Major Trends in Dynamics of Chemical Elements during Formation and Decomposition of Forest Litter in Soils of Background Southern Taiga Catena (Central Forest Nature Reserve)

The dynamics of major and trace elements during the formation, fermentation, humification, and mineralization of forest litter, as well as the analysis of its spatial variability in relation to landscape conditions, contribute to a better understanding of the forest ecosystem biogeochemistry. The study focused on the dynamics of 17 elements (Ca, K, Fe, Mn, Mg, P, S, Ti, Zn, Sr, Rb, Cr, Cu, Pb, Ni, Co, and Cd) by determining their concentrations using ICP-MS/OES methods in the organic and mineral horizons of Retisols and Stagnosols, as well as in the green phytomass of tree species within the background catena located in the southern taiga zone. Along the catena, with an increase in soil hydromorphism and the transition from mixed (coniferous and broad-leaved) to coniferous forest communities, a significant decrease in the ash content in organic horizons and a drop in the concentrations of Mn, Cr > Fe, Ti, Sr > Ca, K, Mg, Zn, Ni, Rb, and Co were observed. A comparison of the elements concentrations in freshly fallen leaves and living green parts of woody plants revealed significant disparities. Specifically, fallen leaves and needles exhibited higher concentrations of Cu, Co, Cr, Fe, Ni, Sr, Ti, Zn, Mn, and Cd, but lower levels of K, P, and Rb. This discrepancy can be attributed to the retranslocation of these elements within the living organs of plants. The transformation of fresh litter (Oi horizon) into fermented litter (Oe) in the summit and slope landscapes was accompanied by a loss of alkaline and alkaline-earth elements of K, Mg, Rb, and an accumulation of Mn, Pb, Zn, Cd, and Co. The further humification of plant residues and the transformation of the Oe horizon into the Oa horizon led to the accumulation of Ti, as well as Fe, Pb, K > Co, Cr, Rb > Cd, Ni > Mg, Mn, Zn > Cu. In waterlogged footslope and toeslope positions of the catena, where coniferous litter predominates, the fermentation of organic residues in the Oe horizon resulted in the accumulation of Mn, Pb, Zn, and Cd. The development of reduction processes in waterlogged footslope and toeslope soils contributed to the removal of alkaline elements from acidic organic horizons, as well as Fe and Mn and associated elements such as Cr, Co, Ni, and Zn.