Plant diversity enhances ecosystem responses to elevated CO2 and nitrogen deposition (vol 410, pg 809, 2001)

Human actions are causing declines in plant biodiversity, increases in atmo spheric CO2 concentrations and increases in nitrogen deposition; however, t he interactive effects of these factors on ecosystem processes are unknown( 1,2). Reduced biodiversity has raised numerous concerns, including the poss ibility that ecosystem functioning may be affected negatively(1-4), which m ight be particularly important in the face of other global changes (5,6). H ere we present results of a grassland field experiment in Minnesota, USA, t hat tests the hypothesis that plant diversity and composition influence the enhancement of biomass and carbon acquisition in ecosystems subjected to e levated atmospheric CO2 concentrations and nitrogen deposition. The study e xperimentally controlled plant diversity (1, 4, 9 or 16 species), soil nitr ogen (unamended versus deposition of 4 g of nitrogen per m(2) per yr) and a tmospheric CO2 concentrations using free-air CO2 enrichment (ambient, 368 m u mol mol(-1), versus elevated, 560 mu mol mol(-1)). We found that the enha nced biomass accumulation in response to elevated levels of CO2 or nitrogen , or their combination, is less in species-poor than in species-rich assemb lages.