Diversity and Ecological Features of Dynamic States of Psammophylous Grass Vegetation in the Southern Nechernozemye of Russia

Based on a comparative analysis of 711 relevés and field surveys, the authors compiled a scale of dynamic states of psammophylous grass vegetation in the Southern Nechernozemye of Russia. The following main criteria were chosen for their selection: the area of the total projective cover in communities, the presence of renewal of tree species (Pinus sylvestris and Betula pendula) and their age stage, and life forms of pioneer species colonizing the primary substrate or substrate after disturbance. In habitats of six types, in which successions of six variants are realized (A, xerophytic cereal; B, moss–lichen xerophytic; C, undershrub xerophytic; D, forb–cereal xeromesophytic; E, forb–cereal mesophytic; and F, forb fallow xerophytic), five stages of succession were identified, ending with the restoration of forest communities. Certain dynamic states of vegetation are formed in the listed habitats at each of the stages. The associations of the floristic classification of the vegetation are represented by different dynamic states. According to the results of the study, three stages of succession are distinguished for psammophylous grass vegetation. Coenofloras of the samples of communities at the identified stages have statistically significant differences in the total projective cover, and floristic saturation, evenness of abundance, and habitats differ by individual environmental factors. The general patterns of changes in the spectra of life forms according to I.G. Serebryakov were revealed in samples of relevés at different stages of succession: species of different life forms can act as pioneer species forming communities at the initial stage of succession; in the course of succession from stage 1 to 3, the proportion of monocarpic annuals decreases in community samples of all variants; and the total diversity of life form types increases from stage 1 to 3. Considering the high commonality of the coenofloras of psammophylous grass vegetation of different syntaxa due to the wide representation of psammophilic oligotrophic species in their communities, as they invade and take root in the communities, the differences in the coenofloras are leveled. During succession, a convergence of dynamic states occurs, leading to a decrease in their number over time as the oligotrophic pine or birch–pine forest is restored in the studied climatically homogeneous region.