Differential responses of shrubs and herbs present at the Upper Minjiang River basin (Tibetan Plateau) to several soil variables

Vertical structure in plant communities is well recognized, but questions remain about the response of different stratal layers in a plant community to resource use. This study provides a quantitative approach to compare the relationships of nine edaphic factors and species distributions in shrub and herb layers, respectively, in an arid valley of the upper Minjiang River, Sichuan Province, China. Classification (TWINSPAN) determined three groups of shrubs and four groups of herbs. Ordination (both DCA and DCCA) found a correlation among species and edaphic variables. Borcardʹs method [Borcard, D., Legendre, P., Drapeau, P., 1992. Partialling out the spatial component of ecological variation. Ecology 73, 1045–1055.] was employed to partition the variation of species abundance data into independent components: pure spatial, pure environmental, spatial component of environmental influence, and undetermined. Based on those four components, a quantitative comparison of ecological variation between shrubs and herbs further eluidated their different response to the environment. Although soil moisture (SM) content, pH, soil organic matter (OC) and available potassium (AK) were the most important factors to both, the explained ecological variation of herbs was lower than that of shrubs. Understanding differences between stratal layers in resource use can shed light on plant–environment relationships.