Aboveground biomass and nutrients in developing northern hardwood stands in New Hampshire, United States.

摘要

Accurate estimates of biomass and nutrient stocks in young second-growth forests are critical for assessing ecosystem productivity and the contribution of these forests to regional and global nutrient cycles. Forest biomass in northeastern temperate forests is commonly estimated using previously established allometric equations. Most allometric equations for smaller trees (2-12 cm dbh) and corresponding nutrient stock estimations have been developed using smaller trees from older stands (>50 yrs since last cut). To study how the prediction of biomass and nutrients stocks based on tree diameter vary with stand age, we studied six developing stands in and around the Bartlett Experimental Forest, in the White Mountains of New Hampshire. We developed allometric equations for aboveground biomass and nutrients of six northern hardwood species in two young (∼15 yrs old) and two middle-aged stands (∼30 yrs old). We also conducted non-destructive tissue sampling and made measurements to estimate biomass and nutrients in two old stands (>100 yrs old). Results from this study indicate that most allometric equations developed from this study in younger stands are very similar to those developed by other authors for the same species in older stands for total aboveground and wood biomass. However, we suggest that for components such as foliage, bark and branches, site- or age-specific biomass equations should be used in order to accurately assess aboveground biomass. Additionally, some tissue nutrient concentrations (K, P and N) were significantly different in young and old stands, necessitating age-specific nutrient concentrations for accurate estimations of some nutrient stocks.; Keywords. forest productivity, stand age, allometry, nutrient cycling, White Mountains, New Hampshire