Patterns of plant species richness along the drawdown zone of the Three Gorges Reservoir 5 years after submergence.

This study was conducted to understand the patterns of plant species richness in the Three Gorges Reservoir after 5 years after 175 m submergence. We hypothesized that hygrophyte and xerophyte species would show different species richness patterns, which was tested by collecting species composition and environmental variable data in 50 m long and 5 m wide transects in the drawdown zone from 145 m to 180 m. Xerophyte species richness (XSR) was highest in the middle of the drawdown zone, whereas hygrophyte species showed a continuous downward trend from 145 m to 180 m. Correlation analyses showed that the flooding period was significantly negatively correlated with the total species richness (TSR), XSR, and hygrophyte species richness (HSR). The TSR and XSR showed a significant positive correlation with soil type and a significant negative correlation with available K. HSR was significantly correlated with soil type and negatively correlated with ammonium N.