DECAY LOSSES IN SUBALPINE SPRUCE ON THE ROCKY MOUNTAIN FOREST RESERVE IN ALBERTA

Abstract

Subalpine spruce on the Rocky Mountain Forest Reserve in Alberta was found to have decay amounting to 20% of the gross merchantable volume with variations in the amount of decay among the different sample areas ranging from 1.4% to 41.9%. A large part of this variation is attributed to the influence of site since it was possible to distinguish two types of sites which differed in the nature of the ground vegetation, the growth rate of the trees, and in the incidence and amount of decay. The average gross volume for survival trees on sites which were described as moist on the basis of distinctive ground cover associations was 174 board feet compared with 87 board feet on the dry sites. The average percentage of cull for trees in each of the two site classes was 24.5 and 9.2 respectively. In trees with a d.b.h. of 8 ins., 4.2% of the gross merchantable volume was cull, increasing to 24.7% in trees of 21 ins. The percentage of cull was higher in the faster-growing trees of the over-storey (20.6%) than in the slower-growing trees of the understorey (16.4%). In cubic feet, the percentage of decay was 7.8% and 5.4% respectively for the two classes of trees.