Plant-microbe interactions derive the rhizosphere microbial assembly and nitrogen cycling in a subtropical forest

1. Interactions between plants and soil microorganisms in the rhizosphere are vital for maintaining the nutrient cycle and stability of terrestrial ecosystems. Nitrogen, closely related to carbon (C) cycling and ecosystem productivity, undergoes transformation by soil microorganisms into forms that can be assimilated by plants. However, the mechanism by which plants impact nitrogen (N) cycling in acid subtropical forest soil by governing the rhizosphere microbial community remains unclear. 2. This study examined the impact of host phylogeny, root traits, and soil properties on microbial communities and N cycles in the rhizospheres of Fagaceae and Lauraceae, the two dominant families in the subtropical forest of Heishiding Natural Reserve in southern China. 3. Our findings revealed that host phylogeny dominates the variation in the richness and composition of the rhizosphere microbial community. Furthermore, antibacterial exudates from Lauraceae might reduce the stability of microbial network structure and enrich fatty acid biosynthesis function for antimicrobial resistance. Net nitrification rates (NNR) and nitrifying enzyme activities (NEA) of arbuscular mycorrhizae (AM) trees of Lauraceae were significantly higher than that of ectomycorrhizae (ECM) trees of Fagaceae. The positive relationships among NNR, NEA, and root nitrogen content (RNC) suggests a close correlation between soil nitrification activity and N uptake efficiency by plants. Complete ammonia oxidizer (comammox) dominated the ammonia-oxidizing communities of these acid soils, followed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). The niche differentiation among these groups was strongly influenced by soil properties and plant traits, which in turn affects plant N uptake efficiency. 4. In conclusion, we conducted a comprehensive analysis of the root-mediated plant-microbe interactions and the regulated microbial N cycles in the rhizosphere soils of an acid subtropical forest. These findings are crucial for elucidating the biological mechanisms guiding microbial assembly in the rhizosphere and refining biological strategies to mitigate N loss in forest ecosystems. --