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. --