Figure 18.12 Reversing the effects of added nutrients on species richness. When fertilizer alone is added to a grassland community, species richness declines. When light is added under the canopy of the grasses, species richness is not affected. However, when fertilizer is added in combination with light under the canopy, there is no decline in richness. These results suggest that adding fertilizer causes richness to decline because increased fertility favors the tall and competitively dominant plants, which in turn shade the competitively inferior plants. Error bars are 95 percent confidence intervals.

Data from Y. Hautier et al., Competition for light causes plant biodiversity loss after eutrophication, Science 324 (2009): 636–638.