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Background. The most of ecosystem models do not take into account the asymmetry of crowns resulted from the competition between trees. Thus, the objective of the current study is to estimate quantitatively the effect of competition on shape and size of tree crowns. Materials and methods. The study was carried out in mixed and pure spruce, pine and birch stands in the Moscow and Novgorod regions. Mapping of trees was carried out on 14 sample plots of 25×25 m in size. Stem diameter, crown length and crown spread in four cardinal directions were measured for each tree. The relationship between crown size and tree stem size was analysed, as well as spatial distribution of stem bases and centroids of crown projections. Results. We found that crown size and shape is strongly dependent on tree species, its location in stand, and stand density. Pioneer tree species are characterized by relatively narrower crowns with high relative crown base height while the late-successional tree species have relatively wider crowns. The asymmetry of crown projection was shown to be strongly influenced by a tree neighbourhood. We also found that centroids of crown projections are distributed in space more regularly than stem bases. Conclusions. The species-specific features in crown development were shown. The analysis of results confirmed the previously described mechanism of adaptation to competition from neighbouring trees through asymmetric crown expansion in different directions. The relationships derived can be used for development of improved algorithm of simulation of aboveground competition. New procedure will allow us account the influence of a tree neighbourhood on the size and shape of its crown.

THE EFFECT OF ABOVEGROUND COMPETITION ON SPATIAL STRUCTURE AND CROWN SHAPE OF THE DOMINATING CANOPY SPECIES OF FOREST STANDS OF EUROPEAN RUSSIA