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The potential impacts of CO2-induced climate change on terrestrial carbon storage was estimated using the Holdridge Life-Zone Classification and four climate change scenarios derived from general circulation models. Carbon values were assigned to life-zones and their associated soils from published studies. All four scenarios suggest an increase in area occupied by forests although details of predicted patterns vary among the scenarios. There is a poleward shift of the forested zones, with an increase in the areal extent of tropical forests and a shift of the boreal forest zone into the region currently occupied by tundra. Terrestrial carbon storage increased from 0.4% (8.5 Gt) to 9.5% (180.5 Gt) above estimates for present conditions. These changes represent a potential reduction of 4 to 85 ppm on elevated atmospheric CO2 levels.

The response of terrestrial C storage to GCM derived climate change scenarios was investigated over a range of temporal and spatial scales. The potential changes in the global distribution of major ecosystem complexes were examined by combining changes in land cover and corresponding soil type with C storage estimates for each of the ecosystem types. All scenarios consistently showed an overall increase in global carbon storage. On a more regional basis, the potential impacts of climate change on the structure, composition and biomass dynamics of major forest types within the North American Boreal zone were investigated using individual based stand models. Biomass fluxes were found to be dependent on the tree species, site and GCM parameters. A method to simulate corresponding changes in intra- and interannual patterns of CO2 flux by combining a gap model with an ecosystem model which incorporates photosynthesis, respiration (both canopy and decomposer) and transpiration is demonstrated.

Data derived from the Advanced Very High Resolution Radiometer (AVHRR) on board the NOAA series of operational, polar orbiting, meteorological satellites have previously been shown to be quite useful for monitoring vegetation dynamics at scales ranging from regional (104 km2) to global. In this report, we demonstrate that these same data can be used to monitor potential breeding habitat for a highly mobile, granivorous African weaver-bird, the red-billed quelea (Quelea quelea). This species is often considered to be an agricultural pest, affecting cereal production throughout sub-Saharan Africa. The temporal resolution and very large (continental) spatial coverage provided by these data can provide a unique context within which to examine species distribution and abundance patterns.

[1] Abrupt forest disturbances generating gaps >0.001 km 2 impact roughly 0.4–0.7 million km 2 a 1 . Fire, windstorms, logging, and shifting cultivation are dominant disturbances; minor contributors are land conversion, flooding, landslides, and avalanches. All can have substantial impacts on canopy biomass and structure. Quantifying disturbance location, extent, severity, and the fate of disturbed biomass will improve carbon budget estimates and lead to better initialization, parameterization, and/or testing of forest carbon cycle models. Spaceborne remote sensing maps large-scale forest disturbance occurrence, location, and extent, particularly with moderate- and fine-scale resolution passive optical/near-infrared (NIR) instruments. High-resolution remote sensing (e.g., 1 m passive optical/NIR, or small footprint lidar) can map crown geometry and gaps, but has rarely been systematically applied to study small-scale disturbance and natural mortality gap dynamics over large regions. Reducing uncertainty in disturbance and recovery impacts on global forest carbon balance requires quantification of (1) predisturbance forest biomass; (2) disturbance impact on standing biomass and its fate; and (3) rate of biomass accumulation during recovery. Active remote sensing data (e.g., lidar, radar) are more directly indicative of canopy biomass and many structural properties than passive instrument data; a new generation of instruments designed to generate global coverage/sampling of canopy biomass and structure can improve our ability to quantify the carbon balance of Earth’s forests. Generating a high-quality quantitative assessment of disturbance impacts on canopy biomass and structure with spaceborne remote sensing requires comprehensive, well designed, and well coordinated field programs collecting high-quality ground-based data and linkages to dynamical models that can use this information.

Recent developments in individual-based forest simulators have made it possible to extend the basic approach to a wider range of forest ecosystems. One recent trend is toward more general representations of abiotic processes, and more attention to the role of tree life-history traits in generating forest response to environmental gradients. Gap models that explicitly attend spatial aspects of the light regime can be extended to simulate forest pattern at scales larger than the forest gap; examples at landscape and geographic scales are presented.

The National Research Council Earth Science Decadal Survey, Earth Science Applications from Space, recommends that DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice), an integrated L-band InSAR and multibeam Lidar mission, launch in the 2010-2013 timeframe. The mission will measure surface deformation for solid Earth and cryosphere objectives and vegetation structure for understanding the carbon cycle. InSAR has been used to study surface deformation of the solid Earth and cryosphere and more recently vegetation structure for estimates of biomass and ecosystem function. Lidar directly measures topography and vegetation structure and is used to estimate biomass and detect changes in surface elevation. The goal of DESDynI is to take advantage of the spatial continuity of InSAR and precision and directness of Lidar. There are several issues related to the design of the DESDynI mission, including combining the two instruments into a single platform, optimizing the coverage and orbit for the two techniques, and carrying out the science modeling to define and maximize the scientific output of the mission. ©2008 IEEE.

[1] Mangroves are salt tolerant plants that grow within the intertidal zone along tropical and subtropical coasts. They are important barriers for mitigating coastal disturbances, provide habitat for over 1300 animal species and are one of the most productive ecosystems. Mozambique's mangroves extend along 2700 km and cover one of the largest areas in Africa. The purpose of this study was to determine the countrywide mean tree height spatial distribution and biomass of Mozambique's mangrove forests using Landsat ETM+ and Shuttle Radar Topography Mission (SRTM) data. The SRTM data were calibrated using the Landsat derived land-cover map and height calibration equations. Stand-specific canopy height-biomass allometric equations developed from field measurements and published height-biomass equations were used to calculate aboveground biomass of the mangrove forests on a landscape scale. The results showed that mangrove forests covered a total of 2909 km2 in Mozambique, a 27% smaller area than previously estimated. The SRTM calibration indicated that average tree heights changed with geographical settings. Even though the coast of Mozambique spans across 16 degrees latitude, we did not find a relationship between latitude and biomass. These results confirm that geological setting has a greater influence than latitude alone on mangrove production. The total mangrove dry aboveground biomass in Mozambique was 23.6 million tons and the total carbon was 11.8 million tons.

Predicting ecosystem response to climate change is a dynamic version of the classic problem of understanding vegetation-climate interrelations. Computer models can synthesize current knowledge and are important tools for understanding possible ecosystem dynamics under changed conditions. Models based on individual plant biology and natural history have been tested with respect to their ability to simulate vegetation response to changed climate, and are being applied to assess the potential effects of future climate change.

A gap model of environmental processes and vegetation patterns in boreal forests was used to examine the sensitivity of permafrost and permafrostfree forests in interior Alaska to air temperature and precipitation changes. These analyses indicated that in the uplands of interior Alaska, the effect of climatic warming on the ecology of boreal forests may not be so much a direct response to increased air temperature as it may be a response to the increased potential evapotranspiration demands that will accompany climatic warmings. On poorlydrained north slopes with permafrost, the drier forest floor reduced the flux of heat into the soil profile. This was offset by increased fire severity, which by removing greater amounts of the forest floor increased the depth of soil thawing and converted the cold black spruce forests to warmer mixed hardwood-spruce forests. On well-drained south slopes, the increased potential water loss reduced available soil moisture, converting these mesic sites to dry aspen forests, or if too dry to steppe-like vegetation. Increases in precipitation offset the effects of increased potential evapotranspiration demands and mitigated these forest changes.

An Appalachian-oak forest in a small montane watershed was sampled to calibrate and test an existing forest dynamics simulation model. Indices developed in earlier studies by Whittaker were used to estimate the response of different tree species to soil moisture. As is the case in many forest modeling applications, neither detailed environmental data at a micro-spatial scale nor quantitative historical stand data were available for the study.

As part of SAFARI 2000, this study investigated fire severity associated with, and emissions released from, a wildfire that burned a total area of approximately 3200 km2 of semi‐arid savannahs in the region of Etosha National Park, Namibia. Percent tree cover derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to scale up from site‐level field measurements to landscape‐level emission fields. Empirical relationships relating fuel load and combustion completeness to tree cover were developed from field observations. These relationships were coupled to the remotely sensed data to determine the emissions released over the entire area burned. Emissions from this single fire event were estimated to be 1.4×1012 g of CO2, 52.4×109 g of CO, 1.5×109 g of CH4, 1.85×109 g of non‐methane hydrocarbons (NMHC), and 2.4×109 g of particles less than 2.5 µm (PM2.5). A Normalized Burned Index difference (NBI diff), representative of fire severity and modified for MODIS data was used to assess the...

Understanding patterns of biodiversity distribution is essential to conservation strategies1, but severe data constraints make surrogate measures necessary2,3,4. For this reason, many studies have tested the performance of terrestrial vertebrates as surrogates for overall species diversity, but these tests have typically been limited to a single taxon or region3,4,5,6,7,8,9,10. Here we show that global patterns of richness are highly correlated among amphibians, reptiles, birds and mammals, as are endemism patterns. Furthermore, we demonstrate that although the correlation between global richness and endemism is low, aggregate regions selected for high levels of endemism capture significantly more species than expected by chance. Although areas high in endemism have long been targeted for the protection of narrow-ranging species11,12, our findings provide evidence that endemism is also a useful surrogate for the conservation of all terrestrial vertebrates.

A striking change associated with modern human society has been the increase in atmospheric CO2 due to the increased burning of fossil fuels (coal, petroleum, natural gas) since the industrial revolution (Sarmiento and Siegenthaler 1992; Sarmiento and Bender 1994). One potential consequence of this atmospheric change is the so-called “greenhouse effect”, a global climatic warming induced by elevated atmospheric CO2 modifying the atmosphere’s opacity to infra-red radiation. Because CO2 is an essential component of plant photosynthesis, an increase in ambient CO2 levels immediately leads to the question as to whether these changes might be altering plant function globally and might also be changing vegetation patterns.

[1] In the biomass, soils, and peatlands of Siberia, boreal Russia holds one of the largest pools of terrestrial carbon. Because Siberia is located where some of the largest temperature increases are expected to occur under current climate change scenarios, stored carbon has the potential to be released with associated changes in fire regimes. Our concentration is on estimating a wide range of current and potential emissions from Siberia on the basis of three modeled scenarios. An area burned product of Siberia is introduced, which spans from 1998 through 2002. Emissions models are spatially explicit; therefore area burned is extracted from associated ecoregions for each year. Carbon consumption estimates are presented for 23 unique ecoregions across Siberia, which range from 3.4 to 75.4 t C ha−1 for three classes of severity. Total direct carbon emissions range from the traditional scenario estimate of 116 Tg C in 1999 (6.9 M ha burned) to the extreme scenario estimate of 520 Tg C in 2002 (11.2 M ha burned), which are equivalent to 5 and 20%, respectively, of total global carbon emissions from forest and grassland burning. Our results suggest that disparities in the amount of carbon stored in unique ecosystems and the severity of fire events can affect total direct carbon emissions by as much as 50%. Additionally, in extreme fire years, total direct carbon emissions can be 37–41% greater than in normal fire years, owing to increased soil organic matter consumption. Mean standard scenario estimates of CO2 (555–1031 Tg), CO (43–80 Tg), CH4 (2.4–4.5 Tg), TNMHC (2.2–4.1 Tg), and carbonaceous aerosols (4.6–8.6 Tg) represent 10, 15, 19, 12 and 26%, respectively, of the global estimates from forest and grassland burning. Accounting for smoldering combustion in soils and peatlands results in increases in CO, CH4, and TNMHC and decreases in CO2 emitted from fire events.

Fires, which are an intrinsic feature of southern African ecosystems, produce biogenic and pyrogenic losses of nitrogen (N) from plants and soils. Because of the long history of fires in these savannas, it was hypothesized that N2 fixation by legumes balances the N losses caused by fires. In this study, the N2 fixation activity of woody legumes was estimated by analyzing foliar delta15N and proportional basal area of N2 fixing species along experimental fire gradients in the Kruger National Park (South Africa). In addition, soil carbon (C) and N pools, foliar phosphorus (P) and gross N mineralization and nitrification rates were measured, to indicate the effects of fires on nutrient stocks and the possible N cycling processes modified by fires. Although observations of increased soil C/N and mineralization rates in frequently burned plots support previous reports of N losses caused by fires, soil %N did not decrease with increasing fire frequency (except in 1 plot), suggesting that N losses are replenished in burned areas. However, relative abundance and N2 fixation of woody legumes decreased with fire frequency in two of the three fire gradients analyzed, suggesting that woody legume N2 fixation is not the mechanism that balances N losses. The relatively constant %N along fire gradients suggests that these ecosystems have other mechanisms to balance the N lost by fires, which could include inputs by atmospheric deposition and N2 fixation by forbs, grasses and soil cyanobacteria. Soil isotopic signatures have been previously used to infer patterns of fire history. However, the lack of a relationship between soil delta15N and fire frequency found in this study indicates that the effects of fires on ecosystem delta15N are unpredictable. Similar soil delta15N along fire gradients may reflect the contrasting effects of increased N gaseous emissions (which increases delta15N) and N2 fixation other than that associated with woody legumes (which lowers delta15N) on isotopic signatures.

[1] Available fuel loads for burning in savanna ecosystems in the southern African region have been estimated using a new Fuel load-Net Primary Production model based on ecophysiological processes such as respiration and Potential Evapotranspiration. The model outputs 15-day standing available fuel load layers for an entire year (a total of 24 layers). Published data from the Southern African Fire-Atmosphere Research Initiative (SAFARI-92) project and from the Southern African Regional Science Initiative (SAFARI 2000) field campaigns were generally in agreement with the estimations. Consistently with previous studies, precipitation was recognized to be the major climatic driver for fuel production. As a consequence, even though there was a regional increase in precipitation in 1999–2000 as compared to the 1991–1992 periods, the temporal and spatial variability in precipitation at fine scales (site level) was important enough to restrict generalities over the entire region for fuel load production. Four areas of interest, Etosha National Park (Namibia), Mongu (Zambia), Kasama (Zambia), and Kruger National Park (South Africa), were selected to reconstruct an aridity gradient and analyze their fuel load variability over the two years. These areas presented contrasting fuel load distributions for the two very different studied periods with arid areas producing heavier fuel loads in 1999–2000, and the more humid areas producing heavier fuel loads in 1991–1992. The consequences of such fuel load variability and the use of such results are discussed. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1615 Global Change: Biogeochemical processes (4805); 1640 Global Change: Remote sensing; 3354 Meteorology and Atmospheric Dynamics: Precipitation (1854); 9305 Information Related to Geographic Region: Africa; KEYWORDS: climate, precipitation, net primary production, Fire, NOVI, tree cover

[1] Source strengths to the atmosphere for different forms of carbon (CO2, CO, CH4, nonmethane hydrocarbons (NMHC), and PM2.5) produced by biomass burning were calculated during the Southern African Regional Science Initiative (SAFARI 2000) intensive study period (August and September 2000) for Africa south of the equator. For a given pixel burned, these calculations are a product of the aboveground biomass before a fire, the proportion of biomass that is burned by the fire, and the emission factor for a given carbon compound based on the combustion efficiency. The total emission for the region is the summation of such calculations for all the burned pixels. Products used for these calculations are a prototype satellite-based burned area based on the SPOT-VGT-S1 satellite product, a fuel load map produced by a simulation model developed and applied to southern Africa at 1 km2 resolution, information from fire experiments from our own research in southern Africa to compute combustion completeness, and emission factors published for the region. Over August and September 2000, 31,067 fires detected by the SPOT satellite are calculated to have emitted 96.9 × 1012 g CO2, 4.6 × 1012 g CO, and lesser amounts of CH4, NMHC, and PM2.5. These calculations are in the range of previous estimates of the emissions of these compounds for southern Africa. Along with documenting the estimates of the emissions during the SAFARI 2000 campaign, regional emission estimates are very strongly controlled by the burned area of fires due to a correlation between the cumulative distribution of percent burned area and the cumulative distribution of percent emissions.

We analyzed half-hourly tower-based flux measurements of carbon dioxide (CO2) from a boreal aspen forest and a temperate mixed deciduous forest in Canada to examine the influences of clouds on forest carbon uptake. We showed that the presence of clouds consistently and significantly increased the net ecosystem exchanges (NEE) of CO2 of both forests from the level under clear skies. The enhancement varied with cloudiness, solar elevation angles, and differed between the two forests. For the aspen forest the enhancement at the peak ranged from about 30% for the 20°–25° interval of solar elevation angles to about 55% for the 55°–60° interval. For the mixed forest the enhancement at the peak ranged from more than 60% for the 30°–35° interval of solar elevation angles to about 30% for the 65°–70° interval. Averaged over solar elevation angles >20°, the aspen and mixed forests had the maximal NEE at the irradiance equivalent to 78 and 71% of the clear-sky radiation, respectively. The general patterns of current sky conditions at both sites permit further increases in cloudiness to enhance their carbon uptake. We found that both forests can tolerate exceedingly large reductions of solar radiation (53% for the aspen forest and 46% for the mixed forest) caused by increases in cloudiness without lowering their capacities of carbon uptake. We suggest that the enhancement of carbon uptake under cloudy conditions results from the interactions of multiple environmental factors associated with the presence of clouds. An edited version of this paper was published by AGU. Copyright 1999 American Geophysical Union.

JOHN F. LAMOREUX,∗†† JOHN C. MORRISON,† TAYLOR H. RICKETTS,† DAVID M. OLSON,†∗∗ ERIC DINERSTEIN,† MEGHAN W. MCKNIGHT,‡ AND HERMAN H. SHUGART∗ ∗Department of Environmental Sciences, University of Virginia, 291 McCormick Road, Charlottesville, Virginia 22904, U.S.A. †World Wildlife Fund–US, 1250 24th Street NW, Washington, D.C. 20037, U.S.A. ‡Curriculum in Ecology, Miller Hall, University of North Carolina, Chapel Hill, North Carolina 27599, U.S.A.

Prediction of the response in vegetation either locally or globally to a change in the climate presents a rich array of scientific challenges. One must understand the dynamics of ecological systems at different time and space scales (Delcourt et al. 1983). One must understand how to handle the mutual causality between the structure of ecosystems and their functioning (Shugart in press). One must extrapolate from the physiological responses of the few species that we know fairly well to a vast array of species that we hardly know at all.

Accurate quantification of terrestrial carbon storage and its change is of key importance to improved understanding of global carbon dynamics. Forest management influences carbon sequestration and release patterns, and gap models are well suited for evaluating carbon storage. An individual-based gap model of forest dynamics, FAREAST, is applied across Russia to estimate aboveground carbon storage under management scenarios. Current biomass from inventoried forests across Russia is compared to model-based estimates and potential levels of biomass are estimated for a set of simplified forestry practices. Current carbon storage in eastern Russia was lower than for the northwest and south, and lower than model estimates likely due to high rates of disturbance. Model-derived carbon storage in all regions was not significantly different between the simulated ‘current’ and hypothetical ‘even-aged’ management strategies using rotations of 150 and 210 years. Simulations allowing natural maturation and harvest after 150 years show a significant increase in aboveground carbon in all regions. However, it is unlikely that forests would be left unharvested to 150 years of age to attain this condition. These applications indicate the value of stand simulators, applied over broad regions such as Russia, as tools to evaluate the effect of management regimes on aboveground carbon storage.

Fire is a major disturbance regime for boreal forest and is also a major factor in the exchange of carbon between biotic components and the atmosphere. The occurrence of fire in boreal forests is extensive, and individual fire events typically cover large areas, with fires between 1000 and >1000000 ha in size accounting for >98% of all area burned. The effects of these large fire events can easily be discriminated on a variety of satellite remote sensing system. Studies are currently underway to compare field data of surface characteristics in a fire-disturbed spruce forest in east-central Alaska to a variety of satellite data collected over this region. These studies have shown that remote sensing data collected in different regions of the electromagnetic spectrum can be used to estimate different surface characteristics related to the effects of the fire. The authors discuss how these satellite-derived surface parameters can be used to study patterns of carbon storage and release in fire-disturbed spruce forests. Three different aspects of the carbon cycle are presently being studied using multi-sensor satellite data: (1) the amount of carbon released during into the atmosphere via biomass burning during the fire event; (2) carbon flux rates after the fire due to aerobic (CO/sub 2/) and anaerobic (CH/sub 4/) decomposition; and (3) patterns of carbon storage in aboveground biomass during secondary succession. The authors illustrate how satellite-remote sensing data can be used to study these processes. >

Gap-phase replacement is a general phenomenon found in forest ecosystems, worldwide. Different tree species can be expected to produce different sizes of gaps when they die. Species also vary in their regeneration success in gaps of different sizes. In this paper, the gap-phase interactions among tree species in a forest stand are simulated by a role-type stand model called ROPE. By incorporation of environmental effects on tree height, ROPE can simulate forest composition and stand leaf area under different climate conditions. The model was developed for forest ecosystems in northeastern China and was used to simulate the forest landscape structures under current climate conditions and under four climate change scenarios for greenhouse gas related warming. These scenarios were obtained from general circulation models developed by different atmospheric research centers. Korean pinebroadleaf mixed forest and larch forest are the major stand types in the study area under present conditions. Under the four climate change scenarios, Korean pine-broadleaf mixed forest would be expected to occur only on the higher parts of large mountains. Larch forest only would be found north of the study area. Broadleaf forest would become the dominant vegetation over the study area. Use of the Kappa statistic to test for similarity in spatial maps, indicates that each climate change scenario would result in a significant change of forest distributions.

O'Connell, M.J.; Shugart, H.H., and Okin, G.S., 2012. Measurement and monitoring of barrier island forest sensitivity to ecohydrological change using LIDAR remote sensing. Both sea-level rise and the attendant changes in wave overwash events can greatly modify or destroy coastal terrestrial ecosystems; thus, it is essential to have a priori identification of particularly sensitive forests (and other ecosystems). This article reports an application of airborne LIDAR (light detection and ranging) to study vulnerable coastal forests—the important case of natural mid-Atlantic maritime pine forests. We investigate the Experimental Advanced Airborne Research LIDAR (EAARL) for its accuracy in making detailed forest structural measurements, producing inferential statistics for remote monitoring, and detecting changes in barrier island forest ecohydrology. Results show that EAARL can be deployed with high confidence in loblolly pine (Pinus taeda L) ecosystems for baseline biophysical descriptions. EAARL m...

An analysis is undertaken to examine the potential impacts of a global climate chang on patterns of potential terrestrial C storage and resulting fluxes between terrestrial any atmospheric pools. A bioclimatic model relating the current distribution of vegetation to globe climate patterns is used to examine the potential impacts of a global climate change on the glob distribution of vegetation. Climate change scenarios are based on the predictions of two genera circulation model equilibrium simulations for a 2XCO2 atmosphere. Current estimates of 1 reserves in the vegetation types and associated soils are then used to calculate changes i potential terrestrial C storage under the two climate change scenarios. Results suggest a potentia negative feedback to increasing atmospheric concentrations of CO2, with the potential fo terrestrial C storage increasing under both scenarios. These results represent an equilibriun analysis, assuming the vegetation and soils have tracked the spatial changes in climate patterns An approach for providing an estimate of the transient response between the two equilibria (i.e. current and 2XCO2 climates) is presented. The spatial transitions in vegetation predicted by th equilibrium analyses are classified as to the processes controlling the transition (eg., succession dieback, species immigration). Estimates of the transfer rates related to these processes are the used to estimate the temporal dynamics of the vegetation/soils change and the associated pools. Results suggest that although the equilibrium analyses show an increased potential for storage under the climate change, in the transient case the terrestrial surface acts as a source c CO2 over the first 50 to 100 yrs following climate change.

List of contributors 1. Introduction Herman H. Shugart, Rik Leemans and Gordon B. Bonan Part I. Processes in Boreal Forests Gordon B. Bonan: 2. Silvics of the circumpolar boreal forest tree species Nedialko Nikolov and Harry Helmisaari 3. The reproductive process in boreal forest trees John C. Zasada, Terry L. Sharik and Markku Nygren 4. Soil temperature as an ecological factor in boreal forests Gordon B. Bonan 5. Fire as a controlling process in the North American boreal forest Serge Payette 6. The role of forest insects in structuring the boreal landscape C. S. Holling Part II. Patterns in Space and Time in Boreal Forests Herman H. Shugart: 7. The transition between boreal forest and tundra Luc Sirois 8. The southern boreal-northern hardwood forest border John Pastor and David J. Mladenoff 9. Transitions between boreal forest and wetland F. Z. Glebov and M. D. Korzukhin 10. Remote sensing technology for forest ecosystem analysis K. Jon Ranson and Darrel L. Williams 11. The nature and distribution of past, present and future boreal forests: lessons for a research and modeling agenda Allen M. Solomon Part III. Computer Models for Synthesis of Pattern and Process in the Boreal Forest Rik Leemans: 12. Individual-tree-based models of forest dynamics and their application in global change research Herman H. Shugart and I. Colin Prentice 13. Population-level models of forest dynamics M. D. Korzukhin and M. Ya. Antonovski 14. A spatial model of long-term forest fibre dynamics and its applications to forests in western Siberia M. Ya. Antonovski, M. T. Ter-Mikaelian and V. V. Furyaev 15. A simulation analysis of environmental factors and ecological processes in North American boreal forests Gordon B. Bonan 16. The biological component of the simulation model for boreal forest dynamics Rik Leemans 17. Role of stand simulation in modeling forest response to environmental change and management interventions Peter Duinker, Ola Sallnas and Sten Nilsson 18. Concluding comments Herman H. Shugart, Rik Leemans and Gordon B. Bonan References Index.

Introduction The problem of predicting ecological responses to global environmental change has generated a rich array of scientific challenges for ecosystem ecologists. The International Geosphere–Biosphere Program (IGBP), chartered by the International Council of Scientific Unions in 1986, has as its objective: ‘… to describe and understand the interactive physical, chemical, and biological processes that regulate the total earth system, the unique environment that it provides for life, the changes that are occurring in this system, and the manner in which they are influenced by human activities.’ (International Council of Scientific Unions 1986.) IGBP is one of the most exciting scientific opportunities of our time. The intellectual challenge is ultimately to unify ecological and geophysical sciences at the global scale: a large undertaking in which ecosystem ecology must play a central part. One of the major tools for this multidisciplinary undertaking will be ecosystem simulation models implemented on high-speed computers. Global dynamics models exist for the atmosphere and oceans as physical systems, but not yet for ecosystems and their interactions with the atmosphere and oceans. This book represents the first attempt to develop a unified model of a major biome (the boreal forest) at the global scale. The model described in the chapters by Bonan (Chapter 15) and Leemans (Chapter 16) belongs to a well-established class of models that simulate the dynamics of forests by projecting the change in size of individual trees over time, through explicit representations of the interactions between arrays of individuals and their local resource environment.

The conservation and management of tropical ecosystems must consider the temporal and spatial dynamics of vegetation. An understanding of the patterns and processes of ecosystems as they relate to environmental gradients is of particular importance in the face of potential global climate change as a result of increasing atmospheric levels of CO2.

Publisher Summary This chapter is a review on the modeling of the potential response of vegetation to global climate change.. Models provide a means of formalizing a set of assumptions/hypotheses linking pattern and process, allowing for extrapolation beyond the range of observed phenomena. The purpose of this chapter is not to provide an exhaustive review of models relating climate and plant pattern; rather it is to examine a specific set of models which are currently being used to investigate the question of plant response to climate change at a global scale. The focus is on developing a methodology for predicting changes in the large-scale distribution of vegetation (that is, global distribution of biomes or ecosystem complexes) under changing global climate patterns. This chapter starts with a discussion on climate–vegetation classification. The chapter focuses on the application of holdridge life-zone classification to climate change at a global scale, followed by the application of a plant energy balance model to predicting changes in leaf area under changing climate conditions. This is followed by the description of modeling temporal dynamics. Furthermore, this chapter introduces individual-based forest gap models. The chapter ends with the discussion of application of gap models to predict forest response to climate change.

Climate warming could strongly influence the structure and composition of the Eurasian boreal forest. Temperature related changes have occurred, including shifts in treelines and changes in regeneration. Dynamic vegetation models are well suited to the further exploration of the impacts that climate change may have on boreal forests. Using the individual-based gap model FAREAST, forest composition and biomass are simulated at over 2000 sites across Eurasia. Biomass output is compared to detailed forest data from a representative sample of Russian forests and a sensitivity analysis is performed to evaluate the impact that elevated temperatures and modified precipitation will have on forest biomass and composition in Eurasia. Correlations between model and forest inventory biomass are strong for several boreal tree species. A significant relationship is shown between altered precipitation and biomass. This analysis showed that a modest increase in temperature of 2 ◦ C across 200 years had no significant effect on biomass; however further exploration with increased warming reflective of values measured within Siberia, or at an increased rate, are warranted. Overall, FAREAST accurately simulates forest biomass and composition at sites throughout a large geographic area with widely varying climatic conditions and produces reasonable biomass responses to simulated climatic shifts. These results indicate that this model is robust and useful in making predictions regarding the effect of future climate change on boreal forest structure across Eurasia.

We review the state-of-the-art of models of forests and grasslands that could be used to predict the impact of a future climate change arising from increased atmospheric carbon dioxide concentration. Four levels of resolution are recognized: physiologically based models, population models, ecosystem models, and regional or global models. At the physiological level a number of important processes can be described in great detail, but these models often treat inadequately interactions with nutrient cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand, encapsulate relationships between the plants and the soil system, but at the expense of requiring more ad ho formulations of processes. At the regional and global scale we have so far only steady-state models, which cannot be used to predict transients caused by climate change. However, our conclusion is that, in spite of the gaps in knowledge, there are several models based on dominant processes that are well enough understood for the predictions of those models to be taken seriously.

No adequate community-wide mechanism or set of standards currently exists to ensure the long-term reproducibility of results from numerical modeling in biogeochemical research. Various investigators maintain copies of code and supporting materials through ad hoc methods, and some models and modeling studies are not archived by any mechanism other than the published manuscripts describing specific research results. This state of affairs invites trouble. To illustrate this situation, one of the authors of this article was recently involved in producing a state-of-the-art review on the topic of the effects of climate change on forests. The literature on this topic contains a rich array of results from dynamic models of global or regional vegetation produced by forcing these models with climate change scenarios.

are used to generate two separate, canopy-disturbance chronologies dating to the early 1700s. Additionally, ages of Q. alba and other tree species provide estimates of decadal establishment in both forests. Comparing these dendrochronological reconstructions of forest history with an analysis of letters and descriptive information from the Madison family and more recent landowners clarifies both the timing and relative magnitude of disturbance and establishment events set forth by the documentary reconstructions. Furthermore, this comparison also reveals that disturbance and establishment events in these two forests frequently coincide with changes in land use and ownership with notable canopy disturbances occurring in 1749, 1880s, 1920s, and 1987 and an establishment episode in the mid-1800s. These events have most likely increased the dominance of L. tulipifera; however, both forests still retain trees that pre-date Madison-family settlement.

KIRWAN, J. L. (College of Natural Resources, Virginia Tech, Blacksburg, VA 24061), and H. H. SHUGART (Department of Environmental Sciences, Univ. of Virginia, Charlottesville, VA 22903). Vegetation and two indices of fire on the Delmarva Peninsula. J. Torrey Bot. Soc. 127:44-50. 2000. Vegetation, soil charcoal, and fire modeling measurements were used to test the hypothesis that beech (Fagus grandifolia Ehrh.) is an indicator of long-term fire history on the Delmarva Peninsula. Three forest communities were determined using principal components analysis, and beech and red maple (Acer rubrum L.) were shown to correlate negatively and significantly with fire. These results confirm the observations of early ecologists who recognized disturbance as a major influence on southeastern coastal plain forests.

The successful use of natural abundances of carbon (C) and nitrogen (N) isotopes in the study of ecosystem dynamics suggests that isotopic measurements could yield new insights into the role of fungi in nitrogen and carbon cycling. Sporocarps of mycorrhizal and saprotrophic fungi, vegetation, and soils were collected in young, deciduous-dominated sites and older, coniferous-dominated sites along a successional sequence at Glacier Bay National Park, Alaska. Mycorrhizal fungi had consistently higher δ15N and lower δ13C values than saprotrophic fungi. Foliar δ13C values were always isotopically depleted relative to both fungal types. Foliar δ15N values were usually, but not always, more depleted than those in saprotrophic fungi, and were consistently more depleted than in mycorrhizal fungi. We hypothesize that an apparent isotopic fractionation by mycorrhizal fungi during the transfer of nitrogen to plants may be attributed to enzymatic reactions within the fungi producing isotopically depleted amino acids, which are subsequently passed on to plant symbionts. An increasing difference between soil mineral nitrogen δ15N and foliar δ15N in later succession might therefore be a consequence of greater reliance on mycorrhizal symbionts for nitrogen supply under nitrogen-limited conditions. Carbon signatures of mycorrhizal fungi may be more enriched than those of foliage because the fungi use isotopically enriched photosynthate such as simple sugars, in contrast to the mixture of compounds present in leaves. In addition, some 13C fractionation may occur during transport processes from leaves to roots, and during fungal chitin biosynthesis. Stable isotopes have the potential to help clarify the role of fungi in ecosystem processes.

Boreal forest fires in Russia in 1998 may have covered a much larger area than originally reported and may have been mostly crown fires, releasing more greenhouse gases into the atmosphere than surface fires. These conclusions are based on analysis of Advanced Very High Resolution Radiometer (AVHRR) data and discussions with Russian fire officials. A more complete analysis of AVHRR data collected since 1980 is underway to determine overall fire patterns in Russia's boreal forests. The year 1998 was an extreme fire year throughout the boreal forest regions of both North America and Eurasia. Over 11 million hectares burned. In Alaska and Canada alone, 4.7 million hectares of boreal forests burned in 1998, according to estimates by national fire monitoring systems in those places.