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The boreal forests of North America are undergoing major changes because of the direct effects of global warming and increased CO sub(2) levels. Plant production in the boreal forest is nutrient limited, and we examined how long-term fertilization affected growth of white spruce Picea glauca in the face of these major changes. We conducted a large-scale experiment by fertilizing two 1 km super(2) stands of white spruce in the southwestern Yukon with commercial NPK fertilizer from 1987 to 1994. Tree growth was measured by the width of annual increments in 60 trees from each of 2 control and of 2 matched fertilized 1 km super(2) sites for the period from 1977 to 1997 in a before, during, and after experimental design....
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Two population oscillations dominate terrestrial community dynamics in northern Canada. In the boreal forest, the snowshoe hare (Lepus americanus) fluctuates in cycles with an 8–10 year periodicity and in tundra regions lemmings typically fluctuate in cycles with a 3–4 year periodicity. I review 60 years of research that has uncovered many of the causes of these population cycles, outline areas of controversy that remain and suggest key questions to address. Lemmings are keystone herbivores in tundra ecosystems because they are a key food resource for many avian and mammalian predators and are a major consumer of plant production. There remains much controversy over the role of predation, food shortage and social...
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The classic 10-year population cycle of snowshoe hares ( Lepus americanus, Erxleben 1777) and Canada lynx ( Lynx canadensis, Kerr 1792) in the boreal forests of North America has drawn much attention from both population and community ecologists worldwide; however, the ecological mechanisms driving the 10-year cyclic dynamic pattern are not fully revealed yet. In this study, by the use of historic fur harvest data, we constructed a series of generalized additive models to study the effects of density dependence, predation, and climate (both global climate indices of North Atlantic Oscillation index ( NAO), Southern Oscillation index ( SOI) and northern hemispheric temperature ( NHT) and local weather data including...
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Small mammals in boreal forest ecosystems fluctuate dramatically in abundance and 1 possible mechanism to explain these changes is the bottom-up hypothesis of variation in food supplies. Here we ask if variation in berry crops produced by 6 major species of dwarf shrubs and herbs, epigeous mushroom crops, and white spruce seeds allow us to predict changes in the abundance of the red-backed vole (Myodes [= Clethrionomys] rutilus), the deer mouse (Peromyscus maniculatus), and field voles (Microtus oeconomus and M. pennsylvanicus combined) over 13 years (1997-2009) in the Kluane Lake region of the southwestern Yukon, Canada. M. rutilus is the dominant rodent in these forests, comprising 64% of the catch. Overwinter...
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We review the population dynamics of red-backed voles (Myodes species) in North America, the main deciduous and coniferous forest-dwelling microtines on this continent, and compare and contrast their pattern with that of the same or similar species in Eurasia. We identify 7 long-term studies of population changes in Myodes in North America. Using autoregressive and spectral analysis, we found that only 2 of the 7 show 3- to 5-year cycles like those found in some Eurasian populations. There was no relationship between latitude and cycling. The general lack of cyclicity is associated with two key aspects of their demography that act in tandem: first, poor overwinter survival in most years; second, chronically low...
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The Kluane forest is unusual in that it is less productive than other boreal forests because it lies in a rain-shadow zone in the Yukon Territory. Densities of the boreal red-backed vole Clethrionomys rutilus are known to be food-limited in the Kluane region, and its food sources, mostly plants, could be rainfall-limited. Above-average rainfall in the Kluane region could reduce the summer water deficit, which would in turn enhance primary production and reduce food limitation in voles, ultimately leading to a population outbreak. We experimentally tested these two predictions by irrigating three sites in the boreal forest from 1995 to 1999, and concurrently comparing numbers of voles and availability of their potential...
map background search result map search result map Trophic effects of rainfall on Clethrionomys rutilus voles: an experimental test in a xeric boreal forest in the Yukon Territory Do changes in berry crops drive population fluctuations in small rodents in the southwestern Yukon? Population dynamics of red-backed voles (Myodes) in North America Linking climate change to population cycles of hares and lynx Population limitation of the northern red-backed vole in the boreal forests of northern Canada Of lemmings and snowshoe hares: the ecology of northern Canada The Community Ecological Monitoring Program Annual Report 2008 Climate and nutrient influences on the growth of white spruce trees in the boreal forests of the Yukon Cyclic dynamics of snowshoe hares on a small island in the Yukon What factors determine cyclic amplitude in the snowshoe hare (Lepus americanus) cycle? Estimating snowshoe hare population density from pellet plots: a further evaluation The role of red squirrels and arctic ground squirrels Experimental design and practical problems of implementation Herbivores - Forest grouse and ptarmigan Is the relationship between predator and prey abundances related to climate for lynx and snowshoe hares? Arctic ground squirrel population collapse in the boreal forests of the Southern Yukon Ecosystem Dynamics of the Boreal Forest: the Kluane Project Why Do the Boreal Forest Ecosystems of Northwestern Europe Differ from Those of Western North America? The impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem Cyclic dynamics of snowshoe hares on a small island in the Yukon Trophic effects of rainfall on Clethrionomys rutilus voles: an experimental test in a xeric boreal forest in the Yukon Territory Why Do the Boreal Forest Ecosystems of Northwestern Europe Differ from Those of Western North America? Climate and nutrient influences on the growth of white spruce trees in the boreal forests of the Yukon Herbivores - Forest grouse and ptarmigan Is the relationship between predator and prey abundances related to climate for lynx and snowshoe hares? The role of red squirrels and arctic ground squirrels Experimental design and practical problems of implementation Arctic ground squirrel population collapse in the boreal forests of the Southern Yukon Do changes in berry crops drive population fluctuations in small rodents in the southwestern Yukon? Estimating snowshoe hare population density from pellet plots: a further evaluation Ecosystem Dynamics of the Boreal Forest: the Kluane Project The Community Ecological Monitoring Program Annual Report 2008 The impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem Population dynamics of red-backed voles (Myodes) in North America What factors determine cyclic amplitude in the snowshoe hare (Lepus americanus) cycle? Linking climate change to population cycles of hares and lynx Population limitation of the northern red-backed vole in the boreal forests of northern Canada Of lemmings and snowshoe hares: the ecology of northern Canada