A regional‐scale consideration of the effects of species richness on above‐ground biomass in temperate natural grasslands of China

Question: Can species richness be a predictor for above‐ground biomass in natural grasslands at a regional scale? Location: A total of 647 sites across temperate natural grasslands of northern China. Methods: Structural equation modelling (SEM) was used to examine the effect of species richness on above‐ground biomass. Asymptotically distribution‐free estimation was selected for parameter estimation. The SEM process was performed at five sample sizes (n=50, 100, 200, 300 and 647). Spatial structure in the original data was examined by calculating Moran's I. Results: SEM run at n=647 revealed a positive effect of species richness on above‐ground biomass after controlling for the influences of bioclimatic factors and grazing. At the four reduced sample size levels, the positive effect held true for most cases in 400 observations (>92%). Conclusions: Contrary to observations in previous studies in natural grasslands, our data showed a positive effect of species richness on above‐ground biomass. This suggests that, as a short‐term effect of diversity on productivity, niche complementarity among coexisting species tends to be an important process in arid and semi‐arid natural grasslands. We hold that biodiversity conservation is among the fundamental approaches required to maintain productivity of grasslands in arid and semi‐arid areas.