The soil seed bank of a rehabilitated draw-down zone and its similarity to standing vegetation in the Three Gorges Reservoir Area

Abstract

The reverse seasonal flooding that resulted from the construction of the Three Gorges Project has induced a drastic degradation of draw-down zone vegetation and the seed bank in the reservoir. The composition and distribution of seed banks and their similarities to standing vegetation were determined through field investigations and germination experiments on the vegetation as well as soil seed bank data collected from three restoration sites in Zigui county, Wanzhou city, and Zhongxian county to uncover the effects of vegetation restoration on seed bank development in the Three Gorges Reservoir region. The results showed the soil seed banks were composed of 44, 43, and 50 herbaceous species, and an average seed density of 9418.79 ± 804.92, 4283.44 ± 427.89, 6539.28 ± 432.22 seeds/m2, respectively. The soil seed bank was mainly composed of annual and perennial herbaceous plants. Most of the dominant species of soil seed banks came from introduced species. Reverse seasonal flooding induced the spatial variation of species diversity and seed density of the soil seed bank. The species diversity in the upper part of the draw-down zone was higher than that in the middle and lower parts. The highest seed density occurred in the middle upper parts of the draw-down zone, followed by the lower part. The similarity coefficient between the soil seed bank and the extant vegetation community was 0.495, 0.526, and 0.550 at Zigui, Wanzhou, and Zhongxian restoration sites, respectively.