Restorative Successions with Participation of Ulmus pumila L. on Postagrogenic Lands in the Western Transbaikalia
At the present moment, studies of succession in abandoned agricultural lands are quite urgent due to their wide distribution within Russia. Invasions of tree species (Betula, Pinus sylvestris, Larix sibirica) in the steppe and forest-steppes of Buryatia have been described so far. However, successions with Ulmus pumila L. are not yet srudied. Last 20-30 years Ulmus pumila is widely distributed in abandoned fields, where it forms relatively dense communities. It is registered in the foothill plain areas and slopes of the basins of Selengiskoe medium-altitudinal mountain range on sandy and loamy chestnut soils.The study aims to characterize communities of U. pumila and assess their role in the succession processes in the postagrogenic fallow lands within Western Transbaikalia by methods of phytosociological classification, comparative analysis of structure differences based on the ages of fallow lands and description of successional stages. Sites of varying degrees of overgrowth and different ages were selected in 5 administrative districts of Buryatia. All descriptions are stored in the electronic database of the Department of Botany of the Buryat State University. The seed source for renewal of U. pumila in the studied areas is protective forest belts and indigenous plant communities. The wide ecological amplitude of the species and resistance to dry conditions allow the species to grow in fallow lands successfully. Analysis of the zonal structure of the elms flora shows that dominant species have steppe origin. This study concludes that the succession of the elm communities proceeds along the steppe type, complicated by the development of the tree-shrub layer, while sequentially occurring stormy stage (Artemisia scoparia), friable tussock stage (Achnatherum sibirica, Poa botryoides). The phytocenotic characteristics of the stages are given. On the soils of light mechanical composition, rhizomatous-weed with elms and Leymus chinensis are formed. Also, we provide phytosociological description of the stages. Under the conditions of grazing pressure, succession proceeds with the formation of elm communities with digressional species Artemisia frigida and Carex duriuscula in the grassy layer. In general, within Selenginskoe medium-altitudinal mountain range the succession of elm communities has not reached their final stage. The wheatgrass stage is absent. Ulmus pumila has relatively high adaptive abilities and plays an important role in the succession of fallow lands in arid conditions of Transbaikalia. Taking into account the distribution of elm communities in fallow lands, it is necessary to continue studying succession them in order to assess the duration of succession and the degree of restoration of indigenous vegetation.