Soil pH as a Dual Regulator: Balancing Bacterial Community Stability and Flavor Metabolite Synthesis for Sustainable Tea Agroecosystems
Tea (Camera sinensis L.), an acidophilic crop, thrives in acidic soils, 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, we identified soil pH as the paramount driver of bacterial diversity (importance: 56.3% and 65.8%), surpassing climatic and edaphic factors. Stratifying soils into three pH regimes (<4.5, 4.5-5.5, >5.5) revealed distinct microbial assemblies. Neutral and null models demonstrated stochastic processes (dispersal limitation, drift) dominated community assembly across all pH gradients, challenging deterministic dominance assumptions under acidification. 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, pH <4.5 optimized tea metabolites (amino acids, caffeine) through selective enrichment of quality-promoting taxa (e.g., Chloroflexi) and suppression of nitrifiers (Nitrospirae), yet at ecological costs: diminished diversity, metabolic activity, and system resilience. 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 crop quality.