Species Loss from Nitrogen Deposition in Grasslands: The Differing Environmental Conditions that Cause Competitive-Exclusion-Driven vs. Acidification-Driven Declines in Species Richness

Recent increases in the atmospheric deposition of biologically active nitrogen (N), resulting from human activities such as fossil fuel combustion and agricultural fertilization, have spurred dramatic declines in the species richness of grasslands in Europe and the United States. While many studies highlight either competitive exclusion or acidification as the major mechanisms that drive declines in species richness in the presence of N deposition, few explain the particular conditions that determine which mechanism drives N induced species loss at a specific site. This paper examines the environmental factors of European and North American grasslands that determine whether competitive exclusion or acidification acts as the principle driver of declines in species richness in the presence of N loading