The role of plant species in biomass production and response to elevated CO2 and N

Joseph M. Craine*, Peter B. Reich, G. David Tilman, David Ellsworth, Joseph Fargione, Johannes Knops and Shahid Naeem Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN 55108, USA Department of Forest Resources, University of Minnesota, Saint Paul, MN 55108, USA School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA Department of Biology, University of Washington, Seattle, WA 98195, USA *Correspondence: E-mail: [email protected] Abstract In an experiment that factorially manipulated plant diversity, CO2, and N, we quantified the effects of the presence of species on assemblage biomass over 10 time points distributed over 5 years. Thirteen of the 16 species planted had statistically significant effects on aboveground and/or belowground biomass. Species differed dramatically in their effects on biomass without any relationship between aboveground and belowground effects. Temporal complementarity among species in their effects seasonally, successionally, and in response to a dry summer maintained the diversity–biomass relationships over time and may be the cause behind higher diversity plots having less variation in biomass over time. The response of plant biomass to elevated N, but not CO2, was at times entirely dependent on the presence of a single species.