Soil microbial community contributes more to plant-soil feedback and plant-plant interactions than root traits under warming and drought

The interactions between aboveground and belowground biota are crucial for determining plant community composition and the response of ecosystem stability to climate change, but how warming and drought further impact plant performance and plant competition during plant-soil feedback (PSF) remains unclear. We investigated the impact of soil community compositions and root traits on the PSF and plant competition. We used two types of plants: Leymus chinensis (perennial and dominant), and Kalimeris integrifolia (annual and subordinate) subjected to warming and drought in both monoculture and competitive conditions. Soil bacterial and fungal community compositions, aboveground biomass, and plant root functional traits were assessed. We found that in most cases, L. chinensis remained the dominant position in interspecific competition due to its stronger root system and other aspects. However, K. integrifolia exhibited higher competitiveness after plant-soil feedback, particularly in soil that had been conditioned by K. integrifolia. Our path analysis results indicate that warming had an impact on the PSF and plant competitiveness by negatively influencing the soil bacterial community composition and positively influencing the soil fungal community composition rather than affecting plant root traits. Drought did not affect the PSF and plant competitiveness via affecting soil microbial community and plant root traits. Our findings indicated that soil microbial communities may have a greater impact on the PSF under climate change. Our study also highlights the mechanisms by which climate change alters the PSF and the structure of plant communities by altering the interactions between plant and soil microorganisms.