A PROCESS-BASED MODEL FOR THE DIMENSIONAL GROWTH OF EVEN-AGED STANDS

An individual tree, process-based stand growth model is presented. It is based on the carbon balance, according to which tree growth depends on the activities of photosynthesis, respiration and senescence. A simple model is specified for each component of the carbon balance. Next, equations for the tree structure, in which e.g. pipe-model theory is utilized, are presented. The growth model for dry-weights of tree compartments based on the carbon balance is transformed using these equations to allow the expression of growth in terms of diameter and height. It is also possible to aggregate a number of physiological and biometrical coefficients into a small number of generalized coefficients of the dimensional growth model. Additional components. including the equations for recession of the crown base and tree survival that are necessary for a stand growth model, are specified. Comparison of the stand growth model with a yield table and a growth model for a sapling stand suggests that the model is capable of accounting for the basic features of stand growth. Furthermore, simulations with varying initial density and some of the model's coefficients indicate that the stand growth model is approximately consistent with the so-called self-thinning rule.