Effects of substrate improvement on winter nitrogen removal in riparian reed (Phragmites australis) wetlands: Rhizospheric crosstalk between plants and microbes

Abstract

Abstract With continued anthropogenic inputs of nitrogen (N) into the environment, non-point source N pollutants produced in winter cannot be ignored. This study explores the effects of substrate improvement on N removal in winter and rhizospheric crosstalk between reed (Phragmites australis) and microbes in subtropical riparian reed wetlands. The rates of wetland N removal in winter, root metabolite profiles and rhizosphere soil microbial community compositions were determined following addition of different substrates (gravel, gravel + biochar, ceramsite + biochar and modified ceramsite + biochar) to natural riparian soil. The results showed that the addition of different substrate to initial soil enhanced N removal from the microcosms in winter. The root metabolite characteristics and microbial community compositions showed some variations under different substrate addition compared to the initial soil. The three treatments involving biochar addition decreased lipid metabolites and enhanced the contents and variety of carbon sources in rhizosphere soil, while modified ceramsite + biochar addition treatment had a greater impact on the microbial community structure. There was evidence for a complex crosstalk between plants and microbes in the rhizosphere, and some rhizosphere metabolites were seen to be significantly correlated with the bacterial composition of the rhizospheric microbial community. These results highlighted the importance of rhizospheric crosstalk in regulating winter N removal in riparian reed wetland, provided a scientific reference for the protection and restoration of riparian reed areas and the prevention and control of non-point source pollution.