Abstract: Aimed to provide scientific basis for understanding and maintaining the biodiversity in water level fluctuation littoral zone, the Kaixian reach of Pengxihe River was chosen to study the spatial pattern and gradient variation of plant communities in the drawdown area of Three Gorges Reservoir. In the study area, there was an obvious variation in the kind and dominance of dominant and companion species in each plant community. With increasing elevation, the total species richness decreased after an initial increase, and α- and β-diversity had a greater fluctuation, among which, Shannon diversity and Simpson diversity showed a distribution of “M” and “W” types, respectively, while Pielou diversity showed the same variation pattern with species richness. Jaccard index and Cody index all increased after an initial decrease, with the lowest values at middle elevation and the highest values at higher elevation. It was considered that the variation of α-diversity in the study area was originated from the habitat difference induced by the difference in the flooding time caused by different elevation, while the reason of β-diversity change was more complicated, which should be further studied.

Key words: Houhe Nature Reserve, Rare and endangered plant, Fractal properties, Box counting dimension, Inflexion scale