Divergent response of soil microbes to environmental stress change under different plant communities in the Loess Plateau

Soil microorganisms play a crucial role in the proper functioning and stability of grassland ecosystems, and are influenced by the nutrient acquisition strategies of their host plants. The Loess Plateau in China, is known for its severe soil erosion and distinctive loess deposits, with soil nutrient levels declining from southeast to northwest. However, little is known about the relative effects of different host plants on soil microbial communities under different environmental stress in the Loess Plateau. We investigated the microbial community within soil profiles (0-100 cm) under two types of grasses community (Agropyron cristatum and Stipa spp.) with different drought tolerances, which are widely distributed in three different climate regions of the Loess Plateau. The diversity, composition, community assembly, and predicted functions of the bacterial and fungal community were evaluated. We discovered that the climate-plant-soil microbe interactions were the most significant factor affecting the community composition of bacteria and fungi on the regional scale. In addition, the effects of edaphic factors (e.g., soil organic carbon [SOC], total nitrogen [TN], and total phosphorus [TP]) on the soil bacterial and fungal communities increased from the warm-temperate to the desert steppe environment. Furthermore, the microbial community and assembly processes were driven by TP content of Agropyron grass, which is more resistant to environmental stress, while the soil of Stipa grass was driven by SOC. This may have occurred because the soil microbes in the Agropyron grassland had a stronger ability to utilize refractory organic matter thus reducing dependence on SOC, compared to soil microbes in the Stipa grassland. Collectively, our results show that the soil microbes recruited by the different plant communities responded differently in microbial composition, assembly, and functions to adapt the environmental stress change.