Snowpack Characteristics following Wildfire on a Simulated Transport Corridor and Adjacent Subarctic Forest, Tulita, N.W.T., Canada

Abstract

A simulated transport corridor research site established in a permafrost-affected upland black spruce forest in 1984 was burned by a wildfire in 1995. A data set consisting of four mid-winter snow surveys conducted prior to the fire was supplemented by two postfire surveys (including a new, unburned forest control). Mean daily winter winds increased significantly on the cleared rights-of-way/ simulated pipeline trench (ROW/trench). Increased winds were attributed to postfire reductions in stem density and surface roughness, which offered less resistance to the wind. Maximum winter winds were not significantly greater at 1.5 m on the postfire ROW/trench where the postfire modification of the forest reduced funnelling and acceleration of winds along the cleared ROW/trench. ROW/ trench snowpack depth increased and water equivalence declined after the fire, except in leading-edge forest sites where the reverse occurred. Depth and water equivalence changes resulted from the altered wind regime, where reduction in effective wind erosion on ROW/trench locations left more snow in these areas and reduced the amount available for deposition in leading-edge forest sites. The postfire snowpack was generally less dense on the anthropogenic disturbances, and with greater insulation potential, less heat loss should occur through the snowpack. The postfire forest snowpack was unchanged in comparison to prefire characteristics which suggests that thaw season conditions have the greatest effect on active layer thickening and surface subsidence following wildfire.