Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island, Yukon Territory, Canada
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.
KeywordsArctic Tundra Climate change Willows (Salix spp.) Shrub encroachment Yukon
The authors wish to thank C.R. Burn for reading and providing helpful comments on the manuscript; D. Reid, S. Gilbert, and V. Loewen for field logistical support; and F. Doyle for contributing repeat photographs. The authors also wish to thank Qikiqtaruk–Herschel Island Territorial Park wardens and park management, in particular, Lee John Meyook and Richard Gordon; the 2008 and 2009 ArcticWOLVES Herschel Island field crews, M. Grabowski, C. Henry, and A. Trimble for field assistance; David Neufeld for providing old photographs; and the Aurora Research Institute for theirr logistical support. Support in the form of funds received from the Government of Canada International Polar Year Program, NSERC, the Polar Continental Shelf Program, the Canon National Parks Science Scholars Program, the Alberta Ingenuity, W. Garfield Weston Foundation, the Northern Scientific Training Program INAC, and the C-BAR Grant Program, the Canadian Circumpolar Institute, and the Air North (flight discounts) is gratefully acknowledged. The authors thank the Inuvialuit people for the opportunity to conduct research on their traditional lands.
- ACIA. 2005. Arctic Climate Impact Assessment—scientific report, 1st ed. Cambridge: Cambridge University Press.Google Scholar
- Arft, A.M., M.D. Walker, J. Gurevitch, J.M. Alatalo, M.S. Bret-Harte, M. Dale, M. Diemer, F. Gugerli, et al. 1999. Responses of tundra plants to experimental warming: Meta-analysis of the International Tundra Experiment. Ecological Monographs 69: 491–511.Google Scholar
- Argus, G.W., C.L. McJannet, and M.J. Dallwitz. 1999. Salicaceae of the Canadian Arctic Archipelago: Descriptions, illustrations, identification, and information retrieval. Version: 29 March 1999. In Flora of the Canadian Arctic archipelago, ed. S. Aiken, M. Dallwitz, L. Consaul, C. McJannet, R. Boles, G. Argus, J. Gillett, P. Scott, et al. (2003). NRC Research Press. http://www.mun.ca/biology/delta/arcticf/. Retrieved 4 March 2010.
- Bigelow, N.H., L.B. Brubaker, M.E. Edwards, S.P. Harrison, I.C. Prentice, P.M. Anderson, A.A. Andreev, P.J. Bartlein, T.R. Christensen, W. Cramer, et al. 2003. Climate change and Arctic ecosystems: 1. Vegetation changes north of 55 N between the last glacial maximum, mid-Holocene, and present. Journal of Geophysicsal Research 108:8170.Google Scholar
- Hardy Associates Ltd. 1979. Vegetation of King Point, Pauline Cove and Baillie Islands/prepared for Dome Petroleum Ltd., published report. Calgary: Hardy Associates Ltd.Google Scholar
- Inter-Disciplinary Systems Ltd. 1972. Report on the Herschel Island Environmental Reconnaissance for Amoco Cana Petroleum Co. Ltd. Unpublished Report, Inter-Disciplinary Systems Ltd, Winnipeg, MB, Canada.Google Scholar
- Johnstone, J.F., and S.V. Kokelj. 2008. Environmental conditions and vegetation recovery at abandoned drilling mud sumps in the Mackenzie Delta region, Northwest Territories, Canada. Arctic 61: 199–211.Google Scholar
- Kennedy, C.E., C.A.S. Smith, and D.A. Cooley. 2001. Observations of change in the cover of Polargrass, Arctagrostis latifolia, and Arctic Lupine, Lupinus arcticus, in upland tundra on Herschel Island, Yukon Territory. Canadian Field-Naturalist 115: 323–328.Google Scholar
- Lantz, T.C., S.E. Gergel, and G.H.R. Henry. 2010. Response of green alder (Alnus viridis subsp. fruticosa) patch dynamics and plant community composition to fire and regional temperature in north-western Canada. Journal of Biogeography 37: 1597–1610.Google Scholar
- Mackay J.R., and Burn C.R. 2011. A century (1910–2008) of change in a collapsing pingo, Parry Peninsula, Western Arctic Coast, Canada. Permafrost and Periglacial Processes 22. doi: 10.1002/ppp.723.
- Molau, U., and P. Mølgaard. 1996. International Tundra Experiment (ITEX). http://www.geog.ubc.ca/itex/library/index.php. Retrieved 1 November 2010.
- Myers-Smith, I.H. 2011. Shrub encroachment in Arctic and alpine tundra: Mechanisms of expansion and ecosystem impacts. PhD Thesis, University of Alberta.Google Scholar
- Smith, C.A.S., C.E. Kennedy, A.E. Hargrave, and K.M. McKenna. 1989. Soil and vegetation of Herschel Island. Research Branch, Agriculture Canada.Google Scholar
- Thorpe, N., S. Eyegetok, N. Hakongak, and K. Elders. 2002. Nowadays it is not the same: Inuit Quajimajatuqangit, climate caribou in the Kitikmeot region of Nunavut, Canada. In The Earth is Faster Now: Indigenous Observations of Arctic Environmental Change, ed. I. Krupnik, and D. Jolly, pp. 198–239. Fairbanks/Washington, DC: Arctic Research Consortium of the United States/Smithsonian Institution.Google Scholar
- van Wijk, M.T., K.E. Clemmensen, G.R. Shaver, M. Williams, T.V. Callaghan, F.S. Chapin, J.H.C. Cornelissen, L. Gough, et al. 2004. Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: Generalizations and differences in ecosystem and plant type responses to global change. Global Change Biology 10: 105–123.CrossRefGoogle Scholar
- Walker, M.D., C.H. Wahren, R.D. Hollister, G.H.R. Henry, L.E. Ahlquist, J.M. Alatalo, M.S. Bret-Harte, M.P. Calef, et al. 2006. Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences of the United States of America 103: 1342–1346.CrossRefGoogle Scholar
- Yukon Territorial Government, Heritage Branch. 2001. Virtual Museum Canada—Herschel Island. http://www.virtualmuseum.ca/Exhibitions/Herschel/English/menu.html. Retrieved 16 November 2010.