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Effects of microbivorous nematodes on microbial necromass accumulation under changing precipitation in tropical forests
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DOI：10.1016/j.apsoil.2026.107374.png)
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Abstract
En 中文
Microbial necromass represents a major source of stable soil organic carbon, yet the role of soil fauna in regulating its accumulation remains poorly understood, particularly under changing precipitation regimes. We hypothesized that microbivorous nematodes promote microbial necromass accumulation through selective grazing on microorganisms, and that altered precipitation weakens these trophic interactions. To test these hypotheses, we conducted a one-year field microcosm experiment within a long-term precipitation manipulation experiment in a tropical forest. Bacterivorous Acrobeloides sp. and fungivorous Aphelenchoides sp. were independently introduced into soils subjected to ambient rainfall, delayed wet season, and wetter wet season treatments. Microbial necromass was quantified using amino sugars, and changes in microbial communities, oxidative enzyme activities, and lignin phenols were determined. Nematode grazing significantly increased microbial necromass accumulation. Addition of Acrobeloides sp. increased bacterial necromass by 3–9%, whereas addition of Aphelenchoides sp. increased fungal necromass by 4–14%. These responses were accompanied by declines in the relative abundances of Proteobacteria and Ascomycota, respectively, suggesting that selective grazing altered microbial community composition and enhanced microbial turnover. Both nematode genera stimulated oxidative enzyme activities and reduced lignin phenol concentrations, indicating accelerated decomposition of chemically complex organic matter. However, altered precipitation regimes weakened these positive effects. Wetter wet season conditions reduced bacterial necromass accumulation by weakening the interaction between Acrobeloides sp. and Proteobacteria, whereas delayed wet season conditions reduced fungal necromass accumulation by weakening the interaction between Aphelenchoides sp. and Ascomycota. Our findings demonstrate that microbivorous nematodes are important regulators of microbial necromass accumulation through selective trophic interactions with microorganisms. More importantly, precipitation-induced weakening of nematode–microbe interactions can alter microbial necromass accumulation, highlighting an overlooked pathway through which changing rainfall regimes may influence microbial necromass accumulation in tropical forests.
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