

� () �� '

�� (

�� %�/

��/%

�))#�-��"�0�12+?��

9��

( ��#�"��

�� $ � ,�"��

)� ��-��

��)/�-

"� �) ��'�( ��

&��

��"��

��

��

��

�� "�"��"��

��

��

��*��

��)��/�� ,

B��

B��8

��)� ��-��/

� "" -��

��-�) 8

� ��#�(

��

0�#�� "��

��

0�#��"��&

��.��#�

<��$��

�"�-#�(

�� #��

��

� () �� '

�(� ��"�.��

� >�� (��"��

�# ��

� �(

�"�� "��

� ��#

��(��

(�� #�)��(

� ��

��(�-�

)� -�)��'

#��-�) ��

(�3�(�(

��/�

. ��

) ��

Tab

le 1

0.1

A li

st o

f mod

els

and

thei

r ch

arac

teri

stic

s th

at c

an b

e re

adily

ada

pted

for

stud

ying

clim

ate

chan

ge e

ffect

s in

Ont

ario

.

%��

��&

��(�/��!��&

�+��

��

��

��

��

��"��

��

!��

��

��4@8

��(�#�� / ��.

�/��*��( �

2��/#��(

��

;��

<��$��#�� .�/

)/��#��

��

�� #��"��"��

�)��#

��( �C45'�(

��/#�

��.

�/�� #�

(��# ��/��#�� 3��

-� �

��

��"��

(��()#

/�(��

)� -�)��'�(

��

��(�#��"��

��-�#�� "��&

��

)/��#��-�#�)��-�)# �

�"��#,8

��(� ��

"�"��"�

)�� <��

#��

�) -� �'�� #��D ##�(��

��(��/

��) ��(

��/

6 .

�E �#��

��# �*��,�"��

�(��#

��(�#��"��

��(

��

@ � ��-�

0��

��'

��)� ��-��/

� "" -��

4#��8

<��#�(

��

<))#� ��

6��(��"�-�� >�� '

�-/(��#��

�"�� () �� -/��

��-�*)� ��-��

(��(�(

��"�.

��

"��/

��

��

�� / ��/��.�/

�/ �/ ��/��

� () ��

/��.��) -� �

��(

�� )�� "� �

"��(�(

�#��#�-��

��

* � %��#��(

�"��%

�/ �)� ��-��

)��$ ��- ��#��

� ) ��

�� ./�� )�� %

�) -� �,

:�-��)�� %�./��

�)��- %�

�- ,

4#��

B��0#�(

8��(�#�� / � "" -��

�8��/�8

2��/#��(

��

� �� "��

�#��

! >�� -�#��"��

��-- ��

��(��

�"�-#�(

�� "��

��

� () �� '

��(� ��

"�� /

&��'�� #��D ##�(��

��-�� %�-�(

)��

(��/#�

+��) ��<#)��

��# �*��,

��(�-�

)� -�)��

6��/�<( ��-�

@��.�/��

D ##�(�� #

��(�#�� .

�/�8��/�8

2��/#��(

��

� �� .�/

! >�� -�#��"��

�� #�

��

�� #��"��

��

� () �� '

�� #��# ��"��

&��'�� #��

��"��(

(��/#�

�-��)�� %�6��.��

��

)/��#��-�#�)��-�)# �

)� -�)��

�)��- %��-/

�)) ��B��#��

4�� #

��)� ��-�� #

��8

2��/#��(

��

5��#��"��

0�#��"��&

��.��#�

��'

�� #��-#�� "��

(��

� () �� '

�)��- ��-��#��

� >�� #�� %��)��##�

��# �� #

#��

�(�-#�(

��-

(��/#�

��

��

"�-��

)� -�)��

#��

�(�)��-��$��"

"��

� ��(

�� #�./ � ��/ ��)��"��

��F >��#��(F�-��/��(

�� )��/ � "�� F��-F%��- ��)� ��-��#��# �F�� F

��!��"��

��

�

%��

��&

��(�/��!��&

�+��

��

��

��

��

��"��

��

!��

�� !��

��

William C. Parker, Stephen J. Colombo, Marilyn L.Cherry, Sylvia Greifenhagen, Chris S. Papadopol,and Taylor Scarr, Ministry of Natural Resources

If the forecast changes in climate dueto increasing atmospheric CO2 are realized,forests established now will mature in anenvironment that is substantially differentfrom today. This report considers possibleclimate effects on Ontario’s forests basedon projections from published literatureand our interpretations of likely effects inOntario. The question that naturally fol-lows from this consideration of climateeffects is what, if anything, can be done tominimize negative consequences to ourforests arising from climate change.

Forest management is the practice ofsilviculture to direct forest succession in away that a desired combination of forestbenefits is obtained, be it for timber, wil-derness areas, wildlife habitat, old-growthforests, or other valued products. Despiteuncertainties as to specific impacts, climatechange is likely to significantly alter forestecosystems and their management. Cur-rent socioeconomic trends emphasizingnon-commodity values of forests willlikely expand if forests begin to be man-aged as sinks for atmospheric CO2, fortheir ability to modify climate, and asreservoirs of biodiversity (Woodman1990). As a result, traditional silviculturemay become increasingly less effective atmeeting future forest management objec-tives.

Table 11.1 lists some possible ap-proaches to forest management in a chang-ing climate. The timely development andselective, appropriate use of innovative

approaches to forest management in re-sponse to climate change are imperativegiven the inherently long planning scale offorestry and the economic importance offorests to Ontario. In this section we de-scribe some potential silvicultural activitiesthat forest managers may use to reducenegative impacts of climate change. Wealso address the possible use of forests andtree plantations to store CO2 and slow therate of climate change.

��

Disequilibrium between forest vegeta-tion and climate will occur where rotationlength exceeds the development of a newclimatic regime. This disequilibrium willbe associated with regional episodes offorest decline as overstory species are nolonger adapted to the prevailing climate(see Section 9). This will requiresilvicultural systems that address themanagement and regeneration of decliningstands. Harvesting is the most effectivetool available to forest managers for alter-ing forest condition and may be used tomaintain forest health and productivity.For example, in younger stands not readyfor commercial harvest, stand productivityand health may be maintained or im-proved by thinning to remove suppressed,damaged or poor quality individuals,increase the vigour of selected overstoryindividuals, and reduce the likelihood ofdecline (Table 11.1). Alternatively, in olderstands productivity has declined as a resultof overstory species being poorly adaptedto the new climate, logging and plantingprior to stand deterioration may be used to

�/�� # ��/�%�./ �

�))��)��

�/��

4#��/��)� ��) -� �

�� ) �

1�-� �� "��#� ��$ ��

-# ��-��* � %��/ #� �.��%

� # -�� (�,

1�-� �� -��) ��

(�� ( ��)� )��

4#��-#�(

�� )� ��) -� �

2�� -��#��-�#

��$ ��

!�)��#�� #��/��

/��$ �� "��

G� �-#�(

�� 9��

1�-� �� "�� "�� ))� ��

<""�� "�� #��

4� " � ��##��

"�� #��#�$ ��.��

)��-��

1�-� �� "��$��-

� )��-��

;��$ ��-/��-�##�� "�#�.

�$��#�.

��.�/�� /�� - )��# �� -��

! ��- �� -�� - )��#��%��-� �� $��/��/��/��%�.

/ �� )��#��

� $ � �(��

! � � �� /��)�� /��.��/�� )#�� ) -� �'�� # -�� /��# �� ) �

4�� -�� "��(

�"�� .��( �%�� #�� $��(

�� 1�-� �� / ��(

��"�-�� -� ��

�/ �) �� --�)� �� %�� -� ��- ��"�� "#��%��-� ��/ �� "�� "�� ./ �

��$��- �� )��-��

@� �� -�� - ��"� 3�� ( � $ ��/�� 3) -� ��-� �� - )��#�� -��) ��

1��- ��/ ��) -� �� - ��/ �� #�(

��./ �� () �� $ �� 3�� (

��/�$ �.��( �

��""�-� ��#�

4�� -��$ ��-� �� / �#�� #�/��/��/ � �.�##�� $��#�%��) -� �%�� -�� (

��/�� )� ��

"�� -#�(

�� -��'�� >�� "�� -�-�� $�� -�� (�)�� -��

1�-� ��/ ��(

��"�-�� -� ��/ �) �� --�)� ��

4 ��-��)��"�� 9�� () �� $ �� 3�� (

�

�� .�� %�.��( �� () �� - ��)� -�)��(��#� ��/�$ ��-� �� "�� "�� -��$��

4�� -��"�$�#� ��"�� >�� -�() ��-� �� "�� "�� ))� ��

1�-� ��/ ��(

��"�-�� -� ��/ �� -�$ � ��"��

1�-� ��/ ��(

��"�-�� >� �� -� ��/ �# ��/��"��( �� >� �� * � %�� "��-� ��

� >� ��(

H�� -�-#��# �)�) �'�� -�-#��# �)�) �'��'�#�(

� ��-��-��,

<�$��- �� )��-�� >�� # �� )��-�(

)�� "�-��#�� -� �� / �� "�� "�� '

� �� $ #�)�� (��"� ��/��$ �� -/��>� ��)�� -�� )��-�� #��$ ��./ ��#��

Tab

le 1

1.1.

Pot

enti

al fo

rest

man

agem

ent a

ctiv

itie

s to

min

imiz

e th

e ne

gati

ve e

ffect

s of

clim

ate

chan

ge o

n O

ntar

io’s

fore

sts.

The

sui

tabi

lity

of th

ese

acti

viti

es w

illva

ry w

ith

the

exte

nt o

f clim

atic

cha

nge,

the

cond

itio

n of

the

stan

d in

que

stio

n, m

anag

emen

t obj

ecti

ves,

and

fore

st p

olic

y.

��!��

��)��

speed the replacement of forest types(Table 11.1). Techniques for monitoring thehealth of existing stands will be critical tothe timely identification of areas needingprotection or silvicultural intervention.

Harvesting can serve the dual pur-pose of facilitating the regeneration of thenext stand if applied to protect or promotethe advance reproduction of more site-adapted species in the understory, if theyoccur. Where the understory is not prop-erly matched to the prevailing site orclimate conditions, and not acceptable as asource of regeneration, planting will berequired. As artificial regeneration isvulnerable to environmental stressesfollowing planting, partial cutting systemscan be used to moderate the warmer, drierseedling environment predicted for thefuture (see Section 2). Partial cutting andthinning need to be tailored to the ecologyof the species desired for regeneration(Hedden 1989, Ostofsky 1989). However, ifclimate change alters basic elements offorest ecology, the species or populationsdesired and the practices required forregeneration success may change in as yetunpredictable ways.

As many insect pests and forest dis-eases are stress-related, “stress manage-ment” practices such as partial cutting orthinning may also be useful to reducesusceptibility to insects and diseases(Wargo and Harrington 1991). However, asthese same practices can sometimes in-crease vulnerability to other insects anddiseases (e.g., jack pine budworm,Hypoxylon canker of aspen, andArmillaria in conifers), site and speciesspecific application will be needed. Short-ening the rotation length can be used todecrease the period of vulnerability tostress. Other silvicultural techniques thatreduce stress and susceptibility to insectsand diseases include the regulation ofspecies composition (i.e., planting appro-priate species on sites) and maintainanceof biological diversity.

Climate change will affect the lifecycle of forest pathogens, and therefore,the amount of damage suffered due toinsects and diseases (see Sections 4 and 5).Gypsy moth, a significant defoliatinginsect in southern Ontario, could increasein severity if the incidence of fall droughtand warm spring temperatures is favouredby climate change (Wagner 1990). In con-trast, warm weather in the spring and fallcould adversely affect spruce budworm,reducing tree losses to this insect(Safranyik 1990). Shifts in the geographicrange of insects may result in the introduc-tion of new species to Ontario. Accordingto Safranyik (1990), the mountain pinebeetle, presently found in South Dakota,could migrate northward if winter mini-mum temperatures warm. This seriousforest insect pest could cause losses to pineforests in northwestern Ontario. Wereclimate change to result in periods ofsevere insect infestation, insecticides mightbe needed to protect young stands andreduce losses in timber volume and forestcover (Table 11.1).

�� If the 3 to 4o C increase in annual

average temperature predicted for the next50 years occurs, species will have to mi-grate approximately 300 km to the northover that time to be matched to climate.However, the migration rates of forest treespecies are too slow to keep pace with thismagnitude of climate change (Roberts1989). Human-caused landscape fragmen-tation (e.g., agricultural lands, urbaniza-tion), lack of suitable habitat, and naturalbarriers to plant migration (e.g., the GreatLakes) will also hinder the movement ofspecies from their current to potentialfuture ranges.

Forest management provides anavenue to assist the movement of speciesfrom current to future ranges, but majorartificial regeneration efforts will be re-quired to accomplish this (Davis 1989,Mackey and Sims 1993). Experimentalplanting of selected species and

populations to appropriate sites up to 100km north of their current range could beused to test the ability to assist speciesmigration. Provenance trials that testpopulations from a wide variety of siteslocated across the range of a species willcontribute to this effort by providing infor-mation about the transferability of speciesand populations to new environments.Species and population transfer northwardneeds to also account for photoperiodadaptation, since day length affects theonset and cessation of growth. It has beensuggested that reserve areas, such as parks,be linked through connective corridors in anorth-south gradient to aid species migra-tion (Halpin 1997). However, northwardmovement of species in Ontario is compli-cated by the lack of suitable soil types andthe expected lag in soil development dur-ing climate change. The movement of morenutrient demanding hardwoods to acidic,less fertile sites now occupied by conifersmay benefit from mixed planting withspecies that ameliorate site conditions (e.g.,N-fixers). This may also require plantinghardwood species inoculated with site-adapted mycorrhizal species. Habitatsexpected to become drier in the futuremight be regenerated with novel, moredeeply rooted species (Table 11.1).

The amount of silvicultural interven-tion needed to maintain a productive forestwill depend on the forest species in ques-tion, but it is clear that an effective geneticresource management program will be animportant component of forest manage-ment response to climate change. Widelydistributed species (e.g., black spruce andwhite spruce), which have broad geneticdiversity, may require little attention, butlocal ecotypes may be lost and geneticdiversity reduced. Maintaining speciescurrently of economic importance but withgreatly diminished natural abundance dueto past management practices (e.g., whitepine, red pine and red oak) may require theidentification, production, and planting ofsouthern ecotypes adapted to the longer

photoperiods of more northern regions.Assessing genetic variation within thesespecies will help to determine the limits oftransferability along climatic gradients and,perhaps, will require periodic adjustmentof existing climate-based seed zones (Table11.1). Given the current uncertainty regard-ing regional shifts in climate, planting stockrepresenting widely adapted populationsand diverse seed source mixtures can beused to increase the likelihood of regenera-tion success. Aggressive genetic tree im-provement programs designed to promoteincreased genetic diversity and allow forfuture adaptation will also be needed toincrease pest resistance and tolerance toenvironmental stresses (Roberts 1989)(Table 11.1).

Climate change may threaten rarespecies because they lack enough economicvalue to warrant addressing the potentialloss of suitable habitat (Peters 1990).Butternut, red mulberry, and red spruce area few of the comparatively rare tree speciesin Ontario that are confined to small, dis-junct populations. These and similarly rarespecies may require more intensive, costlysilvicultural activities to sustain them ifsuitable habitat becomes difficult to find orcreate due to climate change. As a conse-quence, conservation plans andsilvicultural approaches to sustain rare,threatened and endangered species areneeded. Increasing the number of largenatural areas or reserves to maintain a widevariety of habitat conditions has beenrecommended to reduce the risk of localextinction of rare species (Peters 1990), butthis by itself may be insufficient to preventextinction. Breeding plans for rare speciesthat incorporate systems to increase geneticdiversity should be used. However, ourability to only forestall rather than preventlocal extinction needs to be weighed againstthe cost of preservation activities. In addi-tion, severe habitat loss could mean thatlong-term preservation of rare species mayonly be possible in “zoo-like” arboreta,rather than in natural environments.

More intensive vegetation managementtreatments to control less desirable treespecies and other plants may, in the future,be required to assist the regeneration ofpreferred commercial forestry species. Thismay occur because of the comparativelypronounced growth response of someplants to elevated CO2 and warmer tem-peratures. Hardwoods show a greaterproportional increase in biomass underelevated CO2 and may increase in competi-tive fitness relative to conifer species(McGuire et al. 1995). Further, fast grow-ing, short-lived herbaceous species arebetter able to adapt genetically to increasedatmospheric CO2. As a result, a generalincrease in the abundance of aggressiveherbaceous plants may occur, particularlywhere stand senescence exceeds the rate ofingress of more adapted tree species(Bazzaz 1996). Poplar and aspen species arelikely to become more aggressive in borealregions, as their high relative growth ratesand reproduction from root suckers favourtheir colonization after clearcutting andwildfire. It is predicted that such changes inthe competitive interaction among treespecies could result in the development ofplant communities for which we have nomanagement experience, requiring newsilvicultural approaches to control non-cropspecies (Davis 1989, Bazzaz 1996).

Mycorrhizal associations with plantsare important to forest regeneration effortsbecause they help reduce plant stress byimproving the absorption of nutrients andsoil moisture. Practices such as clearcutting,whole-tree harvesting and prescribed burn-ing can decrease the diversity and totalbiomass of mycorrhizae and may poten-tially increase adverse effects where climatechange increases the severity and frequencyof drought (Harvey et al. 1980, Miller andLodge 1997). Harvey et al. (1980) recom-mend keeping clearcuts small and maximiz-ing edges to promote the ingress ofmycorrhizae from surrounding uncutstands. Such practices help maintain thediversity of soil microorganisms, whichincreases the ability of ecosystems to adaptto a range of climatic conditions. Mixedplantings of conifers and hardwoods can

increase microbial diversity and enhancelitter decay (Hendrickson et al. 1982), as canharvest and site preparation techniques thatpromote litter accumulation or retention.Fire frequency is expected to increase inmany areas of Ontario and, although cer-tain mycorrhizal communities may be moreabundant after a fire, they may not besuited to the desired tree and plant species(see Section 5). In such instances, novelapproaches to maintaining fungal diversitymay be needed.

Biodiversity has been defined as “thevariability among living organisms and theecological complexes of which they are apart” (Canadian Council of Forest Ministers1997). It can be viewed in the context of thebiodiversity of ecosystems, species andgenes (Canadian Council of Forest Minis-ters 1997). The conservation of biodiversityis an important goal of sustainable forestmanagement. However, should a change inclimate alter a crucial aspect of the environ-ment, then, regardless of forest manage-ment activities, biodiversity will change.One way to retain biodiversity is to protectold-growth forests and other natural areas,as these habitats serve as biodiversityreservoirs (while also acting as forest car-bon storage areas, as described later). How-ever, the ability to retain such areas is likelyto decline if climate changes rapidly andthe frequency and severity of forest distur-bance increases. A more dynamic approachrecognizing that conditions may change isneeded to protect natural areas through aperiod of climate change (Halpin 1997)

�� The influence of climate change on

forest productivity will depend on regionaldifferences in effects of elevated CO2 con-centration and altered climatic regimes oncarbon, water and nutrient relations, envi-ronmental stress response, and the uniqueecophysiological characteristics of species(Bazzaz et al. 1990, McGuire et al. 1995,Wayne et al. 1998). Although enhancedphotosynthetic activity at elevated CO2

concentrations will increase forest netprimary productivity (NPP), the relativeincrease in photosynthesis is stronglydependent upon nitrogen availability(Melillo et al. 1993, McGuire et al. 1995).For example, the potential increase in NPPof northern and temperate forest ecosys-tems under elevated CO2 may be con-strained by nitrogen availability in soils ofthese regions, with NPP being largelydependent on effects of elevated tempera-ture on mineralization rates (Melillo et al.1993). Further, the beneficial effects of CO2fertilization on NPP expected under cli-mate change may decline with time (Caoand Woodward 1998).

Rigorous predictions of climatechange effects on NPP must await furtherprogress in our understanding of therelationship between carbon and nitrogencycles (McGuire et al. 1995). However,general statements regarding the possibleeffects of climate change on forest produc-tivity can be made. As shown in Table 11.2,stand productivity will tend to increase inall regions as a result of increased tem-perature and atmospheric CO2 concentra-tion. Increased spring and fall tempera-tures will tend to lengthen the growingseason, while elevated CO2 will increasephotosynthesis and water use efficiency(see Section 7). Nitrogen availability insoils would tend to increase with tempera-ture as a result of increased rates of miner-alization and decomposition (see Sections5 and 9), although the effect could berelatively less in the south due to thewarmer temperatures that already prevailthere. However, reduced precipitation andincreasing severity of drought in the north-west and south could counter the positiveeffects of warmer temperature, increasedCO2, and greater nitrogen availability. Incontrast, there could be large increases instand productivity in the northeast ifprecipitation increases and the incidenceof drought decreases as predicted (seeSections 2 and 3). Perennial herbaceousplant competition (e.g., fireweed andstrawberry) may become a more seriousproblem that would slow crop tree estab-lishment, since herbaceous plants are

favoured under higher concentrations ofatmospheric CO2 (see Sections 7 and 9).

On a regional basis, an increasedincidence of severe disturbance could haveserious consequences on timber supply. Innorthwestern Ontario, reduced precipita-tion could trigger severe pest outbreaks(see Sections 4 and 5) and forest fires (seeSection 6). Similar effects, although per-haps less severe, may also occur in south-ern Ontario. Despite predicted increases inprecipitation in the northeast, there may bean increase in fire severity due to dryingcaused by elevated temperatures and highevaporative demands (see Sections 3 and6).

�� The total global carbon content is

constant; it occurs as atmospheric CO2 andoceanic carbon or in storage as living anddead biomass, fossil fuels, limestone, andmarble. Atmospheric CO2 concentrationdepends on the balance between carbon“fixed”, or added, in storage and releasedfrom storage. Since the beginning of theindustrial era, atmospheric CO2 concentra-tion has increased from about 280 ppm to360 ppm. Approximately 7 Gt CO2-carbonper year (Gt=gigaton; 1 Gt=1015 g) arebeing released to the atmosphere by fossilfuel combustion and, to a much lesserextent, tropical deforestation and burning(Krauchi 1994). Of this carbon, 3.6 Gt areabsorbed by oceans and terrestrial vegeta-tion, with 3.4 Gt being added annually tothe atmosphere.

Forests play an integral role in theglobal carbon cycle, fixing CO2 throughphotosynthesis, storing carbon in aboveand below ground biomass, and releasingCO2 to the atmosphere through decompo-sition and respiration (D’Arrigo et al. 1987,Tans et al. 1990, Krauchi 1994). Forestbiomass contains about 70% of the amountof carbon in the atmosphere, while carbonin detritus and soil organic matter is twicethat of the atmosphere. Natural and

anthropogenic disturbances influence thecarbon cycle of forest ecosystems througheffects on the amount of carbon stored andits rate of transfer from organic storageforms to the atmosphere. Generally, a reduc-tion in rotation length and shorter naturaldisturbance intervals reduce carbon storage(Cooper 1983). The carbon storage life offorest products also influences the forestcarbon cycle. Currently, harvesting andindustrial processing of boreal and temper-ate forests results in two-thirds of the storedcarbon being emitted to the atmosphere asCO2 (Harmon et al. 1990, Freedman andKeith 1996).

Atmospheric CO2 concentrations canbe reduced by decreasing fossil fuel com-bustion and increasing the rate of carbonremoval from the atmosphere. For a varietyof reasons, significant reductions in fossilfuel emissions are unlikely in the nearfuture (Freedman and Keith 1996). Forestryis one of the few human activities that canreduce atmospheric CO2. Using forests as

sinks to reduce net CO2 emissions is a prom-ising way to mitigate climate change, butshould be used in conjunction with efforts toreduce fossil fuel combustion and deforesta-tion (Sedjo 1989, Freedman and Keith 1996).Managing forests as carbon sinks wouldrequire some changes in the forest land useparadigm to add the maximization of car-bon storage and afforestation to the goals ofrapid reforestation and increased productiv-ity.

Afforestation for carbon storage byestablishing tree plantations on marginalcropland and pasture can be used as aneffective, ecologically viable means of in-creasing CO2 sequestration (Winjum andSchroeder 1997). However, in Ontario theamount of land available for afforestation issmall compared to the existing forested landbase. The potential reduction in CO2 byafforestation depends on availability oflands that can grow forests, the maximumattainable biomass of these forests,

+�$��( ��H # $�� () �� -� �� 0&

��-��- ��

�� $��#��#��

;��#��H)� -�)�� /� ��

1�-� �� / ��- ��-�() ��

B�� - ��

1�� -� ��

5��

#� ��$$� �� %� � � � �#� ��$$� �� !��

Table 11.2 Possible effects of altered environment induced by climate change on forest productivity and timber supply innorthwestern, northeastern and south central Ontario in the next 50 to 100 years1.

)��%�� $�� $�� $��

��)� #�(��$ ��"��/��# �.��)� )�� 0/��/��4 ��%�&B!1

the degree to which management alters thismaximum, and the long-term fate of storedcarbon (Table 11.1) (Cooper 1983, Vitousek1991, Winjum and Schroeder 1997). Largemonoculture tree plantations are moresusceptible to insects and pathogens(Winjum and Schroeder 1997), and theiruse to maximize carbon storage requiresthat they be protected from fire and insects.

A total of 61 million ha, or 62%, ofOntario’s total land area is productiveforested land (OMNR 1996). Forest man-agement can increase the productivity andcarbon storage of these existing forests, butthe contribution to carbon sequestration ona per hectare basis would be less than thecontribution from afforestation of non-forested land. Other broad managementpractices recommended to maximize car-bon sequestration of forest land include: (i)clearing and prompt regeneration of unpro-ductive, poorly stocked forest, (ii) interme-diate stand treatments (e.g., thinning) inoverstocked, stagnating forests, and (iii)

increasing the rotation length (Birdsey andHeath 1997).

The net amount of carbon stored inforest ecosystems will differ with thesilvicultural system used (Figure 11.1). Aclearcut silvicultural system has the great-est CO2 output from fossil fuels per unitrotation while a selection system producesthe smallest CO2 output. Clearcuttingfollowed by tree planting produces a largerelease of CO2 from fossil fuels because ofthe energy requirements for tree seedlingproduction, transportation, site prepara-tion and tending, and from accelerateddecomposition of forest floor detritus andorganic matter after harvest. Selectionsilviculture requires CO2 output for har-vesting only, disturbance to the forest flooris minimized, and planting is not required,but these gains are partially offset by theneed for a larger road network, greaterfrequency of return to harvest, and lowerefficiency (i.e., lower m3 of wood perhectare of forest).

��

Partial cutting systems (e.g., shelterwoodsand strip cuts) are intermediate in termsof carbon sequestration, as they relyheavily on seeding and advance growthfor regeneration, but may require plantingand some site preparation where naturalregeneration is inadequate. Moreover,carbon sequestration decreases with thelength of time a forest site is not fullyoccupied with a tree crop. Despite sugges-tions to the contrary, conversion of old-growth forest ecosystems to intensivelymanaged, commercial forests results in asignificant net decrease in on-site carbonstorage capacity (Harmon et al. 1990,Vitousek 1991, Freedman and Keith 1996).The value of old-growth forests as vehi-cles for carbon storage and preservationof biodiversity may require developmentof silvicultural approaches to maintain thehealth of these forests under a changingclimate.

Figure 11.2 shows theoretical differ-ences in net carbon sequestration withdifferent silvicultural practices. Not allforms of silviculture will result in in-creased net sequestration of carbon. Forexample, tree improvement is asilvicultural practice that requires rela-tively small release of CO2 to achieveincreased growth rates over large areas offorest. Vegetation management activitiesreduce the interval between harvestingand full site occupancy with a tree crop,but the burning of fossil fuels and there-fore CO2 released in producing, transport-ing and applying herbicide reduces the netbenefit of this practice to carbon sequestra-tion. Pruning does not add to net seques-tration of carbon and increases short-termcarbon release due to increased branchdecomposition rates, while adding little tostand growth. Thinning increases indi-vidual tree vigour and concentratesgrowth on fewer stems but, because itrequires an expenditure of energy to

��

��

��

��

��

� �

��

� ��

��

��

��

��

��

��

��

��

��

��

��

�

��

conduct thinning mechanically and alsoreduces full site occupancy, thinning re-duces CO2 sequestration (thinning maycontribute positively to CO2 sequestrationif it reduces stand stress due to drought,insects or disease). Finally, increases ingrowth due to forest fertilization would beoffset by the large amount of CO2 emittedin producing and applying fertilizer.

The consequences of managementpractices on the forest carbon cycle will beof increasing concern, particularly if mini-mizing net CO2 emissions becomes animportant objective of forest managers andthe forest industry. Such net calculations,to our knowledge, have not yet beenwidely made.

��It is clear that the increase in green-

house gases in the atmosphere over the lasttwo centuries is due to human activities(Vitousek 1993). Despite current uncer-tainty as to the absolute effects of thesegases on the earth’s climate and biota,there is compelling evidence to supportassertions that global climate change is aserious threat to the biosphere. A signifi-cant warming of the earth’s atmosphere iscurrently occurring, with the period since1980 being the warmest in the past 200years (Jacoby et al. 1996, Myneni et al.1997, Mann et al. 1998). In fact, globalaverage temperatures for January to May1998 indicate the spring of 1998 was thewarmest in the last 1000 years (Vogel andLawler 1998).

The warmer than normal tempera-tures in recent years may be responsiblefor increased plant growth in the northernlatitudes, due to earlier disappearance ofsnow in the spring and lengthening of thegrowing season (Jacoby et al. 1996, Myneniet al. 1997). However, in addition to, andmore important than, changes in tempera-ture averages, climate change is expected

to increase the likelihood of extreme cli-matic events and associated natural distur-bances (fire, insects), which will havedramatic impacts on forest ecosystems.Although it is difficult to state unequivo-cally that the warming already observed isa direct result of increased greenhousegases, recent climate patterns and in-creased frequency of wildfire have alreadyhad major effects on Ontario’s forests (VanWagner 1988, Schindler 1998).

Regardless of some continuing disa-greement over the extent of the effect ofgreenhouses gases on future global tem-perature, the increase in atmospheric CO2will by itself be sufficient to substantiallyalter forest ecosystems in Ontario. Someeffects of climate change and increasedatmospheric CO2 will be insidious andprogressive. For example, changes in thecompetitive ability of different plants mayalready be undergoing changes in a slow,progressive manner. However, suchchanges might not be apparent withoutcareful monitoring of plant species abun-dance and growth rates. Other ecosystemchanges, such as long-range species migra-tion, might not be observed for hundredsof years. Because of the uncertainty overthe timing and extent of climate changeand its effects on forest ecosystems, wepropose that “no risk” forest managementpractices (i.e., practices that increase theresilience of forests to climate variability,such as the protection of genetic diversity)be identified now and, where feasible,implemented to minimize the potentialnegative impacts of climate change andincreased atmospheric CO2 on forests inOntario. More dramatic responses toclimate change (e.g., the large-scale plant-ing of southerly genetic sources and spe-cies hundreds of kilometers north of theirpresent ranges) should be considered onceimproved regional climate change projec-tions are made.

��

��

The Ontario Ministry of NaturalResources seeks to sustain the ecologicaland social benefits of healthy ecosystemson forested Crown lands. However, forestsare increasingly being affected by acidifi-cation and deposition of nitrogen to soilsas a by-product of industrial pollution,ground-level ozone pollution, and thereduction of ozone in the earth’s upperatmosphere that has increased ultravioletradiation. Overlain on these factors is apotentially unprecedented rapid change inclimate resulting from increased atmos-pheric CO2. This report outlines the poten-tial effects of CO2-induced climate changeon the stability of Ontario’s forest ecosys-tems.

The evidence reviewed in this reportidentifies the following major effects ofclimate change on Ontario’s forests:• in northwestern Ontario, fires and

droughts will become more frequent andsevere;

• insect outbreaks and disease are ex-pected to mirror fire and drought inci-dence;

• new plant associations are expected tooccur as individual species are favouredover others and as rates of migrationdiffer between plant species;

• northeastern Ontario may experienceenhanced forest growth and productiv-ity, while drought, fire, insects, anddisease in northwestern Ontario are

expected to reduce growth rates andthreaten wood supplies, perhaps withinthe next 30 years;

• unique ecosystems and threatened andendangered species may be unsustainableif they have highly specific climate re-quirements;

• biodiversity conservation may changemeaning as a management objective ifclimate change allows species to migrateto new areas, there is strong genetic selec-tion pressure, and the ability to reproduceis reduced in some species.

The potential changes in climate de-scribed here would alter the traditionaleconomic and social benefits that society inOntario is accustomed to receiving from itsforests. It is therefore important that forestland managers realize that existing forestecosystems and traditional approaches tomanaging these lands may not be valid in aclimatically altered environment. As aresult, dynamic management practices andpolicies governing forests in Ontario will beneeded in anticipation of such changes.Careful sensitivity analysis to identifyspecies and ecosystems at greatest risk fromclimate change is also needed. Optimizingfuture forest management practices re-quires an understanding of the potentialconsequences of climate change that canonly be obtained by modeling climaticinfluences on biological systems.

&'"�()#��(#�*)+,"�()#

Armson, K.A., W.R. Grinnell and F.C. Robinson. 1998. Thehistory of reforestation. in Regenerating the CanadianForest, R.G. Wagner and S.J. Colombo, (eds.) Chapter 1.FitzHenry & Whiteside, Toronto, ON. (in press).

Hengeveld, H.G. 1995. Understanding atmospheric change.Environ. Can., State of the Environment Report SOE 95-2.68 p.

Joyce, L.A., M.A. Fosberg and J.M. Comanor. 1990. Climatechange and America’s forests. USDA For. Serv., RockyMount. For. Range Exp. Sta., Gen. Tech. Rep. RM-187. 12 p.

Kräuchi, N. 1994. Climate change and forest ecosystems - anoverview. Pp. 53-76 in Long-term Implications of ClimateChange and Air Pollution on Forest Ecosystems, R.Schlaepfer (ed.), IUFRO World Series Vol. 4, IUFRO,Vienna, Austria.

Kuo, C., Lindberg, C, and Thomson, D.J. 1990. Coherenceestablished between atmospheric carbon dioxide andglobal temperature. Nature 343: 709-714.

Schindler, D.A. 1998. A dim future for boreal waters andlandscapes. Bioscience 48: 157-164.

&'"�()#��)#�-*().&�"/(0-�'�(#��1'��&�"'#�,*2

Boer, G.J., N.A. McFarlane, and M. Lazare. 1992. Greenhousegas-induced climate change simulated with the CCCsecond-generation General Circulation Model. J. Clim 5:1045-1077.

Caya, D., R. Laprise, M. Giguère, G. Bergeron, J.P. Blanchet,B.J. Stocks, G.J. Boer and N.A. McFarlane. 1995. Descriptionof the Canadian regional climate model. Water Air SoilPoll. 82: 477-482.

Environment Canada. 1993. Canadian Climate Normals 1961-90; Vol 4. Ontario. Atmos. Environ. Serv., Ottawa, ON.

Gullett, D.W. and W.R. Skinner. 1992. The state of Canada’sclimate: Temperature change in Canada 1895-1991.Environ. Can., Atmos. Environ. Serv., State of the Environ-ment Rep. 92-2.

Hare, F.K. and M.K. Thomas. 1974. Climate Canada. WileyPubl. Can., Ltd. Toronto, ON.

Intergovernmental Panel on Climate Change (IPCC). 1996.Climate Change 1995 Impacts, Adaptations and Mitigationof Climate Change: Scientific-Technical Analyses. Cam-bridge Univ. Press, Cambridge, U.K.

Karl, T.R. and R.W. Knight. 1998. Secular trends of precipita-tion amount, frequency, and intensity in the United States.Bull. Am. Meteorol. Soc. 79: 231-241.

Lau, K.-M., J.H. Kim and Y. Sud. 1996. Intercomparison ofhydrologic processes in AMIP GCMs. Bull. Am. Meteorol.Soc. 77: 2209-2227.

McFarlane, N.A., G.J. Boer, J.-P. Blanchet and M. Lazare. 1992.The Canadian Climate Centre second-generation GeneralCirculation Model and its equilibrium climate. J. Clim. 5:1013-1044.

Trewartha, G.T. and L.H. Horn. 1980. An introduction toclimate, 5th ed. McGraw-Hill Book Co., New York, NY.

Weber, M.G. and M.D. Flannigan. 1997. Canadian borealforest ecosystem structure and function in a changingclimate: Impact on fire regimes. Environ. Rev. 5: 145-166.

&'"�()#��)*'&��12+*)/)32�(#�*'/-�()#�)�3/)4-/�"1-#3'

Bolin, B., B.R. Doos, J. Jagger and R.A. Warrick (eds.).1986. The Greenhouse Effect, Climate Change, andEcosystems. John Wiley and Sons, Toronto, ON.

Thornthwaite, C.W. 1946. The moisture factor in climate.Trans. Am. Geogr. Union, 27(1): 41-48.

&'"�()#��(#&'"�&�-#+�"/(0-�'�"1-#3'

Fleming, R.A. 1996. A mechanistic perspective ofpossible influences of climate change on defoliating insectsin North America’s boreal forests. Silv. Fenn. 30: 281-294.

Fleming, R.A. and J.-N. Candau. 1997. Influences of climatechange on some ecological processes of an insect outbreaksystem in Canada’s boreal forests and the implications forbiodiversity. Environ. Monit. Assess. 49: 235-249.

Fleming, R.A. and G.M. Tatchell. 1995. Shifts in flight periodsof British aphids: A response to climate warming? Pp. 505-508 in R. Harrington and N. E. Stork (eds.), Insects inChanging Environment. Academic Press, London, U.K.

Fleming, R.A. and W.J.A.Volney. 1995. Effects of climatechange on insect defoliator population processes inCanada’s boreal forest: some plausible scenarios. Water,Air, Soil Poll. 82: 445-454.

Hardy, Y., M. Mainville and D.M. Schmitt. 1986. An atlas ofspruce budworm defoliation in eastern North America,1938-1980. USDA For. Serv., Co-op. Stat. Res. Serv. Misc.Publ. No. 1449. 51p.

Hedden, R.L. 1988. Global climate change: Implications forsilviculture and pest management. Pp. 555-562 in Proc.Fifth Biennal Southern Silvicultural Research Conference.Memphis, Tennessee, Nov. 1-3, 1988. USDA For. Serv.,South. For. Exp. Sta., Gen. Tech. Rep. SO-74.

��

Logan, J.A., P.V. Bolstad, B.J.Bentz and D.L. Perkins. 1995.Assessing the effects of changing climate on mountain pinebeetle dynamics. Pp. 92-105 in Interior West Global ChangeWorkshop. April 25-27, 1995, Fort Collins, Colorado. USDAFor. Serv. Rocky Mount. For. Range Exp. Sta. Gen. Tech.Rep. RM-GTR-262.

Sandberg, D.V. 1992. Adaptive response to forest disturbancein a changing climate - fire, insects, and disease. Pp. 294-305 in Proc. North American Conference on ForestryResponses to Climate Change, May 15-17, 1990, ClimateInstitute. Washington, D.C.

&'"�()#��1'�(05-"��)��"/(0-�'�"1-#3'�)#�,#3(�(#��1'��)*'&��'")&2&�'0

Batjes, N.H. 1996. Total carbon and nitrogen in the soils of theworld. Eur. J. Soil Sci. 47: 151-163.

Cannell, M.G.R., J. Grace and Booth, A. 1989. Possible impactsof climatic warming on trees and forests in the UnitedKingdom: A review. Forestry 62: 337-364.

Couteaux, M., P. Bottner, and B. Berg. 1995. Litter decomposi-tion, climate and litter quality. Trends Ecol. Evol. 10: 63-66.

Dance, B.W. and D.F. Lynn. 1963. Excessive red oak mortalityfollowing ice-storm damage. Can. Dep. For., Entomol.Path. Bi-monthly Prog. Rep. 19(6): 3.

Gross, H.L., D.B. Roden, J.J. Churcher, G.M. Howse and D.Gertridge. 1992. Pest-caused depletions to the forestresource of Ontario, 1982-1987. For. Can., Ont. Reg., GreatLakes For. Cent. Joint Rep. 17. 23 p.

Lekkerkerk, L.J.A., J.A. van Veen and S.C. de Geijn. 1990.Influence of climatic change on soil quality; consequencesof increased atmospheric CO2-concentration on carboninput and turnover in agro-ecosystems. Pp. 46-47 in J.Goudriaan, H. van Keulen, H.H. van Laar (eds.), TheGreenhouse Effect and Primary Productivity in EuropeanAgro-Ecosystems. Pudoc, Wageningen, The Netherlands.

Lodge, D.J., W.H. McDowell and C.P. McSwiney. 1994. Theimportance of nutrient pulses in tropical forests. TrendsEcol. Evol. 9: 384-387.

McDonald, G.I., N.E. Martin, and A.E. Harvey. 1987.Armillaria in the Northern Rockies: pathogenicity and hostsusceptibility on pristine and disturbed sites. USDA For.Serv., Intermountain Res. Stat., Res. Note INT-371. 5 p.

Meyer, T., Schoenberger, M. and D.A. Perry. 1982. The effectof soil disturbance on growth and ectomycorrhizae ofDouglas-fir and western hemlock seedlings: A greenhousebioassay. Can. J. For. Res. 12: 343-353.

Miller, R.M. and D.J. Lodge. 1997. Fungal responses todisturbance: Agriculture and forestry. Pp. 65-84 in Wicklow,Söderström (eds.), The Mycota IV; Environmental andmicrobial relationships. Springer-Verlag, Berlin, Germany.

Molina, R., H. Massicotte and J.M. Trappe. 1992. Specificityphenomena in mycorrhizal symbioses: community-ecological consequences and practical implications. Pp.357-423 in M.J. Allen (ed.), Mycorrhizal Functioning, AnIntegrated Plant-Fungal Process. Chapman and Hall, NewYork, NY.

Monz, C.A., H.W. Hunt, F.B. Reeves and E.T. Elliot. 1994. Theresponse of mycorrhizal colonization to elevated CO2 andclimate change in Pascopyrum smithii and Boutelouagracilis. Plant and Soil 165: 75-80.

Nechleba, A. 1927. Notizen uber das Vorkommen einigerforstlish bemerkenswerter pathogener Pilze in Bohmen.[Notes on the occurrence in Bohemia of somesilviculturally remarkable pathogenic fungi.].Pflanzenschutz 37: 237-270.

Ojima, D.S., T.G.F. Kittal, T. Rosswall and B.H. Walker. 1991.Critical issues for understanding global change effects onterrestrial ecosystems. Ecol. Appl. 1: 316-325.

O’Neill, E.G. 1994. Responses of soil biota to elevatedatmospheric carbon dioxide. Plant and Soil 65: 55-65.

Redmond, D.R. 1955. Studies in forest pathology, 15. Rootlets,mycorrhiza and soil temperatures in relation to birchdieback. Can. J. Bot. 33: 595-627.

Schimmel, D.S. 1995. Terrestrial ecosystems and the carboncycle. Global Change Biol. 1: 77-91.

Wargo, P.M. and T.C. Harrington. 1991. Host stress andsusceptibility in C.G. Shaw III and G.A. Kile (eds.),Armillaria root disease. USDA For. Serv., Agric. Handb. No.691. 233 p.

&'"�()#� ��1'�(05-"��)��"/(0-�'�"1-#3'�)#�(*'�-#+��(*'�0-#-3'0'#��(#�)#�-*()

Canadian Forestry Service 1987. Canadian forest fire dangerrating system - users’ guide. Can. For. Serv., Fire DangerGroup. (unnumbered publication).

Flannigan, M.D. and C.E. Van Wagner. 1991. Climate changeand wildfire in Canada. Can. J. For. Res. 21: 66-72.

Fosberg , M.A., J.G. Goldammer, D. Rind, and C. Price. 1990.Global change: Effects on forest ecosystems and wildfireseverity. Pp. 463-486 in J.G. Goldammer (ed.), Fire in theTropical Biota: Ecosystem Processes and Global Challenges.

Price, C. and D. Rind. 1994. Possible implications of globalclimate change on global lightning distributions andfrequencies. J. Geophys. Res. 99:108-123.

Simard, A.J. 1997. National workshop on wildland fireactivity in Canada. Workshop rep. Can. For. Serv., Ottawa,ON. Info. Rep. ST-X-13.

Stocks, B.J. 1990. The extent and impact of forest fires innorthern circumpolar countries. Pp. 198-202 in J.S. Levine(ed.), Global biomass burning; Atmospheric, Climatic andBiospheric Implications. MIT press, Cambridge, MA.

Stocks, B.J., M.A. Fosberg, T.J. Lynham, L. Mearns, B.M.Wotton, Q. Yang, J-Z Jin, K. Lawrence, G.R. Hartley, J.A.Mason and D.W. McKenney. 1998. Climate change andforest fire potential in Russian and Canadian boreal forests.Clim. Change 38: 1-13.

Van Wagner, C.E. 1970. Conversion of William’s SeverityRating for use with the Fire Weather Index. Can. For. Serv.,Petawawa For. Exp. Sta. Info. Rep. PS-X-21, 3 p.

Van Wagner, C.E. 1987. Development and structure of theCanadian forest fire weather index system. Can For. Serv.,Ottawa, ON. For. Tech. Rep. 35. 37 p.

Williams, D.E. 1959. Fire Season Severity Rating. Can. Dep.North. Aff. Nat. Res., For. Res. Div. Tech. Note No. 73. 13p.

Wotton, B.M. and M.D. Flannigan. 1993. Length of the fireseason in a changing climate. For. Chron. 69: 187-192.

&'"�()#��5/-#��512&()/)3("-/�*'&5)#&'&�)�-�"1-#3(#3�'#6(*)#0'#�

Battaglia, M, C. Beadle and S. Loughhead. 1996. Photosyn-thetic temperature responses of Eucalyptus globulus andEucalyptus nitens. Tree Physiol. 16: 81-89.

Colombo, S.J. 1998. Climate warming and its potential effectson bud burst and risk of frost damage to white spruce inCanada. For. Chron. 74 (in press).

Drake, B.G., M.A. Gonzàlez and S.P. Long. 1997. Moreefficient plants: A consequence of rising atmospheric CO2?Ann. Rev. Plant Physiol. Mol. Biol. 48: 609-639.


Körner, C. 1993. CO2 fertilization: The great uncertainty infuture vegetation development. Pp. 53-70 in VegetationDynamics & Global Change. A.M. Solomon and H.H.Shugart (eds.), Chapman & Hall, New York. 338 p.

Murray, M.B., R.I. Smith, I.D. Leith, D. Fowler, H.S.J. Lee, A.D.Friend and P.G. Jarvis. 1994. Effects of elevated CO2,nutrition and climatic warming on bud phenology in Sitkaspruce (Picea sitchensis) and their impact on risk of frostdamage. Tree Physiol. 14: 691-706.

Reed, D.D. and P.V. Danseker. 1992. Ecological implications ofprojected climate change scenarios in forest ecosystems innorthern Michigan, USA. Int. J. Biometeorol. 36: 99-107.


Tissue, D.T., R.B. Thomas and B.R. Strain. 1996. Growth andphotosynthesis of loblolly pine (Pinus taeda) after exposureto elevated CO2 for 19 months in the field. Tree Physiol. 16:49-59.

Walker, B. and W. Steffen (eds.). 1997. The terrestrial bio-sphere and global change: Implications for natural andmanaged ecosystems. A synthesis of GCTE and relatedresearch. The International Geosphere-Biosphere Pro-gramme, Stockholm, Sweden. 32 p.

&'"�()#��3'#'�("�(05/("-�()#&�)��"/(0-�'"1-#3'

Bazzaz, F.A., M. Jasienski, S.C. Thomas and P. Wayne. 1995.Microevolutionary responses in experimental populationsof plants to CO2-enriched environments: Parallel resultsfrom two model systems. Proc., Nat. Acad. Sci. USA 92:8161-8165.

Brubaker, L.B. 1986. Responses of tree populations to climaticchange. Vegetatio 67: 119-130.

Cantin, D., M.F. Tremblay, M.J. Lechowicz and C. Potvin.1997. Effects of CO2 enrichment, elevated temperature, andnitrogen availability on the growth and gas exchange ofdifferent families of jack pine seedlings. Can. J. For. Res. 27:510-520.

Carter, K.K. 1996. Provenance tests as indicators of growthresponse to climate change in 10 north temperate treespecies. Can. J. For. Res. 26: 1089-1095.

Dudley, N., J-P. Jeanrenaud, and A. Markham. 1996. Conser-vation in boreal forests under conditions of climate change.Silv. Fenn. 30 (2-3): 379-383.

Eriksson, G., G. Namkoong and J. Roberds. 1995. Dynamicconservation of forest tree gene resources. Forest GeneticResources 23, United Nations Food and Agric. Org. 64 p.

Harris, L.D., M.E. McGlothlen and M.N. Manlove. 1984.Genetic resources and biotic diversity. Pp. 93-107 in Harris,L.D. (ed.). The Fragmented Forest: Island Biogeographyand the Preservation of Biotic Diversity. Univ. ChicagoPress, Chicago, IL. 211 p.


Ledig, F.T. and J.H. Kitzmiller. Genetic strategies for reforesta-tion in the face of global climate change. For. Ecol. Manage.50: 153-169.

Matyas, C. 1994. Modeling climate change effects withprovenance test data. Tree Physiol. 14: 797-804.

Namkoong, G. 1984. Strategies for gene conservation in foresttree breeding. Pp. 79-89 in Yeatman, C.W., D. Kafton, andG. Wilkes (eds.), Plant Gene Resources: A ConservationImperative. AAAS Selected Symp. 87, Boulder, Co.

Nowak, C.L., R.S. Nowak, R.J. Tausch and P.E. Wigand. 1994.Tree and shrub dynamics in northwestern Great Basinwoodland and steppe during the late-Pliestocene andHolocene. Am. J. Bot. 81: 265-277.

Peters, R.L. 1990. Effects of global warming on forests. For.Ecol. Manage. 35: 13-33.

Peters, R.L. and T.E. Lovejoy (eds.). 1992. Global Warmingand Biological Diversity. Yale Univ. Press, New Haven, CT.

Rehfeldt, G.E., C.C. Ying, D.L. Spittlehouse, and D.A.Hamilton, Jr. 1998. Genetic responses to climate for Pinuscontorta in British Columbia: Niche breadth, climatechange, and reforestation. Ecol. Monogr. [in press].

Slocum, R.W. Jr. 1985. Major climate change likely, sayscientists. J. For. 83: 325-327.

Stettler, R.F. and H.D. Bradshaw Jr. 1994. The choice of geneticmaterial for mechanistic studies of adaptation in foresttrees. Tree Physiol. 14: 781-796.

Vitousek, P.M. 1994. Beyond global warming: Ecology andglobal change. Ecology 75: 1861-1876.

Walker, B. and W. Steffen. 1997. An overview of the implica-tions of global change for natural and managed terrestrialecosystems. Cons. Ecol. [online] 1(2). 18 p.

&'"�()#��"/(0-�'�"1-#3'�-#+��)*'&�6'3'�-�()#�+2#-0("&�(#�)#�-*()

Attiwill, P.M. 1994. The disturbance of forest ecosystems:The ecological basis for conservative management. For.Ecol. Manage. 63: 247-300.

Bazzaz, F.A. 1979. The physiological ecology of plantsuccession. Annu. Rev. Ecol. Syst. 10: 351-371.

Bazzaz, F.A. 1996. Plants in Changing Environments.Cambridge Univ. Press, Cambridge, UK, 320 p.

Canham, C.D. and O.L. Loucks. 1984. Catastrophicwindthrow in the presettlement forest of Wisconsin.Ecology 65: 803-809.

Dahir, S.E. and C.G. Lorimer. 1996. Variation in canopy gapformation among developmental stages of northernhardwood stands. Can. J. For. Res. 26:1875-1892.

Davis, M.B. and D.B. Botkin. 1985. Sensitivity of cool-temperate forests and their fossil pollen record to rapidtemperature change. Quat. Res. 23: 327-340.

Flannigan, M.D. and C.E. van Wagner. 1991. Climate changeand wildfire in Canada. Can. J. For. Res. 21: 66-72.

Fleming, R.A. 1996. A mechanistic perspective of possibleinfluences of climate change on defoliating insects in NorthAmerica’s boreal forests. Silv. Fenn. 30: 281-294.

Grime, J.P. 1993. Vegetation functional classification systemsas approaches to predicting and quantifying vegetationchange. Pp. 293-305 in Vegetation Dynamics and GobalChange, A.M. Solomon and H.H. Shugart (eds.), Chapman-Hall, New York, NY.

Heinselman, M.L. 1973. Fire in the virgin forests of theBoundary Waters Canoe Area, Minnesota. Quat. Res. 3:329-382.

Hogg, E.H. and P.A. Hurdle. 1995. The aspen parkland inwestern Canada: A dry-climate analogue for the futureboreal forest? Water , Air, Soil Poll. 82: 391-400.

Johnson, E.A. 1992. Fire and Vegetation Dynamics. Cam-bridge Univ. Press, Cambridge, U.K. 128 p.

LeBlanc, D.C. and J.R. Foster. 1992. Predicting effects of globalwarming on growth and mortality of upland oak species inthe midwestern United States: A physiologically baseddendroecological approach. Can. J. For. Res. 22: 139-1752.

Leniham, J.M. and R.P. Neilson. 1995. Canadian vegetationsensitivity to projected climatic change at three organiza-tional levels. Clim. Change 30: 27-56.

Loehle, C. and D. LeBlanc. 1996. Model-based assessments ofclimate change effects on forests: A critical review. Ecol.Model. 90: 1-31.

Mackey, B.G. and R.A. Sims. 1993. A climatic warminganalysis of selected boreal tree species, and potentialresponses to global climate change. World Res. Rev. 5: 469-487.

Millers, I., D.S. Shriner and D. Rizzo. 1989. History of hard-wood decline in the eastern United States. USDA For. Serv.,Gen. Tech. Rep. NE-126. 75 p.

Oliver, C.D. 1980. Forest development in North Americafollowing major disturbances. For. Ecol. Manage. 3: 153-168.

Overpeck, J.T., D. Rind and R. Goldberg. 1990. Climate-inducedchanges in forest disturbance and vegetation. Nature 343: 51-53.

Pastor, J. and W.M. Post. 1988. Response of northern forests toCO2-induced climate change. Nature 334: 55-58.

Peterson, C.J. and W.P. Carson. 1996. Generalizing forestregeneration models: The dependence of propagule avail-ability on disturbance history and stand size. Can. J. For. Res.26: 45-52.

Pickett, S.T.A., S.L. Collins and J.J. Armesto. 1987. Models,mechanisms and pathways of succession. Bot. Rev. 53: 335-371.

Reed, D.D. and P.V. Desanker. 1992. Ecological implications ofprojected climate change scenarios in forest ecosystems innorthern Michigan, USA. Int. J. Biometeorol. 36: 99-107.

Sargent, N.E. 1988. Redistribution of the Canadian boreal forestunder a warmed climate. Climatol. Bull. 22: 23-34.


Solomon, A.M. 1986. Transient response of forests to CO2-induced climate change: Simulation modeling of experimentsin eastern North America. Oecologia 68: 567-579.

Solomon, A.M. and P.J. Bartlein. 1992. Past and future climatechange: Response by mixed deciduous-coniferous ecosystemsin northern Michigan. Can. J. For. Res. 22: 1727-1738.

Stocks, B.J. 1987. Fire potential in the spruce budworm-damaged forests of Ontario. For. Chron. 63: 8-14.

Whitney, G.G. 1986. Relation of Michigan's presettlement pineforests to substrate and disturbance history. Ecology 67:1548-1559.

Wotton, B.M. and M.D. Flannigan. 1993. Length of the fireseason in a changing climate. For. Chron. 69: 187-192.

&'"�()#��1'�,&'�)��0)+'/&�(#�3/)4-/"/(0-�'�"1-#3'�&�,+('&

Allison, S.M., M.F. Proe and K.B. Matthews. 1994. Theprediction and distribution of general yield classes of Sitkaspruce in Scotland by empirical analysis of site factors usinga geographic information system. Can. J. For. Res. 24: 2166-2171.

Antonovski, M.Ya., M.T. Ter-Mikaelian and V.V. Furyaev. 1992.A spatial model of long-term forest fire dynamics and itsapplications to forests in western Siberia. Pp. 373-403 in H.H.Shugart, R. Leemans, and G.B. Bonan eds.), A SystemsAnalysis of the Global Boreal Forest. Cambridge UniversityPress, Cambridge, UK.

Arp, P.A. and X. Yin. 1992. Predicting water fluxes throughforests from monthly precipitation and mean monthly airtemperature records. Can. J. For. Res. 22: 864-877.

Brasier, C.M. 1996. Phytophthora cinnamomi and oak declinein southern Europe. Environmental constraints includingclimate change. Ann. Sci. Forest. 53(2-3): 347-358.

Bugmann, H.K.M. 1996. A simplified forest model to studyspecies composition along climate gradients. Ecology 77:2055-2074.

Carter, K.K. 1996. Provenance tests as indicators of growthresponse to climate change in 10 north temperate treespecies. Can. J. For. Res. 26: 1089-1095.

Goudriaan, J., H.H. Shugart, H. Bugmann, W. Cramer, A.Bondeau, R.H. Gardner, T. Hunt, W. Lauenroth, J.Landsberg, S. Linder, I. Noble, W. Parton, L. Pitelka, M.Stafford Smith, B. Sutherst, C. Valentin and F.I. Woodward.1998. Use of models in global change studies. In Walker,B.H., W.L. Steffen, J. Canadell, and J.S.I. Ingram (eds.), TheTerrestrial Biosphere and Global Change: Implications forNatural and Managed Ecosystems. Cambridge UniversityPress, Cambridge, UK. (in press).

Gross, H.L. 1985. White pine blister rust: A discussion of thedisease and hazard zones for Ontario. Proc., Entomol. Soc.Ont., Suppl. Vol. 116: 73-79.

Kellomäki, S., H. Väisänen, H. Hänninen, T. Kolström, R.Lauhanen, U. Mattila and B. Pajari. 1992. A simulationmodel for the succession of the boreal forest ecosystem.Silv. Fenn. 26: 1-18.

Korzukhin, M.D., M.T. Ter-Mikaelian, R.G. and Wagner. 1996.Process versus empirical models: which approach for forestecosystem management? Can. J. For. Res. 26: 879-887.

Landsberg, J.J. and R.H. Waring. 1997. A generalised model offorest productivity using simplified concepts of radiation-use efficiency, carbon balance and partitioning. For. Ecol.Manage. 95: 209-228.

Loehle, C. and D. LeBlanc. 1996. Model-based assessments ofclimate change effects on forests: A critical review. Ecol.Model. 90: 1-31.

Proe, M.F., S.M. Allison and K.B. Matthews. 1996. Assessmentof the impact of climate change on the growth of Sitkaspruce in Scotland. Can. J. For. Res. 26: 1914-1921.

Schmidtling, R.C. 1994. Use of provenance tests to predictresponse to climatic change: Loblolly pine and Norwayspruce. Tree Physiol. 14: 805-817.

Street, R.B. 1989. Climate Change and Forest Fires in Ontario.Pp.177-182 in Proceedings of 10th Conference on Fire andForest Meteorology, Ottawa, ON.

Sutherst, R.W., G.F. Maywald and D.B. Skarratt. 1995.Predicting insect distributions in a changed climate. Pp. 59-61 in R. Harrington and N.E. Stork, (eds.), Insects in aChanging Environment. Academic Press. London, UK.

Urban, D.L., and H.H. Shugart. 1992. Individual basedmodels of forest succession. Pp. 249-292 in D.C. Glenn-Lewin, R.K. Peet and T.T. Veblen, (eds.), Plant Succession.Theory and Prediction. Chapman & Hall, London, UK. 352p.

&'"�()#��)*'&��0-#-3'0'#��*'&5)#&'&�)�"/(0-�'�"1-#3'

Bazzaz, F.A. 1996. Plants in Changing Environments.Cambridge Univ. Press, Cambridge, UK. 320 p.

Bazzaz, F.A., J.S. Coleman and S.R. Morse. 1990. Growthresponses of seven major co-occurring tree species of thenortheastern United States to elevated CO2. Can. J. For. Res.20: 1479-1484.

Birdsey, R.A. and L.S. Heath. 1997. The forest carbon budgetof the United States, Pp. 81-85 in USDA Forest Serviceglobal change research program highlights, R. Birdsey, R.Mickler, D. Sandberg, R Tinus, J. Zerbe and K. O’Brian,(eds.), USDA For. Serv., Gen. Tech. Rep. NE-237. 122 p.

Canadian Council of Forest Minsters. 1997. Criteria andindicators of sustainable forest management in Canada.Nat. Resour. Can., Can. For. Serv., Ottawa, ON., Tech. Rep.137 p.

Cao, M. and F.I. Woodward. 1998. Dynamic responses ofterrestrial ecosystem carbon cycling to global climatechange. Nature 393: 249-252.

Cooper, C.F. 1983. Carbon storage in managed forests. Can. J.For. Res. 13: 155-166.

D’Arrigo, R., G.C. Jacoby and I.Y. Fung. 1987. Boreal forestsand atmosphere-biosphere exchange of carbon dioxide.Nature 329: 321-323.

Davis, M.B. 1989. Lags in vegetation response to greenhousewarming. Clim. Change 15: 75-82.

Freedman, B. and T. Keith. 1996. Planting trees for carboncredits: A discussion of context, issues, feasibility, andenvironmental benefits. Environ. Rev. 4: 100-111.

Harmon, M.E., W.K. Ferrell and J.F. Franklin. 1990. Effects oncarbon storage of conversion of old-growth forests toyoung forests. Science 247: 699-702.

Halpin, P.N. 1997. Global climate change and natural-areaprotection: management responses and research directions.Ecol. Appl. 7: 828-843.

Harvey, A.E., M.F. Jurgensen and M.J. Larsen. 1980. Clearcutharvesting and ectomycorrhizae: Survival of activity onresidual roots and influence on a bordering forest stand inwestern Montana. Can. J. For. Res. 10: 300-303.

Hedden, R.L. 1989. Global climate change: Implications forsilviculture and pest management. Pp. 555-562 in Proc.Fifth Biennial Southern Silviculture Research Conf., USDAFor. Serv. Gen. Tech. Rep. SO-74.

Hendricksen, O., J.B. Robinson and L. Chatarpaul. 1982. Themicrobiology of forest soils: A literature review. Can. For.Serv., Dept. Environ., Petawawa Nat. For. Inst., Inf. Rep. PI-X-19. 75 p.

Jacoby, G.C., R.D. D’Arrigo and T. Davaajamts. 1996. Mongo-lian tree rings and 20th-century warming. Science 273: 771-773.

Kräuchi, N. 1994. Climate change and forest ecosystems - anoverview, Pp. 53-76 in Long-term Implications of ClimateChange and Air Pollution on Forest Ecosystems, R.Schlaepfer, (ed.), IUFRO World Series Vol. 4, IUFRO,Vienna, Austria.

Mackey, B.G. and R.A. Sims. 1993. A climatic warminganalysis of selected boreal tree species, and potentialresponses to global climate change. World Res. Rev. 5: 469-487.

Mann, M.E., R.S. Bradley and M.K. Hughes. 1998. Global-scale temperature patterns and climate forcing over thepast six centuries. Nature 392: 779-787.

McGuire, A.D., J.M. Melillo and L.A. Joyce. 1995. The role ofnitrogen in the response of froest net primary productionto elevated atmospheric carbon dioxide. Annu. Rev. Ecol.Syst. 26: 473-503.

Melillo, J.M., A.D. McGuire, D.W. Kicklighter, B. Moore III,C.J. Vorosmarty and A.L. Schloss. 1993. Global climatechange and terrestrial net primary production. Nature 363:234-240.

Miller, R.M. and D.J. Lodge. 1997. Fungal responses todisturbance: Agriculture and forestry. Pp. 65-84 in TheMycota IV; Environmental and microbial relationships,Wicklow, Söderström (eds.), Springer-Verlag, Berlin.

Myneni, R.B., C.D. Keeling, C.J. Tucker, G. Asrar and R.R.Nemani. 1997. Increased plant growth in the northernlatitudes from 1981 to 1991. Nature 386: 698-701.

OMNR. 1996. Forest resources of Ontario. Ont. Min. Nat.Resour., Toronto, ON. 86 p.

Ostofsky, W.D. 1989. The health of northern hardwoodforests in relation to timber management practices. Pp. 49-56 in New perspectives on silvicultural management ofnorthern hardwoods, C.W. Martin, C.T. Smith, L.M.Tritton, eds. USDA For. Serv., Gen. Tech. Rep. NE-124. 107 p.

Peters, R.L. 1990. Effects of global warming on forests.For. Ecol. Manage. 35: 13-33.

Roberts, L. 1989. How fast can trees migrate? Science243: 735-737.

Safranyik, L. 1990. Temperature and insect interactionsin western North America. Pp. 166-170 in Are Foreststhe Answer?, Proc. Soc. Am. For. Nat. Conv., SAFPub. 90-02, Bethesda, Maryland. 614 p.

Schindler, D.W. 1998. A dim future for boreal watersand landscapes. Bioscience 48: 157-164.

Sedjo, R.A. 1987. Forests to offset the greenhouse effect.J. For. 85: 12-15.

Tans, P.P., I.Y. Fung and T. Takahashi. 1990. Observa-tional constraints on the global atmosphere CO2budget. Science 247: 1431-1438.

Van Wagner, C.E. 1988. The historical pattern of annualburned area in Canada. For. Chron. 64: 182-185.

Vitousek, P.M. 1991. Can planted forests counteractincreasing atmospheric carbon dioxide? J. Environ.Qual. 20: 348-354.

Vitousek, P.M. 1993. Beyond global warming: ecologyand global change. Ecology 75:1861-1876.

Vogel, G. and A. Lawler. 1998. Hot year, but coolresponse in Congress. Science 280:1684.

Wagner, M.R. 1990. Individual tree physiologicalresponses to global climate scenarios: A conceptualmodel of effects on forest insect outbreaks. Pp. 148-153 in Are Forests the Answer? Proc. Soc. Am. For.Nat. Conv., SAF Pub. 90-02, Bethesda, Maryland. 614p.

Wargo, P.M. and T.C. Harrington. 1991. Host stress andsusceptibility. In Armillaria root disease, C.G. Shawand G.A. Kile, eds., USDA For. Serv., Agric. Handb.No. 691. 233 p.

Wayne, P.M., E.G. Reekie and F.A. Bazzaz. 1998.Elevated CO2 ameliorates birch response to hightemperature and frost stress: Implications for model-ling climate-induced geographic range shifts.Oecologia 114: 335-342.

Winjim, J.K. and P.E. Schroeder. 1997. Forest plantationsof the world: their extent, ecological attributes, andcarbon storage. Agric. For. Meteorol. 84: 153-167.

Woodman, J.N. 1990. Adapting silviculture to forestsimpacted by climatic change. Pp. 204-207 in AreForests the Answer? Proc. Soc. Am. For. Nat. Conv.,SAF Pub. 90-02, Bethesda, Maryland. 614 p.

Home - Credit Valley Conservation Credit Valley Conservation...effects of climate change on forests...

Documents

Transcript of Home - Credit Valley Conservation Credit Valley Conservation...effects of climate change on forests...