Soil viral and microbial interactions facilitate microbial necromass carbon accumulation in the semiarid typical steppe under altered precipitation_Research Data

Viruses are regarded as indispensable biotic components of soil ecosystems, where they play critical roles in microbial community succession and soil carbon cycling. However, the formation mechanisms of microbial necromass carbon (MNC), a major stable source of soil organic carbon (SOC), remain unclear under altered precipitation, particularly regarding the regulatory effects of virus–microbe interactions. Based on a multi–year precipitation manipulation experiment in a typical temperate steppe on the Loess Plateau, this study systematically examined the influence of soil viral and microbial community structures, as well as their interactions, on microbial necromass carbon accumulation. The results showed that decreased precipitation significantly reduced microbial necromass carbon (BNC, MNC, and BNC/MNC) and their relative contributions to SOC (BNC/SOC and MNC/SOC), whereas increased precipitation had relatively weaker effects. Altered precipitation changed soil viral and microbial community composition, and their co–occurrence networks were dominated by positive within–trophic and cross–trophic associations. Pearson correlation analysis revealed that microbial necromass carbon and its contribution to SOC were positively correlated with network complexity (e.g., node number, edge number, average degree, network density), as well as with positive WTAs and CTAs. Structural equation modeling further indicated that altered precipitation affected virus–microbe interactions by changing soil moisture, thereby jointly regulating the formation and accumulation of microbial necromass carbon. Collectively, these findings highlight the pivotal role of virus–microbe interactions in shaping microbial necromass carbon dynamics under altered precipitation, offering new insights into the mechanisms underlying soil carbon stabilization.