Effects of plant diversity on primary productivity and community stability along soil water and salinity gradients

Ecosystem stability is particularly important for the biodiversity conservation and sustainable development in arid and semi-arid areas in northwest China. In this study, taking the desert plant community in the Ebinur Lake Basin in Xinjiang, China as the research object, the impacts of plant diversity on primary productivity and community stability along soil water and salinity gradients were investigated by calculating the species diversity, functional diversity, primary productivity, and community stability. The results showed that (1) the evenness index increased with decreasing soil water and salinity, while the Rao index and species diversity indices (ShannonWiener index, Simpson diversity index, and Patrick richness index) increased with increasing soil water and salinity. (2) The above-ground and below-ground biomass increased with increasing soil water and salinity, and the community stability in the low-water and low-salinity soil was the highest (0.272), followed by that in the medium-water and moderate-salinity soil (0.285) and the high-water and low-salinity soil (0.348). (3) In the high-water and high-salinity soil, functional diversity, above-ground biomass, and community stability were positively correlated with species diversity (R2 = 0.83, P < 0.05). In the medium-water and moderate-salinity soil, Patrick richness index and functional diversity were positively correlated with community stability (R2 = 0.74, P < 0.05), and soil pH and P concentration indirectly affected community stability by affecting functional diversity. In the low-water and low-salinity soil, Patrick richness index and belowground biomass were positively correlated with community stability (R2 = 0.14), with effect coefficients of 0.287 and 0.160, respectively (P > 0.05). This study is of great significance to make clear the responses of primary productivity and community stability to the changes in plant diversity under global warming.