Prediction of individual tree growth in managed stands of mixed Picea abies (L) Karst, and Betula pendula Roth & Betula pubescens Ehrh.

Abstract

The individual tree growth in stands of mixed Norway spruce (Picea abies (L.) Karst.) and birch (Betula pendula Roth & Betula pubescens Ehrh.) is estimated using basal area and height growth functions for each species separately. The individual tree growth models are distant dependent and the number, size and proximity of neighbours are expressed as size‐ratio competition indices. The competition indices were calculated using a basal area factor gauge to define competitors. The tree growth functions are based on data from nine mixed stands of Norway spruce and birch. The recursive multivariate regression approach is used. The growth functions have standard deviation about the function/standard deviation about the mean (sf/sm) values between 31 and 61% and the evaluations made with root mean square error (rmse) give estimates which vary between 8 and 45 % of the observed mean value. These values are comparable with the precision reported in other studies. In the present investigation the distant dependent ...