The Biotic and Abiotic Factors of Regulation of Arbuscular Mycorrhizal Fungi Activity in Litter Decomposition: Review

Arbuscular mycorrhizal fungi (AMF) play an important role on litter decomposition, which is the keyways for nutrients returning to natural ecosystems. Although having no known saprotrophic abilities like ectomycorizal and ericoid fungi, AMF can affect litter decomposition by releasing low molecular compounds such as sugar, amino acids and organic acids through extraradical mycorrhizal hyphae, or deposit dead hypha fragments as nutrient (e.g., carbon) input and to stimulate microbial decomposers, i.e., priming effect. Besides, interactions of AMF with saprotrophic microorganisms through ways such as niche competition, synergistic cooperation, specific microorganisms recruitment and by soil nutrient removal that can influence litter decomposition. Under different microenvironments, AMF display various nutrient acquisition strategies, which also affects this process. The magnitude and direction of AMF effects on litter decomposition depend on plant communities, litter quality, soil and litter nutrient dynamics, soil physical and chemical properties (mainly, physical structure, temperature, humidity, pH and nutrient content). The exacerbation of global changes (drought, chemical fertilization and soil acidification) is exerting pervasive impacts on ecosystem processes and functions mediated by AMF. In this review, we explore the current state of knowledge about the impacts of AMF on litter decomposition from microenvironment perspective. The summary of the potential influence of various microsite abiotic and biotic factors on this process in order to provide theoretical reference for comprehensive analysis of ecosystem functions of AMF is made.