Patterns of Changes in the Composition of Petrophytic Vegetation in Southern Ural and Adjacent Territories on a Moistening Gradient

Abstract

Southern Ural is a unique region in Eurasia with a high variety of flora and vegetation. Mountain relief predominates in the steppe and forest-steppe landscapes. Stony habitats and petrophytic vegetation are widespread here. It is characterized by a high diversity of flora and numerous endemic, rare, and endangered plants. The dataset of 3614 releves of forb and shrub communities from the territory of Southern Ural and adjacent regions is analyzed. Formalized methods of cluster analysis, an assessment of moistening using the ecological indices of plants, and the definition of indicator species are used. Patterns of changes in the species composition of petrophytic communities along the moistening gradient are determined. It is found that, with an increase in moisture, the number and cover of petrophytic species in communities on rocky habitats decreases. On the contrary, the role of indifferent species is growing. Five groups of species indicating different gradient segments are determined. Based on the results of cluster analysis, four large units of petrophytic vegetation are identified. Desert-steppe communities have the greatest floristic originality among vegetation on rocky habitats. Obligate petrophytes predominate in their diagnostic combination, many of which grow on limestone outcrops. These communities are found in the south of Orenburg oblast, mainly in the dry steppe landscapes of Southern Ural. Dwarf subshrub–bunchgrass steppes are widespread within the steppe landscapes and are common in the forest steppe of Ural. Forb–bunchgrass petrophytic steppes are widely represented in the northern part of the steppe zone and in the southern forest-steppe regions, as well as in the forest-steppe landscapes of Middle Ural. Meadow petrophytic steppes are found in forest-steppe and forest landscapes.