engleski

Crown volume in forest stands of pedunculate oak and common hornbeam

Background and Purpose: Structure of the crown volume in a forest stand is one of the main factors that drive the growth and development of trees. It changes dynamically with the age of the forest stand and according to the management activities and natural disturbances that remove trees from the stand. Aim of this article is to analyze crown volume structure in relation to stand age and diameter at breast height (DBH) of pedunculate oak and common hornbeam trees in one of the most important forest types in Croatia. Materials and Methods: Data for the research were collected on set of 47 permanent sample plots established as a chronosequence over the distribution range of pedunculate oak and common hornbeam forests in Croatia. Combined area of all plots amounts to 33.45 ha. Trees were measured for DBH, total height and height to crown base, and a detailed map of crown projection areas was made for each plot. In total, crowns of 1609 trees of pedunculate oak and 1979 trees of common hornbeam were measured. Crown volumes were calculated for each tree, trees were pooled into age classes of 20 years, and the analysis were done per tree species, per age class. Nonlinear regression with exponential function of crown volume was performed to establish the relationship between the crown volume and DBH in each age class. Results and discussion: Up to the stand age of 40 years, crowns of pedunculate oak dominate in the canopy layer (66%), after which crowns of common hornbeam trees assume dominance. Coefficients of determination for the regression lines for pedunculate oak crowns are higher than the coefficients for common hornbeam, in all age classes being higher than 0.50, except for the first age class in common hornbeam and seventh age class for pedunculate oak. Shape of the regression lines of pedunculate oak crown volume shift more to the right side of the diameter range as the stand matures, while those of common hornbeam are more static and form a bundle of lines. Conclusions: Results indicate that relationship of crown volume of pedunculate oak and common hornbeam trees with DBH can be described by nonlinear regression model with exponential function. Further research is needed to asses the possibilities of integration of the obtained regression models into simulators of forest growth and development.

stand structure; crown structure; crown volume; pedunculate oak; common hornbeam; nonlinear regression

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