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In 1989, the Chisana caribou (Rangifer tarandus) herd in the northern Wrangell Mountains, Alaska, U.S.A., declined substantially in population size and productivity. Grasses, sedges, forbs, and willows (Salix spp.) are critical components of the diet of caribou in spring and summer, and the abundance and quality of forage are influenced by climate. To evaluate effects of climatic variation on caribou forage we conducted a field experiment in subarctic tundra where light, air temperature, and precipitation were manipulated. We used a plastic tarpaulin to increase air temperature and decrease precipitation. We also decreased light intensity with a shade cloth and increased precipitation by adding water to determine...
The following is a book review found at http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v416/n6882/full/416679a_fs.html in the journal Nature. Just as every picture tells a story, so too does every scientific project. This book is the story of the Kluane Boreal Forest Ecosystem Project, told brilliantly by the researchers who toiled for ten years from 1986 to uncover the drama and complexity of this Canadian ecosystem. Whoever wants to learn about the boreal forest of North America, one of the largest ecosystems of the world, and the stage on which a classic ecological drama — the ten-year population cycle of the snowshoe hare — is played out repeatedly, should definitely read this book. Equally...
In the White River basin, water demand has increased with human development. Water development projects impact White River hydrology and sediment transport which can, in turn, affect resident Colorado pikeminnow populations. The objectives for this study were: 1) to compile historical biological, hydrological and physical data for the White River, 2) to analyze physical, chemical and biological features of the White River important to endangered fishes and, 3) to identify parameters for long-term monitoring to insure these features are maintained. We examined physical, chemical and biological characteristics during three development periods in the UCRB: early (1895-1945), middle (1946-1984) and post Taylor Draw...
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Although natal dispersal has received considerable attention from animal ecologists, the causes and consequences of breeding dispersal have remained largely unexplored. We used telemetry, direct observation, and long-term mark-recapture (9 yr) to study breeding dispersal in the North American red squirrel (Tamiasciurus hudsonicus) at Kluane, Yukon, Canada. We recorded the postbreeding behavior (keep the territory, share it with juveniles, or bequeath it to juveniles) of mothers from 485 litters, and monitored the fates of eight cohorts of weaned juveniles (680 individuals). The proportion of mothers that bequeathed their territory to one of their offspring was roughly one-third of that keeping or sharing it. Breeding...
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A demographic study was conducted on field populations of Lupinus arcticus S. Wats. [Arctic lupine] growing in the understory of a white spruce dominated forest, near Kluane Lake, Yukon. The relative effects of soil fertility level, neighbours, and herbivory were assessed using a factorial experiment of plus or minus fertilizer (N-P-K [nitrogen, phosphorus, potassium]), plus or minus neighbour removal, and plus or minus clipping. We monitored the dynamics of leaves and collected data on reproduction, survival, and size for two growing seasons. Fertilizing increased the incidence of disease on leaves and reduced reproductive efficiency. Clipping reduced leaf cohort survivorship, total leaf density, and the incidence...
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The Slims River was monitored for global solar radiation, air temperature, discharge, suspended sediment, and dissolved load in 1993 and 1994. Peak seasonal discharge occurred late in the summer and reflects a typical glacierized basin hydrograph, with increased bare ice surfaces contributing strongly to discharge in July and August. Air temperature, rather than global solar radiation, was most strongly correlated with discharge in both years, but during sustained ablation, air temperature becomes a poor index of meltwater production. Precipitation was infrequent and of low magnitude. The variance in suspended sediment concentration could be explained only in part by discharge; frequent clockwise hysteresis and...
We used radio-telemetry to monitor the survival of dispersing and philopatric juvenile snowshoe hares (Lepus americanus) in southwestern Yukon Territory, Canada, during a cyclic population increase. Neither 28-day survival nor the proportion of hares surviving to breed differed significantly between juvenile hares that dispersed and those that did not, nor was there a significant relationship between dispersal distance and fate (dead or alive). Our results indicate that the overall survival cost associated with natal dispersal is low for snowshoe hares during the early increase of the hare cycle.
Categories: Publication; Types: Citation; Tags: M1-Mammals, White River
In 1989, the Chisana caribou (Rangifer tarandus) herd in the northern Wrangell Mountains, Alaska, U.S.A., declined substantially in population size and productivity. Grasses, sedges, forbs, and willows (Salix spp.) are critical components of the diet of caribou in spring and summer, and the abundance and quality of forage are influenced by climate. To evaluate effects of climatic variation on caribou forage we conducted a field experiment in subarctic tundra where light, air temperature, and precipitation were manipulated. We used a plastic tarpaulin to increase air temperature and decrease precipitation. We also decreased light intensity with a shade cloth and increased precipitation by adding water to determine...
    map background search result map search result map Breeding dispersal in female North American red squirrels Population dynamics response of Lupinus arcticus to fertilization, clipping, and neighbour removal in the understory of the boreal forest Hydrometeorology, Suspended Sediment, and Conductivity in a Large Glacierized Basin, Slims River, Yukon Territory, Canada (1993-94) Climate change and caribou: Effects of summer weather on forage Hydrometeorology, Suspended Sediment, and Conductivity in a Large Glacierized Basin, Slims River, Yukon Territory, Canada (1993-94) Population dynamics response of Lupinus arcticus to fertilization, clipping, and neighbour removal in the understory of the boreal forest Breeding dispersal in female North American red squirrels Climate change and caribou: Effects of summer weather on forage