Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island,Yukon Territory,Canada |
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Authors: | Isla H Myers-Smith David S Hik Catherine Kennedy Dorothy Cooley Jill F Johnstone Alice J Kenney Charles J Krebs |
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Institution: | (1) Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada;(2) Department of Environment, Yukon Territorial Government, Whitehorse, YT, Canada;(3) Department of Environment, Yukon Territorial Government, Dawson City, YT, Canada;(4) Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada;(5) Department of Zoology, University of British Columbia, Vancouver, BC, Canada |
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Abstract: | Canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic. Our results indicate expansion
in canopy cover and height of willows on Herschel Island located at 70° north on the western Arctic coast of the Yukon Territory.
We examined historic photographs, repeated vegetation surveys, and conducted monitoring of long-term plots and found evidence
of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century. A simple model of patch initiation indicates that the majority of willow patches for each
of these species became established between 1910 and 1960, with stem ages and maximum growth rates indicating that some patches
could have established as late as the 1980s. Collectively, these results suggest that willow species are increasing in canopy
cover and height on Herschel Island. We did not find evidence that expansion of willow patches is currently limited by herbivory,
disease, or growing conditions. |
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Keywords: | Arctic Tundra Climate change Willows (Salix spp ) Shrub encroachment Yukon |
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