Meta-analysis reveals the influence of mycorrhizal fungi on decomposition: insights for plant-mycorrhizal co-invasions
E.M. CHOREÑO-PARRA, K.K. TRESEDER
Department of Ecology and Evolutionary Biology, University of California, Irvine, California, 92697.

Mycorrhizal fungi can diminish decomposition of different substrates through the “Gadgil effect” or augment it through the “priming effect”. Determining which phenomenon predominates globally can provide insights into the potential influence of plant-mycorrhizal co-invasions on ecosystem functioning. We synthesized 43 studies on the influence of mycorrhizal fungi on decomposition to evaluate whether this effect was widespread and identified conditions mediating it. Our meta-analysis showed that mycorrhizal fungi, either ectomycorrhizal or arbuscular-mycorrhizal, promote decomposition by 6.7%. However, this effect was context dependent. Specifically, mycorrhizal fungi increased decomposition at substrates with low C:N ratio, such as leaf litter, organic horizon and soil. Contrarily, decomposition remained unaffected in substrates with a high C:N, like wood and needle litter. Our findings challenge the universality of the Gadgil effect but highlight the potential of mycorrhizal fungi to negatively influence soil C storage by promoting the priming effect. Furthermore, our results suggest three implications for plant-mycorrhizal co-invasions: they may modify local decomposition dynamics by 1) priming native organic matter, and 2) determining the type and chemical quality of substrates in the soil. Additionally, 3) mycorrhizal fungi may confer a competitive advantage to their invasive plant host, by facilitating nutrient release and plant absorption through increased decomposition.