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

Abstract

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.