EFFECTS OF THINNING IN A 43-YEAR-OLD DOUGLAS-FIR STAND ON ABOVE-GROUND AND BELOW-GROUND BIOMASS ALLOCATION AND LEAF STRUCTURE OF UNDERSTORY GAULTHERIA SHALLON

The above- and below-ground biomass allocation and leaf structure of understory salal (Gaultheria shallon) were compared between an unthinned and a heavily thinned (two-thirds of basal area removed) 43-year-old Douglas-fir (Pseudotsuga menziesii) plot 6 years after thinning at Shawnigan Lake on southern Vancouver Island, British Columbia. The increase in both above- and below-ground resources caused by thinning resulted in a smaller fine-root/leaf biomass ratio in the thinned (1.2) than the unthinned (2.0) plot. The balance between the production of fine-roots to acquire limited water and of foliage to acquire limited light is suggested as an explanation for this shift in carbon allocation from fine-root to leaf biomass between the two plots. The responses of G. shallon to thinning are discussed in relation to its role as a competitor for below-ground resources.