Stochastic assembly and molybdenum regulation govern diazotrophic community function in subtropical paddy soils
This study investigated the community composition, diversity, and driving factors of nitrogen-fixing (diazotrophic) bacteria in paddy soils from the Yangtze River Delta, one of the most important rice-producing regions in China. Soil samples were collected from 12 representative paddy soil types across the Yangtze River Delta during the tillering, heading, and grain-filling stages of rice. The diazotrophic community was characterized by high-throughput amplicon sequencing of the nifH gene, which encodes the iron protein subunit of the nitrogenase enzyme and serves as a universal molecular marker for nitrogen-fixing microorganisms. The primary objectives of this project were to: (1) elucidate the spatiotemporal patterns of nitrogenase activity and nifH gene abundance across different soil types and rice growth stages; (2) reveal the community structure, co-occurrence networks, and assembly processes of diazotrophic communities; and (3) identify key environmental drivers (including soil moisture, pH, organic carbon, available potassium, and total molybdenum) and keystone diazotrophic taxa associated with high nitrogenase activity. This project provides critical insights into the microbial mechanisms underlying biological nitrogen fixation in paddy ecosystems and offers scientific support for green, low-nitrogen rice cultivation in the Yangtze River Delta region.