崇明东滩湿地土壤生物固氮沿潮滩水淹梯度的特征

In this study, potential rate of nitrogen fixation (BNF), functional gene (nifH) abundance and soil properties were investigated in the rhizosphere soil and bulk soil of Chongming Dongtan wetland in the Yangtze estuary. The rates of soil BNF decreased from high tidal habit to low tidal habit and varied significantly in the water intrusion frequencies (P < 0.05). The rates of BNF were higher in summer than in winter, and higher in rhizosphere soil than bulk soil. The BNF rates ranged from 0.61 to 17.90μmol N/(kg•h) and from 1.41 to 12.10μmol N/(kg•h) in rhizosphere soil and bulk soil in summer, while they were in the range of 0.64~3.54μmol N/(kg•h) and 0.47~2.60μmol N/(kg•h) in winter. The abundances of nifH functional gene ranged from 1.28×10⁷ to 4.61×10⁷copies/g and 2.56×10⁷ to 12.3×10⁸copies/g in rhizosphere soil and bulk soil, respectively. The abundance of nifH gene was significantly related to the rates of BNF (P<0.01). In addition, soil salinity, nitrate, Fe³⁺ and total phosphorus had great influence on BNF activity. Therefore, these results highlight that water intrusion can alter soil microbial quantity and soil properties, which furthermore affect nitrogen biogeochemical cycling.