Functional Roles of Microbial Communities in Litter Decomposition Across Pure and Mixed Forest Types

Background Mixed forests are often considered superior to pure forests because they can increase biodiversity, enhance productivity, improve carbon storage, and strengthen resistance and resilience. However, the role of microorganisms in litter decomposition in mixed forests remains unclear. In this study, we examined litter decomposition in three forest stand types—pure Robinia pseudoacacia , pure Platycladus orientalis , and mixed R. pseudoacacia–P. orientalis —through in situ experiments combined with high-throughput sequencing. Results Litter decomposition were fastest in mixed forests compared with pure forests. Bacterial and fungal diversity exhibited pronounced variations across forest types and decomposition stages, with Proteobacteria, Bacteroidetes, and Actinobacteria dominating bacterial communities, and Ascomycota and Basidiomycota prevailed among fungi. Early-stage cellulose and hemicellulose decomposition was driven by bacterial genera Sphingomonas , Hymenobacter , Pseudomonas , Pedobacter , and Spirosoma, together with fungal taxa including Nothophoma , Cladosporium , Septoria , and Alfaria . In contrast, lignin degradation after 270 days was facilitated by bacterial Amycolatopsis and Streptomyces alongsidefungal Helicodendron, Lecanicillium, Chalara, and Trechispora . Bacterial diversity indices exhibited stronger positive correlations with litter weight loss rates than fungal indices. Partial least squares path modeling further indicated that microorganisms directly regulated litter decomposition, while also indirectly modulating decay rates through enzyme-mediated alterations of organic matter composition. Conclusions These findings demonstrate that mixed plantations enhance microbial-mediated litter decomposition and nutrient restoration, highlighting their role as effective strategies for improving soil fertility and ecosystem functioning in temperate forests.