Floristic composition and plant community diversity of water-level fluctuation zone of Nanwan Reservoir

To study the vegetation community structure and diversity characteristics in the water-level fluctu- ation zone of Nanwan Reservoir, the water-level fluctuation zone of Nanwan Reservoir was divided into two water level elevations, one being 95–100 m and the other being 100–105 m. Subsequently, 3 typical plant communities of the water-level fluctuation zone of Nanwan Reservoir were selected for investigation. In the present study, a total of 34 species of plants were found. In listing the number of plants by family in order, the most abundant was Compositae , the second most abundant plant was Gramineae and the third most abundant was Legumes. In the present survey, Compositae accounted for 40.9% of the total number of species in the present survey, Gramineae accounted for 20.7% of the total number of species, and legumes accounted for 19.8% of the total number of species. According to the important values, the dominant species of different water level elevations in the descending zone of Nanwan Reservoir were sequenced. In the low water level elevation region, the first domi- nant species was Hemarthria altissima , the second dominant species was Erigeron canadensis , and the third dominant species was Kummerowia striata . However, in the high water level elevation region, the first dominant species was Kummerowia striata , the second dominant species was Hemarthria altissima , and the third dominant species was Carex neurocarpa . At the same time, in the low water level elevation region, a total of 19 species of plants were found. Among the 19 species of plants, annual herbs had the highest proportion at 47.37%, and there were 9 kinds of annual herbs. In the high water level elevation region, a total of 28 species of plants were found. In the 28 species of plants, perennial herbs had the highest proportion at 53.57%, and there were 15 kinds of perennial herbs. As the elevation of the water level rose, the diversity index, the evenness index and the richness index all increased, while the dominance index decreased. In conclusion, there was variation in the water level elevation in the water-level fluctuation zone of Nanwan Reservoir. An observation can be made that the different intensity of flood disturbance caused by the elevation change in the water- level fluctuation zone of Nanwan Reservoir is a significant factor in the structure and diversity of plant communities.