Differentiation of humus composition in soils of the near-terrace floodplain in the Selenga river delta

The article analyzes humus composition of the soils of near-terrace part of the left-bank floodplain in the Selenga river delta, since soils are accumulators of substances brought with water and ensure the stability of the soil cover of the entire ecosystem. We have noted the influence of hydromorphism and the intensity of alluvial and floodplain processes on the formation and profile distribution of organic matter in soils. The polymodal nature of the content and distribution of humus substances along the profiles of the studied soils is the result of periodic flooding of the floodplain surface and the formation of buried humus accumulation horizons. A decrease in the total content of humic and fulvic acids and a corresponding increase in the proportion of non-hydrolyzable residue were revealed in gleyed soil horizons. The analysis of the composition of humus in the studied soils revealed common features that are caused by the influence of groundwater, floodplain and alluvial processes. There are also differences, which manifest themselves in the content of humus acids and insoluble residue both in the organic-accumulative horizons and in the mineral part of the profiles and are closely dependent on the type of humus and the degree of humification of organic matter. The established differentiation of humus composition in the soils of near-terrace part is an informative indicator reflecting the influence of the mesorelief of near-terrace part of the floodplain, soil texture, temperature and water regimes of the soil which ensure the fertility and stability of the soil cover of the territory.