The effect of soil microbial traits on soil organic carbon in alpine grassland was limited by depth

Abstract

Microorganisms play an important role in regulating the formation and accumulation of soil organic carbon (SOC). However, it has not yet been determined which microbial factors (community, biomass, and necromass) play a role in SOC pool at different depths in alpine grassland ecosystems and how this is achieved. We conducted a large-scale survey and sampling in two alpine grassland habitats on the Qinghai-Tibetan Plateau at two soil layers (topsoil: 0–10 cm and subsoil: 20–30 cm) over an area spanning 1500 km. The distribution patterns of SOC pools and microbial communities in alpine grasslands were analyzed. We found that microbial biomass carbon decreased significantly with depth, and alpine meadow MBC was significantly larger than alpine steppe. Fungal nercomass carbon was the main contributor to SOC in alpine grasslands. Compared to microbial communities, microbial carbon pools had a greater influence on SOC pools, and they were mainly accumulated through microbial nercomass carbon. Soil moisture affects microbial composition, so microbial diversity and associated network complexity were affected by a wide range of moisture factors (including mean annual precipitation and soil moisture). In deeper soils within alpine grasslands, microbial network complexity reduces the SOC pool by influencing microbial community diversity. This study revealed the controls on microbial communities and SOC at different soil depths within different grassland types on the Qinghai-Tibetan Plateau, and the results emphasize the importance of microbial necromass in SOC pool within alpine ecosystems.