Analysis of the structure and diversity of rhizosphere soil bacterial communities in Pinus koraiensis of different forest ages

To investigate how increasing forest age affects the structural composition and functional characteristics of rhizosphere microbial communities in Pinus koraiensis plantations, we studied 10-, 32-, 42-, 52-, and 62-year-old Pinus koraiensis plantations. We measured the physicochemical properties of rhizosphere soil and analyzed bacterial community features and functions using high-throughput sequencing technology. Results indicated: 1) From June to August, bacterial communities from Pinus koraiensis at different stand ages yielded 61 phyla, 138 classes, 290 orders, 390 families, 921 genera, and 711 species.2) Soil organic matter, total nitrogen, alkali-hydrolyzable nitrogen, available potassium, and available phosphorus concentrations in 32-year-old Pinus koraiensis plantations were significantly higher than in other age classes. Total potassium concentrations showed no significant differences among age classes, while total phosphorus concentrations gradually decreased with increasing age, from 1.54 g·kg⁻¹ to 0.81 g·kg⁻¹.3) α diversity (Shannon index) exhibited a trend of “initial decline followed by increase” with increasing forest age, reaching its lowest point in 32-year-old stands (9.84–9.91) and recovering to its highest level in 62-year-old mature forests (10.27–10.44). 4) At the phylum level, bacterial communities were dominated by the phyla Proteobacteria (19.54%–34.09%), Acidobacteria (14.75%–20.70%), and Verrucomicrobia (9.96%–21.53%).At the genus level, Ca. Udaeobacter was most significantly enriched in 32-year-old stands (up to 18.97%). 5) Bacterial functions encompassed 6 KEGG level-1 pathways (metabolism, environmental signaling, etc.) and 34 level-2 functions. Amino acid metabolism (10.52%–10.70%) and carbohydrate metabolism (9.93%–10.29%) were dominant functional pathways , peaking at 32-year-old. 6) Soil available potassium, pH, and alkaline-hydrolyzable nitrogen were primary factors influencing soil bacterial diversity. Total phosphorus, alkaline-hydrolyzable nitrogen, and total potassium were key factors affecting soil bacterial community structure.