The effects of observed and experimental climate change and permafrost disturbance on tundra vegetation in the western Canadian High Arctic

Abstract

The response of vegetation to climate change and permafrost disturbance was studied at the Cape Bounty Arctic Watershed Observatory (CBAWO) on Melville Island, Nunavut. Climate change is expected to alter the terrestrial ecosystem of this area and cause non-linear responses. This study focussed on two predicted outcomes of climate change in the western Canadian High Arctic: the occurrence of a permafrost disturbance termed active layer detachments (ALDs), and increased air temperature and precipitation. To study the effects of ALD formation twenty 1 m2 plots were established within two ALDs. One ALD (ALD05) was formed in July 2007 and represented the initial impact of slope failure caused by an exceptionally warm year. The other (ALD04) was formed at least sixty years ago and represented the long-term impact of slope failure. Physical soil measurements and vegetation surveys were completed in both disturbances. ALD formation creates depressions on the landscape that increase snow accumulation. Snow accumulation was greater in the more recent ALD than in the older one and this resulted in greater changes to the physical environment. Vegetation was not significantly impacted by disturbance, although phenology was delayed due to snowcover retention. To study the effects of increased air temperature and precipitation an International Tundra Experiment (ITEX) site was established at CBAWO in July 2008. Snow fences and open-top chambers (OTC) were erected to increase snow accumulation and air temperature. Physical soil measurements and vegetation surveys were completed through the summer of 2009. Soil temperature and active layer depth were affected by snow and phenology was delayed in plots with snow enhancement. Experimental warming also had some effects on the parameters measured but only in conjunction with snow enhancement. This study found that in the first year of experimentation snow enhancement has a greater effect than increased air temperature. These studies represent the beginning of two long-term projects at CBAWO and the results from this study represent baseline data for future research. Continued monitoring will show the evolution of vegetation in the ALDs and the potential long-term effects of temperature and snow manipulation.