Forest composition and litter quality shape bacterial community dynamics and functional genes during litter decomposition

Abstract

Microbial community plays essential roles in forest nutrient cycling and ecosystem functioning, particularly through their involvement in litter decomposition. This study investigated bacterial dynamics over a three-year litter decomposition experiment in pure Pinus thunbergii forests and mixed P. thunbergii–Liquidambar formosana forests. We assessed bacterial community succession in two litter types (needle and twig) using high-throughput sequencing and functional gene analysis. The results showed that bacterial community richness, diversity, and evenness significantly increased over time, accompanied by a taxonomic shift from early dominance by Proteobacteria to late-stage dominance by Acidobacteria. Pine needle litter decomposed faster and supported more rapid microbial turnover than twig litter. Principal Coordinate Analysis (PCoA) and PERMANOVA revealed significant variation in bacterial community structure across decomposition stages and between litter types (P < 0.05). Functional prediction indicated that chemoheterotrophy and nitrogen fixation were dominant functional guilds. Additionally, genes involved in denitrification and organic phosphorus mineralization were more abundant in twig litter in mixed forests during the third year of decomposition. These findings demonstrate that both forest composition and litter quality strongly influence bacterial community succession and functional potential. Mixed forests supported greater microbial functional diversity, highlighting their ecological value in sustaining nutrient cycling. This study provides valuable insights into bacterial contributions to litter decomposition and forest ecosystem processes.