SPECIFIC STRUCTURAL ELEMENTS IN MIXED STANDS OF NORWAY SPRUCE, SILVER FIR AND EUROPEAN BEECH IN THE NORTHERN PART OF ORIENTAL CARPATHIANS.

Recent studies have given more emphasis to mixed stands, highlighting the importance of species diversity, their growth and development are an important subject of research, given the advantages of the functions and services offered. The research material consisted of three representative experimental plots installed in mixed stands of Norway spruce, Silver fir and European beech. Researched aspects related to stand density, species proportion, stand composition, horizontal spatial model, vertical model, dimensional parameters distribution in the stands, and the homogeneity of the stands were addressed. The density of the Norway spruce, Silver fir and European beech mixed stands shows that the number of trees·ha^-1 range between 336 and 760, the basal area·ha^-1 between 38.5 m² and 41.2 m² and the volume·ha^-1 between 570.0 m³ and 651.4 m³. Horizontal spatial tree pattern is an important attribute of the stands structure that provides an idea of the variation of tree spacing and has a direct ecological influence in many processes in forest ecosystems. The vertical structure of the mixed stands is directly related to the main processes in the dynamics of the tree, being closely related to the capacity of the adaptation of ecosystems against abiotic disturbing factors. The distribution of dimensional parameters in a stand can be understood as a property that detaches from the data of individuals, therefore, represents an intermediate scale between the tree and the stand. The use of uni-modal statistical distributions when attempting to apply distribution patterns to characterize the distribution of the number of trees by diameters can lead to simplistic descriptions, altering the characterization of the stand structure. In the Norway spruce, fir and European beech mixed stands, the high degree of structural heterogeneity is highlighted. The results obtained showed that mixed Norway spruce, fir and European beech stands can develop in a fundamentally different way, the regeneration mode as well as the different growth characteristics of the component species having a significant influence. [ABSTRACT FROM AUTHOR]