Plant community characteristics of the Dongting Lake aquatic terrestrial ecotone

Dongting Lake is the second largest freshwater lake in China, the conditions of which have been influenced for a number of year by changing water level in the Xiangjiang, Zishui, Yuanjiang, Lishui, and Yangtze Rivers, following completion of the Three Gorges Dam. This has resulted in marked alternating changes in the area of the lake between the flood and dry seasons characterized by a distinct aquatic-terrestrial ecotone, the coexistence of multiple wetland types, and vegetation types showing a certain pattern of ecological succession. In this study, we sought to determine the plant community characteristics associated with the Dongting Lake aquatic-terrestrial ecotone, based on the measurement of six main indices using unmanned aerial vehicle remote sensing technology combined with fixed-point investigation and analysis. For each index, plant community characteristics were assessed based on principal component and cluster analyses. The main results are as follows. During the dry season, the plant communities of 38 sample plots were found to be cold tolerant, among which Triarrhena lutarioriparia and Phragmites australis are dormant, whereas at a number of sites, Artemisia selengensis and Carex community types have become the dominant species. Plants recorded at the sample plots belong to 53 families, 115 genera, and 197 species, and the main distribution range is 26.2～32.5 m. Among these species, the constructive species in summer are Triarrhena lutarioriparia, Phragmites australis, Phalaris arundinacea, Polygonum hydropiper, Carex, and Nelumbo nucifera, with the succession of Artemisia selengensis and Carex in winter. Principal component analysis indicated that plant community characteristics are associated with two main principal components. The first principal component, denoted “community species” traits, includes coverage, the number of companion species, and the number of dominant species. whereas the second principal component, referred to as “species ecological environment” traits, includes wetland type, community height, and elevation. The results of this study reveal the succession of vegetation in the aquatic-terrestrial ecotone of Dongting Lake associated with alternating water levels. These findings will contribute to a better understanding of the plant communities and provide a basis for the construction of this ecological economic zone.