The Three Gorges Reservoir (TGR) is one of the largest hydropower projects around the world which greatly alters the ecological function of the original ecosystem. The riparian zone of TGR is subject to a frequent fluctuation of water level, leading to severe nitrogen loss by leaching. Cyndon dactylon, a perennial stress tolerant plant, is one of the dominant plant species in the riparian zone of TGR. The underlying mechanism that C. dactylon can survive the nitrogen limitation has been under debate. In this study, we sampled the plant tissues of C. dactylon and the surrounding soils across different water levels and seasons in the riparian zone of TGR to explore the possible strategy for them to mining nitrogen. Our study found that the C. dactylon in the TGR riparian zone had endophytic nitrogen-fixing bacteria, particularly enriched in the plant foliage. The abundance of endophytic nitrogen-fixing bacteria was significantly negatively correlated with soil ammonia, nitrate, and organic matter, and significantly positively correlated with total phosphorous and moisture content. The endophytic nitrogen-fixing bacteria in C. dactylon were highly diverse, with Proteobacteria as the main dominant genera. The mutual cooperation mode among bacterial species made the endophytic nitrogen-fixing bacteria community of C. dactylon more resilient to environmental pressure, thus more readily adapting to conditions of repeated long-term flooding in the riparian zone of the TGR.

三峡水库（TGR）是世界上最大的水电工程之一，极大地改变了原有生态系统的生态功能。三峡库区河岸带水位波动频繁，氮素淋失严重。紫檀是多年生耐逆性植物，是三峡库区河岸带优势植物之一。C. dactylon可以在氮限制下存活的潜在机制一直存在争议。在本研究中，我们对三峡库区河岸带不同水位和季节的龙舌兰植物组织和周围土壤进行了采样，以探索它们可能的氮素开采策略。我们的研究发现TGR 河岸带的C. dactylon具有内生固氮细菌，特别是在植物叶子中富集。内生固氮细菌丰度与土壤氨氮、硝酸盐和有机质呈显着负相关，与全磷和水分含量呈显着正相关。指节草内生固氮细菌种类繁多，变形菌门是主要的优势属。菌种间的相互合作模式，使长尾草的内生固氮菌群落对环境压力具有更强的适应能力，从而更容易适应三峡库区河岸带长期反复淹没的条件。