Abstract: Aims Plant invasion often leads to the loss of local species diversity and causes significant economic losses. The Enhanced Mutualisms Hypothesis used to explain that some alien species have shown a remarkable ability to capitalize on novel but strong soil mutualists, which enhance their invasion success. In this study, the contributions of arbuscular mycorrhizal fungi (AMF) and litter to the growth of invasive plant under different nutrient conditions was investigated. Methods We inoculated AMF, Glomus etunicatum and leaf litter to explore the roles of AMF-litter interactions in the responses of notorious invasive Solidago canadensis to low nutrient stress. Important findings The results showed that litter addition significantly increased the mycorrhizal colonization rate and ratio of abundance class in S. canadensis. Under low-nutrient conditions, both AMF and litter promoted the stem length, leaf area and above-ground biomass, respectively, but significantly decreased the root-shoot ratio, and with the most pronounced synergistic enhancement observed in AMF-litter interactions. Under normal nutrient conditions, only AMF-litter interactions significantly inhibited the development of root system but increased the above-ground biomass in S. canadensis. Relative Interaction Intensity (RII) analysis revealed that AMF and litter significantly stimulated above-ground growth, with stronger effects under low-nutrient conditions compared to normal nutrient levels. These findings suggest that S. canadensis could adjust the allocation strategies for aboveground-belowground resource by AMF-litter interactions to respond low-nutrient stress. This study provides novel insights into how invasive plant utilize symbiotic AMF and litter interactions to mediate resource allocation under nutrient heterogeneity, advancing our understanding of the mechanism of successful invasion of alien plants.

Key words: Plant invasion, Arbuscular mycorrhizal fungi (AMF), Litter, Nutrient stress, Plant-microbe interaction