Allometric biomass equations for Scots pine (Pinus sylvestris L.) seedlings during the first years of establishment in dense natural regeneration

Abstract

A dense natural regeneration of Scots pine (Pinus sylvestris L.) exhibits a considerable biomass build-up in the first four years, with amounts of 7.03 Mg ha-1 for aboveground biomass, and 0.88 Mg ha-1 for coarse root biomass (> 1 mm). Power equations were developed, which relate collar diameter (ranging from 0.3 to 2.7 cm) and height to total aboveground and coarse root biomass of two, three and four-year-old seedlings in a regeneration of 16 seedlings m-2 at one site in Belgium. During the first years of establishment, seedling allometry changes with age, whilst the density remains constant. Biomass equations developed for one of the three ages can produce biased predictions for the other ages. Even when an equation is based on data for all ages and information on height is included, age still has to be considered as a potential predictor variable. For pooled ages, linear regression after logarithmic transformation of the power equation, selected other predictors than weighted non-linear regression. The former approach indicated significant interactions between predictors, while the latter does not reveal interactions.