Climate-driven silicate weathering and biogeochemical coupling in black soils

Abstract The black soil region of Northeast China has revealed widespread silica-clay composite layers that constrained crop root, yet their origin—chemical weathering versus biological enrichment remains debated. Here, we applied a sequential chemical extraction method and biogeochemical coupling analysis to demonstrate that the total Si pool in black soil consists predominantly of Si (residual silicon (Sires): 96.02%−97.34%), with non-crystalline silicon (Sinoncry) accounting for 2.66%−3.98%. Silica neoformation accumulation layers demonstrated marked enrichment in Sires. Overall, soil pH, organic carbon content, and bulk density regulated the vertical differentiation of Si fractions by influencing silicate dissolution-precipitation dynamics and cementation processes. A quantitative model of Si biogeochemical ratio was proposed and used to quantify interaction intensity between biological and chemical processes. Holocene climatic cycles drove silicate migration and transformation, with chemical weathering dominating during glacial periods and biological processes intensifying during interglacial phases, revealing co-dominant roles of biological and chemical processes in forming silica neoformation accumulation layers. This study clarifies that climate-driven biogeochemical coupling shapes silica neoformation accumulation layers in black soils, providing a theoretical basis for understanding pedogenesis.