Upland Xerophyte Communities of Valley Landscapes of the Upper Reaches of the Chanty-Argun River (Mountainous Chechnya, Eastern Caucasus)

. The paper discusses the features of plant communities of the upland xerophyte complex of the valley landscape of the upper reaches of the Chanty-Argun River. Regularly repeating and interconnected with environmental factors phytocenoses of the Itum-Kalinsky semiarid basin are noted. The abundance of species, their distribution by elements of the lower and middle mountain relief and communities were determined by experts on the basis of field information. Peculiarities of mountain-steppe communities, factors of their spatial differentiation are revealed. The studied communities are rich in species and are of significant conservation interest. With our research, we sought to emphasize the regional specificity of the studied communities, due to geographical, ecological, cenotic, and historical features.


Introduction
Arid mountain ecosystems are distinguished by an extremely high degree of spatial heterogeneity. Vertical zonality and climatic features of slopes of different exposure determined the diversity of landscapes and ecosystems. Over a distance of several kilometers vertically and several tens of kilometers horizontally, all transitions are observed from the harsh arid conditions of continental deserts through mountain semi-deserts, steppes, meadows, forests, to the subnival and nival belt. The excess of heat and lack of moisture at the foot of the mountains is replaced by a relative excess of moisture and lack of heat at the tops. Features of the orography of mountainous countries determine the high rates of abiogenic transport in these landscapes [1].
Here, in the upper reaches of the Chanty-Argun River, there is the intermountain Ushkaloy-Itumkala semiarid basin, one of the most interesting areas of wide development of upland xerophytes of the Eastern and Central Caucasus. On the territory of the North Jurassic intramountain structural-erosive depression, in the "rain shadow" of the Lateral Range, along with typical mountain phytocenoses (forest, meadow subalpine, and others), there are communities of upland xerophyte complex. The spatial distribution of the last two is subject to the geographical laws of their localization as products of orographic-climatic conditions. The distribution of hemi-and euxerophyte vegetation within the basin is associated with the arid and relatively warm climate of the semi-arid low-and midmountain landscapes, as well as the nature of the relief.
All elements of the valley landscape -relief, climate (balance of heat and moisture), geological substrate, surface layer of the atmosphere, vegetation, etc. -are in complex interaction and interdependence, forming a single natural-territorial complex of the basin. The valley of the upper reaches of the Chanty-Argun itself is characterized by a stepped bed and an uneven height of eroded slopes (usually concave).
The upland xerophyte vegetation of the Ushkala-Itumkala basin is heterogeneous, it consists of separate formations that differ in floristic composition, structure, and seasonal rhythm of development. The differences are due to the conditions of the habitat, including the nature of the relief and the skeletal nature of the substrate, the composition of the rocks, the exposure and steepness of the slopes, the height of the terrain, and others.

Research Methodology
The actual material for the work was the data collected by the authors during the

Results and Discussions
The vegetation of the slope surfaces bordering the flat bottom of the arid basin of the Chanty-Argun is differentiated. It is due to the heterogeneity of the relief, exposure and soil-climatic conditions.
A successive change in the vegetation component of landscape belts occurs with an increase in absolute height. Climatic and soil-vegetative differences are especially significant in the lower parts of the slopes of the valley, where there is a noticeable redistribution of heat and moisture over the relief elements, redeposition of surface rocks. In addition, the contrast in the manifestation of local conditions is also associated with the composition of rocks. All this is reflected in the parameters of heat and moisture supply of habitats.
The climatic features of the upper slope surfaces, flowing in the free atmosphere, are smoothed out.
The general regularity of the vegetation cover of the extended Chanty-Argun valley is the widespread development of upland xerophyte communities on insolated, with excess warming up primary slopes of the eastern, southern (and close to it) exposures in the left bank of the river. In the right bank, in conditions of sufficiently moistened landscapes of the western macroslope of the river valley, mesoxerophyte formations of mountain meadowsteppe forbs and grasses predominate.
Key area number 1. A complex of meadow-steppe microcommunities and sparse xeromorphic forest-shrub groups. Slope, slightly inclined (4-10°) part of the extended river valley of the river. Chanty-Argun. It is characterized by a significant steppe formation of herbage on loose and well-permeable colluvial-deluvial deposits (near the village of Ushkaloy, h ~ 720 m above sea level).
A small strip (belt) of upland xerophytic vegetation with elements of "proshibljak" Key area number 4. "Shibljak" vegetation in the form of xerophytic light woodlands in the medial part of insolated sloping and moderately steep (20-40º) slopes. It is represented by sparse woody and herbaceous vegetation, which is formed in a relatively warm climate and insufficient moisture. In the low-mountain transeluvial landscape, it occupies a belt above the tragacanths. The "Shiblyak" complex is most pronounced in the area of the valley between the village Ushkaloy and Kokada (h ~ 800-840 m above sea level).
Thermophilic sparse upland xerophyte woody groups are characterized by low density; the height of the tree-shrub layer is 2.0-2.5 m. Among them are slope grass communities on fragmented mountain-steppe stony soils and products of destruction of rocks.

Conclusions
The upland xerophytic complex of the Ushkaloy-Itumkala semiarid intramountain basin occupies significant areas in the lower and middle mountain steppe belts, where it is distinguished by the greatest diversity of habitable habitats on the southern, eastern and intermediate slopes.
Xerophytic vegetation is heterogeneous. The differences relate to the ecological and biological characteristics of plant formations, floristic composition, structure, and seasonal rhythm of the development of individual communities and groups. They are due to the complexity and dissection of the relief, habitat conditions: microclimate, degree of stony substrate, soil moisture, and others. The most typical and large in area formations of upland xerophytes are confined to rocky-scree outcrops, clayey, mountain-steppe and primitive skeletal soils of insolated slopes.
The coenotic diversity and variety of developed habitats of the complex is not as high as the originality of its components.