Canada and Alaska occupy an area of 11.1 million km2, almost 10% of the vegetated cover of the Earth's surface. In the Western Hemisphere North of 50o N, terrestrial interactions with the climate system are dominated by the land mass of Canada and Alaska. The forests of this region, which occupy an area of approximately 4 million km2 (~10% of global forest area), represent a wood resource of global economic significance with Canada responsible for approximately 11% of global industrial roundwood production in the 1990s (Perez-Garcia, 2002). Land cover in Canada and Alaska has been undergoing substantial changes in recent decades (Kurz and Apps, 1999; Stocks et al., 2000; Sturm et al., 2001; Silapaswan et al., 2001; Podur et al., 2002; Lloyd et al., 2003a).

Wildfire is a common occurrence in ecosystems of northern high latitudes, and changes in the fire regime of this region have consequences for carbon feedbacks to the climate system. To improve our understanding of how wildfire influences carbon dynamics of this region, we used the process‐based Terrestrial Ecosystem Model to simulate fire emissions and changes in carbon storage north of 45°N from the start of spatially explicit historically recorded fire records in the twentieth century through 2002, and evaluated the role of fire in the carbon dynamics of the region within the context of ecosystem responses to changes in atmospheric CO 2 concentration and climate. Our analysis indicates that fire plays an important role in interannual and decadal scale variation of source/sink relationships of northern terrestrial ecosystems and also suggests that atmospheric CO 2 may be important to consider in addition to changes in climate and fire disturbance. There are substantial uncertainties in the effects of fire on carbon storage in our simulations. These uncertainties are associated with sparse fire data for northern Eurasia, uncertainty in estimating carbon consumption, and difficulty in verifying assumptions about the representation of fires that occurred prior to the start of the historical fire record. To improve the ability to better predict how fire will influence carbon storage of this region in the future, new analyses of the retrospective role of fire in the carbon dynamics of northern high latitudes should address these uncertainties.

The arctic tundra and boreal forest were once considered the last frontiers on earth because of their vast expanses remote from agricultural land-use change and industrial development. These regions are now, however, experiencing environmental and social changes that are as rapid as those occurring anywhere on earth. This paper summarizes the role of northern regions in the global system and provides a blueprint for assessing the factors that govern their sensitivity to social and environmental change.

Abstract Strategies to mitigate anthropogenic climate change recognize that carbon sequestration in the terrestrial biosphere can reduce the build-up of carbon dioxide in the Earth's atmosphere. However, climate mitigation policies do not generally incorporate the effects of these changes in the land surface on the surface albedo, the fluxes of sensible and latent heat to the atmosphere, and the distribution of energy within the climate system. Changes in these components of the surface energy budget can affect the local, regional, and global climate. Given the goal of mitigating climate change, it is important to consider all of the effects of changes in terrestrial vegetation and to work toward a better understanding of the full climate system. Acknowledging the importance of land surface change as a component of climate change makes it more challenging to create a system of credits and debits wherein emission or sequestration of carbon in the biosphere is equated with emission of carbon from fossil fuels. Recognition of the complexity of human-caused changes in climate does not, however, weaken the importance of actions that would seek to minimize our disturbance of the Earth's environmental system and that would reduce societal and ecological vulnerability to environmental change and variability. © 2003 Elsevier Science Ltd. All rights reserved.

In 2002 a project in Saskatchewan became the first forest carbon (C) sequestration project to be formally reviewed and approved in Canada under the Greenhouse Gas Emission Trading (GERT) Pilot. GERT concluded that the project will result in real, measurable, verifiable and surplus net sequestration, calculated as C stock changes in the with-project case less C stock changes in the reference (without project) case. The project is a 50-year agreement (2000–2050) in which Saskatchewan Environment sells net C sequestration to the provincial electrical utility Saskatchewan Power Corporation. Net sequestration of 1.6 Mt C is expected to result from the establishment of white spruce plantations on 3300 ha and from forest protection through creation of 206 000 ha of Forest Carbon Reserves. Issues that arose in the review included leakage, the permanence of the sequestered carbon and risk of losses, establishment of the reference case, methodologies for projections of impacts, approaches for sampling and measurements, and accounting methods. GERT established a number of reporting and other conditions to be fulfilled when estimates of actual net sequestration are registered. Future forest C sequestration projects, project reviews and policy development will be able to draw upon the lessons learned from the Saskatchewan project. Key words: carbon sequestration, carbon sequestration projects, Saskatchewan, Greenhouse Gas Emission Reduction Trading Pilot, plantations, forest protection, leakage, permanence, carbon accounting, carbon measurement

Carbon (C) budgets of Ontario’s forest ecosystems for the period 1920–1990 were calculated using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2). Results show that total forest biomass C in Ontario increased from 1.83 Pg (1015 g) to 2.56 Pg between 1920 and 1970, then decreased to 1.70 Pg by 1990. Carbon in soil and forest floor dead organic matter (DOM) increased from 8.30 to 11.00 Pg between 1920 and 1985 but decreased to 10.95 Pg by 1990. Ontario’s forest ecosystems acted as a C sink sequestering 41–74 Tg (1012 g) C per year from 1920 to 1975, but became a C source releasing 7–32 Tg C per year (5-year average) after 1975. Disturbances (fire, insects and harvesting) enhanced both direct and indirect C emissions, and also affected average forest age and C sequestration. Net primary production (NPP), net ecosystem production (NEP), and net biome production (NBP) were affected by both disturbances and average forest age. Forests in the boreal (BO, 62.66 M ha), cool temperate (CT, 7.77 M ha) and moderate temperate (MT, 0.20 M ha) regions had different C dynamics. However, boreal forests dominated Ontario’s forest C budget because of the large area and associated C stock. Detailed C budgets for 1990 were also analyzed. The average forest ages in 1990 were 36.2 years for BO, 43.4 years for CT, and 92.1 years for MT regions, respectively. The total C stock of Ontario’s forest ecosystems (excluding peatlands) was estimated to be 12.65 Pg, including 1.70 Pg in living biomass and 10.95 Pg in DOM and soil. Average C density was 179 Mg ha−1 (106 g) (24 Mg ha−1 for biomass and 155 Mg ha−1 for DOM and soil). The total net C balance (excluding harvest removal) was −31.8 Tg. NPP, NEP and NBP were 267.6, −28.2 and −40.6 Tg per year, respectively. The young age (36.2) of Ontario’s boreal forests indicates a great potential for C sequestration and storage. Roughly 1 Pg C could be sequestered with a 10-year increase in forest age. A less severe disturbance regime and/or higher NPP would convert Ontario’s forest ecosystems back to a C sink.

Abstract The responses of high latitude ecosystems to global change involve complex interactions among environmental variables, vegetation distribution, carbon dynamics, and water and energy exchange. These responses may have important consequences for the earth system. In this study, we evaluated how vegetation distribution, carbon stocks and turnover, and water and energy exchange are related to environmental variation spanned by the network of the IGBP high latitude transects. While the most notable feature of the high latitude transects is that they generally span temperature gradients from southern to northern latitudes, there are substantial differences in temperature among the transects. Also, along each transect temperature co-varies with precipitation and photosynthetically active radiation, which are also variable among the transects. Both climate and disturbance interact to influence latitudinal patterns of vegetation and soil carbon storage among the transects, and vegetation distribution appears to interact with climate to determine exchanges of heat and moisture in high latitudes. Despite limitations imposed by the data we assembled, the analyses in this study have taken an important step toward clarifying the complexity of interactions among environmental variables, vegetation distribution, carbon stocks and turnover, and water and energy exchange in high latitude regions. This study reveals the need to conduct coordinated global change studies in high latitudes to further elucidate how interactions among climate, disturbance, and vegetation distribution influence carbon dynamics and water and energy exchange in high latitudes.

Canada's forests play an important role in the global carbon (C) cycle. Forest management activities, implemented at the operational scale, can have a significant impact on the C budget of Canada's forests. With the increasing national and international recognition that forest management activities can contribute to national C sources and sinks, forest managers could benefit from having a scientifically credible tool to assess the potential impacts of alternate management activities on the C stocks and stock changes on their land base. Such a tool must incorporate the best available science, be compliant with evolving international accounting rules and have enough flexibility to address the types of scenarios and management questions that are of interest to forest managers. To be cost effective and efficient for use by forest managers, the tool should make use of existing information on inventory, growth and yield, and disturbances that their analysts routinely use in their forest management planning activities. The readily available information must be augmented with additional data and modelling to estimate changes in those C pools that are not commonly included in forest inventories, such as carbon in the dead organic matter associated with litter, coarse woody debris and soil C. Building upon the past decade of work in the development and application of the C Budget Model of the Canadian Forest Sector (CBM-CFS2), the Canadian Forest Service C Accounting Team is now working with the Model Forest Network to develop, test and deliver an operational scale C accounting tool and its supporting databases with regional parameter values. When fully developed (2004), the operational model will be made available without charge to anyone interested in using it to estimate landscape level forest C stocks and C stock changes. Expertise developed within the extensive network of Model Forests and their partners in Canada will facilitate technology transfer and training of the larger user community. The tools and the technology transfer program will empower forest managers to include considerations of the impacts of the planned activities on forest C stocks. This will increase the potential use of forests and forest management activities in contributing towards a greenhouse gas emission reduction strategy.

Most ecosystem simulation models are large monolithic simulation programs that are machine dependent and difficult to reuse by other modelers. One way to effectively reuse existing ecosystem models is to break the models into smaller functional parts. These parts are then reconstructed into standardized model components which can be pieced together to form a new model with the desired characteristics. triplex is a flexible and customizable prototype model for forest ecosystem simulation that was constructed using three existing models: 3-pg, treedyn3, and century 4.0. Well-established parts of these models were rebuilt as Component Object Model (COM) objects with borland c++ Builder. These components can be integrated through triplex's intuitive user interface to form a customized new model. Model developers from different modeling environments (such as visual basic, visual c++, and delphi) can easily reuse these COM objects. triplex features a public information unit that supports various components working together. In contrast with most existing models, triplex also supports component overload, where two or more components that have the same or a similar role in the customized model, can work together. This further increases the flexibility of model reuse.

The three objectives of this paper were: to summarize net primary production (NPP) and carbon allocation patterns for boreal forests, to examine relationships between climatic and biological variables and NPP, and to examine carbon allocation coefficients for all boreal forests or types of boreal forests that can be used to estimate NPP from easily measured components of NPP. Twenty-four Class I stands (complete NPP budgets) and 45 Class II boreal forest stands (aboveground NPP [NPPA] and budget only) were identified. The geographic distribution of the Class I stands was not uniform; 46% of the stands were from two studies in North America, and only one stand was from the important larch forests of Eurasia. Total (above- and belowground) net primary production (NPPT) ranged from 52 to 868 g C·m−2·yr−1 and averaged 424 g C·m−2·yr−1. NPPA was consistently larger for deciduous than for evergreen boreal forests in each of the major boreal regions, especially for boreal forests in Alaska. Belowground net primary production:total net primary production (NPPB : NPPT) ratios were consistently larger for evergreen (0.36) than deciduous (0.19) boreal forests. NPP of different-aged stands in age sequence varied from 44% to 77%, a magnitude equal to or greater than that of climatic factors or vegetation type. NPP and NPPA were positively correlated (r2 = 0.66–0.68) to mean annual aboveground increment for Class I stands, and this empirical relationship explained 81% of the observed variation of NPPA for Class II stands. These robust relationships provide an approach for increasing the number and spatial coverage of boreal forest NPP data needed to evaluate NPP estimates from ecosystem models. Notable deficiencies of boreal forest NPP data were ground layer vegetation and belowground NPP data, NPP data for boreal forest age sequences, and NPP data for boreal larch ecosystems in Eurasia.

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Canada is a signatory to the Kyoto Protocol and must report on reforestation, afforestation and deforestation activities since 1990. Reporting commitments also include a baseline estimate of forest carbon stocks in 1990 and the monitoring of changes in carbon stocks leading up to the reporting period 2008 to 2012. Canada has 10% of the world's forests (418 million hectares), which account for a significant amount of stored carbon. The determination of above-ground carbon stocks in the forest can be based on several sources: remote sensing, models of vegetation growth, book-keeping carbon models, and traditional forest inventories. Estimating above-ground carbon with remote sensing requires the fusion and integration of remote sensing data with topographic, forest cover and other geospatial information. Multi-temporal LANDSAT TM imagery was used in conjunction with GIS data to compute above-ground biomass from which the carbon content is determined. In addition to biomass, other key factors, which play a role in the determination of carbon stocks, include species and age distribution, forest structure, and climate variables. The paper reports on remote sensing experiments to determine the above-ground carbon stocks for a test site near Hinton, Alberta, Canada. It is expected that this approach will be useful in supporting Canada's reporting commitments on the sustainability its forest resources.

Implementation of some of the articles of the Kyoto Protocol will require rules for accounting and for defining baselines against which reduction of greenhouse-gas emissions, or enhancement of greenhouse-gas removals, are to be measured. Project accounting needs to provide incentives to ensure that the objective of the United Nations Framework Convention on Climate Change (UNFCCC) is served and that the interests of all participating parties are respected. To establish the emission reduction achievements of activities is complex as it is inherently very difficult to define the counterfatctuel baseline. Here, we articulate four basic principles — accuracy, comprehensiveness, conservativeness and practicability — that can be used to guide the construction of baselines for greenhouse-gas mitigation projects. The overall aim is to have accurate, comprehensive, and conservative baselines; but this aim needs to be balanced to yield baselines that are as simple as possible, can be practically implemented, and provide incentives to fulfill the ultimate objective of the UNFCCC.

The Kyoto Protocol achieved a significant breakthrough by including terrestrial carbon sources and sinks into a legally binding emissions reduction framework. The effectiveness of the portocol can be improved by adopting a full carbon budget. Terrestrial carbon sinks are part of an active biological cycle and can offset fossil fuel emissions only temporarily, from decades to a century. They can thus buy time to address anthropogenic perturbation emissions.

In this paper, which was prepared as part of IEA Bioenergy Task XV (“Greenhouse Gas Balances of Bioenergy Systems”), we outline a standard methodology for comparing the greenhouse gas balances of bioenergy systems with those of fossil energy systems. Emphasis is on a careful definition of system boundaries. The following issues are dealt with in detail: time interval analysed and changes of carbon stocks; reference energy systems; energy inputs required to produce, process and transport fuels; mass and energy losses along the entire fuel chain; energy embodied in facility infrastructure; distribution systems; cogeneration systems; by-products; waste wood and other biomass waste for energy; reference land use; and other environmental issues. For each of these areas recommendations are given on how analyses of greenhouse gas balances should be performed. In some cases we also point out alternative ways of doing the greenhouse gas accounting. Finally, the paper gives some recommendations on how bioenergy systems should be optimized from a greenhouse-gas-emissions point of view.