No abstract

Rice cultivation is the main method for mudflat reclamation. However, changes in the community structure of microbes involved in nitrogen (N) cycling in response to mudflat reclamation via rice cultivation remain poorly understood. This study used quantitative polymerase chain reaction to characterize the distribution of various inorganic N-cycling pathways in response to mudflat reclamation via rice cultivation. The results show that the abundance of functional genes followed an increasing trend, while the relative abundance showed a decreasing trend. The relative richness of functional genes in the inorganic N-cycling network showed different fluctuation trends and indicated that the nifH, archaea amoA, narG, nirS, nirK, norB, and nosZ genes greatly contribute to inorganic N-cycling. Redundancy analysis showed that soil properties, in particular, organic matter increased, while electrical conductivity decreased, driving the changes of gene distribution in the inorganic N-cycling network over the course of reclamation. Mudflat reclamation under long-term rice cultivation promoted the reproduction of microbes related to the N cycle, and also changed the distribution of functional genes that are involved in the inorganic N cycle due to changes of soil properties. K E Y W O R D Smudflat reclamation, nitrogen-cycling gene, quantitative PCR, rice cultivation

Fungi play a critical role in farmland ecosystems, especially in improving soil fertility; however, little is known about the changes in fungal communities caused by mudflat reclamation under rice cultivation. In this study, mudflats located in Yancheng, China, which were divided into nine plots with 0, 11, and 20 years of successive rice cultivation histories, were sampled to determine the fungal community composition by using Illumina MiSeq sequencing. Results show that the Shannon diversity of the fungal communities did not change significantly but the species richness increased under mudflat reclamation with long-term rice cultivation. Ascomycota was the dominant phylum throughout the reclaimed mudflats samples, while Sordariomycetes was the dominant class. Fungal functional prediction found that the relative abundance of saprotrophs gradually increased with mudflat reclamation and mainly belonged to Ascomycota after 20 years of successive reclamation. Redundancy analysis showed that electrical conductivity, organic matter, and total nitrogen were the main factors affecting the composition and ecological function of the fungal community during mudflat reclamation. In short, a fungal community dominated by Ascomycota was established during mudflat reclamation under rice cultivation, which is more conducive to promoting soil fertility because of the higher proportion of saprotrophic fungi in Ascomycota.