V. R. Belyaev

Problems in determining spatial inhomogeneity of 137Cs fallout for estimating rates of erosion-accumulative processes

The issues of assessing variability of 137Cs fallout of global and Chernobyl origin at reference sites are discussed with a purpose to use this isotope as a tracer for estimating the rates of erosion-accumulative processes. It is shown that local variability of soil contamination by 137Cs at reference sites is within 7–20%, which makes it possible to use the isotope as a tracer. When studies are conducted within drainage basins, the available trend of the atmospheric 137Cs fallout should be taken into account in assessing the soil and sedimentation redistribution.

Effect of irrigation-induced erosion on the degradation of soils in river valleys of the alpine Pamir

Results of a study were analzyed, which was conducted on the arable stony alpine soils in the Gunt River valley and the upper Panj River. Such soils are occurring in different regions of the Western Pamirs. The physicochemical properties of the soils were studied using conventional methods, and the degradation rate of the soil cover was determined using the radiocesium method. Low contents of humus (<2.5%) and nutrients, primarily related to the natural pedogenesis conditions, were indentified for the subsoils of the studied river valleys. The limiting factors are temperature and precipitation. The irrigation-induced erosion, which is manifested on slopes of >2–3° with furrow irrigation, is the main anthropogenic factor of soil degradation. The lower content of humus in the soils of the Panj River valley is due to the larger portion of slopes >3° with furrow irrigation, on which also maximum rates of irrigation-induced erosion (>30 ha/year) were observed.

Comparative assessment of the contents of magnetic spherules, 137Cs, and 210Pb in soils as applied for the estimation of soil erosion

The contents of magnetic spherules and 137Cs and 210Pb isotopes were determined in gray forest soils of the Novosil Agroforest Experimental Station in Orel oblast (central part of European Russia). The spatial variability in the contents of these substances was studied, and their distribution in the soil profiles and along soil transects within the afforested and cultivated slopes was analyzed. Factors and processes favoring the accumulation of magnetic spherules and 137Cs and 210Pb isotopes in the soils, as well as their removal from the soils, were revealed. Similarities and distinctions in the patterns of their behavior were interpreted. Prospects for the combined use of these three tracers to estimate the rates of soil erosion and sediment deposition on the soil surface were tested.

Transformation of soil cover within a small catchment area over 300 years of agricultural development (Tver oblast)

The main causes of the soil cover transformation within a small ravine catchment area over 300 years of agricultural development were considered. The current status of the soil cover was estimated from thorough soil-geomorphological field studies. The morphological features of the subarable soil horizons and the diagnostic horizons remained intact under accumulated sediments allowed the soil cover of the preagricultural period to be reconstructed. It was found that plowing and related erosion-accumulation processes are the main transformers of the soil cover in the catchment area under study.

ОСОБЕННОСТИ ТРАНСФОРМАЦИИ РЕЛЬЕФА МАЛОГО ВОДОСБОРА РАЙОНА ТОРЖОКСКОЙ КОНЕЧНО-МОРЕННОЙ ГРЯДЫ ЗА ПЕРИОД АГРИКУЛЬТУРНОГО ОСВОЕНИЯ

Estimations of erosion-accumulation processes rate during intensive agricultural development were obtained by different methods for one of the small watersheds of secondary-glacial relief (Tverskaya region, Osuga river). Though the watershed has maximum treated area and relatively high field gradient, the average rates of erosion and accumulation are low. This helps to draw a conclusion that agriculture development has little impact on the other watersheds’ relief while they have the same deposits composition (moraine on the surface).