Tolerable Soil Erosion Losses and Soil Formation Rates in the Context of Carbon Balance Regulation

Abstract

Erosion–accumulation processes are implemented through paragenetic processes of soil destruction, transport, redeposition, and accumulation of pedosediments enriched with organic carbon. A promising approach in modern methods for substantiating tolerable soil erosion losses is the integration of assessments of the quality of soil resources and the rate of erosion and soil formation, including calculations of the balance of organic carbon in soils of agroecosystems. The range of research tasks included: analysis of current integrated approaches to justifying the tolerable erosion losses of soils that are most promising in terms of the completeness of reflection of agropedogenesis; assessment of the effectiveness of the process of regeneration of the humus horizon under primary, recent, and postagrogenic variants of soil reproduction; identification of patterns of formation of natural soil cover on dated and full Holocene erosional pedotopocatenas; determination of the effectiveness of erosion–accumulation processes in the formation of pedosediments enriched with organic carbon in the thalwegs of runoff depressions during an extreme hydrological event and in accumulative elements of the landscape over a centuries-long period. The main objects of the study were soils of different ages in the state of renaturation, which were selected in anthropogenically disturbed geosystems of the European forest-steppe. In addition, soil-geomorphological features within different-age erosional pedotopocatenas and processes of accumulation of pedosediments at different scale levels have been studied. The results of mathematical modeling of the soil-forming process over time based on an extensive database of soil-chronological data show significant differences in the rate of formation of the humus horizon at the initial and quasi-final stages of pedogenesis, as well as the relationship between the ontogenetic maturity of the humus profile and the rate of pedogenesis, which should be taken into account when justifying acceptable erosion losses. Long-term studies of the processes of renaturation of disturbed soils in the forest-steppe zone have identified a special type of reproduction in agro-abrozems, when functional rehabilitation of the residual humus horizon occurs, which differs from primary pedogenesis during the formation of a humus profile on parent rocks. Depending on the erosional transformation of the predecessor soil profile, the average rates of the formation of the postagrogenic humus horizon in forest-steppe chernozems range from 3.6 to 6.0 mm/yr. As is shown by the results of studying different-age and full-Holocene pedotopocatenas, the natural soil cover, which reflects the processes of erosion–accumulation and landscape slope microzonality, and soil-geomorphological relationships can be adequately formalized by improving the formula for calculating the relief function in erosion models through the introduction of a variable power value for the slope length index.