Abstract: Soil environment is a key factor affecting plant community structure. To address the relationship between spatial distribution of plant community and soil environmental factors in water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir area, plant community characters of 30 sampling transects in the WLFZ of Xiangxi River were analyzed using cluster analysis. Redundancy analysis (RDA) was used to examine the roles of 11 soil physicochemical factors in driving the spatial distribution and diversity of vegetation. Clustering analysis showed that the herbaceous communities could be grouped into seven types in the Xiangxi River riparian zone dominated by annual plant communities. Results from correlation analysis of RDA and environmental factors revealed that the first axis of RDA was significantly correlated with soil water content (SWC), and significantly negatively correlated with elevation (P<0.01). The second axis was negatively related to soil pH, iron-bound phosphorus (Fe-P), soil organic matter (SOM) and organic/ortho P (O-P) (P<0.05). Correlation analysis between vegetation diversity index and soil physical-chemical properties revealed that there were significant correlations between species richness (R) and elevation, soil pH as well as SOM. Plant dominance index (D) was significantly negatively correlated with elevation (P<0.01), but significantly positively correlated with SWC. Shannon diversity index (H) was significantly positively correlated with elevation, SOM and total P (TP), but significantly negatively correlated with SWC and pH. There were no significant relationships between species evenness index (E) and other environmental factors except for elevation and SWC (P<0.05). Our results indicated that the main factors affecting the vegetation distribution in the WLFZ of Xiangxi River included elevation, SWC, SOM, soil pH, soil TP, and inorganic phosphorus (O-P and Fe-P).

Key words: heterogeneous habitat, vegetative reproduction, bud, juvenile tiller, Leymus chinensis, potential population