Relationships between site productivity and environmental variables of Oriental beech forests in northeastern Turkey

This study examined the relationships between soil, climatic and physiographic variables and site productivity in Fagus orientalis Lipsky stands in Artvin, Northeastern Turkey. The site productivity described by the site index (SI, top height at stand age of 100 years) was available for three forest locations. SI varied significantly depending on the edaphic, climatic and physiographic variables. A linear regression model was constructed to test the hypothesis that soil, climatic and physiographic variables could be used to predict the SI of the Fagus orientalis forest types in the study region. The most important single variable in the model was precipitation in the driest quarter of the year, which accounted for 55.1% of the variability in SI and was positively correlated. In a multiple regression model, precipitation in the driest quarter, radiation index, slope and physiological soil depth were the most important variables for explaining SI in the study region. 80% of the observed SI variation was explained by these variables. The SI models developed in this study provide a basis for understanding the complex relationship between forest productivity and site conditions. The findings of this study will assist resource managers in making cost-effective decisions about the management of Fagus orientalis forests in the northeastern region of Turkey.