Diameter at breast height-crown diameter prediction models for Picea orientalis

Seven models for predicting crown diameter using diameter at breast height were tested for Picea orientalis L. (Link.) in Artvin. Data were obtained from 4208 trees measured on 117 temporary sample plots. Sample plots were grouped into categories with 20 year mean age class intervals. Similarly, sample plots were grouped into categories based on mean tree diameter at breast height (2 cm diameter class interval). Mean diameter at breast height and mean crown diameter of sample plots in age class were analyzed statistically. One linear and six non-linear diameters at breast height-crown diameter functions were selected as candidate functions to model diameters at breast height-crown diameter relationship. Regression analysis showed that there were statistically significant (P > 0.05) and strong (R-2 > 0.80) relationship between diameter at breast height and crown diameter variables in P. orientalis. The results of the study indicated that the diameter at breast height-crown diameter relationship can be described by cubic, compound, growth or exponential model because of the same R2 values. But the cubic model gave the best result for relationship between diameter at breast height and crown diameter.