Competition-induced changes in developmental features of planted Douglas-fir in southwestern British Columbia

Abstract

One- to five-year-old Douglas-fir, planted operationally, were measured for various developmental characteristics indicative of competition-induced acclimation to resource limitations. Characteristics were tested against a competition index based on measures of the brush canopy surrounding individual trees. The most promising developmental characteristics for assessing competition stress were the specific leaf area of foliage, the allometric relationship of height to basal area, and bud production on nodal shoots. Measures of foliar nitrogen status and leaf internode length were less well correlated with the competition index. Comparing these results with those of controlled laboratory studies gives an indication that on the sites studied, brush competition effects on planted trees are expressed through developmental acclimation to reduced light intensity. Developmental expression of changing nutrient or moisture availability was less evident, but may be confounded by reduced demand or secondary brush canopy effects.