Effects of a thinning regime on stand growth in plantation forests using an architectural stand growth model

摘要

The architectural form of a tree results from a combination of its physiology and mechanical support requirements. Using mathematical models of tree architecture that describe the mechanical relationships between different tree organs, a forest growth model was developed to predict the effect of thinning operations on tree/stand growth. The model is based on the height growth of trees, which is strongly correlated with forest site condition. The crown form of a tree alters as a result of available growing space within the stand, which, thus, affects crown depth. The parameter crown depth is a key characteristic for quantifying individual tree growth in order to reflect the effect of the thinning regime in plantation forests. The applicability of the model was verified using real stand growth data under various thinning regimes. Since the model includes not only the crown form but also the stem form of individual trees, we can predict tree size (clear bole length, stem diameter, ring width), stem shape, tree weight and stand biomass over the course of stand development for a variety of thinning operations. Without any thinning, the forest canopy will close at an early growth stage, there will be a high stand density, and the crown depth will be restricted and will exhibit poor growth. In contrast, forest plantations that are exposed to a number of thinning operations, at an appropriate intensity and timing, will exhibit the required biomass growth and wood quality. The effects on CO_2 fixation were also discussed with reference to thinning regimes in plantation forests.