%0 Research article
%T Distance-dependent models for predicting the development of mixed coniferous forests in Finland
%A Vettenranta, Jouni
%D 1999
%J Silva Fennica
%V 33
%N 1
%R doi:10.14214/sf.670
%U https://silvafennica.fi/article/670
%X Distance-dependent growth models and crown models, based on extensive  material, were built for Scots pine and Norway spruce growing in a mixed  forest. The crown ratio was also used as a predictor in a diameter  growth model to better describe the thinning reaction. The effect of  crown ratio on the growth dynamics was studied in simulation examples.  Monte Carlo simulation was used to correct the bias caused by nonlinear  transformations of predictors and response. After thinnings the crown  ratio as a predictor was found to be a clear growth-retarding factor.  The growth retarding effect was stronger among pines with thinnings from  below, whereas the estimated yield of spruces over rotation was  slightly greater when the crown ratio was included than without it. With  each type of thinning the effect of crown ratio on pine growth was  almost the same, but the growth of spruces was clearly delayed when the  stand was thinned from above. Simulation examples also showed that it is  profitable to raise the proportion of spruces during rotation, since  spruces maintain the growth more vigorous at older ages. The total yield  during 90 years rotation was about 20% higher if the stand was  transformed into a pure spruce stand instead of pine.