Arbuscular mycorrhizal fungi modulate litter decomposition dynamics through alterations in stoichiometry, chemical composition, and microbial communities

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Introduction Arbuscular mycorrhizal fungi (AMF) are primarily recognized for their obligate symbiotic associations with the majority of terrestrial plants; however, an emerging body of research indicates their potential capacity to accelerate litter decomposition and facilitate the sequestration of soil organic carbon. Previous studies on AMF-mediated litter decomposition have primarily focused on the colonization of plant root systems, whereas mycorrhizal colonization of leaves has received comparatively limited attention. The effects of AMF leaf colonization on leaf substrate and microbial community structure remains largely understood due to limited direct evidence. Methods In this study, a Petri dish experiment was conducted using in-situ soil, AMF inoculum and litter derived from Amorpha fruticosa , encompassing four treatments: CK (non-mycorrhizal substrate + surface-sterilized leaves), S (mycorrhizal substrate + surface-sterilized leaves), L (non-mycorrhizal substrate + non-surface-sterilized leaves), and SL (mycorrhizal substrate + non-surface-sterilized leaves). Results With respect to litter decomposition and substrate stoichiometry, AMF specifically promoted the decomposition of aliphatic components in leaves, as reflected by a 12.75–24.58% reduction in the C–H/C=O ratio in AMF inoculation compared with AMF– treatments. Regarding microbial community shifts, AMF substantially elevated the abundance of Hypocreales (21.71- to 35.59-fold), Sordariales (2.79- to 12.57-fold) within the fungal community, and Rhizobiales (1.52- to 2.36-fold) within the bacterial community, facilitating the breakdown of recalcitrant carbon sources. In terms of carbon cycling implications, these findings suggest that AMF accelerated litter conversion into labile, high-quality material (lower C/N ratio), enhancing microbial utilization of aliphatic compounds and promoting saprophytic functional group proliferation, ultimately expediting litter decomposition. Discussion Although this short-term experiment primarily captures the decomposition phase, the observed shifts in substrate chemistry and microbial processing provide a mechanistic basis for understanding how AMF may influence the quality and potential long-term stabilization of soil organic carbon.

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