Environment, climate and tree growth relationships at the western Canadian Arctic treeline.

The latitudinal forest-tundra ecotone is an area that is experiencing substantial changes with respect to tree growth and climate change. We examined the response of radial tree growth to climate in adjacent regions of northern Yukon and Northwest Territories, Canada, across environmental and spatial gradients using dendrochronological methods. Principal components analysis was used to derive the primary modes of variation in the tree-ring records, which were subsequently attributed to environmental and climatic features. We found that slope gradient (small spatial scales) and ecoregional classification (larger spatial scales) played substantial roles in determining the response of tree growth to climate. Climate correlations were found for current and previous years to growth, many of which challenge currently held assumptions regarding the dominant climatic determinants of tree growth at high latitudes. These findings indicate that Arctic forest environments are highly complex, and that expected changes in the biosphere will occur at various rates, times and places. --P. ii.