Biochemical Stability of Water-Soluble Organic Matter in Litter of Iron-Illuvial Podzol before and after Interaction with Mineral Horizons

Resumo

Mineralization resistance of water-soluble organic matter (WSOM) extracted from litter of podzol becomes higher upon the interaction with mineral horizons. Both the portion of WSOM susceptible to mineralization and its mean decomposition rate decrease two and three times, respectively, after its migration through the E eluvial horizon. Sorption in the BF horizon enhances the stability of the input organic matter. The relative content of mineralized carbon decreases to 2% (eight times). In natural soils, adsorbed organic matter may be even more resistant to mineralization due to lower temperatures and biological activity and thus represent the basis for the formation of humus reserve. Taking into account the calculated mineralization rate, the organic carbon accumulation in the BF horizon as a result of WSOM sorption may reach 13.5 mg/100 g per year, but it depends on the concentration of organic substances in soil solutions, hydrological regime, and other factors.