RESPONSE OF RED SQUIRRELS AND FEEDING DAMAGE TO VARIABLE STAND DENSITY IN YOUNG LODGEPOLE PINE FOREST

This study was designed to test the hypothesis that large-scale habita t alteration by stand thinning would reduce red squirrel (Tamiasciurus hudsonicus) populations and feeding damage in young lodgepole pine (F inns contorta) forest. An additional objective included integration of stand protection with an optimum thinning regime for growth rates of crop trees. Study areas were located near Penticton, Kamloops, and Pri nce George in south-central British Columbia, Canada. Each study area had three stands thinned to densities of approximate to 500 (low), 100 0 (medium), and 2000 (high) stems/ha, with an unthinned/juvenile Fine stand and old-growth pine stand for comparison. Squirrel populations w ere sampled intensively in the thinned stands from 1989 to 1991; feedi ng damage was assessed annually from 1989 to 1993. Five-year diameter and height increments of crop trees were measured in the thinned stand s at Penticton and Prince George, and 4-yr increments in these stands at Kamloops. Red squirrel populations were significantly reduced in th e low-density stand compared with either the medium- or high-density s tands at Penticton and Prince George. Squirrels were less abundant in both the low- and medium-density stands at Kamloops. Squirrel populati ons in the unthinned and old-growth stands were similar or lower in ab undance than those in the thinned stands. There were significantly hig her numbers of red squirrel first captures in the medium- and high-den sity stands than in the low-density stand. There were no consistent si gnificant differences between stands in proportion of squirrels breedi ng, recruitment, mean survival over summer and winter periods, or mean body mass. More tries per hectare were damaged in the high than in ei ther low- or medium-density stands at all study areas. Mean diameter i ncrements of trees in the low-density stands were significantly higher than there in the medium- and high-density stands at all study areas. Trees grew significantly faster in height in the high- than in the lo w-density stands at Penticton and Prince George; the converse was true at Kamloops. Manipulation of stand density on an operational basis in young lodgepole pine has clearly indicated that both stand protection from squirrel feeding damage and productivity of crop trees are enhan ced by reducing the number of stems per hectare. This result has been achieved in replicated study areas covering three different forest eco logical zones.