The Response of<i>Pinus radiata</i>to Initial Spacing

Abstract

SYNOPSIS This paper deals with the statistical analysis of growth data, obtained from the C.C.T. spacing trial at Tokai in Pinus radiata. The Chapman-Richards growth model was used to fit equations with live basal area as predicted variable. The estimated parameters were subsequently regressed on nominal stems per hectare. A linear regression with log age as predictor variable was used to obtain estimates for mean diameter at different ages. The coefficients of this equation were also regressed on nominal stand stems per hectare. A regression equation with stems per hectare and mean height as independent variables was used to estimate top height, which was subsequently regressed on age. A regression analysis with nominal stems per hectare as independent and coefficients of the top height-age regression as dependent variables revealed a maximum top height in stands of medium stand density. The growth curves for u.b. volume were derived from the corresponding basal area growth curves. An analysis of the observed height/D.B.H. ratios revealed remarkably high values in the densest plots. Crown length and crown length percent were closely correlated with stems per hectare and prediction equations were obtained to estimate these characteristics from stems per hectare. An analysis of growth responses in thinned stands revealed an average basal area growth which is 7% above that of the expected growth, derived from unthinned stands.