UBC Theses and Dissertations
Ecosystem responses to climate variability, disturbances and environmental factors in southwest Yukon of Canada Paudel, Shyam Krishna
The south-western part of the Yukon Territory of Canada has experienced an unprecedented spruce bark beetle outbreak and frequent forest fires beyond the historical trends. Accumulating evidence also suggests that the southwest Yukon has experienced the impacts of recent climate change: warmer winters and warmer and drier summers over the past 15 years have contributed to the severe spruce bark beetle infestation, affecting white spruce on approximately 340,000 hectares of the traditional territory of the Champagne and Aishihik First Nations in southwest Yukon. The mortality caused by the bark beetle outbreak has also increased the risk of wildfire severity and frequency in the region. I studied the impacts of climate variability, disturbances and environmental factors on stand structure, forest regeneration and vegetation diversity within the CATT. The research was conducted in close collaboration with the Ministry of Energy, Mines and Resources of the Yukon Government and the Champagne and Aishihik First Nations Government. Data were collected in the summer of 2008 from the forested landscape of the Champagne and Aishihik Traditional Territory. I found that stand structure varied significantly by edaphic and topographical factors with higher forest productivity at lower elevation and on lower slope positions where there was a higher soil moisture regime. Overall stand productivity and vegetation diversity were higher on warmer aspects and in mixed stands. Although regeneration of all tree species was higher in burned areas, broadleaved species prevailed in these areas, indicating that persistent disturbances associated with the predicted increase in temperatures in the region may promote broadleaved species. A higher diversity was found in moderately disturbed open areas with higher mean temperature and precipitation. Salvage harvested areas had the highest diversity and highest composition of broealeaved trees. The undisturbed mixed stands had the ecosystem characteristics that would closely meet the ecological goals of the Strategic Forest Management Plan (2004) in the region. The vegetation distribution were closely linked with topographical, climatic and disturbance regime in the study area, which could be a basis for vegetation classification, which is still lacking in the study area.
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