Changes in the species richness, spatial pattern and species frequency associated with the decline of oak forest

Abstract

In the Bialowieża Primeval Forest a decrease in the extent of the Potentillo-albae Quercetum has been observed for the last few decades, both with regard to the number of stands and size of the remaining phytocoenoses. In this paper the decline of an oak forest stand is analysed in terms of species richness, species frequency, spatial pattern and proportion of various ecological groups in the patch. Investigations were carried out from 1969 to 1992 on a permanent plot of 512 square meters divided into 128 quadrats. During this period: 1) 60 species disappeared from the plot whereas only 4 species invaded it; 2) frequency of most species considerably decreased; 3) species diversity decreased; 4) spatial homogeneity of the patch increased; 5) the number of species per unit area markedly decreased; 6) domination structure changed: the proportion of hornbeam-forest species was constantly increasing, eventually reaching the value comparable to that recorded for hornbeam forests. Finally, the oak forest was replaced by a community resembling hornbeam forest, with a small proportion of heliophilous species.