One of the most striking patterns within ecological assemblages is the decline in species richness with increasing resource availability. This ubiquitous paradox of enrichment has been noted for at least a century but remains unexplained. Three prominent hypotheses, spatial resource heterogeneity, colonization limitation, and assemblage level thinning offer independent explanations to the paradox of enrichment in plant assemblages. This research will test these three hypotheses simultaneously using an experimental fertility gradient in a perennial dominated old field plant assemblage. These three hypotheses comprise three major conceptual themes in ecology that have previously been marshaled to explain patterns of diversity and coexistence. They are not mutually exclusive, and this research will be able to offer an integrated explanation of the paradox of enrichment. Currently, the experimental fertility gradient is generating the paradox of enrichment, and light quantity and light heterogeneity decline sharply as fertility rises. This research is now poised to test the extent to which each of these three hypotheses contributes to the paradox of enrichment.
