The litter decomposition dynamics under land-type conversion by microbial communities in the Yellow River floodplain

Land-type conversion contributes significantly to litter decomposition, yet microbial feedback mechanisms remain unclear in river-floodplain areas. The distinct roles of bacteria versus fungi in wetland litter decomposition remain a key unresolved issue requiring further investigation. Litter decomposition dynamics and microecological mechanisms of three diverse land-types (riparian higher-beach wetland (RHW), cultivated wetland (CW), mesophytic wetland (MW)) within the Yellow River tidal flat were studied via litter bag method and high-throughput sequencing method for 2 years. Results indicated that land-use conversion induced obvious changes in the dominant microbial community composition, thereby regulating the facilitative role of soil microbiota in wetland litter decomposition processes. Agricultural reclamation on wetland changed microbial habitat and accelerated the litter decomposition 35.7–38.05% and the net release of total carbon 4.15–9.78%. Mesophytization of wetland increased the bacterial species and OTU, and facilitates local carbon retention. Cellulose and lignin content of litter in RHW, CW and MW decreased exponentially over time (R 2 = 0.960, 0.775, 0.896 and 0.959, 0.822, 0.918). C/N ratio (MSE = 15.37%), litter carbon content (8.30%) and soil moisture (6.94%) best predict litter mass loss ( P < 0.01). Furthermore, the DOC, NH 4 + -N, NO 3 - -N etc. content in soil were correlated with microbial Chao1 index and Shannon diversity. Cellulose, lignin DRs were positively related to the DR of nitrogen, fungi Shannon-diversity and bacterial Chao1, with lignin DR being more susceptible to fungi. During the decomposition process, bacteria account for 77.44–84.49% and fungi 0.08–0.22% at kingdom level. Land-use change reduced moisture (r = -0.79) but didn’t significantly increases soil N, both lowering bacterial α-diversity (r = -0.49, -0.76) and accelerating decomposition (r = 0.81) (R 2 = 0.61). Soil N and environment enhance fungal diversity non-significantly. Conclusively, land-use conversion in the Yellow River wetland soil reshapes the microbial engines, mesophytization of natural wetland and anthropogenic reclamation enhance litter decomposition and carbon–nitrogen degradation.