Stronger network connectivity with lower diversity of soil fungal community was presented in coastal marshes after sixteen years of freshwater restoration

Abstract

Freshwater input for salt marsh restoration in the Yellow River Delta induced Phragmites australis expansion and thus may cause shifts of soil fungi from halophilic to desalination-adapted species for increased litter decomposition. In this study, soil fungal communities of restored and natural salt marshes were determined to reveal further details of shift in soil fungal community and its probable prediction for salt marsh restoration. Our results showed a stronger network within Ascomycota (e.g. Sordariales, Aspergillus, Hypocreales and Cladosporium herbarum) in restored marshes, but with a lower diversity of halophilic taxa (e.g. Chytridiomycota and Nematoda) in comparison with natural salt marshes. Contrarily, the occurrence of Chytridiomycota, Ichthyosporea and Discicristoidea in the soil fungal networks of the natural salt marsh emphasized the importance of salt tolerant species at the land-sea transition zone. The Sordariales was dominant and had a strong correlation with other fungal species and aggregate associated soil organic carbon (SOC), which probably contributed to SOC accumulation in restored marshes. But the reduced halophilic species specific to salt marsh elucidated that the formation of monospecific stands of P. australis along with the freshwater input induced desalination to the saline habitats changed the native patterns of vegetation and soil organisms. As the buffer between terrestrial and marine systems, a single habitat type such as dense monocultures of P. australis must be avoided and diverse saltmarsh habitats across a salinity gradient should be reserved. In this way, the diversity and specificity of coastal halophytes and related microorganisms could be maintained and thus might confer benefits in balancing various functions of the salt marsh ecosystem and preserving the system's elasticity and resistance to stress.

Keywords: Freshwater input; Microbial community shift; Phragmites australis expansion; Salt marsh restoration; Soil fungal community; Yellow River Delta.