Growth model for predicting stand development of Acacia mangium in South Sumatra, Indonesia, using the reciprocal equation of size–density effect

A growth model consisting of a polymorphic site index equation, a reciprocal equation for the diameter–density effect, and a self-thinning equation was presented to predict the course of stand development of Acacia mangium. This model firstly predicts height growth with the polymorphic site index equation, and then density-related growth and mortality, that is, diameter and stand density, are calculated to satisfy the mathematical relationship for the reciprocal and self-thinning equations. The latter equation relates the rate of reduction in stand density to the diameter increment derived from a fitted trend of the distance from the maximum size–density line. The cumulative predictions, starting with stands 3 years after planting and continuing until they were 9 years old, agreed well with observations of group-age means of measurements calculated for the three levels of initial density. Contrasting height diameter relationships among the three levels of initial density were described reasonably well with this model, and the predicted basal area growth was found to agree well with observations. This indicated a good potential for its use in yield prediction. Simulations for stand growth under different spacing and thinning options were demonstrated in a stand density control diagram, which suggested a reasonable flexibility for practical application.