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Recent studies have shown that ice duration in lakes and rivers over the Northern Hemisphere has decreased over the 19th and 20th centuries in response to global warming. However, lake ice trends have not been well documented in Canada. Because of its size, considerable variability may exist in both freeze-up and break-up dates across the country. In this paper, results of the analysis of recent trends (1951-2000) in freeze-up and break-up dates across Canada are presented. Trends toward earlier break-up dates are observed for most lakes during the time periods of analysis which encompass the 1990s. Freeze-up dates, on the other hand, show few significant trends and a low degree of temporal coherence when compared...
Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska,...
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The use of Croucher Creek, a small non-natal tributary of the Upper Yukon River, by juvenile chinook salmon (Oncorhynchus tshawytscha) was investigated. Fish utilization of the stream was assessed by fishing minnow traps once a week between May and October, 1993. Age-1 chinook juveniles with a mean fork length of 79 mm and mean weight of 4.8 g were present at the beginning of May and increased rapidly in size before apparently leaving Croucher Creek in June at a mean size of 89 mm and 7.3 g. After mid-June only 2 age-1 chinook juveniles were caught. Age-0 chinook were first caught in Croucher Creek in June. Their mean fork length was 53 mm and mean weight was 1.5 g. Age-0 juveniles were caught in the stream for...
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High-latitude northern ecosystems are experiencing rapid climate changes, and represent a large potential climate feedback because of their high soil carbon densities and shifting disturbance regimes. A significant carbon flow from these ecosystems is soil respiration (RS, the flow of carbon dioxide, generated by plant roots and soil fauna, from the soil surface to atmosphere), and any change in the high-latitude carbon cycle might thus be reflected in RS observed in the field. This study used two variants of a machine-learning algorithm and least squares regression to examine how remotely-sensed canopy greenness (NDVI), climate, and other variables are coupled to annual RS based on 105 observations from 64 circumpolar...
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Epigeous mushroom production in the boreal forest ecosystem varies dramatically from year to year. We tested the hypothesis that the aboveground production of epigeous mushrooms in the Kluane region, Yukon, could be predicted by summer rainfall. There is a single crop in this part of the boreal zone with maximum production during the first 2 weeks of August. We measured standing crops from 1993 to 2007 at 13 areas along 210 km of the Alaska Highway and Haines Road in the southwestern Yukon. Aboveground mushroom crops averaged 24 kg/ha wet weight but varied from 0.0 to 117 kg/ha over the 15 years of study, with a coefficient of variation among years of 143%. Epigeous mushroom production could be predicted from June...
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A large barren-ground caribou (Rangifer tarandus granti) population (the Bering Seacoast Herd) historically ranged across southwest Alaska. The size of this herd peaked in the early 1860s but declined by the late 1880s. Caribou numbers remained low in southwest Alaska for the next 100 years. Biologists have argued that periodic dispersal has been an important factor in caribou population dynamics. However, others conclude there was no credible evidence that significant interchange between herds has ever occurred in Alaska. Since 1981, we monitored 318 radiocollared caribou and documented dramatic population growth, erratic movements, shifts from traditional ranges, and changes in migratory behavior. We also documented...
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The 48-km stretch of the Yukon Valley from the mouth of Tatchun Creek to Minto Crossing was surveyed. 110 islands, just over 50 back channels, plus 14 off-channel ponds constitute the wetland habitat most used by birds. Two key areas were groupings of islands and mid-channel bars, one near Yukon Crossing and one near the mouth of McCabe creek. We found 31 species of water birds using the area. Vegetation on river bars and islands was key. In constant successional stage, riparian willow bordered by a grass and sedge community with horsetail as the key emergent was used principally by migrating waterfowl. Breeding by waterfowl was a minor use, (5 species). A relatively dense assemblage of birds of prey indicate a...
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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 we assume 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. I quantified biological change 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...


map background search result map search result map Baseline Water Bird Surveys submitted to U.S. Fish and Wildlife Service, Region 7 Juvenile chinook salmon (Oncorhynchus tshawytscha) utilization of Croucher Creek, a small non-natal tributary of the upper Yukon River during 1993 Molecular Genetic Approaches in Wildlife Management INFLUENCE OF POPULATION GROWTH ON CARIBOU HERD IDENTITY, CALVING GROUND FIDELITY, AND BEHAVIOR Moose Population Survey of the Western Yukon Flats: November 2008 Modeling Breeding Waterfowl Distribution in the Southern Lakes Region of the Yukon A survey of bird use of the wetlands of the Tatchun-to-Minto Yukon valley.  RECENT CHANGES IN PLANT AND AVIAN COMMUNITIES AT CREAMER’S REFUGE, ALASKA USING FIELD AND REMOTE SENSING OBSERVATIONS Mushroom crops in relation to weather in the southwestern Yukon Partitioning sources of soil respiration in boreal black spruce forest using radiocarbon A Burning Interest in Boreal Forests: Researchers in Alaska Link Fires with Climate Change Multi-Year Lags between Forest Browning and Soil Respiration at High Northern Latitudes Vegetation and climate controls on potential CO2 , DOC and DON production in northern latitude soils Recent trends in Canadian lake ice cover Characteristics of the Landscape Surrounding Golden Eagle Nest Sites in Denali National Park and Preserve, Alaska Ecosystem Dynamics of the Boreal Forest: the Kluane Project Recent trends in Canadian lake ice cover Baseline Water Bird Surveys submitted to U.S. Fish and Wildlife Service, Region 7 A survey of bird use of the wetlands of the Tatchun-to-Minto Yukon valley.  RECENT CHANGES IN PLANT AND AVIAN COMMUNITIES AT CREAMER’S REFUGE, ALASKA USING FIELD AND REMOTE SENSING OBSERVATIONS Partitioning sources of soil respiration in boreal black spruce forest using radiocarbon Molecular Genetic Approaches in Wildlife Management Characteristics of the Landscape Surrounding Golden Eagle Nest Sites in Denali National Park and Preserve, Alaska Modeling Breeding Waterfowl Distribution in the Southern Lakes Region of the Yukon Mushroom crops in relation to weather in the southwestern Yukon Moose Population Survey of the Western Yukon Flats: November 2008 Ecosystem Dynamics of the Boreal Forest: the Kluane Project Juvenile chinook salmon (Oncorhynchus tshawytscha) utilization of Croucher Creek, a small non-natal tributary of the upper Yukon River during 1993 INFLUENCE OF POPULATION GROWTH ON CARIBOU HERD IDENTITY, CALVING GROUND FIDELITY, AND BEHAVIOR Vegetation and climate controls on potential CO2 , DOC and DON production in northern latitude soils A Burning Interest in Boreal Forests: Researchers in Alaska Link Fires with Climate Change Multi-Year Lags between Forest Browning and Soil Respiration at High Northern Latitudes