Herbivory and eutrophication modulate grassland plant nutrient responses across a global climatic gradient

Authors: ANDERSON, T - Wake Forest University; GRIFFITH, DANIEL - Wake Forest University; LIND, ERIC - University Of Minnesota; ADLER, PETER - Utah State University; BIEDERMAN, LORI - Iowa State University; Blumenthal, Dana; BORER, ELIZABETH - University Of Minnesota; DALEO, PEDRO - Universidad Nacional Del Sur (UNS); FIRN, JENNIFER - Queensland University - Australia; HAGENAH, NICOLE - University Of Kwazulu-Natal; HARPOLE, W - German Centre For Integrative Biodiversity Research (IDIV); MACDOUGALL, ANDREW - University Of Guelph; MCCULLEY, REBECCA - University Of Kentucky; PROBER, SUZANNE - Csiro European Laboratory; RISCH, ANITA - Swiss Federal Institute; SANKARAN, MAHESH - National Centre For Integrated Pest Management; SCHUTZ, MARTIN - Swiss Federal Institute; SEABLOOM, ERIC - University Of Minnesota; STEVENS, CARLY - Lancaster University; SULLIVAN, LAUREN - Iowa State University; WRAGG, PETER - University Of Minnesota; GRACE, JAMES - Us Geological Survey (USGS)

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2017
Publication Date: 3/31/2018
Citation: Anderson, T.M., Griffith, D.M., Lind, E.M., Adler, P.B., Biederman, L.A., Blumenthal, D.M., Borer, E.T., Daleo, P., Firn, J., Hagenah, N., Harpole, W.S., MacDougall, A.S., McCulley, R.L., Prober, S.M., Risch, A.C., Sankaran, M., Schutz, M., Seabloom, E., Stevens, C.J., Sullivan, L., Wragg, P., Grace, J.B. 2018. Herbivory and eutrophication modulate grassland plant nutrient responses across a global climatic gradient. Ecology. 99(4):822-831. doi:org/10.1002/ecy.2175.
DOI: https://doi.org/10.1002/ecy.2175

Interpretive Summary: Human activities are altering plant nutrient content around the world. We measured changes in plant nutrients with eutrophication (nutrient enrichment) and large herbivore loss at eighteen sites on five continents. Increases in plant nutrients following eutrophication were highest in fenced, ungrazed plots at low rainfall, whereas herbivores dampened community nutrient responses to fertilization. Across sites, climate and atmospheric nitrogen deposition strongly influenced plot-level nutrients. Within sites, fertilization increased plot biomass but also the response also depended on soil fertility. Our study highlights (i) the role of climate in determining grassland nutrient content across global gradient through effects on plant biomass, (ii) that eutrophication affects grassland nutrients via both soil and atmospheric pathways and (iii) interactions among soils, herbivores and eutrophication drive plant nutrient responses at small scales, especially at water-limited sites.

Technical Abstract: Human activities are altering plant stoichiometry in terrestrial systems. We measured plant nutrient responses (C, N, P and K) to eutrophication and large herbivore loss at eighteen sites on five continents. Nutrients pools diverged strongly in response to herbivore removal when fertilized: response ratios were highest in fenced, ungrazed plots at low rainfall, whereas herbivores dampened community nutrient responses to eutrophication. Across sites, climate and atmospheric N deposition emerged as strong predictors of plot-level nutrients, mediated by both biomass and plant chemistry. Within sites, fertilization increased plot biomass but also interacted with soil fertility. Our study highlights (i) the role of climate in determining grassland stoichiometry across global gradient through effects on plant biomass, (ii) that eutrophication affects grassland stoichiometry via both soil and atmospheric pathways and (iii) interactions among soils, herbivores and eutrophication drive plant nutrient responses at small scales, especially at water-limited sites.