The dynamics of erosion and soil deflation processes in the Russian part of the Selenga basin is considered for the period of agrarian land use in relation to a combination of natural and anthropogenic factors. Periods with a different directedness and intensity of the processes have been identified. It is shown that a large-scale degradation of lands within the Selenga basin was caused by massive destruction of forests in the first half of the 19th century. Special attention is centered on the disastrous manifestations of the processes associated with extreme high-intensity storm rains or with heavy droughts. Strategies are suggested for optimizing land use practices in order to avoid a further degradation of soil cover.
We revealed the regional features of the functioning of the erosion-channel systems of the Angara, Upper Lena, Selenga, and Upper Amur basins in the south of Eastern Siberia and examined the action of sloping non-channel, temporary, and permanent channel water flows, and presented the patterns of the spatial distribution of soil and gully erosion belts. The development conditions and factors of fluvial processes are considered and the role of cryogenic processes in the increasing activity of water flows is emphasized. The interdecadal dynamic cycles of the erosion-accumulative processes are revealed. A quantitative assessment of soil loss from erosion on agricultural land in the forest-steppe basins was carried out. We made an assessment of the plane deformation of the upper course of the Lena river (Siberian platform) and Irkut (Baikal rift zone and the Irkutsk-Cheremkhovo plain) using cartographic sources of different times, aerial photographs, and satellite imagery. The contribution of extreme fluvial events to sediment redistribution in river basins is shown. Particular attention is paid to the mudflow impact, floods, and channel deformations on the ecological state of the basin systems.
A conjugate analysis of the processes of morphogenesis and sedimentation within small fluvial basins of Dauria revealed a rhythmic character of change of the Holocene processes which are combined into cycles of a different hierarchical level. It is shown that each cycle begins with an extreme phase of intense fluvial drift and delivery of matter from the system. The fluvial horizons comprise the lower part of deposits of the Holocene macrocycle in the Vesnyanka pad’ (a valley without a permanent watercourse). A disastrous fluvial drift was recorded repeatedly for the period 7–8.5 cal. ka and at the transition time from the Atlantic to Subboreal time. A normal zonal phase of integration of matter within the basins is exhibited by buried humus horizons of soils which give clear evidence of 1800-year cycles. A regional development in Dauria is recorded for the soils with the age of about 8, 6.4 and 4.6 as well as 1.2–1.4 cal. ka. The upper part of the deposits of each cycle is characterized by aeolian horizons of extreme arid phases. The profiles of proluvial trails are indicative of 130-year cycles. Based on results from studying buried soils, data of pollen analysis and radiocarbon dating of the deposits, we determined an enhancement in climate aridization for the last 10 ka and, in general, a decreased of the sedimentation and morphogenesis rate.
We revealed regional features of functioning of a large Transbaikalian aeolian morphodynamic system. Natural pre-conditions, current realities and factors of development of aeolian processes are investigated. The paper considers regularities of spatial distribution of deflation, transit, and aeolian accumulation zones. Main directions of aeolian migration of matter are determined. Pulsating nature of aeolian processes development in Holocene has been established. Identified are intrasecular cycles and Holocene dynamics of aeolian processes. We identified intrasecular (11, 27–35 years old), secular (80 year old) and Holocene (500, 2000 year old) cycles of aeolian process dynamics. The paper shows the influence of anthropogenic activity on the activation of aeolian migration of material for the historical period. It presents an overview of extreme aeolian events. Regionalization of Transbaikalia was carried out according to the degree of probable desertification of the territory due to development of aeolian processes. Areas of catastrophic manifestation of processes are highlighted. The results of long-term experimental observations of deflation and aeolian accumulation are presented. Particular attention is paid to the characteristics of the aeolian corridors. The important role of aeolian processes in the intensive material transport from Transbaikalia to the south and southeast to neighboring regions of Mongolia and China is shown.