About the concept of ecological niche and its role in design of adaptive arid pasture agroecosystems

The concept of ecological niche occupies the central position in modern ecology (Eu. Odum, 1975). The concept of ecological niche may to a certain extent explain how different species can normally function and produce, growing side by side with each other, and absorbing water and mineral resources within a certain ecotope. In the context of the traditional concept of ecological niche, the community can be imagined as extensive n -dimensional hyper space within which each specific population evolves in such direction to correspond to own part of this space (G. Huthinson, 1957). The niche is characterized by its position and the response to the factors within the hyperspace of this community. In recent years, along with the traditional concept of niche, there was a concept of neutralizm which is actively developed by Stephen Hubbel and his supporters (G. Bell, 2001; J. Whitfield, 2002). According to this concept, species coexist thanks to similarity, but not distinctions, as a result of similarity on demographic characteristics, i.e. the similar specific speed of population growth and speed of settling of the released site. A number of authors have tried to unite within one model the neutralistic and niche mechanisms of functioning of species in community (D. Gravel et al., 2006). Now even more often ecologists speak about two types of communities (А.М. Gilyarov, 2010). Communities of the first type are organized according to the principle of a discrepancy of types on different ecological niches. Their existence is possible only because their niches are differing. Communities of the second type are organized and capable to coexist very long if are ecologically identical due to the same probability of an individual of different species to reproduce, die out, and occupy free spaces. It is supposed that if species long live in the same place, then they already are definitely rather close ecologically. We created multispecific, multi-tiered agroecosystems consisting of shrubs, semishrubs and grasses for arid conditions of Central Asia based on the traditional concept of a divergence of species in different ecological niches. For formation floristic and cenotic full-member multispecific pasture agroecosystems, we used fodder shrubs, typical for the southern deserts ( Haloxylon aphyllum, Aellenia subaphylla ), semi-shrubs ( Eurotia ceratoides ), draft semishrubs ( Kochia prostrata, Salsola orientalis, Camphorosma lessingii, Artemisia diffusa ), xerofitic perennial grasses ( Poa bulbosa, Carex pachystylis ) as the members of typical zonal flora. Multispecific shrubs-semishrubs-grassy pasture agrophytocenosis which were formed using zonal dominant species of fodder plants provided for a rapid restoration of biodiversity and the fodder efficiency lost under land degradation. The spring-summer and autumn-winter pasture agroecosystems created from mix of fodder shrubs, semishrubs, draft semishrubs and perennial grasses with different rhythmic of development, different type of root system, different drought resistance and heat resistance are more durable and productive than natural pasture ecosystems of the Central Asian deserts. Along with ecological advantages, multispecific pasture agroecosystems are much more various on structures of forages, they are better eaten and more stoutly satisfy physiological needs of animals for nutrients.