Role of an arbuscular mycorrhizal fungus in vegetation restoration as indicated by bacterial diversity and microbial metabolic limitation in soil underlying moss biocrusts

Abstract

Arbuscular mycorrhizal (AM) fungi contribute to the revegetation of degraded ecosystems such as coal mining areas and may indirectly affect the development of biological soil crusts (biocrusts). However, bacterial diversity and microbial nutrient cycling in the soil underlying biocrusts are seldom considered when assessing ecological restoration effects. Bacterial community composition was quantified and compared using 16S rRNA gene sequencing, metabolic limitation of microbes via extracellular enzymatic stoichiometry and their association with carbon use efficiency (CUE) in soil underlying moss biocrusts in vegetated areas inoculated with an AM fungus or uninoculated and in uninoculated unvegetated areas. The AM fungal inoculum significantly influenced bacterial community composition and diversity, extracellular enzyme activities and CUE in soil underlying moss biocrusts mainly by affecting soil nutrients. Correlation analysis revealed that Actinobacteria, Armatimonadetes, Bacteroidetes, Chlorobi, Cyanobacteria, Saccharibacteria, and Verrucomicrobia were positively correlated with soil nutrients carbon (C), nitrogen (N) and phosphorus (P). A vector analysis of extracellular enzyme activity indicates that soil microbial communities underlying moss biocrusts were limited by P but microbial communities in areas inoculated with the AM fungus had the lowest relative P limitation. The alleviation of microbial P limitation increased the microbial CUE and bacterial phylum community and alpha diversity, leading to an increase in subsoil C content underlying moss biocrusts. This indicates that microbial communities in soil underlying moss biocrusts under in restoration areas containing the AM fungus were more stable under environmental stress, and the inclusion of AM fungal inoculation may be recommended as the preferred option for ecosystem restoration in arid and semi-arid coal mining areas.