Site Index Curves for European Chestnut (castanea Sativa Mill.) in Belasitsa Mountain Krivulje Indeksa Staništa Za Pitomi Kesten (castanea Sativa Mill.) Na Planini Belasici

Richards, Lundqvist-Korf and Hossfeld growth functions were fi tted to age-height data of European chestnut (Castanea sativa Mill.) dominant trees on the northern slopes of Belasitsa mountain, Southwest Bulgaria. Th e model prediction performance was evaluated using quantitative as well as qualitative examinations. Goodness of fi t of each model was estimated by the coeffi cient of determination, F-test for signifi cance of the regression and t-tests for signifi cance of the coeffi cients of the model. Models were further compared by the evaluation of the standard error of the model and Akaike’s Information Criteria. Site index curves were constructed following the "guide curve method" procedure. In accordance with the evaluation tests, the Richards function was chosen as most adequate to express the age-dominant height relationship. Accordingly, it was further employed as a guide function to derive site index curves for studied chestnut population. It was recommended that the growth model and the site index curves elaborated in the current study are used within the data range 10−110 years.