Patterns of Plant Community Species Richness in the Fluctuating Water Level Zone along the Pengxihe River of the Three Gorges Reservoir

The spatial pattern of plant community species richness in the fluctuating water level zone along the Pengxihe River of the Three Gorges Reservoir was studied by sample-plot survey and Spearman correlation analysis.The results showed that along the longitudinal gradient,species richness,longitudinal shrub species richness and longitudinal herb species richness showed significant quadratic relationships with distance to the estuary along the river,while longitudinal tree species richness exhibited a linear relationship with distance to the estuary along the river.Along the lateral gradient,species richness and herb species richness increased first and then decreased along with elevation,while tree and shrub species richness increased with elevation.Correlation analysis showed that along the longitudinal gradient,significant positive correlation existed between species richness and substrate types,and distance to the estuary was critical in the control of species richness.Along the lateral gradient,submergence time,soil moisture and substrate heterogeneity had important impacts on spatial pattern of species richness.On the whole,the pattern of plant species richness in the fluctuating water level zone was still influenced by fluvial geomorphology and flood pulse,but had gradually formed with seasonal water level fluctuation of the Three Gorges Reservoir.