Herbivores and nutrients control grassland plant diversity via light limitation

Borer, Elizabeth T. and Seabloom, Eric W. and Gruner, Daniel S. and Harpole, W. Stanley and Hillebrand, Helmut and Lind, Eric M. and Adler, Peter B. and Alberti, Juan and Anderson, T. Michael and Bakker, Jonathan D. and Biederman, Lori and Blumenthal, Dana and Brown, Cynthia S. and Brudvig, Lars A. and Buckley, Yvonne M. and Cadotte, Marc and Chu, Chengjin and Cleland, Elsa E. and Crawley, Michael J. and Daleo, Pedro and Damschen, Ellen I. and Davies, Kendi F. and DeCrappeo, Nicole M. and Du, Guozhen and Firn, Jennifer and Hautier, Yann and Heckman, Robert W. and Hector, Andy and HilleRisLambers, Janneke and Iribarne, Oscar and Klein, Julia A. and Knops, Johannes M. H. and La Pierre, Kimberly J. and Leakey, Andrew D. B. and Li, Wei and MacDougall, Andrew S. and McCulley, Rebecca L. and Melbourne, Brett A. and Mitchell, Charles E. and Moore, Joslin L. and Mortensen, Brent and O'Halloran, Lydia R. and Orrock, John L. and Pascual, Jesus and Prober, Suzanne M. and Pyke, David A. and Risch, Anita C. and Schuetz, Martin and Smith, Melinda D. and Stevens, Carly J. and Sullivan, Lauren L. and Williams, Ryan J. and Wragg, Peter D. and Wright, Justin P. and Yang, Louie H. (2014) Herbivores and nutrients control grassland plant diversity via light limitation. Nature, 508 (7497). pp. 517-520. ISSN 0028-0836

Abstract

Human alterations to nutrient cycles(1,2) and herbivore communities(3-7) are affecting global biodiversity dramatically(2). Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems(8,9). Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.