TRENDS IN THE SPECIES DIVERSITY AND PHYTOCENOSISES PRODUCTIVITY IN THE ARID ECOSYSTEMS

Abstract

The investigations were carried out in severe continental climatic conditions in the pasture experimental segments of the Kochubei biosphere station in the North-Western Caspian region under natural moisturazing. The facts which shows that under certain hydrothermal conditions some vegetation types don’t survive under the insufficient moisture conditions were mentioned. The vegetation geobotanical characteristics were studied by the L.G Ramensky method, plant groups were divided by the degradation degrees in accordance with criteria proposed by B.M. Mirkin (1984), the plant cover was assessed by the Brown- Blanke scale. The weather pattern varied during the vegetation season. So 2011, 2012, 2016 are wet, and 2013-2015 to the arid. The metrologic data analysis shows the high temperature level from June to August under low precipitation against the backdrop of the high evaporation. In the long-term experience only drought resistant dwarf semishrubs (haloxerophyts) with well-developed root system were survived, which are the fodder basis of the pastures. To compare the pasture phytocoenosis species composition from year to year was used Jaccard index. In the wet years was noted the high similarity index of the plant species: haloxerophyts (sagebrush and saltwort), miscellaneous herbs (Kochia prostrate, Lessing’s camphor-fume), ephemeria (poaceae). In 2013-2015 the variety is low, plant cover from 5 to 25%. Species composition and phytosenoses pasture productivity annually changed depending on environmental conditions. As a result of the plant formation research and monitoring has been established that xerophytization of vegetation and aridization of the climate, which is destructive to the vegetation of natural pastures, takes place.