Distribution of physiochemically defined soil organic carbon pools and their relationship to the soil microbial community in grasslands

Sequestration of carbon (C) in soils provides an important tool for climate change mitigation and grasslands offer significant potential for this approach. In this study, we examined soil organic C (SOC) protection mechanisms in alpine meadow, typical steppe and desert grassland ecosystems located in the Gansu province of China. We also examined which microbial taxonomic groups are associated with physically protected C and unprotected C. Soil samples for the study were collected from 0 similar to 10 and 10 similar to 20 cm soil depths from a desert in Ping Shan Hu county, typical steppe in Huanxian county and alpine meadow in Maqu county. The soil samples were subjected to the soil physiochemical fractionation to identify physically, chemically and biochemically protected and unprotected C. The soil bacterial and fungal communities were examined by DNA metabarcoding using Illumina sequencing, and redundancy analysis was used to identify microbial taxa with close associations with physically protected C and unprotected C. The alpine meadow consisted of the largest SOC stock, mostly physically protected (87.14 %), while also consisting of a large amount of unprotected C. Typical steppe and desert SOC stocks were smaller but the C was in chemically protected stable forms (86.25 % and 60.22 % respectively). The redundancy analysis identified bacterial phyla Proteobacteria, Acidobacteria and Verrucomicrobia and the fungal phyla Zygomycota and Chytridiomycota as microbial groups that were significantly related to physical C protection and unprotected C.

Automated summary

This study found that alpine meadows have the highest soil organic carbon sequestration, with the majority being in physically protected form, while typical steppes and deserts have lower levels of soil organic carbon, mainly in chemically protected forms. Bacterial phyla Proteobacteria, Acidobacteria, and Verrucomicrobia, as well as fungal phyla Zygomycota and Chytridiomycota, were identified as microbial groups significantly related to physical carbon protection and unprotected carbon.