Estimation of stem-volume increment by using sunny crown-surface area and stem-surface area

Abstract

A model for estimating stem-volume increment was devised from the viewpoint that the increment is the difference between assimilation and respiration. The factors used here were limited to only those that could be measured on a standing tree. The tree was divided into three parts, namely, crown, stem, and roots, and it was assumed that the assimilation of the crown supplied the respiration and growth of the three parts. Furthermore, a shaded crown was excepted because within it the assimilation was regarded to be partially proportional to the consumption. Consequently, the stem-volume increment became subordinate to the sunny crown-surface area and the stem-surface area in any single tree and a stand. This model was applied to estimate the change of stem-volume increment with age in sugi (Cryptomeria japonica D. DON) plantations in Oita Prefecture. The estimation was made by using the average sunny crown-surface area and stem-surface area at each age, and a regression equation of stem-volume increment to these two factors obtained on remeasured stands. The annual increment and total yield of stem volume estimated by the model were in fair agreement with those of the yield table.