Ecoclimatic Zonation of Yukon (Canada) and Ecoclinal Variation in Vegetation
An ecological climatic zonation of Canada’s Yukon Territory (1:1 000 000 scale) was developed from field observations, aerial photographs, ecological literature, forest cover maps, and regression models. The 11 recognized ecoclimatic regions include Arctic (1), Subarctic (1), Alpine (4), Subalpine (1), and Boreal (4) entities. Region differentiation was based on vegetation thought to reflect climate more strongly than soil or topographic conditions. Sites with such vegetation are referred to as “reference sites.” The concept of a reference site was used because conventional zonal site criteria are difficult to apply in mountainous terrain and at high latitudes, where permafrost is an integral environmental component. Alpine regions were differentiated from other ecoclimatic regions through regression analysis of tree line elevations (n = 188, ≥ 76% explained variance). An ecocline of vegetation types for each region was developed on the basis of ecological moisture regimes. The climatic distinctiveness of regions was tested by statistical comparison and ordination of monthly temperature and precipitation data (1984 – 2007) from 26 and 24 meteorological recording locations, respectively. Significant differences (p < 0.001) between regions were found in temperature and most precipitation variables. A latitudinal gradient was evident among ordinated meteorological recording locations. Non-forest vegetation represents at least 70 – 75% of Yukon. Forests with closed and semi-closed canopies occurred primarily south of 64˚ N latitude at low elevations.