Soil Ph as a Dual Regulator: Balancing Bacterial Community Stability and Flavor Metabolite Synthesis for Sustainable Tea Agroecosystems

Abstract

Tea (Camellia sinensis L.), an acidophilic crop, thrives in acidic soils. However, the dual effects of soil acidification on bacterial communities and tea quality remain poorly understood. Through a comprehensive analysis of 81 tea plantations in southwestern China, soil pH was identified as the key driver of bacterial diversity (importance: 56.3% and 65.8% for Observed species and Shannon index, respectively), surpassing climatic and edaphic factors. Stratifying soils into three pH regimes (< 4.5, 4.5–5.5, > 5.5) revealed that pH significantly restructured bacterial communities through altered resource availability and interactions among species. Neutral and null models demonstrated stochastic processes (dispersal limitation, drift) dominated community assembly across all pH gradients. Progressive acidification triggered microbial functional transitions from growth–oriented to survival–defense strategies, accompanied by systematic reductions in network complexity and stability, exposing vulnerability mechanisms in extreme acidity. Notably, a pH below 4.5 optimizes the production of tea metabolites (e.g., amino acids and caffeine) through selective enrichment of quality–promoting taxa (e.g., Chloroflexi) and suppression of quality–impairing taxa (e.g., Nitrospirae), yet at ecological costs: diminished diversity, ecosystem stability, and functional integrity. Multidimensional trade–off analysis established pH 4.5 as the critical threshold balancing microbial functional integrity (functional diversity, functional redundancy, etc.) with tea quality enhancement. These findings redefine soil pH management in tea agroecosystems, advocating precision liming at pH 4.5 to reconcile microbiome stability with tea quality.

Keywords: Soil acidification, Bacterial diversity, Bacterial communities, Tea quality