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This particular paper analyzes the age of fir (Abies alba Mill.), spruce (Picea abies Karst.) and beech (Fagus sylvatica L.) trees, with a diameter at breast height of approximately 50 cm (diametar classes 47.5 and 52.5 cm) in mixed uneven-aged multi-leyerd stands. Research data was obtained from four continuous experimental plots on Mt. Igman, with different site conditions and stand structure on which the selective management method is carried out. Based on the number of annual growth rings on the incerement cores to the center of the tree taken at a height of 1.3 m, the so-called “age of growth” was determined (Flury according to Stamenković, Vučković 1988). However, the actual age is greater than the determined age, for the time required to reach a height of 1.3 m. The research indicated that the tree age is of great variability. The range for fir trees is from 70 to 350 years, for spruce trees from 65 to 256 years and for beech trees from 113 to 275 years. Moreover, the research implicates that the differences in age between tree species within one stand aren’t statistically significant in all analyzed cases, while differences between trees of the same tree species from stands of different site and stand conditions are statistically significant. The differences between the observed fir and beech trees in the same stand are not statistically significant, while the differences between the trees of these tree species and spruce trees are statistically significant. For all observed tree species, it was found that the age of trees is on average lower in sites of medium quality, compared to sites of better and lower quality. It was concluded that differences in the age of observed trees are determined by tree species, site conditions and stand structure (competitive relations) and other factors not covered by this study, and that the age of trees of certain species to some extent indicates the production potential of sites. [ABSTRACT FROM AUTHOR]

Spatial structure is the horizontal and vertical arrangement of individual trees. It affects many processes in the stand such as stability, production and regeneration. Stand structure parameters are used to describe spatial structure on experimental plots. The paper presents methods that describe the stand structure through three levels of diversity related to position, species and size. Research has been conducted on two experimental plots from the area of Olovo. Referent trees and their competitors were selected on both experimental plots, and competitors were defined by referent tree distance. The aim of this paper is to describe the spatial structure on experimental plot of European beech (Fagus sylvatica L.) and experimental plot of European beech and Scots pine (Pinus sylvestris L.). Indicators of spatial diversity, dimensional diversity and diversity of tree species have been determined to achieve that aim. For each experimental plots are described: horizontal tree distribution (Poisson Distribution, Clapham's Variance - Mean Ratio and Morisita's Index of Dispersion), diameter differentiation (Diameter Differentiation by Füldner and Dominance Index by Hui et al.), species diversity and structural diversity (Species Profile Index by Pretzsch) and species intermingling (Species Intermingling Index by Füldner). Obtained results show that the stand structure of both experimental plots deviates from random distribution. Dimensional diversity parameters indicate stronger intensity of competition for beech trees. Analysis of species diversity showed that beech trees occur in groups or patches, and the other represented species mix more intensive. [ABSTRACT FROM AUTHOR]