Figure 18.11 Fertility effects on species richness. (a) Researchers of the Park Grass experiment have manipulated the addition of different types of nutrients in grassland plots over time and observed changes in species richness. (b) Plots that received more types of resources—such as nitrogen, phosphorus, and micronutrients—experienced a greater decline in species richness.

Data from W. S. Harpole and D. Tilman, Grassland species loss resulting from reduced niche dimension, Nature 446 (2007): 791–793. Photo © Rothamsted Research Ltd.