Diversity patterns from sequentially restored grasslands support the ‘environmental heterogeneity hypothesis'

The ‘environmental heterogeneity hypothesis’ (EHH) has been proposed as a mechanism that enables species coexistence through resource partitioning. In accordance with this hypothesis, plant diversity is predicted to increase with variability in resources, but there has been weak support for this hypothesis from experimental studies. The objectives of this research were to (1) characterize how resource availability and heterogeneity (coefficient of variation) change as plant communities develop using sequentially restored grasslands, (2) determine if resource heterogeneity relates to plant diversity (effective number of species, richness, and evenness), and (3) reveal if the strength of resource heterogeneity-diversity relationships is different among levels of resource availability. We quantified means and coefficients of variation in soil nitrate and light availability in grasslands established on former agricultural lands for different times and their relationship to plant diversity u...