Plant Rhizospheres Harbour Specific Fungal Groups and Form a Stable Co-Occurrence Pattern in the Saline-Alkali Soil

Abstract

Soil salinisation has been considered a substantial ecosystem issue with negative effects on sustainable agricultural practices. Practices of vegetation restoration are widely conducted for coping with saline soil degradation, especially in saline-alkali abandoned farmland. Compared with bulk soils, the rhizosphere soils of plants have different microbial community structures. However, how associations and functions of microbes vary in the rhizosphere and bulk soils of salt-tolerant plants remains unclear, limiting the successful implementation and efficacy of vegetation in restoring saline-alkali lands. Here, we analysed the fungal community composition, functional guilds, and co-occurrence networks in both rhizosphere and bulk soils of typical plant species in the abandoned farmland of the Yellow River Delta, China. Not all plant species had significantly different fungal community compositions and relative functional guild abundances between the rhizosphere and bulk soil. Soil nutrient concentrations explained more variance in the soil fungal community. Network analyses indicated that the rhizosphere fungal network had more nodes and links, more negative links, and higher modularity; however, fewer species were involved in the meta-module than those in the bulk soil network, indicating a more complex topology and niche differentiation therein. More generalist species and indicator taxa essential for carbon and nitrogen cycling (e.g., Sordariomycetes and Dothideomycetes) were identified in the salt-tolerant plant rhizosphere network. Overall, the salt-tolerant plants’ rhizosphere had a more stable fungal co-occurrence network and recruited more keystone species compared to the bulk soil, which could benefit soil nutrient cycling and soil restoration in abandoned farmlands.