Aboveground biomass and nutrient accumulation in an age sequence of aspen (Populus tremuloides) stands in the Boreal White and Black Spruce Zone, British Columbia

Abstract

A chronosequence of Populus tremuloides Michx. stands ranging from 5 to 95 years of age was measured to document changes on aboveground biomass and nutrient (N, P, K, Ca, Mg) contents for three site classes (good, medium and poor) in the Boreal White and Black Spruce (BWBS) zone in northeastern British Columbia. Allometric equations relating dry weights of stemwood, branches and leaves to tree diameter at breast height were developed to estimate aboveground tree biomass. Total aboveground tree biomass increased with stand age from 34.8 t ha −1 in the 5-year-old stand to 359.7 t ha −1 in the 95-year-old stand on good sites, and from 8.3 t ha −1 to 267.7 t ha −1, respectively, on medium sites. On poor sites, the total aboveground tree biomass ranged from 33.9 t ha −1 in a 15-year-old stand to 245.4 t ha −1 in a 95-year-old stand. As stands aged, an increasing proportion of the aboveground biomass was allocated to stems.Nutrient accumulation in aboveground tree biomass increased with stand age and was in the order of N> Ca> K> Mg> P. Temporal patterns of nutrient accumulation followed the pattern of aboveground biomass accumulation. The nutrient concentrations in different tree tissues decreased in the order leaf> branch> stembark> stemwood, except for K. Understory vegetation contributed little to the nutrient pool of aspen ecosystems. Mineral soil contained the greatest proportion of nutrient capital of the various ecosystem components.