Oscar García
Forest Research Institute, Rotorua, New Zealand
General patterns in the growth of thinned and pruned stands are explored with the help of empirical growth models and graphical analysis of raw data. A variable representing relative stand closure makes possible relatively simple descriptions of stand development and silvicultural responses. It is commonly thought that gross volume increment in closed stands decreases with age, and is independent of stocking. It was found, however, that the increment does not vary significantly within the range of ages studied, but decreases with increasing tree spacing. The increment in an open stand relative to that of a closed stand with the same spacing is non-linearly related to the "degree of closure". Descriptions of the change in the degree of closure caused by thinning and pruning, and of the subsequent rate of recovery, complete the information required to predict the effects of silvicultural treatments. These concepts may contribute to improve the accuracy of growth models, to more robust economic evaluations of silvicultural regimes, and to growth modelling in data-poor situations.
Keywords: growth; growth models; thinning; pruning; radiata pine.