Warming alters the effects of roots and extramatrical mycelia on soil organic carbon and its composition in a Tibetan plateau swamp meadow

Roots and extraradical mycelium (EMM) influence the soil carbon (C) cycle, but it remains unclear how warming alters their effects on soil organic carbon (SOC) and its composition in alpine swamp meadows. A three-year ingrowth core experiment was conducted in swamp meadow plots on the Tibetan Plateau, where experimental warming is being applied. The ingrowth cores were filled with C₄-derived soil to distinguish between new C sequestration and native C decomposition processes. In addition, root functional traits were measured to evaluate the contribution of roots to SOC dynamics under warming. Roots (with EMM) increased SOC concentration and decreased the proportion of recalcitrant C in SOC, whereas EMM without roots did not alter SOC concentration or composition. Warming reduced SOC concentration without altering the overall influence of roots and EMM. Under warming, root-induced C sequestration decreased, whereas root-induced priming enhanced. In contrast, EMM induced C sequestration and priming did not change under warming. The variation in SOC and its composition is primarily explained by specific root length and root diameter. Our findings are of significant importance for understanding how roots and EMM in swamp meadow ecosystems influence SOC and its composition under climate change conditions, as well as how root traits regulate SOC. • Roots (with extraradical mycelium) increased soil organic carbon (SOC) concentration and decreased the proportion of recalcitrant C • Warming did not alter the overall effects of roots and extraradical mycelium on SOC concentration but reduced SOC concentration • Warming reduced root-induced C sequestration but enhanced root-induced priming effects, while the extraradical mycelium remained unaffected • The variation in SOC and its composition is primarily explained by specific root length and root diameter