长江中下游岸带(宜昌-铜陵段)湿生植物的群落构建机制研究

沿长江中下游（宜昌-铜陵段）13座城市共37个位点，分别于丰水期和枯水期对岸带的湿生植物进行调查，从物种和系统发育2个维度研究群落的构建机制，并结合环境和空间因子探讨其驱动因素。结果显示：（1）丰水期湿生植物群落的α多样性高于枯水期，且丰水期α多样性主要与水分条件呈正相关，而枯水期则主要与温度和土壤总氮含量有关。（2）丰水期的系统发育结构指数呈聚集趋势，暗示生境过滤起着主导作用，而枯水期的NRI（net relatedness index）和NTI（nearest taxon index）呈不同趋势，暗示存在近期的群落分化。（3）群落的α多样性在物种层面和系统发育层面存在显著关联性，其多样性水平可在一定程度上互为表征。（4）长江中下游沿岸湿生植物群落的构建机制在不同时期存在差异，丰水期的群落构建是环境筛选和扩散限制共同作用的结果，且以环境筛选作用占主导，而枯水期的群落构建仅在物种层面受一定程度环境筛选作用的影响。（5）大生境的温度变化、微生境的土壤水分和养分条件是影响长江中下游岸带湿生植物群落差异的主要驱动因素。该研究结果可为长江中下游岸带湿地生态系统的管理和保护提供科学支持。

Community assembly of riparian vegetation in the middle and lower reaches of the Yangtze River

In this study, hygrophyte communities at 37 sites in 13 cities along the middle and lower reaches of the Yangtze River (Yichang-Tongling section) were investigated during the wet and dry seasons. Both species composition and phylogenetic structure were examined at each site in the wet and dry seasons. We also revealed the drivers of community assembly combining environmental and spatial factors. Results showed that: (1) α-diversity in the wet season was higher than that in the dry season. There was a positive correlation between hydrological conditions and α-diversity in the wet season, while α-diversity in the dry season was mainly correlated with temperature and soil total nitrogen (TN). (2) The phylogenetic structure in the wet season showed an aggregation, implying that environmental filtering played a dominant role in community assembly; in the dry season, a different pattern was observed between the net relatedness index (NRI) and nearest taxon index (NTI), suggesting the evolution at recent (terminal) phylogenetic nodes. (3) There was a significant relationship between the α-diversity of species and phylogeny, indicating that these two dimensions can represent each other to a certain extent. (4) The composition mechanism of riparian vegetation in the middle and lower reaches of the Yangtze River differed between the wet and dry seasons. Species and phylogenetic structure were both influenced by environmental filtering and dispersal limitation in the wet season, with environmental filtering playing a dominant role in this process. In the dry season, community composition was only somewhat influenced by environmental filtering at the species level. (5) The key drivers of community assembly in our study were temperature at the large scale and aquatic and nutrient conditions of the soil at the small scale. This study should contribute to the management and protection of riparian vegetation in the middle and lower reaches of the Yangtze River.