In order to understand how the supply rate of resources affects species diversity, two nitrogen gradients were created. Twenty-four different mixtures of nitrogen-poor sand (267 ppm

nitrogen) and nitrogen-rich blackdirt (3400 ppm nitrogen) were used in each gradient to vary the nitrogen content between plots. The existing subsurface sand was used for the lowest end of the nitrogen gradients. For the highest end of the gradients, the upper 20cm of subsurface sand was removed and filled with blackdirt. All plots were created by repeatedly rototilling (15- 20 times) a 1.5m x 1.5m area with the appropriate amounts of black dirt and sand such that the mixture was 20 cm deep in each plot. The each gradient has increasing amounts of blackdirt in approximately 0.9cm increments. The first gradient is designed to give a detailed picture (24 points) of the response of species density along a limiting nutrient gradient. The second gradient is designed to understand how recruitment limitation affects species density. In this gradient, seeds are added from the same 59 species of plants on a yearly basis in spring. Using known germination rates, enough seeds of each species are added so that 115 seedlings of each species might germinate.