Variabilitatea dimensională a arborilor şi diversitatea florei vasculare în amestecuri de răşinoase cu fag din rezervaţia Codrul secular Slătioara [Tree size variability and plant diversity in mixed coniferous-beech forests in Slătioara Forest Reserve]

Abstract

The paper analyses, from structural and compositional aspects, the diversity of vascular flora from natural mixed forests with coniferous and beech. Six experimental plots were installed in mixed forest stands with coniferous and beech from Slătioara natural reserve, and the vascular flora was studied on three different layers: trees, seedlings and herbaceous layer. For each layer the species diversity was assessed through Shannon index, and additionally, for trees’ layer, the structural diversity was quantified with respect to the basal area, using the Gini index. It was observed that among the experimental plots, the Gini index ranges between 0.65 and 0.83, corresponding to the uneven-sized balanced structures, and Shannon index computed for species diversity ranges between 0.66 and 1.22 for trees layer, between 0.71 and 1.38 for seedling and between 1.12 and 2.38 for herbaceous layer. The structural diversity of trees layer assessed through the Gini index do not influences directly the species diversity of seedling and herbaceous layers. Nevertheless, when Gini index is higher than 0.48, only shadow tolerant species (ex. Silver fir) might form pure seedling patches. Additionally, regarding the trees layer, pure patches are formed only by beech (92%) or silver fir (8%), and the pure silver fir patches are characterized by low structural diversity (Gini index ranges between 0.27 and 0.32). Also, it was found that beyond certain thresholds of Gini index, the increase of structural diversity is associated with a decrease in the spread of variation of species diversity for all the analyzed layers, and the identified thresholds of Gini index are: 0.6 for trees layer, respectively 0.7 for seedling and herbaceous layer