Abstract

How do microorganisms in litter and soil affect litter decomposition in a temperate forest? Here, we conducted an 18-month laboratory experiment to assess the decomposition of pure Robinia pseudoacacia, pure Platycladus orientalis, and mixed R. pseudoacacia–P. orientalis litters under four treatments, namely “no microbe” (NM), “litter microbes” (LM), “soil microbes” (SM), and “litter and soil microbes” (LM + SM). Results demonstrated that, compared with SM, LM significantly enhanced the litter weight-loss rate and elevated the potential activities of lignocellulolytic enzymes at 180 days, and this was accompanied by lower cellulose and hemicellulose contents. Structural equation modeling indicated that microorganisms may directly or indirectly influence weight mass loss, partly by regulating these potential enzyme activities that are associated with changes in the litter organic matter composition. Across three forest stands, microbial treatments significantly affected litter decomposition. The standardized direct path coefficients linking microorganisms to the litter-mass-loss rate from highest to lowest were LM + SM, LM, and SM, indicating a synergistic effect between LM and SM that promotes decomposition through coordination. Taxonomically, most bacterial genera differed significantly among microbial treatments, whereas most fungal genera did not. Notably, the standardized direct path coefficient linking bacteria to litter mass loss was larger than that for fungi in both the SM and LM + SM groups. Additionally, field decomposition was faster than in the laboratory, with distinct microbial communities, verifying the environmental modulation of decomposers and the home-field advantage. This study clarifies microbial mechanisms underlying litter decomposition and provides a theoretical basis for forest ecosystem stability and sustainable management.

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