Identifying the key factors of lignocellulose degradation at different stages of decomposition in litter from different forest types

The purpose of this paper was to identify the key factors of lignocellulose degradation at different stages of decomposition in litter from three forest types. We investigated undecomposed layer (L), fragmented layer (F), and humus layer (H) of litter in Juglans mandshurica forest (JMF) for broadleaf forest, Pinus tabuliformis var. mukdensis forest (PTMF) for coniferous forest, and mixed broadleaf-coniferous forest (MBCF). Cellulose and hemicellulose degradation rates were significantly higher in JMF and MBCF, correlating with progressively increasing enzyme activities, whereas PTMF exhibited stronger lignin decomposition. Despite elevated enzyme activities in later decomposition stages across all forests, lignocellulose degradation rates declined, suggesting substrate recalcitrance or microbial functional shifts. Network analysis identified bacterial module 1 and fungal modules 2 and 4 as pivotal producers of lignocellulases. Mantel tests revealed distinct driving mechanisms: (1) In JMF, interactions between microbes and enzyme were particularly strong in the early stage; (2) PTMF relied primarily on fungal communities, with direct microbial degradation gaining prominence over time; and (3) litter degradation in MBCF was co-driven by microbial diversity, community structure, and enzymatic activity, with microbe-enzyme-substrate synergy prevailing during early-middle stages. By integrating the “substrate-microorganism-enzyme” framework, this study elucidates stage-specific regulation of litter decomposition, offering mechanistic insights for optimizing carbon sequestration strategies in plantation ecosystems.