STATE OF CENOPOPULATIONS OF SOME RARE SPECIES OF PLANTS OF SAMARA REGION iN THE TERRITORY OF NATURE MONUMENT OF REGIONAL IMPORTANCE "SERNOVODNY SHIKHAN"

Abstract

The condition of cenopopulations of four rare species ( Artemisia salsoloides , Hedysarum grandiflorum , Oxytropis floribunda , Stipa korshinskyi ) in the petrophytic steppes of the High Zavolzh'yе (High Transvolga, Samara region) was studied on the basis of the regularities of their spatial and ontogenetic structure. The data were processed using the software package R, which allows us to perform calculations of spatial statistics. Thus, stationarity, isotropy, and intensity of plant objects location were evaluated. The mosaic distribution of individuals of all species recorded within the boundaries of the study area was characterized. Using local density maps, the sparseness of individuals on the outskirts of the model site, caused by cattle grazing, was revealed. The behavior of the Ripley's function showed an independent distribution of species as a consequence of weak interspecies competition. The spatial pattern and age spectrum of the studied rare protected dominant species were analyzed. The absence of seedlings and senile plants due to exposure to unfavorable factors of exogenous nature was noted. The im-v and g states were the most numerous. In accordance with the behavior of the K(r) function, the random placement of the four predominant species was revealed, indicating their optimal location within the study area. Patterns of mutual placement of pregenerative and generative individuals of Artemisia salsoloides, Hedysarum grandiflorum, and Oxytropis floribunda were studied. Calculation of the Ripley's cross-function showed that individuals of different age groups of the described species are located independently from each other, demonstrating the absence of intraspecific competition. Undoubtedly, the spatial distribution of individuals of the plant species composing the phytocenosis is influenced both by grazing and by the features of the soil cover of the site, which is manifested by significant elimination of plants at the initial stages of ontogenesis. Nevertheless, the cenopopulations of rare species are stable, mature and promising, and the individuals are distributed in an optimal way that minimizes energy costs.