Environmental interpretation of herb species diversity under different site types of Hippophae rhamnoides forest in feldspathic sandstone region

Feldspathic sandstone regions are among the regions with the most severe soil erosion in the Loess Plateau. The planted Hippophae rhamnoides shrub forest reduces soil erosion for local residents. The herb species under the shrub canopy are important biodiversity components of this artificial ecosystem. The objective of this study was to clarify the relationship between the biodiversity of herb species and their site conditions. On the basis of the variation among sites,the planted shrub forests were classified into seven types. At each site,topography(slope,aspect,and slope position) was recorded,herb species were measured in 1 × 1 m~2 quadrats,and soil samples were collected adjacent to each quadrat. In this study,we used the Patrick,Pielou,Shannon,and Simpson indices for analysis of herb species diversity under different site types of H. rhamnoides forest in a feldspathic sandstone region,and studied the relationship between species distribution and the environment through CCA and PCCA. The following results were obtained:(1) The dominant species of the herbage layer under different site types of H. rhamnoides forest were different. The shady-slope mixed forest had the largest number of species(23). The sunny-slope mixed forest had the highest Pielou index of 0.89. The Shannon indices of shady-slope pureforest and mixed forest were the highest,whereas there was no significant difference between the Simpson indices.(2) The order of the environmental factors affecting herb species distribution under different site types of H. rhamnoides forest in the feldspathic sandstone region was terrain factor > soil factor > shrub layer factor,in which slope aspect,slope,soil water content,soil thickness,canopy density and mixed structure made the largest contributions. This study could provide a scientific basis for biodiversity protection and ecosystem development in the local region.