INVESTIGATION OF SUB-ARCTIC STREAM RESPONSE TO CLIMATE CHANGE AS EVIDENCED BY BAR DENDROCHRONOLOGY AND SOIL DEVELOPMENT ALONG THE PELLY RIVER, YUKON TERRITORY, CANADA

River morphology in sub-arctic regions is highly dependent on the volume and timing of discharge. As a result, stream response within sub-arctic regions is more susceptible to climate change due to its impact on snow volume and the timing of melt. However, the effects of climate change are often difficult to quantify because of lack of historical gage data and the complexity of the processes (e.g., avulsion and river migration) that form and rework a floodplain. By investigating bar and terrace morphology, along with their relative ages (as determined by vegetation communities and their related soil development), rate of river migration can help provide a clearer picture of stream response to variations in discharge due to climate change. Bars along the Pelly River, near the towns of Faro and Ross River, have been selected for this study because of minimal impact humans have had on the area due to the sparse population. Vegetation communities on select bars are being mapped, and representative trees are cored or cross-sectioned to determine community ages. Soil character and development along the Pelly River is examined in relation to differing geomorphic surfaces and forest communities to provide further information on rate of stream migration. A soil chronosequence is being developed by examining two bars along the Pelly River. Sampling on each bar incorporates two sets of parallel transects perpendicular to the river. Soil pits are excavated in differing geomorphic and vegetative zones; profile and horizons within each pit are characterized to link soil development to river migration and vegetation age. Preliminary results indicate that vegetation ages range from 5 years (according to willow cross-section ages) at the bar margin to approximately 150 years (according to spruce core ages) towards the valley wall. Because spruce is one of the later species to develop in a boreal succession, the actual maximum bar age must be older than that of the spruce. It is currently unclear how much older the bar is than as evidenced by the spruce ages; however, differences are predicted based on relative soil development between geomorphic surfaces and forest communities of differing age.