Investigation on the Species Diversity of Shrub and Arbor Communities in Xiangxihe Drainage Area of Zigui County

Investigation on the species diversity of shrub and arbor communities in Xiangxihe Drainage Area of Zig- ui County indicates: firstly, species richness index, species diversity index and evenness index have a substantial agreement on the distribution tendency of community gradient; hence, the preceding indices mirror the discrepancy in species composition of various plant coenotypes. Secondly, the species richness index of bush layer is higher than that of tree stratum significantly; and species diversity index and evenness index of tree stratum are lower than those of bush layer. Thirdly, moderate elevation regions share the higher value of species richness index and diversity ri- chness, while high or low elevation regions share the lower values of them. Fourthly, the distribution ranges of higher value and lower value of species evenness index J and E vary from unit to unit. Lastly, the species richness index and diversity index of plant communities tend to be on the high side at low and moderate elevations; however, on the low side at high elevation.