Determining spatial heterogeneity in species richness of plant community

Abstract Species richness (number of species) per small quadrat is an important characteristic of plant communities that, along with cover and biomass, can be readily measured in field surveys. We show that variance in the number of species among quadrats can be used to determine the spatial heterogeneity of plant communities. Comparisons between variance estimated based on the observed number of species among quadrats, and variance calculated based on an assumption that all species are arranged randomly among quadrats, can describe the spatial structure of species richness. We show field examples with different degrees of spatial heterogeneity in species richness to demonstrate how to survey, analyze and interpret: three natural grasslands with low heterogeneity in China, and a weedy grassland community with high heterogeneity in Japan.