• Range, movements, population, and food habits of the Steese-Fortymile caribou herd

      Skoog, Ronald O. (1956-05)
      The Steese-Fortymile caribou (Rangifer arcticus stonei Allen) form one of the most economically important herds in Alaska. This study of the herd took place from September, 1952, to December, 1955, under the auspices of the Alaska Cooperative Wildlife Research Unit at the University of Alaska and of the Federal Aid in Wildlife Restoration branch of the United States Fish and Wildlife Service, Project W3R. The Steese-Fortymile range occupies about 35,000 square miles of east-central Alaska and the Yukon Territory, lying mainly between the Tanana and Yukon Rivers. The terrain is mountainous, but not rugged; roads and towns are scarce, and a maximum of 60,000 people live on the fringes. Seven major plant communities comprise the range vegetation, three of them covering 60 to 70 per cent of the area and furnishing the bulk of the food for caribou. The carrying capacity is computed to be 70,000 to 90,000 caribou. The erratic and continual movements of caribou characterize this game species. Their movements vary from day to day and season to season. Most of the traveling takes place during the early morning and late afternoon; major seasonal movements take place in the spring and fall. Past and present data provide a general picture of the movement pattern of this herd throughout the year. The Steese-Fortymile herd dwindled from a peak of about 500,000 animals in the late 1920's to a low of 10,000 to 20,000 in the early 1940's. The decline is attributed to a population shift. The present population contains at least 50,000 animals and is increasing steadily. Reproduction was high during the years 1950 to 1955. The rut takes place during the first two weeks of October; most of the calves are born during the latter half of May, following a gestation period of about 33 weeks. Valuable information on caribou behavior during the calving period is presented. Counts taken in May show that at least 50 per cent of the calves survive the first year. Wolf and man are the most important mortality factors affecting this herd. The total annual mortality, excluding calves, is estimated at eight per cent. Sex and age data from composition counts and hunter-checking-station operations indicate that this herd is young and that the sex ratio approaches 100:100. The annual increment for the herd is computed to be 10 to 15 per cent. Caribou are cursory feeders and eat a wide variety of plants. The main periods for resting and feeding occur during the middle portions of the day and night. The caribou’s diet hinges upon the available food supply, and thus varies with the seasons. In winter, the diet consists mostly of lichens, grasses, and sedges, with browse plants of some importance; data from 23 stomach-samples are presented. In spring, the new shoots of willow, dwarf birch, grass, and sedge are most important; information is based only on field observations. In summer, a wide variety of plants are eaten; willow and dwarf-birch foliage are of greatest importance, followed closely by grasses and sedges; data from 27 stomach-samples are presented. In fall, the diet shifts from a predominance of woody plants and fungi in late August to one of lichens, grasses, and sedges in late September; data from 70 stomach-samples are presented. The problems of data-gathering are discussed, as related to management practices. The contributions made by this report are outlined, and the important information still needed for proper caribou management is listed.
    • A rapid assessment method to estimate the distribution of juvenile chinook salmon (Oncorhynchus tshawytscha) in an Interior Alaska river basin

      Matter, Allison N.; Falke, Jeffrey; Sutton, Trent; Savereide, James; Lopez, J. Andres (2016-08)
      Identification and protection of water bodies used by anadromous species in Alaska are critical in light of increasing threats to fish populations, yet challenging given budgetary and logistical limitations. Non-invasive, rapid assessment sampling techniques may reduce costs and effort while increasing species detection efficiencies. I used an intrinsic potential (IP) habitat model to identify high quality Chinook Salmon Oncorhynchus tshawytscha rearing habitats and select sites to sample throughout the Chena River basin for juvenile occupancy using environmental DNA (eDNA) and distribution within tributaries using snorkel surveys. Water samples were collected from 75 tributary sites in 2014 and 2015. The presence of Chinook Salmon DNA in water samples was assessed using a quantitative polymerase chain reaction (qPCR) assay targeting that species. Snorkel surveys were conducted and physical habitat was measured for a subset of tributaries examined with the eDNA approach. Juvenile salmon were counted within 50 m reaches starting at the tributary confluence and continuing upstream until no juvenile salmon were observed. The IP model predicted over 900 stream km in the basin to support high quality (IP ≥ 0.75) rearing habitat. Occupancy estimation based on eDNA samples indicated that 80.2% (± 4.3 SE) of previously unsampled sites classified as high IP and 56.4% of previously unsampled sites classified as low IP were occupied. The probability of detection of Chinook Salmon DNA from three replicate water samples was high (0.76 ± 1.9 SE) but varied with drainage area. A power analysis indicated power to detect proportional changes in occupancy based on parameter values estimated from eDNA occupancy models. Results of snorkel surveys showed that the upper extent of juvenile Chinook Salmon within tributaries was from 200 to 1,350 m upstream of tributary confluences. Occurrence estimates based on eDNA and snorkel surveys generally agreed, but care should be taken to ensure that little temporal gap exists between samples as juvenile salmon use of tributary habitats is likely often intermittent. Overall, the combination of IP habitat modeling, occupancy estimation based on eDNA, and snorkel surveys provided a useful, rapid-assessment method to predict and subsequently quantify the distribution of juvenile salmon in previously unsampled tributary habitats. These methods will provide tools for managers to rapidly and efficiently map critical rearing habitats and prioritize sampling efforts to expand the known distribution of juvenile salmon in interior Alaska streams.
    • Recent changes in plant and avian communities at Creamer's Refuge, Alaska using field and remote sensing observations

      Tauzer, Lila Maria; Powell, Abby; Bret-Harte, Syndonia; Sharbaugh, Susan; Prakash, Anupma (2013-05)
      Plant communities in the north are being profoundly altered by climate warming, but our understanding of the extent and outcomes of this ecosystem shift is limited. Although it was assumed local vegetation changes will affect avian communities, few data exist to investigate this relationship. In an interior Alaska boreal forest ecosystem, this study capitalized on available resources to assess simultaneous change in plant and avian communities over 35 years. Biological changes were quantified in summer avian community data (species composition, diversity, and richness) and in vegetation using archived field data, and supplemented this data with remote sensing observations for a similar time period to assess the validity of this method for documenting environmental change. Field and remote sensing data both documented successional changes resulting in denser, more coniferous-dominated habitats. Birds responded accordingly, which indicates a rapid avian response to habitat change and that they are good indicators of environmental change. Information gained provides more accurate evaluations of habitat dynamics throughout the interior boreal forest and highlights the importance of considering successional change in all long-term climate studies. It allows for better predictions of future habitat change and acts as a strong baseline for future environmental monitoring.
    • Red squirrel (Tamiasciurus hudsonicus) ecology during spruce cone failure in Alaska

      Smith, Michael C. T. (1967-05)
      Observations were made on a red squirrel (Tamiasciurus hudsonicus) population in a mature white spruce (Picea glauca) forest near Fairbanks, Alaska, during two years of spruce cone crop failure (July, 1964, to April, 1966). An adequate supply of old spruce cones, cached in previous years, was available during the first winter. A 67% drop in numbers of the squirrel population followed the second crop failure with the remaining squirrels utilizing spruce buds as their primary food during the winter. Stomach analyses revealed that when present, spruce seed is the major constituent in the diet. In its absence, heavy utilization of mushrooms in summer and spruce buds in winter occurs. Feeding trials conducted with captive red squirrels in March, 1965, and April, 1966, showed that about 194 old cones per day were necessary to sustain a squirrel, approximately 35% more than for cones from the current year's crop. Three squirrels survived for eight days on a diet of only white spruce buds. Analysis of old spruce cones showed that 31% of the seed was potentially viable (filled), but that only 1.4% of the seed germinated. Calorimetric determinations of old seed (minus coat), spruce buds, and mushrooms yielded values of 5,976, 4,986, and 4,552 cal/g respectively. Excavation of middens revealed up to 8,518 old, cached cones per midden, despite a crop failure. In years of normal cone production, squirrels may cut and cache 12,000 to 16,000 cones; the excess accrues each year and eventually a sufficient supply exists to maintain the squirrels through a winter following a cone crop failure.
    • Regional climate, federal land management, and the social-ecological resilience of southeastern Alaska

      Beier, Colin Mitchell (2007-08)
      Complex systems of humans and nature often experience rapid and unpredictable change that results in undesirable outcomes for both ecosystems and society. In circumpolar regions, where multiple converging drivers of change are reshaping both human and natural communities, there is uncertainty about future dynamics and the capacity to sustain the important interactions of social-ecological systems in the face of rapid change. This research addresses this uncertainty in the region of Southeast Alaska, where lessons learned from other circumpolar regions may not be applicable because of unique social and ecological conditions. Southeast Alaska contains the most productive and diverse ecosystems at high latitudes and a human population almost entirely isolated and embedded in National Forest lands; these qualities underscore the importance of the region's climate and federal management systems, respectively. This research presents a series of case studies of the drivers, dynamics, and outcomes of change in regional climate and federal management, and theoretically grounds these studies to understand the regional resilience to change. Climate change in Southeast Alaska is investigated with respect to impacts on temperate rainforest ecosystems. Findings suggest that warming is linked to emergence of declining cedar forests in the last century. Dynamics of federal management are investigated in several studies, concerning the origins and outcomes of national conservation policy, the boom-bust history of the regional timber economy, and the factors contributing to the current 'deadlock' in Tongass National Forest management. Synthesis of case study findings suggests both emergent phenomena (yellow-cedar decline) and cyclic dynamics (timber boom-bust) resulting from the convergence of ecological and social drivers of change. Adaptive responses to emergent opportunities appear constrained by inertia in management philosophies. Resilience to timber industry collapse has been variable at local scales, but overall the regional economy has experienced transition while retaining many of its key social-ecological interactions (e.g., subsistence and commercial uses of fish and wildlife). An integrated assessment of regional datasets suggests a high integrity of these interactions, but also identifies critical areas of emergent vulnerability. Overall findings are synthesized to provide policy and management recommendations for supporting regional resilience to future change.
    • Reindeer Range Appraisal In Alaska

      Pegau, Robert Elwyn (1968)
    • Relationships between brown bears and chum salmon at McNeil River, Alaska

      Peirce, Joshua McAllister (2007-08)
      Since 1967, the McNeil River State Game Sanctuary (MRSGS) has been managed by the Alaska Department of Fish and Game to 'provide permanent protection for brown bears'. Up to 144 bears have been identified in a summer at MRSGS, and 72 bears at once have been observed in the vicinity of McNeil Falls. In this study, 155 chum salmon were radio tagged as they entered McNeil River and monitored daily. In 2005 and 2006 bears killed 48% of pre-spawning tagged chum salmon and consumed 99% of all tagged chums below McNeil Falls where most of the run occurs. A retrospective analysis of 31 years of run data using a new stream life, and a correction for observer efficiency, revealed that the current escapement goal of 13,750-25,750 actually represents 34,375-64,375 chum salmon. Considering the large removal of pre-spawning chum salmon, I recommend an additional 23,000 chum salmon be added to the escapement goal. Additionally, an annual escapement of 4,000-6,000 chum salmon above McNeil Falls should be set as an objective. These recommendations should encourage increased chum salmon returns, providing both food for McNeil bears, as well as benefiting the commercial fishery with increased harvest opportunities.
    • Relationships between ecosystem metabolism, benthic macroinvertebrate densities, and environmental variables in a sub-Arctic Alaskan river

      Benson, Emily R. (2010-08)
      The aim of this study was to investigate the environmental drivers of river ecosystem metabolism and macroinvertebrate density in a sub-arctic river. Ecosystem metabolism is the combination of gross primary production and ecosystem respiration within a river. Aquatic macroinvertebrates link primary producers at the base of the food web with secondary consumers. The extent to which photosynthetically active radiation, discharge, and nutrients influence metabolism rates and how primary production and river discharge rates influence benthic macroinvertebrate densities in sub-arctic rivers is not clear. These processes ultimately help regulate prey resources available for upper level consumers such as juvenile salmon. I employed Random Forests model analyses to identify important predictor variables for primary production and respiration rates (estimated using the single-station diel oxygen method) at four sites in the Chena River, sub-arctic Alaska, throughout the summers of 2008 and 2009. I calculated Spearman correlations between nutrient levels and metabolism rates. I used Random Forests models to identify the variables important for predicting benthic macroinvertebrate density and biomass at the study sites. The models indicated that discharge and length of time between high water events were the most important variables measured for predicting metabolism rates. Discharge was identified as the most important variable for predicting benthic macroinvertebrate density and biomass. Phosphorus concentration was low (at times below the detection limit), while nitrogen concentration was more variable; the ratio of nitrogen to phosphorus was above the threshold for phosphorus limitation, suggesting that phosphorus may have been limiting primary production.
    • A remote sensing-GIS based approach for assessment of chinook salmon rearing habitat in the Unuk river floodplain

      Smikrud, Kathy M. (2007-05)
      Remote sensing offers an alternative method to managers in mapping and monitoring the habitat within large rivers. Large rivers are not accommodating for traditional (foot) fish habitat surveys due to their size and typically complex habitat. This study investigates the use of digital aerial photos and thermal infrared images acquired in spring 2003-2005 to map and quantify juvenile chinook salmon (Oncorhynchus tshawytscha) habitat in a 12-river km section of the Unuk River floodplain in Southeast Alaska. Images were processed and analyzed to produce a fluvial landscape classification (7 landcover classes with an overall classification accuracy of ~84%) using a combination of aerial and thermal images. Change detection of large woody debris (LWD) was also examined and revealed both quantitative and distributional changes during the 3 years. A GIS-based habitat suitability analysis was used to identify potential chinook salmon rearing habitats including: river channel edges, sloughs, braids, pools associated with LWD and primary river channels. Overall 77.82 hectares of potentially medium/high chinook rearing habitats were identified. Results from this study provide a promising foundation towards mapping and monitoring salmon habitat in large river systems for purposes of protection, conservation and monitoring to ensure sustainable stocks of salmon.
    • Reproductive behavior and related social organization of the muskox on Nunivak Island

      Smith, Timothy E. (1976-05)
      The sexual behavior and social organization of the muskox (Ovibos moschatus wardi Zimmerman) were studied on Nunivak Island, Alaska, in fall 1972 and summer and fall 1973. Observation effort was concentrated on a single harem group for two months, during the height of courtship activity. Movements and fluctuations in the structure of this group are documented. There was no significant change in mean herd size as a result of the rut, suggesting the existence of a basic social unit independent of the influence of harem bulls. Harem bulls were in the 6-10 year age class. They exerted a stabilizing influence on the harem but did not direct its movements. The rut extended from early July to mid-October. Copulation occurred on September 4 and 5. General patterns of sexual and agonistic behavior are described. Changes in activity patterns as a result of the rut are shown. Bulls displayed more marked changes than cows or juveniles. The proportion of time allocated to sexual and agonistic behavior increased at the expense of maintenance activity as the rut progressed.
    • Reproductive patterns in king eiders

      Bentzen, Rebecca L.; Powell, A. N.; Thomas, D. L.; Kitaysky, A. S.; Flint, P. L. (2009-12)
      Mammalian predation, avian predation, female body condition and food availability on the breeding ground are likely the main factors influencing nesting success in tundra-nesting waterfowl. These driving factors are mediated by the primary life history characteristics; incubation behavior, female body size, nesting associations, and nest site selection. I created a conceptual model illustrating how these factors are interrelated and how they impact nest success through a variety of pathways to better understand the evolution of a species' nesting strategy and patterns observed in the field. The importance of the driving factors likely varies between sites and with the species nesting strategy. Given the conceptual model, I predicted the difference in life history characteristics and nesting success at two sites that vary in any of the four driving factors. I tested the model and associated predictions using King Eider females (Somateria spectabilis) breeding on Alaska's coastal plain by comparing selective forces influencing nesting strategies at two sites, Teshekpuk and Kuparuk, between 2002 and 2006. King Eiders fit the model with some modifications to the mediating pathways. Site differences were found in many of the reproductive parameters which matched the prediction of more available forage at Kuparuk than at Teshekpuk. No differences in either avian or mammalian predation pressure were evident between sites. Eiders at Kuparuk had higher nest survival and incubation constancy than at Teshekpuk. Body mass and nest selection were similar between sites. Although questions concerning the nesting strategies of King Eider remain, I feel that this was a valid approach to identifying selective forces impacting nesting strategies and applicable to tundra nesting waterfowl in general.
    • Resilience of a deer hunting system in Southeast Alaska: integrating social, ecological, and genetic dimensions

      Brinkman, Todd J. (2009-08)
      I examined the interactions of key components of a hunting system of Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Prince of Wales Island, Alaska to address concerns of subsistence hunters and to provide a new tool to more effectively monitor deer populations. To address hunter concerns, I documented local knowledge and perceptions of changes in harvest opportunities of deer over the last 50 years as a result of landscape change (e.g., logging, roads). To improve deer monitoring, I designed an efficient method to sample and survey deer pellets, tested the feasibility of identifying individual deer from fecal DNA, and used DNA-based mark and recapture techniques to estimate population trends of deer. I determined that intensive logging from 1950 into the 1990s provided better hunter access to deer and habitat that facilitated deer hunting. However, recent declines in logging activity and successional changes in logged forests have reduced access to deer and increased undesirable habitat for deer hunting. My findings suggested that using DNA from fecal pellets is an effective method for monitoring deer in southeast Alaska. My sampling protocol optimized encounter rates with pellet groups allowing feasible and efficient estimates of deer abundance. I estimated deer abundance with precision (±20%) each year in 3 distinct watersheds, and identified a 30% decline in the deer population between 2006-2008. My data suggested that 3 consecutive severe winters caused the decline. Further, I determined that managed forest harvested>30 years ago supported fewer deer relative to young-managed forest and unmanaged forest. I provided empirical data to support both the theory that changes in plant composition because of succession of logged forest may reduce habitat carrying capacity of deer over the long-term (i.e., decades), and that severity of winter weather may be the most significant force behind annual changes in deer population size in southeast Alaska. Adaptation at an individual and institutional level may be needed to build resilience into the hunting system as most (>90%) of logged forest in southeast Alaska transitions over the next couple of decades into a successional stage that sustains fewer deer and deer hunting opportunities.
    • Response of northern red-backed vole (Clethrionomys rutilus) populations to a major spruce beetle infestation in the Copper River Basin, Alaska

      McDonough, Thomas (2000-08)
      A spruce bark beetle (Dendroctonus rufipennis) epidemic in the Copper Basin of Alaska beginning in the late 1980's has infested over 200,000 ha of white spruce forests in the region. The impact of spruce beetle-induced habitat changes on the northern red-backed vole (Clethrionomys rutilus) was investigated using mark/recapture techniques for 2 field seasons. Vole abundance and recruitment was significantly greater on low versus heavily infested sites but a large vole survival response was lacking. Vole food resources and protective vegetative cover did not vary substantially in areas with different levels of spruce mortality. Male movement distances were influenced by sex ratio, and females appeared to respond to food resources (epigeous sporocarps). Beetle infestations alone did not influence vole movements, but female movement distances decreased when heavy infestation levels were coupled with female age and sporocarp availability. The impact of beetle infestations on red-backed vole populations in the Copper Basin appears to be relatively small.
    • Responses of captive common eiders to implanted satellite transmitters with percutaneous antennas

      Latty, Christopher J. (2008-05)
      Implanted transmitters have been used for over a decade to track the migrations and habitat use of many sea duck species, but their effects remain largely unstudied. To address this, I assessed the physiological and behavioral responses and characterized the clinical responses of six Common Eiders implanted with a transmitter with a percutaneous antenna. To maintain a semi-natural feeding regime, I fed birds benthicly in a 4.9 m deep dive column. I collected blood, feces, mass, and video data prior to surgery to establish baselines and at staggered intervals for 3.5 months post surgery to determine responses. All birds had some clinical complications, but most abated within 2 weeks of surgery. Mass increased in the first two weeks, but no trend was evident thereafter. Most biomarkers and dive performance metrics were altered at some point after surgery. While most biochemical values returned to baseline within weeks of surgery, a few remained deviated for longer. Additionally, dive speeds were slower for up to 3.5 months after implantation. Although it is uncertain how these changes would ultimately affect birds in the wild, effects on physiological condition and behavior seem likely in the first few weeks after surgery with longer-term effects also possible. Scientists should consider these responses and possible effects on the validity of PIT data when designing studies and analyzing information from implanted transmitters in sea ducks.
    • A review of waterfowl investigations and a comparison of aerial and ground censusing of waterfowl at Minto Flats, Alaska

      Rowinski, Ludwig J. (1958)
      The Minto Flats is one of the important waterfowl concentration areas of interior Alaska. Aerial surveys and ground studies were initiated in this area in 1950 and have continued in succeeding years. This study began in September, 1955, as a research project of the Alaska Cooperative Wildlife Research Unit. The study was financed largely by Pitman-Robertson Project Alaska W-3-R. The Minto Flats is an area of about 450 square miles, located about 35 miles west of Fairbanks. The important nesting species are scaup, pintail and widgeon. The Minto Lakes area serves as an important molting and flocking area for these and other species. Climatically the Minto Flats resemble the rest of interior Alaska. Water levels in the area are highly variable and influence the vegetation and breeding. Minto Lakes, Big Lake, and the Tolovana Flats were selected for concentrated study in 1956. During the 1956 field studies, data were collected for comparison with data available from previous years. Waterfowl production in the Minto Flats area is affected principally by weather, changes in water level, and predation. Among the factors influencing censusing are the census methods, stratification, and sample size. Enumeration of waterfowl is affected by differences in the visibility of birds, population composition, environmental conditions, and the accuracy of observers in relation to the other variables and in regard to individual partiality and talent. The difference between observers, when analyzed statistically points out the need for continuity of observers with known levels of ability. Breeding bird census figures from aerial surveys from 1950 t o 1956 are not comparable due to differences in census methods. Aerial brood surveys are valuable for determining year to year production trends while ground surveys provide data on brood species composition. Together they are the best guide to waterfowl production. Nesting studies have provided some data on nesting terrain, clutch size, and nesting success. The effect of nest hunting on the breeding population and the time necessary for obtaining an adequate sample indicates that nest hunting is not an economical or accurate means of measuring yearly productive success. Aerial surveys are recognized as the most feasible way of measuring production if the accuracy of the information gathered from the air can be increased.
    • River features associated with chinook salmon spawning habitat in Southwest Alaska

      Jallen, Deena M.; Margraf, F. Joseph; Adkison, Milo (2009-08)
      Chinook salmon (Oncorhynchus tshawytscha) is a highly valued traditional, subsistence, and commercial resource in Southwest Alaska. Stream habitat availability is a major component influencing salmon productivity. The objective of this study is to identify river features associated with spawning habitat, and describe upper and lower boundaries of chinook salmon spawning on the Tuluksak River. River distances, elevation, salmon locations, spawning sites, and habitat observations were collected along 75 river kilometers of the Tuluksak River primarily within the Yukon Delta National Wildlife Refuge. Habitat and salmon observations were grouped into strata along the length of the river for comparison and analysis. Chinook salmon were observed spawning in the upper 45 river kilometers of the study area. Map-based observations of elevation and channel sinuosity correlate better with chinook salmon spawning than in stream habitat measurements along the Tuluksak River. The upper boundary of chinook salmon spawning in the Tuluksak River was outside of our study area. The lower boundary for chinook salmon spawning habitat on similar rivers might be determined by examining elevation, sinuosity, and channel features from remote images or maps prior to conducting field studies.
    • River features associated with chum salmon spawning areas: a method to estimate habitat capacity

      O'Brien, John P. (2006-05)
      Diminishing returns of salmon and years of poor commercial and subsistence fishing in western Alaska are a cause for concern. Management tools which recognize the intricate life histories of salmon and incorporate environmental conditions at each particular life stage are needed. Toward that goal a study of spawning habitat for chum salmon Oncorhynchus keta was conducted from 2002 to 2005 on the Tuluksak River in western Alaska. Small-scale river features were measured during two summers of field work. Large-scale river features were identified using remote sensing. Principal components analysis (PCA) denoted an association between spawning sites and channel intersections, gravel bars, islands, and areas of accelerated channel change, forming the basis for a predictive habitat model. Two models were developed that combined them habitat assessment with chum salmon redd size and spatial requirements at three spawning densities. The first model, based on field observations in 2002 and 2003, estimated a greater spawning capacity than the second model, based on large-scale river features. Spawning capacity estimates from both models were consistent with historic escapement data and should be used as a starting point for further research. This study represents progress toward a management strategy that is sensitive to habitat-dependent production potential.
    • The role of fire in the carbon dynamics of the boreal forest

      Balshi, Michael S. (2007-12)
      The boreal forest contains large reserves of carbon, and across this region wildfire is a common occurrence. To improve the understanding of how wildfire influences the carbon dynamics of this region, methods were developed to incorporate the spatial and temporal effects of fire into the Terrestrial Ecosystem Model (TEM). The historical role of fire on carbon dynamics of the boreal region was evaluated within the context of ecosystem responses to changing atmospheric CO₂ and climate. These results show that the role of historical fire on boreal carbon dynamics resulted in a net carbon sink; however, fire plays a major role in the interannual and decadal scale variation of source/sink relationships. To estimate the effects of future fire on boreal carbon dynamics, spatially and temporally explicit empirical relationships between climate and fire were quantified. Fuel moisture, monthly severity rating, and air temperature explained a significant proportion of observed variability in annual area burned. These relationships were used to estimate annual area burned for future scenarios of climate change and were coupled to TEM to evaluate the role of future fire on the carbon dynamics of the North American boreal region for the 21st Century. Simulations with TEM indicate that boreal North America is a carbon sink in response to CO₂ fertilization, climate variability, and fire, but an increase in fire leads to a decrease in the sink strength. While this study highlights the importance of fire on carbon dynamics in the boreal region, there are uncertainties in the effects of fire in TEM 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. Future studies should incorporate the role of dynamic vegetation to more accurately represent post-fire successional processes, incorporate fire severity parameters that change in time and space, and integrate the role of other disturbances and their interactions with future fire regimes.