Phosphorus fractions affect fungal compositions and functions under land use conversions in saline-alkali soil in northeastern China

Abstract

Abstract Background Little is known about the link between the fungal community and phosphorus fractions when land use is converted from cropland to grassland in saline-alkali soil in northeastern China. Therefore, in this study, the diversity, composition, and function of fungi, as well as phosphorus fractions including Olsen-P and inorganic phosphorus (Pi), were investigated under land use conversions from maize cropland (MC) to alfalfa (Medicago sativa L.) (AG), Leymus chinensis (LG), and natural restored grasslands (RG). Results The results showed that the Pi fractions of Ca8-P, Fe-P, Ca2-P, and Ca10-P were closely related with Olsen-P. Significantly increased Olsen-P content was found in 0–10 cm soil layer in the AG treatment, relative to LG and RG treatments (P < 0.05). The occluded P content in 0–10 cm and the Al-P content in 10–20 cm in the RG treatment were the highest. The RG treatment increased the Shannon index of fungi, as well as the abundances of phyla Mortierellomycota and phyla Glomeromycota. Higher abundance of genus Mortierella and lower abundance of genus Cladosporium were observed at RG treatment. Moreover, the RG treatment greatly reduced the abundance of plant pathogens and enhanced the abundances of mycorrhizal and ectomycorrhizal. The Olsen-P was positively correlated with the abundance of plant pathogen (P < 0.01), and the Olsen-P, Ca2-P, and Fe–P were negatively correlated with both the abundances of mycorrhizal and ectomycorrhizal (P < 0.05). Conclusion Land use conversion from maize cropland to natural restored grassland could reduce plant pathogens and enhance useful fungi by decreasing the availability of phosphorus. Graphical Abstract