Models for predicting dry matter content of Norway spruce

Models were developed for predicting the dry matter content of single Norwa y spruce [Picea abies (L.) Karst.] stems from non-destructive field measure ment data such as tree height, diameter and age. The material under study c omprised 1612 stem discs originating from 235 trees grown at nine locations in Denmark and southern Sweden. In total, 153 trees (1054 discs) originati ng from a thinning experiment in southern Denmark were used for establishin g the models, which were later validated on independent material. Results o f the validation were that the 95% confidence interval for single stem dens ity was +/-9 to +/- 16% when based on average ring width at breast height, but within +/-7% when based on wood samples taken at breast height. The den sity models were combined with standard volume models in order to predict d ry matter content. Validation on independent material showed that in genera l the dry matter content of single stems can be estimated with less than 10 % error (RMSE).