Liming Alters Microbial Communities Affecting Nitrification in the Rhizosphere of Camellia sinensis

After years of cultivation, tea garden soils gradually become acidified and compacted. Liming to ameliorate soil acidification alters the soil microbial activity and community structure, ultimately affecting the soil nitrogen cycling and nitrogen use efficiency of tea plants. In this study, ammonium-preferring tea plants (Camellia sinensis) were cultivated in lime-amended soils across a pH gradient (pH 4.5, pH 5.5, pH 6.5, and pH 7.5) to assess the impacts of soil liming on the structure and composition of the rhizosphere microbial community. The results demonstrated that, as the soil pH increased, the diversity and richness of both bacterial and fungal communities exhibited a gradual decline. The biomasses of AOA and AOB were dominated in acid soils and alkaline soils, respectively. The abundance of Proteobacteria, Actinobacteria, and Bacteroidetes in pH 6.5 and pH 7.5 were 16.56–22.56%, 16.29–18.09%, and 1.65–4.52% times higher than those in pH 4.5 and pH 5.5 soils. Ascomycota and Basidiomycota were accounting for 89.93% of all the species. Across the rising pH gradient, the relative abundance of Ascomycota significantly increased by 9.64–20.49%, whereas Basidiomycota decreased by 1.11–15.01%. The RDA analysis results showed the soil pH was the main effect factor for the differences in the structure and composition of bacterial and fungal communities. This conclusion provides theoretical support for the optimization of acidic soil improvement techniques after long-term tea cultivation.