Surface soil microbiome changes in Grain for Green Project accelerates organic carbon mineralization on the Loess Plateau in China

Increasing amounts of greenhouse gases, such as CO2, released into the atmosphere have a profound impact on global climate change. Understanding how soil organic carbon (SOC) mineralization changes as a result of land-use change can shed light on the mechanisms by which SOC mineralization occurs, thus illuminating pathways to achieve global C neutrality targets. Accordingly, the Grain for Green Project (GGP) on the Loess Plateau was used as the starting point to observe how microorganisms affect SOC mineralization through field sampling and laboratory incubation experiments. We found a significant increase in SOC mineralization rates resulting from the GGP, though only at the soil surface (0.47-6.40 mgkg(-1) soilday(-1)). We also found that soil microorganisms had a significant effect on different types of C sources, and Proteobacteria and Ascomycota/Mortierellomycota were the dominant bacterial and fungal groups at the GGP sites. The factors limiting SOC mineralization varied with farmland conversion to other land-use types, and the direct and interactive contributions of these factors were quantified. The explanatory power examined in terms of land-use ability to directly predict SOC mineralization rates was as follows: farmland (0.82), grassland (0.76), shrubland (0.41), and forestland (0.29). Along the increasing vegetative complexity gradient from farmland to forestland, the individual variable explanatory values decreased, while the relative importance of the interactive effects between variables increased. Our research demonstrates that the GGP increased soil biological activity and improved microbial community ability to metabolize C sources, thereby accelerating SOC mineralization. This will provide a scientific basis for decisions to enhance global semidrought recovery.