Precipitation rather than temperature dominates microbial necromass accumulation by regulating soil physicochemical properties in alpine wetlands

Abstract

Microbial necromass is a key component of stable soil organic carbon (C) and contributes substantially to long-term C sequestration, accounting for nearly half of soil C content in terrestrial ecosystems. However, both the contribution of microbial necromass to soil C in wetland soils and the environmental factors regulating the distribution of microbial residues remain poorly understood, especially in alpine regions. Here, we sampled 105 alpine wetlands across the Qinghai-Tibet Plateau to investigate the effects of climatic, soil, and plant factors on microbial-derived C. On average, microbial residues accounted for 17.7 % of soil organic C, with swamp wetlands exhibiting the highest microbial necromass C content but a relatively lower contribution to soil organic C than other wetland types. Fungal residues contributed more to soil C (11.6 %) than bacterial residues (6.1 %), reflecting the predominance of fungal-derived residues in soil C. Mean annual precipitation improved soil moisture and nutrient availability (e.g., soil organic C, N and ammonium-N) and alleviated salinity stress by reducing electrical conductivity, thereby favoring microbial activity and turnover, and ultimately enhancing microbial residue formation. Temperature and plant properties had relatively minor effects within the narrow temperature range (−5 to +5 °C) observed at most sites. Our findings highlight the pivotal role of precipitation in regulating soil physicochemical conditions and promoting microbial residue formation, suggesting that future changes in precipitation regimes may strongly influence residue dynamics and long-term C sequestration in alpine wetlands.