Saturday, 15 July 2006

Applied Aspects of Studying the Holocene Evolution of Soil–Vegetation Complexes in the Middle Amur Region, the Far East of Russia.

Marina I. Skripnikova and Olga N. Uspenskaya. V.V. Dokuchaev Soil Science Inst, Moscow, Russia

A unified concept of evolutionary changes in soils and vegetation within the Zeya-Bureya Plain has yet to be developed by pedologists and geobotanists. It is not clear whether forest of meadow-steppe vegetation predominated on the plain in the prehistorical period, and whether the development of steppe species in meadows and the deforestation of the plain are due to the heavy anthropogenic loads during the last 150 years. There is no unified classification of the soils of plains in the Far East of Russia. Processes that formed silica accumulations in the middle part of the soil profiles cannot be unambiguously identified; were these podzolic or solodic processes? At present, natural vegetation that participated in the development of the soil profiles is either disturbed by the agricultural use of the territory or completely destroyed by fires. In spite of the intense anthropogenic loads, this territory in the middle reaches of the Amur River remains the nesting place for the black, Dahurican, and Japanese cranes; it is also an important place on migration routes of other bird species. The birds are expelled by humans from their usual habitats to fallow lands on the high floodplain and first terrace of the Amur River. Currently, these lands are not used in agriculture. They are overgrown with monodominant vegetation represented by tall Artemisia species that are easily restored after annual fires. These fallow lands are improper for crane nesting, because there are no edible plants and because of the high susceptibility to fires. Frequent fires destabilize the water regime of the soils and contribute to aridization of the territory. Fallow lands occupy more than 50% of the birds' habitats. The Murav'evskii Park is the first nongovernmental area of sustainable nature management. It was organized in order to protect nesting places of the birds and restore degraded natural landscapes. The problem is to replace wormwood vegetation on the fallow lands with more productive and biologically diverse communities that should be tolerant toward frequent catastrophic changes in the moisture supply of the region. The initial virgin forest-steppe vegetation (the Amur prairie) consisted of a unique mixture of meadow-swamp, steppe, and forest species. To determine the optimal combination of species to be seeded on the fallow lands, a paleobotanical approach was used: the palynological method was applied in combination with the original method of Uspenskaya (1982) to determine the Holocene paleoclimate on the basis of the quantitative assessment of organisms of different trophic groups stored in the peat-sapropel deposits. The lists of species to be introduced were suggested on the basis of pollen spectra in those layers, the climatic conditions for which corresponded to the recent period of climatic aridization. The soils of different geneses were investigated in different geomorphic positions. The lists of species were compiled with due account for the particular soil type and its water regime. The analysis of peat-sapropel deposits in the Murav'evskii Park proved the existence of a long period of climatic aridization in the past and several short-term periods with increased aridity. In those periods, the portion of mesoxerophytic and xerophytic plant species increased up to 30-50%. Pollen of xerophytic grasses (Koeleria, Arundinella, Agrostis, Stipa) predominated over pollen of xerophytic forbs and trees (Quercus mongolica). Pollen of mesophytic species with a predominance of grasses (Calamagrostis, Elymus) and sedges such as&#1057 and arex canescens constituted about 40 to 50% of the total pollen spectrum. In the pluvial periods, the portion of mesophytic species (grasses + sedges + forbs) reached 90%. In general, the species composition remained relatively stable. The self-regulation of the viability and productivity of the vegetation community was ensured by changes in the portions of mesophytic and xerophytic species. Overall, ten variants of the list of recommended species to be seeded on the fallow lands in particular geomorphic and soil conditions have been suggested on the basis of the paleogeographic analysis. Mesophytic herb and tree species are recommended for soils with the eluvial-illuvial differentiation of the profile and for cambic soils with the nondifferentiated brown profile. Mesoxerophytic species are recommended for soddy sandy soils.

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