The relationship between plant species richness and productivity has been a central issue in biodiversity and ecosystem functioning research. Despite a number of studies, it remains controversial whether the observed relationship has predictive value in the natural world, where both species richness (SR) and aboveground net primary production (ANPP) are confounded with abiotic factors. In this study, we investigated 321 field sites across the temperate and alpine grasslands of China and tested the SR-ANPP relationship at among- and within-site levels. We found positive linear relationships among sites in both the alpine and temperate region and in different grassland vegetation types. However, after removing the among-site environmental variation, residual SR and ANPP were no longer correlated at the pooled within-site level. Thus, the positive SR-ANPP relationship may largely be the result of climatic variables influence SR and ANPP in parallel. In sum, the results suggest that in natural grasslands there is no direct relationship between SR and ANPP, presumably because the pool of available species for local community assembly is large.

Keywords

species richness–productivity relationship,alpine grassland,among-site variation,China,field study,temperate grassland,envionmental gradients