Summary
This experimental study demonstrates that arbuscular mycorrhizal fungi do not simply enhance soil organic carbon sequestration as previously assumed, but instead regulate the decomposition and chemical form of soil carbon through host plant-mediated interactions with saprobic bacteria. Under Leymus chinensis, AM fungal hyphae were associated with increased actinomycete abundance and polyphenol oxidase activity, shifting carbon towards more labile forms; under Stipa grandis, hyphae correlated with greater Gram-negative bacterial abundance and accumulation of persistent carbon. The findings suggest that grassland plant community composition fundamentally shapes how mycorrhizal associations influence soil carbon dynamics.
UK applicability
The study was conducted on Chinese grasslands and examined grass species (Leymus chinensis and Stipa grandis) not native to the UK. However, the mechanistic insight—that AM fungal effects on soil carbon depend critically on plant identity and associated microbial communities—may be relevant to UK grassland and pasture management under climate change or plant community shifts, particularly if applied to native grass species and agricultural contexts.
Key measures
Soil organic carbon pool size and composition (labile vs. persistent fractions); bacterial community abundance and composition (actinomycetes, Gram-positive, Gram-negative bacteria); polyphenol oxidase activity
Outcomes reported
The study measured how arbuscular mycorrhizal (AM) fungal hyphae affect the composition of soil organic carbon pools (labile vs. persistent fractions) and associated microbial community structure under two grass monocultures. Total soil organic carbon pools were unaffected by AM fungal presence, but the proportional distribution between labile and persistent carbon fractions differed significantly depending on host plant identity and associated microbial communities.
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