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THE RELIC STEPPES OF YAKUTIA (EASTERN SIBERIA, RUSSIA) - UNIQUE ECOSYSTEMS OF THE PAST (PRODUCTIVITY, BIOLOGICAL ACTIVITY, PROTECTION)

М. В. Щелчкова

Abstract

There are areas of extrazonal relic steppes on the territory of Yakutia in the tundra and taiga zones. They are the most extensive in central Yakutia, and sporadic squares of steppes are located in the north, in the Yana, Indigirka and Kolyma rivers basins. There are growing the xerophytic steppe plants which are separated from the main range, characteristic of the Transbaikalia and Mongolia steppes, as well as a number of invertebrate and vertebrate species of animals associated with their origin with the steppe zone. During the cold periods of the Late Pleistocene, the steppes occupied vast territories in Northeast and Central Asia and were the basis for the existence of Mammoth biome animals (mammoth, woolly rhinoceros, bison, horse, saiga-antelope, cave lion, wolf, Arctic fox, voles, lemmings, ground squirrels and others). As a result of the climate warming at the boundary of the Pleistocene and Holocene, extensive steppe areas in most part of the Northeast Asia were replaced by tundra and taiga. At present, isolated areas of relic steppes in central Yakutia are under strong anthropogenic press. In this regard, it is important to conduct a comprehensive monitoring of the state of these ecosystems and to improve measures for their protection. In 2015-2017, we for the first time conducted an integrated study of the hydrothermal, physico-chemical, biological properties of soils and the productivity of relic motley-feather grass steppe in the Middle Taiga subzone of central Yakutia (the basin of the Lena River middle reaches). Soils here are represented by solonetz light-humus salinized. Extreme dryness and high temperature characteristics of the solonetz are sharply distinguished it from the zonal pale soils of the Middle Taiga. The microbial complex of soils of the relic motley grass - feather grass steppe has a characteristic arid features, and actinomycetes play an important role in it. The extrazonal relic steppe soils exceed the zonal forest soils by stocks of microorganisms, hydrolase and oxidoreductase enzymes and decomposition activity of organic matter (cellulose). The net primary productivity (NPP) of the central Yakutia relic motley grass - feather grass steppe is quite high and range from 1678 to 2309 g/m2 per year and close to that of motley grass and grass steppes of Kazakhstan, Western Siberia and Transbaikalia. A characteristic feature of the productivity of the central Yakutia motley grass - feather grass steppe is the active growth of the underground phytomass (BNP), which significantly prevails over the growth of the aboveground phytomass (ANP). The ratio BNP: ANP is 19-22. This feature is determined by a combination of hard edapho-climatic conditions (severe harsh continental climate with short vegetation period and prolonged cold winter, high soil dryness, presence of slope erosion processes) with high anthropogenic press (overgrazing, uncontrolled grass burning). Anthropogenic impact on relic steppes is increasing and poses a huge threat to this unique biogeocenosis. The areas of the relic steppes of Yakutia, inhabited by a number of endemic Red Book listed species of plants and insects, are being constantly reduced. In this regard, it is recommended that the network of specially protected natural areas be expanded to cover more protected areas of relic steppes, and to continuously improve the ecological literacy of people.

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