Age Structure and Growth of the Tree-seedling Bank in Subalpine Spruce-fir Forests of South-central British Columbia

We examined the dynamics of the tree-seedling bank in old-growth, subalpine Picea engelmannii—Abies lasiocarpa forests in south-central British Columbia by collecting all individuals <1.3 m tall within belt transects at two sites (n = ca. 500 per site) and determining their height, basal diameter and age. Seedlings were up to 149 y old. Regressions showed that spruce 1-m tall averaged 65-y old and fir 92-y old. Age structures indicated that recruitment into the seedling bank was variable with time, but that individuals of both species occurred in almost all 5-y age classes. Regressions of height and diameter vs. age had high predictability and showed that spruce grew more rapidly than fir. Allometric (height/diameter) relationships differed significantly between species; spruce had a much greater height/diameter ratio than fir. Seedlings accumulate gradually and persist for long periods in the seedling bank, thus forming a large pool of individuals that can potentially respond to opening of the canopy.