This is a HTML version of the original PDF document. The HTML version is being provided for reading purposes only and is not the official version of the document.
 |
|
|
Forest Research Information Paper No. |
 |
|
The Impacts of Climate Change
|
|||
The Impacts of Climate Change
|
|
S.J. Colombo*, M.L. Cherry, C.Graham
|
Canadian Cataloguing in Publication Data
Main entry under title:
The impacts of climate change on Ontario's forests
S. J. Colombo...[et al.]
(Forest research information paper, ISSN 1319-9118; no. 143)
Includes bibliographical references.
ISBN 0-7778-7588-8
1. Climatic changes - Ontario
2. Forests and forestry - Ontario
3. Forest microclimatology - Ontario. I. Colombo, S. J. (Stephen John). II.
Ontario Forest Research Institute. III. Series.
SD390.7C55146 1998
577.3'722'90713
C98-964023-X
1998, Queen's Printer for Ontario
Printed in Ontario, Canada
Single copies of this publication are available from the address noted below.
Ministry of Natural Resources
Ontario Forest Research Institute
1235 Queen Street East
Sault Ste. Marie, Ontario
Canada P6A 2E5
Telephone : (705) 946-2981
Fax : (705) 946-2030
E0mail : ofriin@gov.on.ca
Cette publication scientifique n'est
disponible qu'en anglais
Abstract
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 have on Ontario’s forests. There is growing evidence that environmental changes caused by elevated atmospheric carbon dioxide (CO2 ) and its potential effects on global climate will alter forest ecosystems 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 the largest increases in northwestern and southern Ontario. Precipitation is predicted to increase in northeastern Ontario, but to decrease in southern and northwestern Ontario. An increase in summer temperatures with no or little increase in precipitation would increase the frequency and severity of drought by elevating evapotranspiration. In addition, the incidence of extreme weather events and variation in weather are expected to increase.
The length of the forest fire season is expected to increase with longer growing seasons. In addition, increased moisture loss from forests due to elevated temperatures would increase forest fire frequency 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. An increase in forest fires, insect outbreaks and diseases would, in turn, alter the age structure and plant species 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 temperatures could further damage or stress plants.
Increased CO2 , drought, and temperature will affect the growth and survival of plants by altering their physiological behaviour. The genetic structure of plant populations may be affected by altered selection pressures resulting from a changed environment, and species with larger genetic variability are likely more adaptable to a variety of climate conditions and as a result may be more successful. Competitive abilities of plant species now present in Ontario’s forests may change, with some species becoming more competitive and others less so (e.g., herbaceous plants are favoured by increased CO2 compared to woody plants). Productivity and timber supply in northwestern and southern 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 along with higher CO2 levels, increased temperatures and longer growing season could significantly in-creaseproductivity and timber supply in that region. Over hundreds of years, plant species may migrate northward. In one scenario, tolerant hardwood forests of central Ontario may migrate as far north as Kapuskasing. Species, such as those of the oak-hickory forests of the central U.S., may eventually migrate into what is currently the Great Lakes-St. Lawrence forest. However, differing migration rates and the reactions of individual species to new environmental conditions could result in new plant species mixes for which we lack forest management experience.
Forest management offers some means of reducing negative impacts to forests if the anticipated levels of climate change occur. Thinning to reduce moisture stress and early harvesting of stands deteriorating due to stress, followed by planting with more climatically adapted populations and species could help maintain higher levels of productivity. Climatic adaptation could be increased through tree breeding aimed at increasing pest and stress tolerance. Forests are important for their role 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. Carbon sequestration is maximized by silvicultural practices that increase tree growth rates but release little carbon 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.
Acknowledgements
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,OMNR |
| 6. Forest Fires | Mike Wotton, CFS Al Tithecott, Aviation, Flood and Fire Management Section, OMNR |
| 7. Physiology | Francine Bigras, CFS |
| 8. Genetics | Cheng C. Ying, B.C. Ministry of Forests |
| 9. Succession | Wayne Bell, OFRI, OMNR |
| 10. Modelling | Art Groot, CFS Rich Fleming, CFS |
| 11. Silviculture | Luc Duchesne, CFS |
Our appreciation is also extended to Lisa Buse for editing the document for style, Trudy Vaittinen for desktop publishing and graphics, and Anne Rovansek for typing.
Contents
| Section1. | Introduction Stephen J. Clombo, Cella Graham, Michael T. Ter- Milkaellan |
| Section2. | Ontario's Climate in the
21st Century Mike D. Flannige |
| Section3. | Forest Hydrologh in Relation
to Global Change Chris S. Papadopol |
| Section4. | Insects and Climate Change Taylor Scarr |
| Section5. | The Impact of Climate
Change on Fungi in the Forest Ecosystem Sylvia Greifenhagen |
| Section6. | The Impact of Climate
Change on Forest Fires and Forest Fire Management Robert S. McAlpine |
| Section7. | Plant Physiological Responses
to a Changing Environment Stephen J. Colombo |
| Section8. | Genetic Implications of
Climate Change Marilyn L. Cherry |
| Section9. | Climate Change and Forest
Vegetation Dynamics in Ontario William C. Parker |
| Section10. | The Use of Models in Global
Climate Change Studies Michael T. Ter - Mikaelian |
| Section11. | Forest Management Responses
to Climate Change William C. Parker, Stephen J. Colombo, Marilyn L. Cherry, Sylvia Greifenhagen, Chris S. Papadopol, Tayol Scarr |
| Section12. | Conclusions |
| References |
Section 1.
Introduction
Stephen J. Colombo, Celia Graham, and Michael T. Ter-Mikaelian, Ministry of Natural Resources.
The accumulation of carbon dioxide(CO2 ) in the atmosphere and the changes this may cause to climate have potentially important consequences for Ontario’s forested ecosystems. While forests tend to be viewed as unchanging due to the long life spans of trees compared to humans, forests in Ontario have been changing as a result of human activity since the middle of the 19th century (Armson et al. 1998). Historically, harvesting has been the major contributor 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 elsewhere in North America have also been affected by other aspects of human activity: the acidification of forest soils and the deposi-tion of nitrogen as a by-product of indus-trial pollution have altered soil chemistry throughout much of central and southern Ontario; ground-level ozone pollution, primarily in southern and central Ontario, has direct damaging effects on forest vegetation; the reduction of ozone high in the earth’s atmosphere has increased ultraviolet radiation reaching the earth, with potentially serious effects on some plant species. Each of these factors by themselves is a contributor to changes in Ontario’s forests. Climate change, resulting from increased atmospheric CO2 , is ex-pected to interact with the above factors to significantly alter the composition and function of forest ecosystems in Ontario (Schindler 1998).
There is growing concern that the increase in atmospheric CO2 (and other gases produced by human activity, such as methane and chlorofluorocarbons) will increase air temperatures as a result of the “ greenhouse effect” (Kuo et al. 1990). The trapping of heat by greenhouse gases that occurs naturally is beneficial as it main-tains warm temperatures over most of the globe at suitable levels for agriculture and forests. However, industrial pollution will result in an approximate doubling of atmospheric CO2 by the end of the next century. Examination of very long time scale 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 CO will trap an increasingly larger portion of the 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 warming seen over the last century is almost cer-tainly (i.e., with greater than 99% probabil-ity) the result of a real warming trend, and this warming is associated with an in-crease in atmospheric CO2 . Precipitation patterns are also likely to be altered in the event of climate warming, with some areas becoming wetter and others drier (Joyce etal. 1990). The frequency of extreme weather events is also expected to increase (Hengeveld 1995), with potential increases in the occurrence of severe drought, very high temperatures, ice storms, and rapidly fluctuating temperatures.
Forest management practices must change to keep pace with climatically induced changes in forest ecosystems. Models are required to predict these changes, since forests are complex ecosystems that often respond to climate in unexpected ways both structurally (i.e., the species and ages of plants and animals in the ecosystem) and functionally (i.e.,physiological and biogeochemical proc-esses).Even our understanding of the effects of the present climate on forest ecosystems is incomplete and climate change effects cannot be predicted solely by interpolation from present day field conditions or from laboratory experiments. In the future, forest ecosystems will be affected by climate change in ways that have never been observed or for which data are unavailable, and predictions based on present forest conditions may not be relevant. Models are also useful because forest ecosystems are hierarchical (i.e.,effects controlling ecosystem structure andfunction can occur at scales ranging from regional to as small as an individual plant and soil microbial populations), and have many components that may be affected differently both in terms of the magnitude and direction of change. Even if one knew the separate effects of climate change on each component, their interactions would prevent assembling these effects into an adequate description of complex ecosystem effects. Thus, models are the best tool we have to predict the effects of climate change on forest ecosystems.
Increasing recognition of climate change has lead to an international agree-ment to reduce greenhouse gas emissions through the United Nations Framework Convention for Climate Change in 1992 and the Kyoto Protocol in December 1997. The role of forests in sequestering and storing carbon is established in this Convention and Protocol. Countries that ratify the Protocol will report on the area of man-aged forests, reforestation (renewal of harvested forests), afforestation (conver-sion of non-forested to forested land) and deforestation (loss of forest). Forests established between 1990 and 2012 may be counted as contributions towards Canada’s emission reduction target of 6%, as defined by the Kyoto Protocol.
Ontario needs to begin to formulate the role of forest ecosystems and forestry as part of a broader response to the inter-national commitment to address climate change. The sustainability, biodiversity, health, and economic benefits of forests may be affected to varying degrees by climate change. The long-lived nature of trees requires that we consider the effects of practices for periods of at least one rotation but preferably for several rotations (e.g., 200-300 years). It is the responsibility of the Ontario Ministry of Natural Resources (OMNR) as the steward of Crown forests to understand the potential effects of climate change on forests and begin to incorporate these effects into its planning. The OMNR’s mandate to sustain the health and integrity of natural re-sources will need to include policies and guidelines to manage for mitigation and adaptation to climate change. One of the first steps is to develop an understanding of the impacts of climate change on Ontario’s natural resources.
This discussion paper examines the multiple effects of climate change on Ontario's forest ecosystems. The co-authors of this report have prepared sections addressing the key issues and impacts in their respective disciplines. Some possible actions to mitigate adverse effects of climate change are addressed in the section “ Forest Management Responses to Climate Change.“
Section 2.
Ontario' s Climate in the 21st Century
Mike D. Flannigan, Canadian Forest Service
While we tend to think of climate as being constant, in fact it is always chang-ing. Some changes follow patterns with extremely long time scales, such as the 21,000 year cycle of the precession of the earth’s axis about the pole. Weather, in comparison, is by definition variable, and is the short-term (hours to months) variation of the atmosphere. Climate is the weather at some location averaged over a specified time period (typically 30 years) plus information on the variability and weather extremes. Climate, and its associated weather, influence the natural envi-ronment directly, through elements such as temperature and precipitation, and indirectly, through its influence on distur-bance and permafrost. Any change in variability in climate could be critical because many of the ecological impacts of climate are the result of extremes. At the local scale, climate is influenced by variations in solar radiation due to latitude, distribution of continents and oceans, atmospheric pressure and wind systems,atmospheric pressure and wind systems, proximity to water bodies, and local fea-tures, such as exposure, local topography, and urbanization (see Trewartha and Horn 1980).
The “ greenhouse effect” is the influ-ence of gases such as carbon dioxide, water vapour and methane on the earth’s radiation budget. The greenhouse gases in our atmosphere allow the shorter wave-length radiation (incoming solar) to reach the earth’s surface while absorbing the longer wavelengths (outgoing terrestrial),which, in part, is re-radiated back to the earth. Human activities have increased carbon dioxide, methane and other natural greenhouse gases, in the atmosphere, as well as added human-made gases such as chlorofluorocarbons (CFCs) and hydroflurocarbons (HFCs). Increases in greenhouse gas concentrations are respon-sible for enhancing the natural greenhouse effect. Global mean surface air tempera-ture has increased by 0.3° to 0.6° C since the late 19 th century (Intergovernmental Panel on Climate Change (IPCC) 1996).For Ontario, surface air temperatures have risen by 0.5° to 0.7° C since 1895 (Gullett and Skinner 1992). The IPCC (1996) states that “ the balance of evidence suggests a discernible human influence on global climate” and that the climate is expected to continue to change in the future. Incontro-vertible attribution of the long-term cause of current climate change is difficult due to the natural short-term variability in the earth’s climate. Future predictions are difficult because of the complex interac-tions in the climate system.
General Circulation Models (GCMs), sophisticated computer models, are the primary tool used to estimate what the future climate will be. Numerous GCMs are used (Lau et al. 1996), including Canadian GCM (Boer et al. 1992, McFarlane et al. 1992). Most GCMs have outputs for 1xCO2 and 2xCO2 scenarios, which roughly correspond to atmospheric CO conditions in the mid-20 th century and the second half of the 21 st century, respectively. GCMs suggest that the aver-age global surface air temperature will increase by 1 to 3.5° C by 2100 (IPCC 1996). However, more pronounced changes should occur at high latitudes and be greatest in winter. The spatial resolution of these models is often around 400 km. Regional Climate Models are now being developed to provide climate estimates at finer spatial resolution (~40km). These will be more suitable for pre-dicting regional effects of climate change in Ontario (Caya et al. 1995).
The present climate of Ontario is best described as continental, with cold winters and warm to cool summers. The climate around the Great Lakes tends to be warmer and wetter in winter because of the heat and moisture available from the large bodies of water. Conditions range from warm and moist in the south to cold and dry in the northwest (Table 2.1). A more detailed discussion of the recent climate of Ontario can be found in Hare and Thomas (1974).
Projected global warming of 1 to 3.5°C over the next century means that the cli-mate would warm at a rate faster than atany time in the past. These increased temperatures could make the next century the warmest so far during this interglacial period. Ontario is a large and diverse geographical region with great variation in climate. Figure 2.1 shows the predicted ncrease in surface air temperature during the 1 May - 31 August period derived from the Canadian GCM, comparing a doubled (i.e., 2xCO2 ) to present (i.e., 1xCO2 ) CO2 concentration. According to this scenerio, temperature increases of 3°C to over 5°C are expected across Ontario. The largest increases are expected over southwestern sections of northwestern Ontario, while the smallest increases are anticipated over the extreme northwestern region of Ontario along Hudson’s Bay. If these predictions are realized, the summer temperature regime in Sudbury at the end of the next century would be similar to the current summer temperature regime in Windsor (Table 2.1).
Figure 2.2 shows the predicted effect of a doubled CO2 environment on summer precipitation across Ontario, according to the Canadian GCM. Values over 1.0 indicate increases in precipitation whereas values less than 1.0 indicate decreases in precipitation for the end of the next century. Precipitation ratios range from just under 1.0 for much of northwestern Ontario and most of southern Ontario to over 1.2 for northeastern Ontario. There is increased potential for water stress over regions with decreased precipitation in. conjunction with increased temperatures. Precipitation has been increasing since 1910 over the continental United States and most of this increase is due to increased frequency of extremely heavy precipitation events (Karl and Knight 1998). An increase in the number and severity of extremeweather events also is predicted to resultfrom climate change.
The impacts of climate change have broad and far reaching implications for Ontario’s forests, ranging from distur-bances (insects, disease, fire and wind) and biotic responses (physiology, genetics and plant succession) to how we manage our forests within this new environment (Weber and Flannigan 1997). The continued development of regional circulation models with shorter time intervals will be important to predict and respond to the impacts of climatechange on Ontario’s forests.
Table 2.1. Selected climate data for selected sites across Ontario from 1961-90 (Environment Canada 1993).
| Station | Latitude (N) | Longitude(W) | Mean annual temp.(C) | Mean annual prec.(mm) | Mean January temp. (C) | MeanJuly temp.(C) | Growingdegree day(base 5C) |
|---|---|---|---|---|---|---|---|
| Windsor | 42 | 83 | 9.1 | 902 | -5.0 | 22.4 | 2544 |
| Sudbury | 47 | 81 | 3.5 | 872 | -13.5 | 19.1 | 1680 |
| Big Trout Lake | 54 | 90 | -2.8 | 598 | -23.9 | 16.2 | 1075 |
Section 3.
Forest Hydrology in to Global Change
Chris Papadopol, Ontario Forest Research Institute, Ministry of Natural Resources
Water availability to forest plants varies with precipitation, evaporative demand and the capacity of the soil to store water. Climate warming may modify water availability by changing precipitation and evaporative demand. The soil water bal-ance of forested sites is important because water availability strongly affects forest productivity; numerous studies show that drier than normal seasons reduce tree ring size.
Forest ecosystems can also modify the local hydrology and environment. Forests affect the environment locally and season-ally through albedo (i.e., reflectivity of sunlight), roughness (i.e., evenness of the canopy) and transpiration. Under favourable conditions, forests also have the potential to mitigate some of the local effects of climate change expected in the next century, for example by acting as CO2 sinks (i.e., enhancing biomass and litter production) (see Section 11).
Climate warming will accelerate the circulation of moisture in the global water cycle (Bolin 1986). Since regional precipitation depends on major air circulation patterns, climate change may either increase or decrease the amount of precipitation in a given area (see Section 2, Figure 2.2). An-ticipated increases in summer temperatures will increase evapotranspiration from forests. The increased Atmospheric Demandfor Evaporation, ADE, is an importantway that climate warming may influencevegetation. Where soil water storage ispoor (e.g., coarse textured and thin soils), an increase in ADE may reduce soil water availability, and through this, gradually change the productivity and survival of forest plants.
Models of forest water balance can provide estimates of soil water availability on sites where soil texture and forest plant species are known. It may be possible to use such models to develop regional estimates of forest water use where the spatial distribution of soil texture and plant species are.known. To show the influence of warming on ADE, the Thornthwaite model for evapotranspiration, ETp (Thornthwaite 1946), was run for three scenarios: (i) nothermal increase, recorded mean air tem-perature (ETpO), (ii) recorded mean air temperature + 2oC (Etp2), and (iii) recorded mean air temperature + 4oC (Etp4), using historic daily data from Blind River, On-tario, and soil hydraulic conductivity for a typical stand in the Kirkwood forest, near Thessalon, Ontario. A water balance model was then run to simulate water availability in past growing seasons.
Warming increases evapotranspiration with every degree Celsius in temperature causing an additional 0.15 mm/day or 4.5 mm/month ADE (Figure 3.1). This increase should be interpreted in the context of the range of daily ADE, which during the growing season in Ontario, roughly varies between 6 and 2 mm/day from south to north. This increase in evapotranspirationwill reduce soil moisture and, in my opin-ion, may limit the distribution of some species and reduce the productivity of others. 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 of Ontario.
An example of the possible site effects of increased evapotranspiration is given in Figure 3.2, for a forest stand located in the Kirkwood forest. The soil on this site has an unavailable water content (i.e., held with a tension greater than -1.5 Mpa) of between 25 and 50 mm of water up to 1.0 m soil depth (based on a column of soil). Soil water balances were reconstructed from weather data from Blind River for 1970, a year with abundant precipitation.
Soil drainage has a great influence on the available moisture (Figure 3.2). For every 10 mm of rain, more than 50% infil-trates the soil, the rest is lost to runoff and evaporation. As the amount of rain per rainfall increases, the proportion of infil-tration increases. Therefore, although the soil is supplied abundantly with water, itdoes not have the capacity to retain this water and supply it steadily to trees. In fact, after an abundant rain, water is easily available for only two to three days. In Ontario’s forests, except for the clay belt, available water varies, approximately, between the limits indicated by Figure 3.2. However, in large areas in northwestern Ontario, where soils are shallow and stony, they are also more prone to water deficit. The expected increase in annual variability of rains (Bolin et al. 1986), may result in more frequent and longer occurrences of soil water stress.
Soil hydraulic conductivity (the rate of water movement in a soil), which signifi-cantlyaffects soil water regime, dependsgreatly on soil texture — the coarser the soil, the greater the conductivity. While organic matter significantly improves soil water retention by reducing hydraulic conductivity, unfortunately, the organic layer of most soils in Ontario (with the
exception of peatlands) is thin. Site disturbances, especially hot ground fires and some mechanical site preparationtechniques, can greatly reduce the thick-ness of the soil organic layer, leading to increased soil water deficits. Sites with coarse-textured soils overlain by thin organic layers are most susceptible to problems with water availability. Organic matter can be enhanced silviculturally by promoting hardwoods.
The forest species that grow in On-tario, and whose distribution and produc-tivity is going to be affected by climate warming include the commercial species black 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, these species are productive because rains are frequent or humidity is high, which either re-supplies the soil with moisture at short intervals or results in low ADE, respec-tively. In a progressively warmer scenario, with increased evapotranspiration but similar soil water holding capacity, these species are likely to suffer moisture stress more frequently and for longer periods.The expected increase in climatic variability may make the situation worse, because large rainfalls, likely to occur under this scenario, do not greatly improve the water regime due to the large amount of precipitation lost to infiltration. These stands will first be affected in terms of reduced pro-ductivity, and then, in the event of a pro-longed drought with high ADE, mortality may occur. Reduced stocking through thinning is a potential means of redistributing soil moisture to prolong the productive life of such stands. In contrast with shallow rooted species, deep rooted ones have the advantage of being able to absorb water from greater soil depths. Deeply rooted species are expected to be better adapted to the increased ADE and soil moisture deficits that may occur in some areas of Ontario.
Across Ontario, the influence of climate warming on the soil water balance will be affected by (i) air circulation pat-terns, (ii) regional soil characteristics, and (iii) inherent natural variability. On typical forest sites in the next century, in my opinion 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 stress should be controllable through thinning. In the clay belt, water availability is ex-pectedto remain high (Section 2). On some low-lying peatland sites in north-eastern Ontario, where water tables are already high and drainage impeded, the forecasted 10 to 20% projected increases in precipitation (Section 2, Figure 2.2) may raise the water table enough to cause flooding 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 shallow over shield or till deposits vegetation is expected to experience high levels of soil moisture stress as a result of climate change. This area is already prone to forest fires, which are predicted to in-crease under a warming scenario (Section 6). The establishment of mixed conifer-hardwood forests should be encouraged to promote the buildup of forest litter andhumus, which will improve soil moisture retention.
Section 4.
Insects and Climate Change
Taylor Scarr, Forest Management Branch, Ministry of Natural Resources
Insect outbreaks have substantial effects on Ontario’s forests. Outbreaks such as spruce budworm and gypsy moth often occur over large areas and can cause widespread tree mortality (Hardy et al. 1986). Together with fire they are the major disturbance influencing the succes-sional patterns in both the Boreal and Great Lakes–St. Lawrence forests (Fleming and Candau 1997). They further affect the nutrient and biogeochemical cycles of forests through the conversion of tree biomass to other trophic levels of the ecosystem.
If the predicted changes in climate occur, resulting in increases in mean annual temperature and more extreme weather, there will be direct effects on insect population dynamics, which in turn will affect forest stand structure, composi-tion, and function. The greatest effect of the predicted climate change is likely to be on the insect disturbance regime; that is, the frequency, duration, and severity of population outbreaks (Fleming 1996). Because fire regimes are often intricately insect outbreak patterns will cause changes in the fire regimes, which to-gether will affect the composition of the forests of Ontario (Fleming and Candau 1997).
The challenge caused by climate change for forest managers is that it will be very difficult to predict which tree species will form the future forest in a region, and which insect species will become the major disturbance forces inthat new forest (Sandberg 1992). Each tree and insect species must be considered individually in terms of its response to climate change (Logan et al. 1995), yet each will influence the other. The uncertainty over future forest condition makes it difficult to project sustainable timber supplies and to determine how to mitigate the effects of climate change to maintain a healthy forest that can meet society’s de-mands (Fleming and Volney 1995).
Tree species will respond differently to climate change (changes in the average and extremes in temperature, precipitation, weather events, CO2 concentration, fire, insect outbreaks, disease). In the southern part of current ranges, tree regeneration rates are expected to decrease while senescence rates are likely to increase (Fleming 1996). Local extinction may result if anout break of an insect occurs that attacks older trees, driving the tree population below the threshold at which it can sustain itself. For northerly sites, tree regeneration rates should increase, while senescence rates should decrease. The result, again, is destabilization of the ecosystem. As described by Fleming (1996), "chance, histori-cal factors, and threshold effects" will significantly affect the condition of the forest ecosystem as this destabilization occurs.
Climate change is expected to have several effects on insect-tree interactions:
- insects that are currently pests may no longer remain so depending on their response, as well that of their host trees, to climate change (Hedden 1988);
- tree growth rates may increase underwarmer temperature conditions, but poikilothermic insects may respond more efficiently, giving them a competitiveadvantage (Fleming and Tachell 1995);
- tree growing seasons may be extended, but insect species may increase their number of populations per year;
- some insect species may become pests if the new temperature or moisture re-gimes are outside the optimum range for their parasites, predators, or pathogens, allowing the host species to escape these natural controls;
- some insect species will be adversely affected by effects of climate change on diapause requirements;
- some insect pheromones may be less stable at higher temperatures, reducing the species' reproductive potential and competitiveness (Hedden 1988);
- the increased CO2 concentration may enable trees to produce more carbon-basedantifeedants, increasing the resist-ance of some tree species to some insects;
- increased CO2 concentration may in-creasethe carbon to nitrogen ratio in tree foliage, resulting in increased feeding by defoliators to obtain sufficient nitrogen;
- increased drought could increase sucroseconcentration in foliage, favouring in-sects;
- increased drought can lead to earlier leaf stomatal closure, increasing temperature and decreasing relative humidity of the leaf outer microclimate, resulting inincreased insect growth rates, decreased mortality, increased fecundity, and de-creasedeffects of pathogens (Fleming 1996).
These effects of climate change are not mutually exclusive, and will be influenced by effects of climate change on trees and their competitiveness with other trees and plants, other disturbance regimes such as fire and extreme weather, the speed at which climate change occurs, and chance. The result of these effects and the destabilized ecosystem will be individual-istic movement of parts of the system in response to climate change. For forest managers, this inherent uncertainty pro-vides only generalizations (Hedden 1988):
- shortening stand rotations to reduce the period of vulnerability and increase vigour;
- aggressive tree breeding to increase resistance to insect pests or to speed adaptation to the emerging climate (see Section 8);
- controlling competing vegetation (e.g., via thinning, weed control) to reduce stress to regenerating trees and help produce desired species composition inthe future forest (see Section 9);
- sanitation cutting to encourage healthy stands;
- minimizing adverse disturbances during harvesting to reduce stress;
- using insecticides to control damaging insects and reduce timber volume losses.
Section 5.
The Impact of Climate Change on Fungi in the Forest Ecosystem
Sylvia Greifenhagen, Ontario Forest Research Institute, Ministry of Natural Resources
Of the many predicted effects of global warming, a rapid increase in aver-age temperatures (1 to 3.5°C over the next century), combined with increased drought periods and increased frequency of catastrophic weather events, will have the most significant impact on fungal communities in Ontario’s forest ecosys-tems.Soil microbes, of which fungi are a major component, are the drivers behind many of the processes occurring below the forest floor. Ecosystems are regulated by the rates at which soil processes occur. These below ground systems will be criti-cal determinants of ecosystem response to climate change (O’Neill 1994). The func-tional biodiversity of an ecosystem, espe-cially of below-ground organisms, plays an important role in regulating the impacts of disease by causing disruptions in eco-logical continuums, thereby limiting dis-ease outbreaks. Climate-caused changes in functional groups may substantially affect this regulatory role. The effects of global warming on tree diseases and the entire soil microbial population, including mycorrhizae, will vary with fungal species, the biotic forest community, the abiotic environment, and interactions and associa-tions between these components.
Forest Tree Diseases. Over 20 million cubic metres of timber are annually de-pleted
by diseases in Ontario’s forests (Gross et al. 1992). Increases in incidence
and severity of diseases because of global warming will substantially affect
the timber resource. Many of the most impor-tant diseases in Ontario’s
forests, such as root diseases, stem decays, and declines, require a stressed
host before infection or disease expression occurs. When a tree is stressed,
less energy is available to sustain
the physiological processes critical to disease resistance, as more energy is
allocated to life-sustaining processes (Wargo and Harrington 1991). Diseases
respond to stress in plants in various ways such as increased incidence or severity.
When stressed, a normally resistant tree species may become suscep-tible to
a certain disease, broadening the host range of the pathogen. Stress caused
by an increase in the number and severity of catastrophic weather events, especially
drought, may increase disease susceptibil-ity, especially where plants are not
physi-ologically adapted to a site or are near the limits of their range (McDonald
et al. 1987). For example:
- above average temperatures, possibly associated with soil drying and fine root death, have played an important role in sugar maple decline (Cannell et al. 1989);
- in one study, a 2°C increase in soil tem-perature above the optimal temperature for growth of white birch (i.e., 18.5°C) caused substantial fine root death (Redmond 1955);
- red spruce dieback may be associated with summer drought and a general increase in temperature since the 1800’s;
- parasitism by Armillaria root disease increases during periods of drought, while wet periods favour its saprophytic (i.e., living on dead organic matter) role (Nechleba 1927);
- certain Armillaria species primarily attack conifers, but will attack hardwoods weakened by ice damage to the crowns (Dance and Lynn 1963).
Drought-induced stress will be most severe on the shallow soils of the boreal forests of northwestern Ontario, and inci-dence and severity of Armillaria ostoyae, the most common root decay fungus in the boreal 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 eastern and northeastern Ontario.
Soil Microbes. Soil contains the largest terrestrial pool of organic carbon (Batjes 1996). Changes in the abundance and diversity of soil microbial communities and functional groups as a result of climate change may have far-reaching impacts on many ecosystem processes. For example, soil microbes, including fungi, are respon-sible for carbon and nutrient cycling and formation of soil structure in forest ecosystems.Climate change may affect the rates of decomposition or organic residues in soil, which will influence the availability of nutrients required for plant growth. Be-cause of the intricate relationships that exist between above-ground plants and soil biota, changes to any one component can have far-reaching effects throughout the ecosystem.
Although the effects of climate change on soil microbes will vary substantially with site and microbial species, in general, drought and fire reduce soil microbial diversity, at least in the short term. Re-duced diversity may have adverse effects on forests, because a highly diverse mycoflora could be important to the ability of plants to adjust to climate change (O’Neill 1994). Increased atmospheric CO2 levels may also significantly affect soil microbial processes. Concentrations of nitrogen and other nutrients in plants may decrease as atmospheric CO2 levels in-crease, resulting in a gradual decrease in degradability of plant residues by microbes (Couteaux et al. 1995) and an accumulation of nutrient-poor organic matter (Lekkerkerk et al. 1990). Mycorrhizae are a highly specialized group of soil fungi that form symbiotic asso-ciations with plant roots, enhancing plant nutrition, water uptake, growth, and stress resistance (Molina et al. 1992). As with soil microbes generally, mycorrhizal associations are 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 of plant-microbial-environment interactions make the prediction of climate change effects extremely difficult! However, under the assumed 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 by up to one third its present rate if annual temperatures rise by 3°C (Cannell et al. 1989, Schimmel 1995). Marginal soils should become more productive, at least in the short term, where drought is not a limiting factor;
- long-term, repeated drought will cause fluctuations in the microfungal biomass, reducing the availability of nutrients and thereby limiting plant growth (Lodge et al. 1994). Drought effects may be mitigated by mycorrhizae, which enhance stress resist-ance and nutrient uptake in trees (Miller and Lodge 1997);
- the migration of many pioneering tree species will depend on the successful migra-tion of their host-specific mycorrhizae (Meyer et al. 1982);
- the productivity of boreal forests in the clay belt of northeastern Ontario, where water availability should remain adequate (see Section 2), could benefit from an increase in the rate of litter decomposition caused by increased temperatures.
Interactions between climate and biotic systems are extremely complex (Ojima et al. 1991) and understanding the potential impacts of climate change on fungi in forest ecosystems is a great chal-lenge. Information is needed on how specific fungi and fungal communities interact with each other, with the forest ecosystem in general, and with the chang-ing global environment. Stress-host-pathogen relationships and interactions need to be identified (Wargo and Harrington 1991). A better understandingof microbial processes, microbial diversity, and variations with site, forest composi-tion, temperature, and moisture in On-tario’s forest soils will provide information needed to predict microbial responses to altered environmental conditions. Moreinformation is needed on the ecological specificity 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 to develop sound forest management prac-tices for a period of rapid global change.
Section 6.
The Impact of Climate on Forest Forest Fires and Forest Fire Management in Ontario
Robert S. McAlpine, Aviation, Flood and Fire Management Branch, Ministry of Natural Resources
There is strong consensus that climate change will increase fire activity in Ontario (Simard 1997). This increase in fire activity can be attributed to three of the implications of global climate change: (i) increased fre-quency and severity of drought years; (ii) increased climatic variability and incidenceof extreme climatic events, and (iii) increased spring and fall temperatures.
The most influential implication of climate change for forest fire management is the predicted increased frequency and sever-ity of drought years. Clearly, during years of much 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 severity rating (Williams 1959, Van Wagner 1970, 1987)—an integration of weather factors (temperature, relative humidity, wind speed and precipitation) over periods of various lengths (daily, monthly, seasonal, etc.). Fire weather severity is an objective yardstick for comparing weather (and hence the risk of forest fires) from site to site and from year to year (Van Wagner 1970). Flannigan and Van Wagner (1991) estimated that climate change would produce a 40% increase in fire weather severity in Canada, resulting in a similar increase in area burned. Stocks et al. (1998) extended this with results from re-fined climate change models to predict altered patterns of fire weather severity in Canada.
Figure 6.1 uses methods similar to thoseof Stocks et al. (1998) to show the impact of a doubling of atmospheric CO2 on the seasonal fire weather severity in Ontario. The figure shows a general increase in severity across the province, with some larger changes in the extreme west (Kenora area) and south-east (Ottawa area) of the province. The most pronounced changes will occur during June and July and to a slightly lesser extent, May(Figure 6.2). While August and September also show a predicted increase in fire weather severity, it is not as conspicuous. The area near Quetico Park (south west of Thunder Bay) changes very little in any month. In contrast, the fire weather severity around Sudbury and for much of Southern Ontario is expected to increase to near prai-rie- like conditions (see Figure in Stocks et al. 1998 for comparison).
A second major element of climate change that will affect fire management is increased variability of the climate and increased incidence of extreme climatic events. Fire “flaps” result from a short-term increase in fire danger caused by two or more weeks without appreciable rain coupled with an ignition source (Canadian Forestry Service 1987). This kind of climatic event could easily be offset by episodic cooler moist weather and would therefore not appear in the monthly fire weather severity plots of Figures 6.1 and 6.2. With increased climatic variability, the incidence of these short term peaks in fire danger will become more prevalent. In addition, Fosberg et al. (1990) and Price and Rind (1994) pre-dict that climate change will be accompanied by increases in lightning activity, the cause of 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 fire weather. With increases in these extreme events along with an increase in lightning activity, an increase in area burned can be expected.
A third element affecting forest fire activity is the predicted increase in spring and fall temperatures, which extends both the growing and forest fire seasons. Wotton and Flannigan (1993) estimate that climate change will extend fire season length in Ontario by 25 days (a 16% increase). Figure 6.2 shows a slight increase in fire weather severity in September, however the monthly resolution of this map is too long to show the predicted increase in fire season length. In ddition, data for the month of April were unavailable. April may show a larger in-crease in fire weather severity than Septem-ber, as the trend from Figure 6.1 shows larger changes in fire weather severity early in the season.
The increases in drought years, extreme climatic events, and fire season length indi-cate that climate change will result in longer fire seasons, with greater fire load and greater incidence of extreme fire load years. Trends since 1985 indicate increased forest fire activity in Ontario. Whether this is the result of climate change, increased weather variability, or some other factor is difficult to assess. In any case, if the current protection levels are to be maintained, and a increases in area burned minimized, the changes in the environment brought on by climate change will necessitate increases in fire management expenditures. How to best minimize the total fire management investment and provide an acceptable level of fire protection will be the challenge of the next few years.
Forest fires are a natural part of the global carbon cycle. Increased fire activity will release more CO2 into the atmosphere, adding to the greenhouse effect. Table 6.1 shows carbon emissions from forest fires in Ontario based on estimates of fuel volume and carbon emission factors published by Stocks (1990, 1998, pers. comm.).
Values in Table 6.1 are presented by fire management zone. The intensive zone corre-sponds to those areas of central and Northern Ontario containing major population centers, recreational areas, and forest industry. Fires in the intensive zone are aggressively de-tected and suppressed (note the smaller average fire size). The measured zone encom-passes a broad east-west band north of the intensive 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, the fire is assessed to determine if suppression action will continue as aggressive, moder-ate, or minimal. The extensive zone repre-sents the far north of Ontario where most fires are allowed to burn unsuppressed unless specific resources are at risk. Esti-mates of carbon emissions from prescribed fire, largely from burning of logging debris, are also provided in Table 6.1.
The combined CO2 emissions from wildfire and prescribed fire is in excess of 3.5 Terragrams (Tg) of CO2 (3.5 million tonnes). This constitutes about 2% of On-tario’s total CO2 emissions. Increases in the level of protection in the measured or exten-sive zones of Ontario (the primary CO2 production zone on a per fire basis) would reduce these emissions. To demonstrate, ifthe entire area of the measured and exten-sive zones were converted to intensive protection, the average forest fire size in these zones would perhaps be reduced to that of the current intensive zone. This would reduce carbon emission by 2.38 Tg CO2 . However, this quantity of sequestered carbon cannot be protected ad infinitum. The carbon will be eliminated from the site either 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 reduce carbon emissions from wildland fires would change the fire return interval of a large part of Ontario’s wilderness. The ecological ramifications and economic costsof this change in fire return interval must be carefully considered.
Table 6.1. Annual average greenhouse gas emissions from Ontario wildland forest fires and prescribed burning from 1989 to 1996.
| Fire management zone CO2 source | Annual area burned (ha) | Average fire size (ha) | Average no. fires annually | CO2 emission (tonnes) | CO2 emissions (tonnes) | Aerosol emissions (tonnes) | Percent of total emissions |
|---|---|---|---|---|---|---|---|
| Intensive | 46,366 | 36 | 1,279 | 515,820 | 52,162 | 5,274 | 15 |
| Measured | 34,071 | 187 | 183 | 379,037 | 38,330 | 3,876 | 11 |
| Extensive | 211,348 | 1658 | 128 | 2,351,248 | 237,767 | 24,041 | 67 |
| Prescribed fire (slash piles)e | not applicable | 36,000 kg 1 | 17,000 piles | 272,340 | 12,255 | 2,785 | 8 |
| Total | 291,785 | 1,881 | 1,589 | 3,518,445 | 340,514 | 35,976 | 100 |
Section 7.
Plant Physiological Respones to a changing Environment
Stephen J. Colombo, Ontario Forest Research Institute, Ministry of Natural Resources
The physiological function of com-mercial tree species is the basis for their productivity and the wood-based eco-nomic benefits derived from Ontario’s forests. In addition, the diversity of forest plants depends on physiological attributes that allow different species to survive and thrive despite environmental stresses. If climate change alters the occurrence of plant physiological stress then the com-mercial benefits derived from forests and the biological diversity of forest ecosystems in Ontario will also be changed(Joyce et al. 1990).
Plant physiology is one means by which environment is translated into effects on forest ecosystems, at first by action on the physiology of an individual plant, and as a consequence on plant populations and communities. Forest vegetation is directly affected by temperature, the concentration of CO2 in the air, mineral nutrition, and water supply, all of which are expected to change in Ontario in coming decades (Walker and Steffen 1997).In addition to such direct effects, climate also affects forest plant communities indirectly through plant-to-plant competition for site resources (e.g., water, light, nutrients). An understanding of the direct and indirect effects of climate change on plant physiology is needed to predict climatically induced changes in forest productivity, forest health, and biodiversity.
Table 7.1 summarizes some of the effects of increased atmospheric CO2 , temperature, and moisture stress due to more frequent and prolonged droughts on plant physiological processes and growth. Rates of photosynthesis are increased by higher concentrations of CO2 and warmer temperatures (Battaglia et al. 1996); however, the magnitude of such increases is proportional to growth rate (Tissue et al. 1996) and nutrient supply (Drake et al. 1997). Stomatal conductance (which is related to the rate of water loss from leaves by transpira-tion) is reduced by increased CO2 and as an aftermath of drought, but increased by warmer temperatures. Water use efficiency (the ratio between the rate of photosynthesis and the loss of water through transpiration) increases with elevated CO2 and drought, but decreases if conditions are warm and very humid. Phenology (the timing of bud burst, flowering, and other growth processes) is increased by warmer temperatures but delayed by drought and elevated atmospheric CO2 (Murray et al. 1994). Warmer temperatures in the spring lead to earlier bud burst, which potentially exposes new growing shoots to freezing damage (Colombo 1998). Warmer temperatures in the fall may delay frost hardening and warmer winters could reduce the amount of chilling plants receive; insufficient chilling may not completely over-come dormancy of some species in southwestern Ontario, which would delay bud burst resulting in a shortened growing season. Drought, in comparison, can shorten the growing season by causing plants to cease growth earlier in the summer. While each climate change factor has an independent effect on plant physiology, in many cases there are potential interactions that produce complicated effects and modified plant responses. In general, more information on such interactions will allow us to better predict the effects of climate change on plant physiology.
Our understanding of plant responses to the environment is largely based on short-term experiments conducted in controlled environments, in which only one or two factors were varied, and small or young plants were used. While this is a logical first step in attempting to understand responses to climate change, caution is required when extrapolating plant-scale results to ecosystems, because of the over-simplification these experiments entail. Scaling effects frequently alter the way finer scale events (e.g., leaf or plant level responses over short time spans) translate into larger scale results (e.g., stand or community function and structure over long time spans) (Körner 1993). Direct observations of plant behaviour and inter-actions in forest plant communities are required to link physiological processes to long-term reactions of forest ecosystems.
Information obtained from studies of physiological behaviour in a plant community is required to develop management options to mitigate the negative effects of climate change. There is probably more value in controlled environment studies that are planned based on observations of plant behaviour in a community; in this top-down approach it is possible to target a particular species and to dis-aggregate the effects seen at higher levels of organization in terms of species interactions and primary physiological processes.
All areas of Ontario will experience a doubling of atmospheric CO2 in the latter half of the next century and this is expected to increase temperatures, with the greatest temperature increase predicted in northwestern Ontario (see Section 2). Precipitation in Ontario is expected to decrease in the northwest and south and increase in the northeast (Section 2). The warmer and drier conditions expected in northwestern and southern Ontario will favour species that are more tolerant of periodic drought (Schindler 1998). Based on their physiology, more frequent and severe drought will affect the growth of the following tree species in northwestern Ontario increasingly in the order: jack pine (least negatively affected), white spruce, aspen, and black spruce (most negatively affected).
Relative physiological responses of competing forest plant species to climate change can be as important as absolute species responses. “Response hierarchies” based on plant physiological responses to increased CO2 , have been developed by Körner (1993). In general, increased CO2 will favour evergreen species less than deciduous woody species, which will in turn be less favoured than perennial species (e.g., fireweed, raspberry, and grasses). Annual herbaceous species will be most favoured by increased CO2 . Elevated CO2 will favour seedlings more than young trees and young trees more than old trees. Late successional species (e.g., maple, yellow birch, white spruce, white pine) will be less favoured than early successional species (e.g., aspen, poplar, oak, jack pine, black spruce). Species with small or infrequent seed and fruit crops (e.g., black spruce, aspen) will be less favoured than species with large frequent seed and fruit crops (e.g., oak, white pine). Nitrogen-fixing species will be more responsive to elevated CO2 than non-nitrogen-fixing species, and mycorrhizal species more so than non-mycorrhizal species. In terms of forest sites, elevated CO2 levels will favour plants growing on non-nutrient deficient and warm soils over those on nutrient deficient and cold soils. Similar response hierarchies are needed to understand the effects of increased temperature and drought on Ontario forest species.
The rise in winter temperatures across the province should help to expand the potential range of less frost hardy species from the Great Lakes-St. Lawrence forest region into what is now the southern boreal forest (Reed and Danseker 1992). In northwestern Ontario, where drought will be more common, drier conditions com-bined with warmer winter temperatures would favour the northern expansion of the ranges of red oak and red pine, while the range of sugar maple could also move north but be limited to moister sites. In northeastern Ontario, where warmer winter temperatures may be accompanied by increased summer precipitation, the southern range of the boreal forest and the northern range of the Great Lakes-St. Lawrence forest should move north. Within perhaps 100 to 200 years, increased winter temperatures in southern portions of northeastern and northwestern Ontario may create conditions favourable to oak-hickory forest species that are presently restricted to Minnesota, Wisconsin, and southern Michigan.
Table 7.1 . The effects of three aspects of climate change (increased atmospheric CO2 concentration, warmer temperature, and drought) on selected important plant physiological processes.
| Physiological process | Elevated CO2 | Warmer temperature/Longer frost-free season | Increased drought severity and frequency |
|---|---|---|---|
| Photosynthesis | Increased, with possible feedback reducations due to resource limitations, (e.g., nutrient supply) | Increased but with possible feedback reducations or resource limitions | Reduced during drought and for a period following drought relief |
| Photorespiration | Decreased (usually) | Increased | Increased |
| Dark respiration | Slightly decreased | Increased | Increased |
| Stomatal conductance | Reduced | Increased at temperature up to 30-35 C | Reduced |
| Light use efficiency | Increased | No Change | Decreased |
| Water use efficiency | Increased | Reduced at warmer temperatures (if vapour pressure deficit unchanged) | Increased |
| Nutrient use efficiency | Increased | No effect | May be increased |
| Phenology | Shortened growing season due to delayed bud burst in the spring and earlier bud set in the fall |
|
Earlier cessation of shoot elonhation |
| Carbon partitioning/plant structure |
|
|
|
| Susceptibility to stress | Increased drought tolerance due to stomatal closure | Potentially increased damage from spring and winter freezing | Increased susceptibility to other stresses (e.g., acis precipitation, ozone) and insects and disease |
Section 8.
Genetic Implications of Climate Change
Marilyn L. Cherry, Ontario Forest Research Institute, Ministry of Natural Resources
The genetic makeup of plant and animal species in Ontario will be affected by the consequences of climate change, including increased temperatures and CO2 levels, changes in moisture patterns, higher occurrence of extreme weather events and forest fires, changes in growing season length, and changes in insect and disease occurrences, due to the selection pressure exerted by these effects. It is generally believed (e.g., Peters 1990) that species which are presently widespread will experience drastic shifts in range boundaries and undergo certain losses of genetic variation and some population extirpation, while smaller, localized species may undergo severe reductions in size or possibly extinction. Effects of climate change are not expected to be smooth and gradual; instead, they will involve thresh-olds to limits of tolerance (Vitousek 1994). Predictions as dire as a 37% decrease in the extent of the boreal forest with a 3°C global temperature increase have been made (Peters 1990). However, as the extent and distribution of genetic variability is poorly known for most forest species, it is difficult to predict how populations will change in relation to the uncertainties surrounding global warming.
General plant and animal responses to changes in the environment include phenotypic plasticity, migration, and evolutionary change (Stettler and Bradshaw 1994). Generalist species are those in which a typical genotype is able to flourish under a wide range of environ-mental conditions. Phenotypic plasticity, the ability to acclimate in response to environmental cues, is a trait of generalist species, and may itself differ between genotypes of a species. Phenotypic plasticity will allow for survival of individuals that may not be the most genetically fit in a particular environment (Eriksson et al. 1995).
Migration rates following climate change will differ for every species, de-pending on how efficiently they are able to disperse and whether migration corridors exist between favourable environments (Peters 1990). Species assemblages will dissociate due to differing rates of migra-tion, and new species combinations will form (Peters 1990; Stettler and Bradshaw 1994; Walker and Steffen 1997). Physical barriers to dispersal, such as the Great Lakes, will impede migration. Dispersal in some animal species will be affected by social requirements (such as territoriality and annual bird migration) (Harris et al. 1984). Migration in plant species will be affected by seed and pollen quantities, dispersal rates (Table 8.1), and whether conditions are favourable for fertilization, seed production, or vegetative propagation.
Evolutionary adaptation to new climate conditions can only occur where sufficient genetic variation exists to allow selective forces to discriminate between adaptive and maladaptive traits (Harris et al. 1984). Once an allele (one form of a given gene) is fixed (only that one form of the gene is present in a population) or lost, only mutation or immigration can restore genetic variability. Adaptation may occur more rapidly in species with shorter life cycles, as long as conditions are favourable for reproduction, than in longlived species such as trees which will undergo a time lag 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 constraints to adaptation and time lags in adapting, local populations are not always the fittest (Matyas 1994). Certain species unable to acclimate or adapt to changing climatic conditions may not be able to disperse rapidly enough to avoid extinc-tion without human intervention.
Species most susceptible to changes in climate are those that are localized, highly specialized, or poor dispersers (Peters and Lovejoy 1992). Populations most at risk are isolated or peripheral communities at the edge of a species’ range, and those that occupy montane, alpine, arctic, or coastal sites (Peters and Lovejoy 1992). Species considered most sensitive to past climate change showed evidence of latitudinal and elevational shifts in response to changing conditions (Nowak et al. 1994).
An increase in atmospheric CO2 will increase growth of some species at the expense of others (Peters 1990). Under conditions 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 expected along the southern edges of a species range and inland, away from the moderat-ing effects of large bodies of water, as a result of increasing temperatures and moisture stress (Peters 1990; Nowak et al. 1994). The latter is expected in northwest-ern Ontario, where drought is expected to become more frequent and severe (see Section 2). Population reductions will also occur if populations shift upwards in elevation; however, this is unlikely to have a major effect in Ontario. Plants subjected to high stress, such as those at the edge of a range, will be more susceptible to insects and pathogens (Ledig and Kitzmiller 1992), which have the advantage of being able to adapt to changing conditions more rapidly because of their much shorter life cycles.
Table 8.1. Relative range size and seed dispersal of some Ontario tree species.
| Species | Range size | Mode of reproduction | Seed dispersal |
|---|---|---|---|
| jack pine | large | seed | poor |
| red pine | small | seed | good |
| eastern white pine | medium | seed | medium |
| black spruce | large | seed, vegetative | medium |
| red spruce | large | seed, vegetative | medium |
| white spruce | large | seed, vegetative | good |
| balsam fir | large | seed | medium |
| sugar maple | medium | seed, vegetative | good |
| red maple | medium | seed, vegetative | good |
| red oak | medium | seed, vegetative | poor |
| trembling | large | seed, vegetative | very good |
With range reductions, population fragmentation will occur, and inbreeding,with its inherent loss of genetic variation,will increase as population size decreases.If selection due to climate change operates differentially on subdivided populations,then the variation between the subpopulations will increase, and discrete ecotypes may be formed (Harris et al.1984). The length of time that a population remains at reduced numbers will have a greater impact on reduction in genetic variability than the actual number of individuals in the isolated population (Harris et al. 1984). Whereas highly hetero-zygous individuals (those with different alleles in a given gene pair over many of the gene pairs) can generally tolerate a broader range of environmental condi-tions, perhaps due to the differing alleles being advantageous under differing conditions (Harris et al. 1984, Ledig and Kitzmiller 1992), favourable complexes ofgenes that have adapted together will be reduced with inbreeding.
The ability of a species to withstandinbreeding and selfing is important in isolated populations (Peters 1990). Populations with reduced reproductive potential or under low levels of selective pressure will carry deleterious, potentially harmful genes for a longer period; with a high reproductive rate and intense selec-tion, fewer adverse effects of inbreeding will occur (Harris et al. 1984). If dramatic climate change occurs over a short time span, selective pressures will be intense, and hence high reproductive rates will be advantageous in isolated populations. Populations in which inbreeding has occurred prior to fragmentation are ex-pected to carry fewer deleterious genes and will not be as adversely affected by subsequent inbreeding (Harris et al. 1984). Species that reproduce both by both sexual and asexual means will be less sensitive to climatic change (Brubaker 1986), whereas species that rely on asexual reproduction will be less likely to adapt (Table 8.1) (Harris et al. 1984).
Forest tree species generally have high levels of genetic variability and gene dis-persal rates (Brubaker 1986; Stettler and Bradshaw 1994). An exception is red pine which demonstrates low levels of genetic diversity, probably because populationswere severely reduced during the last glaciation. Trees also carry a high number of deleterious genes (Stettler and Bradshaw 1994). Due to their longevity, trees withstand a broad range of climatic variation per generation, and some species have demonstrated phenotypically plastic responses to environmental change.
The boreal forest of northern Ontario has lower levels of biodiversity, with fewer plant and animal species, than the decidu-ous forests of southern Ontario (Dudley et al. 1996). Rare, threatened, and endan-gered species are often found on nonforested sites (Harris et al. 1984), and may be especially dependent on habitat characteristics (Eriksson et al. 1995). Pre-dictions for the effects of climate change on forest habitat in Ontario are varied and sometimes conflicting. However, most models of tree migration predict a north-ward movement of coniferous species, particularly spruce, and a corresponding replacement by hardwood tree species such as maples and oaks (Joyce et al. 1990; Slocum 1995).
A climate change model based on provenance trial data (Matyas 1994) predicts a decline in the growth and competi-tive ability of jack pine at the southern limits of its distribution. Under controlled climate experiments, some generalist genotypes for growth traits were identified for seedlings of this species (Cantin et al. 1997). Carter (1996) predicts a decrease in growth due to warmer growing conditions in white ash, yellow birch, black cherry, balsam fir, tamarack, white spruce, jack pine, and eastern white pine, and in-creased growth in red maple and green ash. Other models predict a loss of balsam fir, eastern hemlock, and sugar maple from the Great Lakes region (Joyce et al. 1990).
It is undoubtedly premature to pre-scribe a northward transfer of species until the extent of climate-induced changes can be more accurately predicted. However, it would be wise to revisit old provenance tests to determine current limits to trans-ferability.
Better estimates of the amount and distri-bution of genetic variation within
species are needed before the guiding principles discussed above can be applied
to each species. Selection for pest resistance is also recommended, as pest
infestations are likely to worsen (see Section 4). Conserva-tion plans for rare,
threatened, and endan-gered species should be developed and implemented before
population levels of these species decrease irreversibly. Such plans should
include development of dynamic appraoches that will promote increases in genetic
variance and future adaptation, such as the multiple popula-tion breeding system
proposed by
Namkoong (1984). Genetic implications of global warming cannot be considered
alone; changes in gene frequencies will depend on many factors, some of which
are the intensity of selection pressures, responses of physiological processes,
and changes to forest succession, competition, and pest incidence.
Section 9.
Climate Change aqnd Forest Vegetation Dynamice in Ontario
William C. Parker, Ontario Forest Research Institute, Ministry of Natural Resources
Forest succession may be viewed as the recovery of forest ecosystems following any disturbance. Succession is dependent on the physiological, population, and community ecology of the resident flora and fauna, as well as site and disturbance characteristics (Bazzaz 1996). A distur-bance is a natural or anthropogenic event that destroys biomass and alters ecosystem structure and resource availability (Pickett et al. 1987, Attiwill 1994). Forest fires, insect outbreaks, windthrow, ice damage and harvesting are examples of distur-bances. The size, frequency, intensity and seasonality of disturbances influence successional pathways through effects on resource availability and sources of vegeta-tion (seed, seed bank, vegetative reproduc-tion, advance reproduction) available for the colonization of the new growing space (Oliver 1980, Petersen and Carson 1996).
The Boreal and Great Lakes-St. Law-rence (GLSL) Forest Regions of Ontario differ in their natural disturbance regimes. Boreal forest ecosystem dynamics are driven by disturbance such as wildfire and insects. Large, stand replacing crown fires at 70- to 100-year intervals were the pri-mary natural disturbance in the Boreal Forest Region of Ontario, and favoured the establishment of forests dominated by early successional, fire adapted jack pine, black spruce and poplar (Johnson 1992). Defoliating insects also play a major role in boreal forests. Spruce budworm outbreaks lasting 5 to 15 years occur at 40-year inter-vals, affect large areas and predispose nfested 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 of the GLSL Region, crown fires occur at comparatively longer intervals (ca. 150 to 250 yr.). Frequent (20 to 40 yr.), low inten-sity, surface fires reduce the numbers of fire-sensitive, shade tolerant species, in-crease understory light levels, and favour sub-climax forests dominated by white pine, red pine and red oak (Heinselman 1973, Whitney 1986). In more mesic habi-tats of the GLSL Forest Region, forests are dominated by late successional, tolerant hardwood species and eastern hemlock, as large scale disturbances by fire and cata-strophic windstorms (e.g., tornadoes) are rare, with a return interval >1200 years (Canham and Loucks 1984, Whitney 1986). Comparatively frequent, low intensity wind storms (thunderstorms and periodic high 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 m 2 ) hrough windthrow of single or small groups of trees. Smaller canopy gaps form after the death of single trees, with return intervals of 120 to 190 years (Dahir and Lorimer 1996). These small gaps favour advance reproduction of shade tolerant overstory species.
Climate change can be viewed as a progressive, anthropogenic disturbance with an unusually long time frame relative to natural disturbances. Altered tempera-ture and precipitation regimes and el-evated CO2 will have a direct impact on forest structure through their effectson the physiology and population ecology of plant species, as well as ecosystem processes such as decomposition, nutrient cycling, and plant interactions with other organisms (see Sections 4, 5 and 7). How-ever, the increased frequency of distur-bances due to fire, insects and extreme weather expected to accompany climate change will likely exert a stronger effect on forest vegetation than the effects of modi-fied climate alone, by increasing the rate at which an equilibrium between vegetation and climate is attained (Davis and Botkin 1985, 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, site quality, and relative change in the current climatic and disturbance regimes (Davis and Botkin 1985, Grime 1993).
Changes in temperature and precipitation associated with a doubling of at-mospheric CO2 could increase the forest area burned annually in Canada by almost 50% (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 and southern regions of the province (see Section 6). If the warmer climate results in higher incidence of insect outbreaks, the risk of fire could be further increased (Fleming 1996). In the boreal forest region, more frequent wildfires will increase the number of young, early successional ecosystems dominated by fire-adapted shade intolerant species (Grime 1993, Bazzaz 1996), while in northwest Ontario, boreal forests may be replaced by grasslands and aspen parklands (Hogg and Hurdle 1995).
A preview of the potential conse-quences of climate change in the Boreal Forest Region is illustrated in the Experi-mental Lakes Area in northwestern On-tario (Schindler 1998). The period 1970 to 1990 was abnormally warm and dry. Several, large lightning-ignited forest fires occurred, followed by revegetation of burned areas by fire-adapted jack pine and black spruce. Because of the hot, dry growing seasons that followed, mortality of conifer regeneration was high. Some of these areas burned a second time, result-ing in the replacement of conifers by trembling aspen and balsam poplar, while some sites remained barren of vegetation 17 years after the second fire. In the GLSL Forest Region, the pre-dicted 4 to 6 o C increase in growing season temperature 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 forest stands and initiate “growth decline”, mortality and the formation of canopy gaps (Millers et al. 1989, LeBlanc and Foster 1992, Reed and Desanker 1992). Overstory individuals suffering decline will be vulnerable to secondary attack by insects and diseases, further accelerating stand senescence. Lower quality sites will be affected first, as will species with nar-row ecological amplitude (e.g., red pine, hemlock) (Solomon 1986). Canopy gaps will initiate release of the understory, the species composition of which will depend on climate and past management effects on regeneration (Davis and Botkin 1985). Increased frequency of surface fires, re-lated in part to the higher fuel loading in declining stands, could slow the current successional displacement of fire-depend-ent white pine and red oak by fire-sensi-tive sugar maple and balsam fir.
Models predict dramatic changes in forest composition and cover in Ontario based on changes in temperature and precipitation (Solomon 1986, Pastor and Post 1988, Sargent 1988, Solomon and Bartlein 1992, Lenihan and Neilson 1993, Mackey and Sims 1993). These models predict the Boreal Forest Region will move northward, displaced by the northward expansion of temperate conifer and hard-wood species of the GLSL Forest Region (maple, basswood, oak, white pine). How-ever, these models likely overestimate the impact of changing climate on forest veg-etation dynamics, as they do not ad-equately account for the effects of CO2 enrichment, barriers to migration, compe-tition, soil characteristics, physiological tolerance and acclimation, genetic varia-tion, disturbance regime, etc. (see Section 11) (Lenihan and Neilson 1993, Loehle and LeBlanc 1996). More accurate model pre-dictions must await a better understanding of the long-term effects of the interaction of climate change, CO2 and other environ-mental factors on forest ecosystem structure and function. Despite this current uncertainty, more frequent wildfire and forest decline will likely increase the area occupied by early successional ecosystems at the expense of mid- and late succes-sional ecosystems. In the near term, tech-niques are needed to identify vulnerable, declining stands requiring silvicultural intervention to minimize potential effects of climate change on Ontario’s forests.
Section 10
The Use of Models in Global Change Studies
Michael T. Ter-Mikaelian, Ontario Forest Research Institute, Ministry of Natural Resources
Models are commonly used to predict the effects of climate change on forest eco-systems. Models are popular because: (i) predictions are necessary either for situation(s) that have not yet occurred or for which data are not available; (ii) forest ecosystems develop and change over long periods — studying the effects of potential climate change would require decades, which unfortunately also corresponds to the desired prediction time; and (iii) forest ecosystems are hierarchical multi-compo-nent systems — climate change may affect these components differently both in terms of direction and magnitude. Even if the separate effects of climate change on each component were known, their interactions make assembling a complete description of ecosystem effects difficult. Models provide an indirect method of predicting attributes of forest ecosystems and how they change over time.
Unfortunately, there is no existing model comprehensive enough to predict the response of forest ecosystems in Ontario to climate change. In order to save time and resources, a model predicting climate change effects on forests should be developed using existing blocks (or modules) from other models. Table 10.1 presents examples of potential modules for some key areas of forest ecology and management. The following criteria were used to select these examples: (i) the model included climatic variables that can be manipulated to predict the effects of climate change on the forest; (ii) the temporal resolution of these variables should match the long-term resolution of the climatic models generating future climate scenarios (e.g., a model requiring daily values of some meteorological variable was considered impractical); (iii) preference was given to models that deal with a single process. For comprehen-sive reviews of climate change-related models the reader is referred to Goudriaan et al. (1998), Loehle and LeBlanc (1996), and Urban and Shugart (1992).
Some of the models in Table 11.1 can be applied to climate change predictions for Ontario immediately. Most of the models can be used independently to describe a specific process or assembled into a more complex model addressing several proc-esses simultaneously. In both situations, there are several guidelines to follow when modelling the effects of climate change on forest ecosystems:
Spatial scale. Although many processes operate at a number of scales, direct effects can usually be associated with one particu-lar scale. For example, wildfires operate at tree—stand—landscape scales (they burn individual trees and stands, and change landscape structure); however, the effects are most pronounced at the landscape scale. Therefore, when simulating a process, one has to identify the scale at which the effects are most pronounced (target scale); other relevant scales can be included if the model is multi-scaled.
Spatial hierarchy. Some processes may be adversely influenced by climate change at scales other than the target scale. Con-sider the task of estimating the effects of air temperature increases on forest productivity at the stand level. At the tree level, increased temperature increases individual tree biomass; at the stand level, it decreases stand density since trees compete more intensively as their size increases. Thus, elevated temperature may either increase or decrease productivity at the stand level; the effect cannot be estimated without more accurate quantification of both processes. Similarly, if we were interested in effects at the landscape level, we would have to account for the effect on productivity at the stand level, as well as increased fire frequency which decreases the mean forest age. Therefore, models should include effects at the target scale and one step below the target scale to ensure accuracy.
Temporal scale: Equilibrium state vs. transition state. "Transition state” predictions are given for periods when the climate is actually changing. Transition state models account for transition processes (e.g., rates of species migration to new geographic areas); these models are time-specific, i.e., a time can be specified for each prediction. “Equi-librium state” predictions assume that the climate will change and then remain stable for a period sufficient for ecological proc-esses to come to an equilibrium. Equilibrium models are simpler because they ignore some 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 is reached. Thus, when building a model it is necessary to decide which type of prediction should be made. The majority of existing models are equilibrium models.
Temporal scale: Short-term vs. long-term predictions. If a transition state model is chosen, the length of projection needs to be specified. Rates of climate-induced change will differ for different processes; therefore, depending on the prediction time, some processes may be considered ”stable” and therefore omitted from the model, while others have to be modelled. For example, for a 5-year prediction it is reasonable to assume that the current geographic distribution of species will not change, while in a 50-year prediction possible shifts in species zones must be accounted for.
Temporal resolution. It is important to select appropriate temporal
resolution (time steps) for modelling climate change effects. Large time steps
can inadequately represent a process because (a) the mean of the proc-ess may
be roughly the same but the varia-tion may change dramatically, and (b) some
sub-periods within a selected time step may be more important than others. For
example, warmer winters may have unique effects depending on tree species: (a)
evergreen
species will be affected by increased evapotranspiration more than deciduous
species, (b) warmer winters and earlier springs may adversely influence some
tree
species if they interfere with chilling require-ments for bud break phenology.
At present, time steps should not be shorter than a month, because climatic
models are not accurate at shorter intervals.
Climatic variables. It is important to identify the variables affecting the target ecological process. Most climate change predictions are given in terms of increasing air temperature, which does not necessarily translate into a change of the same magni-tude for some ecological variables. For exam-ple, Street (1989) demonstrated how trends in two variables (temperature and precipita-tion) compensate for each other’s effect on forest fires, resulting in more moderate predictions than those based on a single variable trend.
There will be few chances to validate a “climate change” model in the traditional sense. For this reason, indirect testing of the accuracy of climate change models will be needed. Such testing can be done by inde-pendently testing modules of the larger model. One means of testing the accuracy of a climate change model is to determine whether the model is able to predict past effects of climate on vegetation or ecological processes. Another way to test a climate change model is to evaluate the survival and growth of species planted outside their native ranges (Loehle and Leblanc 1996). In this context, process models (i.e., those based on measurable ecological processes that are causally related to climate) may have advantages over statistical models (i.e., models based on correlations between climate and an ecological process that may not have a causal relationship) for indirect testing of the accu-racy of climate change models (see Korzukhin et al. 1996).
Table 10.1 A list of models and their characteristics that can be readily adapted for studying climate change effects in Ontario.
| Field | Model title / reference | Objective | Spatial scale / time step | Input climate variable | Application | Comments |
|---|---|---|---|---|---|---|
| Hydrology | Arp and Yin in 1992 | To predict major water fluxes through upland forests from commonly available monthly climate records and descriptive site information | Watershed about 1 day | Monthly mean temperature: monthly precipitation: monthly mean snow fraction of precipitation | Calibrated and tested for 2 watersheds (4.62 and 62.3 ha) near Turkey Lakes: Ontario | No modification required |
| Insects | CLIMEX / Sutherst at al. 1995 | To simulate geographic distribution of insects using climate variables and species phenology | Large-scale (continent) / static | Weekly mean temperature: weekly precipitation | Has been applied to predict the distribution of Colorado beetle in North America, and livestock tick in Europe | Requires calibration for Ontario. Since the model assumes that geographic distribution of a species is defined primarily by climate, it may be applicable to certain species (eg, Gypsy moth) |
| Disease | Gross 1985 | To identify white pine blister rust (Cronartium ribicola J.C. Fisch.) hazard zones | Large-scale (province) / static | Mean minimum July temperature; mean daily July temperature; mean annual frostfree period; mean date of first frost | Has been used to identify 4 hazard zones (low, intermediate, high and severe) for Ontario | Needs further analytical development; see also Brasier (1996) for an application of CLIMEX to predict geographic distribution of Phytophthora cinnamomi (tree root pathogen) |
| Fire | For Land / Antonovski et al. 1992 | To predict the effects of climate on longterm forest fire dynamics | Landscape 1 year | Seasonal mean temperature; seasonal precipitation; maximum drought period | Calibrated for 1600 km2 softwood - dominated landscape in western Siberia | Calibration for Ontario would require estimation of key model parameters |
| Tree physiology | 3-PG/Landsberg and Waring 1997 | To simulate the growth and yield of a forestr stand from simple physiological principles | Stand (assumes spatial homogeneity of soil) / 1 month | Monthly mean day time VPD; monthly precipitation; mean number of frost-free days per month | Has been tested as growth and yield simulator of radiata pine in Australia and New Zealand | An individual-tree growth module should be extracted and calibrated for Ontario species; see also Kellomaki et al. (1992) for a module simulating frost damge. |
| Genetics | Cater 1996; Schmidtling 1994 | To predict the effects of temperature change on tree height growth from multi-location provenance trial data | Plantation/static (predicts the height at ages 8-22 years depending on species) | Annual mean minimum temperature | Applied to 12 softwood and hardwood species (eg, balsam fir, eastern white pine, jack pine, white spruce, etc) | No modification required; further studies needed to estimate response after the prediction date |
| Plant succession | ForClim / Bugmann 1996 | To simulate the effects of climate on forest structure, composition and dynamics | 1/12 ha / 1 year | Monthly mean temperature; monthly precipitation | Tested for a large number of sites in the European Alps and North America | Requires calibration for Ontario; see also Kellomaki et al (1992) |
| Growth and yield |
Kellomaki et al. 1992 |
To simulate growth and yield of tree stands from physiological principles |
1/12 ha/ 1 year |
Monthly mean temperature; monthly precipitation |
||
| Proe et al. 1996; Tyler et al. 1995 | To predict general yield classes from long-term climate factors | Stand / 1 year | Monthly mean temperature; monthly precipitation | Douglas-fir and Sitka spruce in Scotland | Calibration for Ontario would require large, spatially distributed data sets on long-term productivity of forests |
1 = a model where the output is for an 'equilibrium' condition has no time step and is therefore 'static', since it predicts only a single 'state'
Section 11.
Forest Management Responses to Climate Change
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 due to increasing atmospheric CO2 are realized, forests established now will mature in an environment that is substantially different from today. This report considers possible climate effects on Ontario’s forests based on projections from published literature and our interpretations of likely effects in Ontario. The question that naturally fol-lows from this consideration of climate effects is what, if anything, can be done to minimize negative consequences to our forests arising from climate change.
Forest management is the practice of silviculture to direct forest succession in a way that a desired combination of forest benefits is obtained, be it for timber, wilderness areas, wildlife habitat, old-growth forests, or other valued products. Despite uncertainties as to specific impacts, climate change is likely to significantly alter forest ecosystems and their management. Cur-rent socioeconomic trends emphasizing non-commodity values of forests will likely expand if forests begin to be man-aged as sinks for atmospheric CO2 , for their ability to modify climate, and as reservoirs of biodiversity (Woodman 1990). As a result, traditional silviculture may become increasingly less effective at meeting future forest management objectives.
Table 11.1 lists some possible ap-proaches to forest management in a chang-ing climate. The timely development and selective, appropriate use of innovative approaches to forest management in re-sponse to climate change are imperative given the inherently long planning scale of forestry and the economic importance of forests to Ontario. In this section we de-scribe some potential silvicultural activities that forest managers may use to reduce negative impacts of climate change. We also address the possible use of forests and tree plantations to store CO2 and slow the rate of climate change.
Silvicultral Systems and Stand Management
Disequilibrium between forest vegeta-tion and climate will occur where rotation length exceeds the development of a new climatic regime. This disequilibrium will be associated with regional episodes of forest decline as overstory species are no longer adapted to the prevailing climate (see Section 9). This will require silvicultural systems that address the management and regeneration of declining stands. Harvesting is the most effective tool available to forest managers for alter-ing forest condition and may be used to maintain forest health and productivity. For example, in younger stands not ready for commercial harvest, stand productivity and health may be maintained or im-proved by thinning to remove suppressed, damaged or poor quality individuals, increase the vigour of selected overstory individuals, and reduce the likelihood of decline (Table 11.1). Alternatively, in older stands productivity has declined as a result of overstory species being poorly adapted to the new climate, logging and planting prior to stand deterioration may be used to speed the replacement of forest types (Table 11.1). Techniques for monitoring the health of existing stands will be critical to the timely identification of areas needing protection or silvicultural intervention.
Table 11.1 . Potential forest management activities to minimize the negative effects of climate change on Ontario’s forests. The suitability of these activities will vary with the extent of climatic change, the condition of the stand in question, management objectives, and forest policy.
| Activity | Purpose |
|---|---|
| Shorten rotation lenghts, where appropriate | Harvest chronically stressed stands of low vigour and slower rates that are susceptible to insects and disease |
| Thinning | Reduce insect and disease susceptility, and increase vigour through thinning, when stands are under prolonged and severe moisture stress |
| Plant drought-adapted species and genotypes | Regenerate drought prone habitats with deeply-rooted species; select and breed drought tolerant genotypes |
| Increase use of alternatives to clearcutting (eg shelterwood, selection systems) | Protect regeneration from future warmer, drier seedling environments. Increase the amount of carbon stored by increasing the period a site is occupied by trees, decreasing disturbance to forest floor, and increasing the rate of reforestation where advance reproduction is used |
| Increase insect pest management preparedness | Greater incidence of extreme events and drought are expected to increase tree stress and susceptibility to insect pests |
| Plant climate-adapted species | Introduce southern species beyond recent northern range limits when temperature averages and extremes have warmed sufficiently |
| Maintain genetic and biological diversity | Protecting diversity increases the likelihood that there will be individuals, species and ecosystems that are adapted to future climate conditions; requires strategies for genetic conservation and ecosystem protection |
| Rapidly reestablish trees in harvested forests | Increasing the amount of carbon stored by increasing the period a site is occupied by trees |
| Use climate-based seed zones | Periodic updating of seed zones based on temperature averages and extremes |
| Increase forest fire suppression | Longer growing seasons, warmer temperatures and reduced precipitation may already have increased forest fire activity. Protection of valued forests requires a compensatory increase in forest fire suppression |
| Afforest non-forested land | Increasing the amount of carbon stored by increasing the area covered by forests |
| Preferentially regenerate trees for use in long lived wood products | Increasing the amount of carbon sequestered by increasing the lenght of time it is sequestered (eg in order of increasing sequestration time : non-recyclable paper; recyclable paper; books; lumber and construction board) |
| Increase use of advance reproduction | Advance reproduction requires less energy input compared to artificial regeneration and increases the rate of reforestation; need to develop and use modified harvesting techniques to protect reproduction and residual overstory when logging |
Harvesting can serve the dual pur-pose of facilitating the regeneration of the next stand if applied to protect or promote the advance reproduction of more site-adapted species in the understory, if they occur. Where the understory is not prop-erly matched to the prevailing site or climate conditions, and not acceptable as a source of regeneration, planting will be required. As artificial regeneration is vulnerable to environmental stresses following planting, partial cutting systems can be used to moderate the warmer, drier seedling environment predicted for the future (see Section 2). Partial cutting and thinning need to be tailored to the ecology of the species desired for regeneration (Hedden 1989, Ostofsky 1989). However, if climate change alters basic elements of forest ecology, the species or populations desired and the practices required for regeneration success may change in as yet unpredictable ways.
As many insect pests and forest dis-eases are stress-related, “stress manage-ment” practices such as partial cutting or thinning may also be useful to reduce susceptibility to insects and diseases (Wargo and Harrington 1991). However, as these same practices can sometimes in-crease vulnerability to other insects and diseases (e.g., jack pine budworm, Hypoxylon canker of aspen, and Armillaria in conifers), site and species specific application will be needed. Short-ening the rotation length can be used to decrease the period of vulnerability to stress. Other silvicultural techniques that reduce stress and susceptibility to insects and diseases include the regulation of species composition (i.e., planting appropriate species on sites) and maintainance of biological diversity.
Climate change will affect the life cycle of forest pathogens, and therefore,
the amount of damage suffered due to insects and diseases (see Sections 4 and
5). Gypsy moth, a significant defoliating insect in southern Ontario, could
increase in severity if the incidence of fall drought and warm spring temperatures
is favoured by climate change (Wagner 1990). In con-trast, warm weather in the
spring and fall could adversely affect spruce budworm, reducing tree losses
to this insect (Safranyik 1990). Shifts in the geographic range of insects may
result in the introduc-tion of new species to Ontario. According to Safranyik
(1990), the mountain pine beetle, presently found in South Dakota, could migrate
northward if winter mini-mum temperatures warm. This serious forest insect pest
could cause losses to pine forests in northwestern Ontario. Were climate change
to result in periods of severe insect infestation, insecticides might be needed
to protect young stands and reduce losses in timber volume and forest
cover (Table 11.1).
Forest Regeneration
If the 3 to 4oC increase in annual average temperature predicted for the next 50 years occurs, species will have to mi-grate approximately 300 km to the north over that time to be matched to climate. However, the migration rates of forest tree species are too slow to keep pace with this magnitude of climate change (Roberts 1989). Human-caused landscape fragmen-tation (e.g., agricultural lands, urbaniza-tion), lack of suitable habitat, and natural barriers to plant migration (e.g., the Great Lakes) will also hinder the movement of species from their current to potential future ranges.
Forest management provides an avenue to assist the movement of species from current to future ranges, but major artificial regeneration efforts will be re-quired to accomplish this (Davis 1989, Mackey and Sims 1993). Experimental planting of selected species and populations to appropriate sites up to 100 km north of their current range could be used to test the ability to assist species migration. Provenance trials that test populations from a wide variety of sites located across the range of a species will contribute to this effort by providing infor-mation about the transferability of species and populations to new environments. Species and population transfer northward needs to also account for photoperiod adaptation, since day length affects the onset and cessation of growth. It has been suggested that reserve areas, such as parks, be linked through connective corridors in a north-south gradient to aid species migra-tion (Halpin 1997). However, northward movement of species in Ontario is compli-cated by the lack of suitable soil types and the expected lag in soil development dur-ing climate change. The movement of more nutrient demanding hardwoods to acidic, less fertile sites now occupied by conifers may benefit from mixed planting with species that ameliorate site conditions (e.g., N fixers). This may also require planting hardwood species inoculated with site-adapted mycorrhizal species. Habitats expected to become drier in the future might be regenerated with novel, more deeply rooted species (Table 11.1).
The amount of silvicultural intervention needed to maintain a productive forest will depend on the forest species in ques-tion, but it is clear that an effective genetic resource management program will be an important component of forest manage-ment response to climate change. Widely distributed species (e.g., black spruce and white spruce), which have broad genetic diversity, may require little attention, but local ecotypes may be lost and genetic diversity reduced. Maintaining species currently of economic importance but with greatly diminished natural abundance due to past management practices (e.g., white pine, red pine and red oak) may require the identification, production, and planting of southern ecotypes adapted to the longer
photoperiods of more northern regions. Assessing genetic variation within these species will help to determine the limits of transferability along climatic gradients and, perhaps, will require periodic adjustment of existing climate-based seed zones (Table 11.1). Given the current uncertainty regard-ing regional shifts in climate, planting stock representing widely adapted populations and diverse seed source mixtures can be used to increase the likelihood of regenera-tion success. Aggressive genetic tree im-provement programs designed to promote increased genetic diversity and allow for future adaptation will also be needed to increase pest resistance and tolerance to environmental stresses (Roberts 1989) (Table 11.1).
Climate change may threaten rare species because they lack enough economic value to warrant addressing the potential loss of suitable habitat (Peters 1990). Butternut, red mulberry, and red spruce are a few of the comparatively rare tree species in Ontario that are confined to small, dis-junct populations. These and similarly rare species may require more intensive, costly silvicultural activities to sustain them if suitable habitat becomes difficult to find or create due to climate change. As a conse-quence, conservation plans and silvicultural approaches to sustain rare, threatened and endangered species are needed. Increasing the number of large natural areas or reserves to maintain a wide variety of habitat conditions has been recommended to reduce the risk of local extinction of rare species (Peters 1990), but this by itself may be insufficient to prevent extinction. Breeding plans for rare species that incorporate systems to increase genetic diversity should be used. However, our ability to only forestall rather than prevent local extinction needs to be weighed against the cost of preservation activities. In addi-tion, severe habitat loss could mean that long-term preservation of rare species may only be possible in “zoo-like” arboreta, rather than in natural environments.
More intensive vegetation management treatments to control less desirable tree species and other plants may, in the future, be required to assist the regeneration of preferred commercial forestry species. This may occur because of the comparatively pronounced growth response of some plants to elevated CO2 and warmer tem-peratures. Hardwoods show a greater proportional increase in biomass under elevated CO2 and may increase in competi-tive fitness relative to conifer species (McGuire et al. 1995). Further, fast grow-ing, short-lived herbaceous species are better able to adapt genetically to increased atmospheric CO2 . As a result, a general increase in the abundance of aggressive herbaceous plants may occur, particularly where stand senescence exceeds the rate of ingress of more adapted tree species (Bazzaz 1996). Poplar and aspen species are likely to become more aggressive in boreal regions, as their high relative growth rates and reproduction from root suckers favour their colonization after clearcutting and wildfire. It is predicted that such changes in the competitive interaction among tree species could result in the development of plant communities for which we have no management experience, requiring new silvicultural approaches to control non-crop species (Davis 1989, Bazzaz 1996).
Mycorrhizal associations with plants are important to forest regeneration efforts because they help reduce plant stress by improving the absorption of nutrients and soil moisture. Practices such as clearcutting, whole-tree harvesting and prescribed burn-ing can decrease the diversity and total biomass of mycorrhizae and may poten-tially increase adverse effects where climate change increases the severity and frequency of drought (Harvey et al. 1980, Miller and Lodge 1997). Harvey et al. (1980) recom-mend keeping clearcuts small and maximiz-ing edges to promote the ingress of mycorrhizae from surrounding uncut stands. Such practices help maintain the diversity of soil microorganisms, which increases the ability of ecosystems to adaptto a range of climatic conditions. Mixed plantings of conifers and hardwoods can increase microbial diversity and enhance litter decay (Hendrickson et al. 1982), as can harvest and site preparation techniques that promote litter accumulation or retention. Fire frequency is expected to increase in many areas of Ontario and, although cer-tain mycorrhizal communities may be more abundant after a fire, they may not be suited to the desired tree and plant species (see Section 5). In such instances, novel approaches to maintaining fungal diversity may be needed.
Biodiversity has been defined as “the variability among living organisms and the ecological complexes of which they are a part” (Canadian Council of Forest Ministers 1997). It can be viewed in the context of the biodiversity of ecosystems, species and genes (Canadian Council of Forest Minis-ters 1997). The conservation of biodiversity is an important goal of sustainable forest management. However, should a change in climate 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 protect old-growth forests and other natural areas, as these habitats serve as biodiversity reservoirs (while also acting as forest car-bon storage areas, as described later). How-ever, the ability to retain such areas is likely to decline if climate changes rapidly and the frequency and severity of forest distur-bance increases. A more dynamic approach recognizing that conditions may change is needed to protect natural areas through a period of climate change (Halpin 1997)
Forest Productivity
The influence of climate change on forest productivity will depend on regional differences in effects of elevated CO2 con-centration and altered climatic regimes on carbon, water and nutrient relations, envi-ronmental stress response, and the unique ecophysiological characteristics of species (Bazzaz et al. 1990, McGuire et al. 1995, Wayne et al. 1998). Although enhanced photosynthetic activity at elevated CO2 concentrations will increase forest net primary productivity (NPP), the relative increase in photosynthesis is strongly dependent upon nitrogen availability (Melillo et al. 1993, McGuire et al. 1995). For example, the potential increase in NPP of northern and temperate forest ecosys-tems under elevated CO2 may be con-strained by nitrogen availability in soils of these regions, with NPP being largely dependent on effects of elevated tempera-ture on mineralization rates (Melillo et al. 1993). Further, the beneficial effects of CO2 fertilization on NPP expected under cli-mate change may decline with time (Cao and Woodward 1998).
Rigorous predictions of climate change effects on NPP must await further progress in our understanding of the relationship between carbon and nitrogen cycles (McGuire et al. 1995). However, general statements regarding the possible effects of climate change on forest produc-tivity can be made. As shown in Table 11.2, stand productivity will tend to increase in all regions as a result of increased tem-perature and atmospheric CO2 concentra-tion. Increased spring and fall tempera-tures will tend to lengthen the growing season, while elevated CO2 will increase photosynthesis and water use efficiency (see Section 7). Nitrogen availability in soils would tend to increase with tempera-ture as a result of increased rates of miner-alization and decomposition (see Sections 5 and 9), although the effect could be relatively less in the south due to the warmer temperatures that already prevail there. However, reduced precipitation and increasing severity of drought in the north-west and south could counter the positive effects of warmer temperature, increased CO2 , and greater nitrogen availability. In contrast, there could be large increases in stand productivity in the northeast if precipitation increases and the incidence of drought decreases as predicted (see Sections 2 and 3). Perennial herbaceous plant competition (e.g., fireweed and strawberry) may become a more serious problem that would slow crop tree estab-lishment, since herbaceous plants are favoured under higher concentrations of atmospheric CO2 (see Sections 7 and 9).
On a regional basis, an increased incidence of severe disturbance could have serious consequences on timber supply. In northwestern 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 in precipitation in the northeast, there may be an increase in fire severity due to drying caused by elevated temperatures and high evaporative demands (see Sections 3 and6).
Carbon Sequestration
The total global carbon content is constant; it occurs as atmospheric CO2 and oceanic carbon or in storage as living and dead biomass, fossil fuels, limestone, and marble. Atmospheric CO2 concentration depends on the balance between carbon “fixed”, or added, in storage and released from storage. Since the beginning of the industrial era, atmospheric CO2 concentra-tion has increased from about 280 ppm to 360 ppm. Approximately 7 Gt CO2 -carbon per year (Gt=gigaton; 1 Gt=10 15 g) are being released to the atmosphere by fossil fuel combustion and, to a much lesser extent, tropical deforestation and burning (Krauchi 1994). Of this carbon, 3.6 Gt are absorbed by oceans and terrestrial vegeta-tion, with 3.4 Gt being added annually to the atmosphere.
Forests play an integral role in the global carbon cycle, fixing CO2 through photosynthesis, storing carbon in above and below ground biomass, and releasing CO2 to the atmosphere through decompo-sition and respiration (D’Arrigo et al. 1987, Tans et al. 1990, Krauchi 1994). Forest biomass contains about 70% of the amount of carbon in the atmosphere, while carbon in detritus and soil organic matter is twice that of the atmosphere. Natural and anthropogenic disturbances influence the carbon cycle of forest ecosystems through effects on the amount of carbon stored and its rate of transfer from organic storage forms to the atmosphere. Generally, a reduc-tion in rotation length and shorter natural disturbance intervals reduce carbon storage (Cooper 1983). The carbon storage life of forest products also influences the forest carbon cycle. Currently, harvesting and industrial processing of boreal and temper-ate forests results in two-thirds of the stored carbon being emitted to the atmosphere as CO2 (Harmon et al. 1990, Freedman and Keith 1996).
Atmospheric CO2 concentrations can be reduced by decreasing fossil fuel com-bustion and increasing the rate of carbon removal from the atmosphere. For a variety of reasons, significant reductions in fossil fuel emissions are unlikely in the near future (Freedman and Keith 1996). Forestry is one of the few human activities that can reduce atmospheric CO2 . Using forests as sinks to reduce net CO2 emissions is a prom-ising way to mitigate climate change, but should be used in conjunction with efforts to reduce fossil fuel combustion and deforesta-tion (Sedjo 1989, Freedman and Keith 1996). Managing forests as carbon sinks would require some changes in the forest land use paradigm to add the maximization of car-bon storage and afforestation to the goals of rapid reforestation and increased productivity.
Afforestation for carbon storage by establishing tree plantations on marginal cropland and pasture can be used as an effective, ecologically viable means of in-creasing CO2 sequestration (Winjum and Schroeder 1997). However, in Ontario the amount of land available for afforestation is small compared to the existing forested land base. The potential reduction in CO2 by afforestation depends on availability of lands that can grow forests, the maximum attainable biomass of these forests, the degree to which management alters this maximum, and the long-term fate of stored carbon (Table 11.1) (Cooper 1983, Vitousek 1991, Winjum and Schroeder 1997). Large monoculture tree plantations are more susceptible to insects and pathogens (Winjum and Schroeder 1997), and their use to maximize carbon storage requires that they be protected from fire and insects.
Table 11.2 Possible effects of altered environment induced by climate change on forest productivity and timber supply in northwestern, northeastern and south central Ontario in the next 50 to 100 years 2.
| Processed and Factors | Northwest | Northeast | South central |
|---|---|---|---|
|
Environment |
|||
| elevated temperature | + | + | + |
| incresed CO2 concentration | + | + | + |
| nitrogen availability | + | + | 0 |
|
Hydrology |
|||
| precipitation | - | + | - |
| drought | -- | + | - |
| Increased herbaceous competition | - | -- | - |
| Fire disturbance | -- | - | -- |
| Insect | -- | 0 | - |
| Disease | -- | 0 | - |
| Net effects on stand productivity | - | + | 0 |
| Net effects on regional timber supply | -- | + | - |
A total of 61 million ha, or 62%, of Ontario’s total land area is productive forested land (OMNR 1996). Forest man-agement can increase the productivity and carbon storage of these existing forests, but the contribution to carbon sequestration on a per hectare basis would be less than the contribution from afforestation of non-forested land. Other broad management practices recommended to maximize car-bon sequestration of forest land include: (i) clearing and prompt regeneration of unpro-ductive, poorly stocked forest, (ii) intermediate stand treatments (e.g., thinning) in overstocked, stagnating forests, and (iii)increasing the rotation length (Birdsey and Heath 1997).
The net amount of carbon stored in forest ecosystems will differ with the silvicultural system used (Figure 11.1). A clearcut silvicultural system has the great-est CO2 output from fossil fuels per unit rotation while a selection system produces the smallest CO2 output. Clearcutting followed by tree planting produces a large release of CO2 from fossil fuels because of the energy requirements for tree seedling production, transportation, site prepara-tion and tending, and from accelerated decomposition of forest floor detritus and organic matter after harvest. Selection silviculture requires CO2 output for har-vesting only, disturbance to the forest floor is minimized, and planting is not required, but these gains are partially offset by the need for a larger road network, greater frequency of return to harvest, and lower efficiency (i.e., lower m 3 of wood per hectare of forest).
Partial cutting systems (e.g., shelterwoods and strip cuts) are intermediate in terms of carbon sequestration, as they rely heavily on seeding and advance growth for regeneration, but may require planting and some site preparation where natural regeneration is inadequate. Moreover, carbon sequestration decreases with the length of time a forest site is not fully occupied with a tree crop. Despite sugges-tions to the contrary, conversion of old-growth forest ecosystems to intensively managed, commercial forests results in a significant net decrease in on-site carbon storage capacity (Harmon et al. 1990, Vitousek 1991, Freedman and Keith 1996). The value of old-growth forests as vehi-cles for carbon storage and preservation of biodiversity may require development of silvicultural approaches to maintain the health of these forests under a changing climate.
Figure 11.2 shows theoretical differ-ences in net carbon sequestration with different silvicultural practices. Not all forms of silviculture will result in in-creased net sequestration of carbon. For example, tree improvement is a silvicultural practice that requires rela-tivelysmall release of CO2 to achieve increased growth rates over large areas of forest. Vegetation management activitiesreduce the interval between harvesting and 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 net benefit of this practice to carbon sequestra-tion. Pruning does not add to net seques-tration of carbon and increases short-term carbon release due to increased branch decomposition rates, while adding little to stand growth. Thinning increases indi-vidual ree vigour and concentrates growth on fewer stems but, because it requires an expenditure of energy to conduct thinning mechanically and also reduces full site occupancy, thinning re-duces CO2 sequestration (thinning may contribute positively to CO2 sequestration if it reduces stand stress due to drought, insects or disease). Finally, increases in growth due to forest fertilization would be offset by the large amount of CO2 emitted in producing and applying fertilizer.
The consequences of management practices on the forest carbon cycle will be of increasing concern, particularly if mini-mizing net CO2 emissions becomes an important objective of forest managers and the forest industry. Such net calculations, to our knowledge, have not yet been widely made.
Conclusions
It is clear that the increase in green-house gases in the atmosphere over the last two centuries is due to human activities (Vitousek 1993). Despite current uncer-tainty as to the absolute effects of these gases on the earth’s climate and biota, there is compelling evidence to support assertions that global climate change is a serious threat to the biosphere. A signifi-cant warming of the earth’s atmosphere is currently occurring, with the period since 1980 being the warmest in the past 200 years (Jacoby et al. 1996, Myneni et al. 1997, Mann et al. 1998). In fact, global average temperatures for January to May 1998 indicate the spring of 1998 was the warmest in the last 1000 years (Vogel and Lawler 1998).
The warmer than normal tempera-tures in recent years may be responsible for increased plant growth in the northern latitudes, due to earlier disappearance of snow in the spring and lengthening of the growing season (Jacoby et al. 1996, Myneni et al. 1997). However, in addition to, and more important than, changes in tempera-ture averages, climate change is expectedto increase the likelihood of extreme cli-matic events and associated natural distur-bances (fire, insects), which will have dramatic impacts on forest ecosystems. Although it is difficult to state unequivo-cally that the warming already observed is a direct result of increased greenhouse gases, recent climate patterns and in-creased frequency of wildfire have already had major effects on Ontario’s forests (Van Wagner 1988, Schindler 1998).
Regardless of some continuing disa-greement over the extent of the effect of greenhouses gases on future global tem-perature, the increase in atmospheric CO2 will by itself be sufficient to substantially alter forest ecosystems in Ontario. Some effects of climate change and increased atmospheric CO2 will be insidious and progressive. For example, changes in the competitive ability of different plants may already be undergoing changes in a slow, progressive manner. However, such changes might not be apparent without careful monitoring of plant species abun-dance and growth rates. Other ecosystem changes, such as long-range species migra-tion, might not be observed for hundreds of years. Because of the uncertainty overthe timing and extent of climate change and its effects on forest ecosystems, we propose that “no risk” forest management practices (i.e., practices that increase the resilience of forests to climate variability, such as the protection of genetic diversity) be identified now and, where feasible, implemented to minimize the potential negative impacts of climate change and increased atmospheric CO2 on forests in Ontario. More dramatic responses to climate change (e.g., the large-scale plant-ing of southerly genetic sources and spe-cies hundreds of kilometers north of their present ranges) should be considered once improved regional climate change projections are made.
Section 12
Conclusions
The Ontario Ministry of Natural Resources seeks to sustain the ecological and social benefits of healthy ecosystems on forested Crown lands. However, forests are increasingly being affected by acidification and deposition of nitrogen to soils as a by-product of industrial pollution, ground-level ozone pollution, and the reduction of ozone in the earth’s upper atmosphere that has increased ultraviolet radiation. Overlain on these factors is a potentially unprecedented rapid change in climate resulting from increased atmospheric CO2 . This report outlines the potential effects of CO2 induced climate change on the stability of Ontario’s forest ecosystems.
The evidence reviewed in this report identifies the following major effects of climate change on Ontario’s forests:
- in northwestern Ontario, fires and droughts will become more frequent and severe;
- insect outbreaks and disease are ex-pected to mirror fire and drought incidence;
- new plant associations are expected to occur as individual species are favoured over others and as rates of migration differ between plant species;
- northeastern Ontario may experience enhanced forest growth and productiv-ity, while drought, fire, insects, and disease in northwestern Ontario areexpected to reduce growth rates and threaten wood supplies, perhaps within the next 30 years;
- unique ecosystems and threatened and endangered species may be unsustainable if they have highly specific climate requirements;
- biodiversity conservation may change meaning as a management objective if climate change allows species to migrate to new areas, there is strong genetic selection pressure, and the ability to reproduce is reduced in some species.
The potential changes in climate de-scribed here would alter the traditional economic and social benefits that society in Ontario is accustomed to receiving from its forests. It is therefore important that forest land managers realize that existing forest ecosystems and traditional approaches to managing these lands may not be valid in a climatically altered environment. As a result, dynamic management practices and policies governing forests in Ontario will be needed in anticipation of such changes. Careful sensitivity analysis to identify species and ecosystems at greatest risk from climate change is also needed. Optimizing future forest management practices requires an understanding of the potential consequences of climate change that can only be obtained by modeling climatic influences on biological systems.
References
SECTION 1. INTRODUCTION
Armson, K.A., W.R. Grinnell and F.C. Robinson. 1998. The history of reforestation. in Regenerating the Canadian Forest, 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. Climate change and America’s forests. USDA For. Serv., Rocky Mount. For. Range Exp. Sta., Gen. Tech. Rep. RM-187. 12 p.
Kräuchi, N. 1994. Climate change and forest ecosystems - an overview. Pp. 53-76 in Long-term Implications of Climate Change 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. Coherence established between atmospheric carbon dioxide and global temperature. Nature 343: 709-714. Schindler, D.A. 1998. A dim future for boreal waters and landscapes. Bioscience 48: 157-164.
SECTION 2. ONTARIO'S CLIMATE IN THE 21ST CENTURY
Boer, G.J., N.A. McFarlane, and M. Lazare. 1992. Greenhouse gas-induced climate change simulated with the CCC second-generation General Circulation Model. J. Clim 5: 1045-1077. Fleming,
Caya, D., R. Laprise, M. Giguère, G. Bergeron, J.P. Blanchet, B.J. Stocks, G.J. Boer and N.A. McFarlane. 1995. Description of the Canadian regional climate model. Water Air Soil Poll. 82: 477-482. Fleming,
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’s climate: 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. Wiley Publ. Can., Ltd. Toronto, ON.
Intergovernmental Panel on Climate Change (IPCC). 1996. Climate Change 1995 Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses. Cam-bridge Univ. Press, Cambridge, U.K. Hedden,
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 of hydrologic 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 General Circulation Model and its equilibrium climate. J. Clim. 5: 1013-1044.
Trewartha, G.T. and L.H. Horn. 1980. An introduction to climate, 5th ed. McGraw-Hill Book Co., New York, NY.
Weber, M.G. and M.D. Flannigan. 1997. Canadian boreal forest ecosystem structure and function in a changing climate: Impact on fire regimes. Environ. Rev. 5: 145-166.
SECTION 3. FOREST HYDROLOGY IN RELATION TO GLOBAL CHANGE
Bolin, B., B.R. Doos, J. Jagger and R.A. Warrick (eds.). 1986. The Greenhouse Effect, Climate Change, and Ecosystems. John Wiley and Sons, Toronto, ON.
Thornthwaite, C.W. 1946. The moisture factor in climate. Trans. Am. Geogr. Union, 27(1): 41-48.
SECTION 4. INSECTS AND CLIMATE CHANGE
Fleming, R.A. 1996. A mechanistic perspective of possible influences of climate change on defoliating insects in North America’s boreal forests. Silv. Fenn. 30: 281-294.
Fleming, R.A. and J.-N. Candau. 1997. Influences of climate change on some ecological processes of an insect outbreak system in Canada’s boreal forests and the implications for biodiversity. Environ. Monit. Assess. 49: 235-249.
Fleming, R.A. and G.M. Tatchell. 1995. Shifts in flight periods of British aphids: A response to climate warming? Pp. 505- 508 in R. Harrington and N. E. Stork (eds.), Insects in Changing Environment. Academic Press, London, U.K.
Fleming, R.A. and W.J.A.Volney. 1995. Effects of climate change on insect defoliator population processes in Canada’s boreal forest: some plausible scenarios. Water, Air, Soil Poll. 82: 445-454.
Hardy, Y., M. Mainville and D.M. Schmitt. 1986. An atlas of spruce 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 for silviculture 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 pine beetle dynamics. Pp. 92-105 in Interior West Global Change Workshop. April 25-27, 1995, Fort Collins, Colorado. USDA For. Serv. Rocky Mount. For. Range Exp. Sta. Gen. Tech. Rep. RM-GTR-262.
Sandberg, D.V. 1992. Adaptive response to forest disturbance in a changing climate - fire, insects, and disease. Pp. 294- 305 in Proc. North American Conference on Forestry Responses to Climate Change, May 15-17, 1990, Climate Institute. Washington, D.C.
SECTION 5. THE IMPACT OF CLIMATE CHANGE ON FUNGI IN THE ECOSYSTEM
Batjes, N.H. 1996. Total carbon and nitrogen in the soils of the world. Eur. J. Soil Sci. 47: 151-163.
Cannell, M.G.R., J. Grace and Booth, A. 1989. Possible impacts of climatic warming on trees and forests in the United Kingdom: 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 mortality following 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 forest resource of Ontario, 1982-1987. For. Can., Ont. Reg., Great Lakes 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; consequences of increased atmospheric CO2- concentration on carbon input and turnover in agro-ecosystems. Pp. 46-47 in J. Goudriaan, H. van Keulen, H.H. van Laar (eds.), The Greenhouse Effect and Primary Productivity in European Agro-Ecosystems. Pudoc, Wageningen, The Netherlands.
Lodge, D.J., W.H. McDowell and C.P. McSwiney. 1994. The importance of nutrient pulses in tropical forests. Trends Ecol. Evol. 9: 384-387.
McDonald, G.I., N.E. Martin, and A.E. Harvey. 1987. Armillaria in the Northern Rockies: pathogenicity and host susceptibility 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 effect of soil disturbance on growth and ectomycorrhizae of Douglas-fir and western hemlock seedlings: A greenhouse bioassay. Can. J. For. Res. 12: 343-353.
Miller, R.M. and D.J. Lodge. 1997. Fungal responses to disturbance: Agriculture and forestry. Pp. 65-84 in Wicklow, Söderström (eds.), The Mycota IV; Environmental and microbial relationships. Springer-Verlag, Berlin, Germany.
Molina, R., H. Massicotte and J.M. Trappe. 1992. Specificity phenomena in mycorrhizal symbioses: community-ecological consequences and practical implications. Pp. 357-423 in M.J. Allen (ed.), Mycorrhizal Functioning, An Integrated Plant-Fungal Process. Chapman and Hall, New York, NY.
Monz, C.A., H.W. Hunt, F.B. Reeves and E.T. Elliot. 1994. The response of mycorrhizal colonization to elevated CO2 and climate change in Pascopyrum smithii and Bouteloua gracilis. Plant and Soil 165: 75-80.
Nechleba, A. 1927. Notizen uber das Vorkommen einiger forstlish bemerkenswerter pathogener Pilze in Bohmen. [Notes on the occurrence in Bohemia of some silviculturally 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 on terrestrial ecosystems. Ecol. Appl. 1: 316-325.
O’Neill, E.G. 1994. Responses of soil biota to elevated atmospheric 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 birch dieback. Can. J. Bot. 33: 595-627.
Schimmel, D.S. 1995. Terrestrial ecosystems and the carbon cycle. Global Change Biol. 1: 77-91.
Wargo, P.M. and T.C. Harrington. 1991. Host stress and susceptibility in C.G. Shaw III and G.A. Kile (eds.), Armillaria root disease. USDA For. Serv., Agric. Handb. No. 691. 233 p.
Section 6 THE IMPACT OF CLIMATE CHANGH ON FIRE AND FIRE MANGEMENT IN ONTARIO
Canadian Forestry Service 1987. Canadian forest fire danger rating system - users’ guide. Can. For. Serv., Fire Danger Group. (unnumbered publication).
Flannigan, M.D. and C.E. Van Wagner. 1991. Climate change and 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 wildfiren severity. Pp. 463-486 in J.G. Goldammer (ed.), Fire in the Tropical Biota: Ecosystem Processes and Global Challenges.
Price, C. and D. Rind. 1994. Possible implications of global climate change on global lightning distributions and frequencies. J. Geophys. Res. 99:108-123.
Simard, A.J. 1997. National workshop on wildland fire activity 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 in northern circumpolar countries. Pp. 198-202 in J.S. Levine (ed.), Global biomass burning; Atmospheric, Climatic and Biospheric 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 and forest fire potential in Russian and Canadian boreal forests. Clim. Change 38: 1-13.
Van Wagner, C.E. 1970. Conversion of William’s Severity Rating 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 the Canadian 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 fire season in a changing climate. For. Chron. 69: 187-192.
SECTION 7. PLANT PHYSIOLGICAL RESPONSES TO A CHANGING ENVIRONMENT
Battaglia, M, C. Beadle and S. Loughhead. 1996. Photosyn-thetictemperature responses of Eucalyptus globulus and Eucalyptus nitens. Tree Physiol. 16: 81-89.
Colombo, S.J. 1998. Climate warming and its potential effects on bud burst and risk of frost damage to white spruce in Canada. For. Chron. 74 (in press).
Drake, B.G., M.A. Gonzàlez and S.P. Long. 1997. More efficient plants: A consequence of rising atmospheric CO2 ? Ann. Rev. Plant Physiol. Mol. Biol. 48: 609-639.
Joyce, L.A., M.A. Fosberg and J.M. Comanor. 1992. Climate change and America’s forests. USDA For. Serv., Rocky Mount. For. Range Exp. Sta., Gen. Tech. Rep. RM-187. 12 p.
Körner, C. 1993. CO2 fertilization: The great uncertainty in future vegetation development. Pp. 53-70 in Vegetation Dynamics & 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 Sitka spruce (Picea sitchensis) and their impact on risk of frost damage. Tree Physiol. 14: 691-706.
Reed, D.D. and P.V. Danseker. 1992. Ecological implications of projected climate change scenarios in forest ecosystems in northern Michigan, USA. Int. J. Biometeorol. 36: 99-107.
Schindler, D.A. 1998. A dim future for boreal waters and landscapes. Bioscience 48: 157-164.
Tissue, D.T., R.B. Thomas and B.R. Strain. 1996. Growth and photosynthesis of loblolly pine (Pinus taeda) after exposure to 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 and managed ecosystems. A synthesis of GCTE and related research. The International Geosphere-Biosphere Pro-gramme, Stockholm, Sweden. 32 p.
SECTION 8. GENETIC IMPLICATIONS OF CLIMATE CHANGE
Bazzaz, F.A., M. Jasienski, S.C. Thomas and P. Wayne. 1995. Microevolutionary responses in experimental populations of plants to CO2 -enriched environments: Parallel results from two model systems. Proc., Nat. Acad. Sci. USA 92: 8161-8165.
Brubaker, L.B. 1986. Responses of tree populations to climatic change. Vegetatio 67: 119-130.
Cantin, D., M.F. Tremblay, M.J. Lechowicz and C. Potvin. 1997. Effects of CO2 enrichment, elevated temperature, and nitrogen availability on the growth and gas exchange of different families of jack pine seedlings. Can. J. For. Res. 27: 510-520.
Carter, K.K. 1996. Provenance tests as indicators of growth response to climate change in 10 north temperate tree species. 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. Dynamic conservation of forest tree gene resources. Forest Genetic Resources 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 Biogeography and the Preservation of Biotic Diversity. Univ. Chicago Press, Chicago, IL. 211 p.
Joyce, L.A., M.A. Fosberg and J.M. Comanor. 1990. Climate change and America’s forests. USDA For. Serv., Rocky Mount. For. Range Exp. Sta., Gen. Tech. Rep. RM-187. 12 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 with provenance test data. Tree Physiol. 14: 797-804.
Namkoong, G. 1984. Strategies for gene conservation in forest tree breeding. Pp. 79-89 in Yeatman, C.W., D. Kafton, and G. Wilkes (eds.), Plant Gene Resources: A Conservation Imperative. 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 Basin woodland and steppe during the late-Pliestocene and Holocene. 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 Warming and 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 Pinus contorta in British Columbia: Niche breadth, climate change, and reforestation. Ecol. Monogr. [in press].
Slocum, R.W. Jr. 1985. Major climate change likely, say scientists. J. For. 83: 325-327.
Stettler, R.F. and H.D. Bradshaw Jr. 1994. The choice of genetic material for mechanistic studies of adaptation in forest trees. Tree Physiol. 14: 781-796.
Vitousek, P.M. 1994. Beyond global warming: Ecology and global change. Ecology 75: 1861-1876.
Walker, B. and W. Steffen. 1997. An overview of the implica-tions of global change for natural and managed terrestrial ecosystems. Cons. Ecol. [online] 1(2). 18 p.
SECTION9. CLIMATE CHANGE AND FOREST VEGETATION DYNAMICS IN ONTARION
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 plant succession. 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. Catastrophic windthrow in the presettlement forest of Wisconsin. Ecology 65: 803-809.
Dahir, S.E. and C.G. Lorimer. 1996. Variation in canopy gap formation among developmental stages of northern hardwood 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 rapid temperature change. Quat. Res. 23: 327-340.
Flannigan, M.D. and C.E. van Wagner. 1991. Climate change and wildfire in Canada. Can. J. For. Res. 21: 66-72.
Fleming, R.A. 1996. A mechanistic perspective of possible influences of climate change on defoliating insects in North America’s boreal forests. Silv. Fenn. 30: 281-294.
Grime, J.P. 1993. Vegetation functional classification systems as approaches to predicting and quantifying vegetation change. Pp. 293-305 in Vegetation Dynamics and Gobal Change, A.M. Solomon and H.H. Shugart (eds.), Chapman-Hall, New York, NY.
Heinselman, M.L. 1973. Fire in the virgin forests of the Boundary Waters Canoe Area, Minnesota. Quat. Res. 3: 329-382.
Hogg, E.H. and P.A. Hurdle. 1995. The aspen parkland in western Canada: A dry-climate analogue for the future boreal 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 global warming on growth and mortality of upland oak species in the midwestern United States: A physiologically based dendroecological approach. Can. J. For. Res. 22: 139-1752.
Leniham, J.M. and R.P. Neilson. 1995. Canadian vegetation sensitivity to projected climatic change at three organiza-tional levels. Clim. Change 30: 27-56.
Loehle, C. and D. LeBlanc. 1996. Model-based assessments of climate change effects on forests: A critical review. Ecol. Model. 90: 1-31.
Mackey, B.G. and R.A. Sims. 1993. A climatic warming analysis of selected boreal tree species, and potential responses 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 America following major disturbances. For. Ecol. Manage. 3: 153-168.
Overpeck, J.T., D. Rind and R. Goldberg. 1990. Climate-induced changes in forest disturbance and vegetation. Nature 343: 51- 53.
Pastor, J. and W.M. Post. 1988. Response of northern forests to CO2 -induced climate change. Nature 334: 55-58.
Peterson, C.J. and W.P. Carson. 1996. Generalizing forest regeneration models: The dependence of propagule availability 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 of projected climate change scenarios in forest ecosystems in northern Michigan, USA. Int. J. Biometeorol. 36: 99-107.
Sargent, N.E. 1988. Redistribution of the Canadian boreal forest under a warmed climate. Climatol. Bull. 22: 23-34. Schindler, D.A. 1998. A dim future for boreal waters and landscapes. Bioscience 48: 157-164.
Solomon, A.M. 1986. Transient response of forests to CO2 -induced climate change: Simulation modeling of experiments in eastern North America. Oecologia 68: 567-579.
Solomon, A.M. and P.J. Bartlein. 1992. Past and future climate change: Response by mixed deciduous-coniferous ecosystems n 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 pine forests to substrate and disturbance history. Ecology 67: 1548-1559.
Wotton, B.M. and M.D. Flannigan. 1993. Length of the fire season in a changing climate. For. Chron. 69: 187-192.
SECTION 10. THE USE OF MODELS IN GLOBAL CLIMATE CHANGE STUDIES
Allison, S.M., M.F. Proe and K.B. Matthews. 1994. The prediction and distribution of general yield classes of Sitka spruce in Scotland by empirical analysis of site factors using a 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 its applications to forests in western Siberia. Pp. 373-403 in H.H. Shugart, R. Leemans, and G.B. Bonan eds.), A Systems Analysis of the Global Boreal Forest. Cambridge University Press, Cambridge, UK.
Arp, P.A. and X. Yin. 1992. Predicting water fluxes through forests from monthly precipitation and mean monthly air temperature records. Can. J. For. Res. 22: 864-877.
Brasier, C.M. 1996. Phytophthora cinnamomi and oak decline in southern Europe. Environmental constraints including climate change. Ann. Sci. Forest. 53(2-3): 347-358.
Bugmann, H.K.M. 1996. A simplified forest model to study species composition along climate gradients. Ecology 77: 2055-2074.
Carter, K.K. 1996. Provenance tests as indicators of growth response to climate change in 10 north temperate tree species. 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.), The Terrestrial Biosphere and Global Change: Implications for Natural and Managed Ecosystems. Cambridge University Press, Cambridge, UK. (in press).
Gross, H.L. 1985. White pine blister rust: A discussion of the disease 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 simulation model 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 forest ecosystem management? Can. J. For. Res. 26: 879-887.
Landsberg, J.J. and R.H. Waring. 1997. A generalised model of forest 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 of climate change effects on forests: A critical review. Ecol. Model. 90: 1-31.
Proe, M.F., S.M. Allison and K.B. Matthews. 1996. Assessment of the impact of climate change on the growth of Sitka spruce in Scotland. Can. J. For. Res. 26: 1914-1921.
Schmidtling, R.C. 1994. Use of provenance tests to predict response to climatic change: Loblolly pine and Norway spruce. 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 and Forest 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 a Changing Environment. Academic Press. London, UK.
Urban, D.L., and H.H. Shugart. 1992. Individual based models 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. 352 p.
SECTION 11.FOREST MANAGEMENT RESPONES TO CLIMATE CHANGE
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. Growth responses of seven major co-occurring tree species of the northeastern United States to elevated CO2 . Can. J. For. Res. 20: 1479-1484.
Birdsey, R.A. and L.S. Heath. 1997. The forest carbon budget of the United States, Pp. 81-85 in USDA Forest Service global 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 and indicators 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 of terrestrial ecosystem carbon cycling to global climate change. 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 forests and atmosphere-biosphere exchange of carbon dioxide. Nature 329: 321-323.
Davis, M.B. 1989. Lags in vegetation response to greenhouse warming. Clim. Change 15: 75-82.
Freedman, B. and T. Keith. 1996. Planting trees for carbon credits: A discussion of context, issues, feasibility, and environmental benefits. Environ. Rev. 4: 100-111.
Harmon, M.E., W.K. Ferrell and J.F. Franklin. 1990. Effects on carbon storage of conversion of old-growth forests to young forests. Science 247: 699-702.
Halpin, P.N. 1997. Global climate change and natural-area protection: management responses and research directions. Ecol. Appl. 7: 828-843.
Harvey, A.E., M.F. Jurgensen and M.J. Larsen. 1980. Clearcut harvesting and ectomycorrhizae: Survival of activity on residual roots and influence on a bordering forest stand in western Montana. Can. J. For. Res. 10: 300-303.
Hedden, R.L. 1989. Global climate change: Implications for silviculture and pest management. Pp. 555-562 in Proc. Fifth Biennial Southern Silviculture Research Conf., USDA For. Serv. Gen. Tech. Rep. SO-74.
Hendricksen, O., J.B. Robinson and L. Chatarpaul. 1982. The microbiology 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 - an overview, Pp. 53-76 in Long-term Implications of Climate Change 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 warming analysis of selected boreal tree species, and potential responses 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 the past six centuries. Nature 392: 779-787.
McGuire, A.D., J.M. Melillo and L.A. Joyce. 1995. The role of nitrogen in the response of froest net primary production to 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 climate change and terrestrial net primary production. Nature 363: 234-240.
Miller, R.M. and D.J. Lodge. 1997. Fungal responses to disturbance: Agriculture and forestry. Pp. 65-84 in The Mycota 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 northern latitudes 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 hardwood forests in relation to timber management practices. Pp. 49- 56 in New perspectives on silvicultural management of northern 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? Science 243: 735-737.
Safranyik, L. 1990. Temperature and insect interactions in western North America. Pp. 166-170 in Are Forests the Answer?, Proc. Soc. Am. For. Nat. Conv., SAF Pub. 90-02, Bethesda, Maryland. 614 p.
Schindler, D.W. 1998. A dim future for boreal waters and 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 CO2 budget. Science 247: 1431-1438.
Van Wagner, C.E. 1988. The historical pattern of annual burned area in Canada. For. Chron. 64: 182-185.
Vitousek, P.M. 1991. Can planted forests counteract increasing atmospheric carbon dioxide? J. Environ.Qual. 20: 348-354.
Vitousek, P.M. 1993. Beyond global warming: ecology and global change. Ecology 75:1861-1876.
Vogel, G. and A. Lawler. 1998. Hot year, but cool response in Congress. Science 280:1684.
Wagner, M.R. 1990. Individual tree physiological responses 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. 614 p.
Wargo, P.M. and T.C. Harrington. 1991. Host stress and susceptibility. In Armillaria root disease, C.G. Shaw and 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 high temperature 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 plantations of the world: their extent, ecological attributes, and carbon storage. Agric. For. Meteorol. 84: 153-167.
Woodman, J.N. 1990. Adapting silviculture to forests impacted by climatic change. Pp. 204-207 in Are Forests the Answer? Proc. Soc. Am. For. Nat. Conv., SAF Pub. 90-02, Bethesda, Maryland. 614 p.
1. estimated average weight of wood per slash pile
2. a preliminary version of this table was prepared by Changhui Peng, OFRI.
This site is maintained by the Government of Ontario
Privacy |
Important Notices
© Queen's Printer for Ontario, 2007
Last modified: Tuesday October 21 2008