Nitrogen discourages legumes

Abstract

Ecology Anthropogenic nutrient enrichment of the global environment has been proceeding for many decades. Nitrogen deposition in particular leads to higher ecosystem productivity at the expense of biodiversity. In a global experiment spanning 45 sites, Tognetti et al. investigated how the addition of nitrogen affected the leguminous plants in grassland. Legumes under natural conditions compete successfully in low-nutrient conditions because of their ability to fix atmospheric nitrogen using their rhizobial symbionts. However, excess nitrogen deposition places them at a competitive disadvantage, leading to declines in their biomass and abundance. In turn, these declines may have adverse consequences for grassland biodiversity and food webs more generally as nitrogen deposition continues. Proc. Natl. Acad. Sci. U.S.A. 118 , e2023718118 (2021).