Diversity and Composition of Soil Microbes Associated with Barringtonia racemosa Communities

Understanding soil microbial community assembly in endangered mangrove ecosystems is crucial for ecological conservation. This study investigated the diversity and drivers of soil microbiomes across Barringtonia racemosa communities (pure: T1; associated: T2, T3) in China’s Leizhou Peninsula, using SMRT sequencing and phospholipid fatty acid analysis. The results reveal that pure B. racemosa communities (T1) harbored the highest microbial diversity (Chao1: 2980 bacteria, 14,378 fungal OTUs), with Pseudomonadota (37.6%) and Ascomycota (52.6%) as dominant phyla. Fungal communities exhibited 3.2-fold higher β-diversity variability than bacteria across communities (Bray–Curtis; p < 0.01). Redundancy analysis identified soil organic carbon (SOC), available nitrogen (SAN), and leaf manganese as primary drivers, collectively explaining 72.4% of microbial variation (p = 0.003). Notably, pure communities showed an elevated SOC (74.3 mg/kg) and fungal: bacterial ratio (0.19 vs. 0.13–0.14 in associated communities), indicating fungal dominance in carbon-rich sediments. Conversely, rice field controls displayed distinct SAP/SAK patterns reflecting agricultural impacts. These findings demonstrate that the B. racemosa community structure differentially regulates fungal assemblages more strongly than bacterial communities, providing critical insights for mangrove restoration through microbial-informed management.