Impact of red squirrel feeding damage on spaced stands of lodgepole pine in the Cariboo Region of British Columbia

Abstract

This study measured the impact of red squirrel (Tamiasciurushudsonicus Erxleben) feeding damage on spaced stands of lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) in the Cariboo Forest Region of British Columbia. A limited regional assessment of animal damage in spaced stands indicated that squirrels were the most important small mammal damage agents and that lodgepole pine was the only tree species susceptible to squirrel feeding (bark and vascular tissues) injuries. Intensive assessment of damage in two stands showed that squirrel attack was significantly greater among large- (>60 mm dbh) than small-diameter stems. Significantly more spaced than control (unspaced) crop trees were attacked. There was a general decline in the proportion of trees wounded from 1980 to 1985. Some damaged trees grew faster in diameter than undamaged trees of the same size. However, at one study area, damaged trees showed faster radial growth than undamaged trees before and after squirrel attack. Squirrels appear to prefer feeding on vigorous stems and the lost growth of these trees may be substantial. Height growth of damaged trees was significantly reduced in one stand in the years following squirrel damage. Some limit to a tree's capacity to sustain damage, beyond which mortality is inevitable, seems likely. Impact of damage to spaced stands may be minimized by delaying spacing in susceptible areas or by increasing the prescribed number of stems remaining after spacing to compensate for expected mortality and severe damage.