Forest-Steppe Relationships in the “Shaitan-Tau” Nature Reserve (the Southern Urals)

Abstract

In the conditions of present-day climate changes forest-steppe landscapes are the effective model for studying boundary shifts between forest and steppe communities as well as degree of soil-phytocoenosis equilibrium under the control of relief. The paper focuses on the existence possibility of several equal-probability landscape states on the example of low-mountain forest-steppe in the State Nature Reserve “Shaitan-Tau” (the Sothern Urals, Orenburg oblast). We tested the hypothesis of discrepancies between the mobile attributes of forest and steppe phytocoenoses and the inert soil attributes. Discriminant models were built to describe how the occurrence of forest and steppe communities depend on their position in various types of landscape patterns. Geocircular patterns were described using morphometrical relief attributes characterizing flow dispersion and accumulation, geostationary patterns–using relief dissection attributes associated with morphology and genesis of landforms and rocks, and biocirculation ones–using attributes of topography-driven redistribution of solar radiation. We established soil-phytocoenotic attributes that indicate expansion or retreat of forest communities in the plots with high probability of correspondence to the ecological niche of forests. Nowadays, steppes can expand to the forest habitats on plateaus under the influence of summer warming and the higher frequency of fires, though features of forest soils can be preserved. At the north-facing slopes and in concave sites forests expand to steppe habitats in some locations. Shrubs have the least specific geomorphic niche and occur in typically forest and steppe habitats with approximately equal probabilities. They are treated as secondary communities increasing their occurrence at the expense of steppes or due to forest fires.