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

SULLIVAN, LAUREN L.; SCHÜTZ, MARTIN; PROBER, SUZANNE M.; HARPOLE, W. STANLEY; DALEO, PEDRO; ADLER, PETER B.; GRIFFITH, DANIEL M.; BORER, ELIZABETH T.; STEVENS, CARLY J.; SANKARAN, MAHESH; MCCULLEY, REBECCA L.; HAGENAH, NICOLE; BLUMENTHAL, DANA M.; LIND, ERIC M.; ANDERSON, T. MICHAEL; WRAGG, PETER D.; SEABLOOM, ERIC W.; RISCH, ANITA C.; MACDOUGALL, ANDREW S.; FIRN, JENNIFER; BIEDERMAN, LORI A.; GRACE, JAMES B.

ECOLOGY

ECOLOGICAL SOC AMER

Año: 2018 vol. 99 p. 822 - 831

0012-9658

Plant stoichiometry, the relative concentration of elements, is a key regulator of ecosystemfunctioning and is also being altered by human activities. In this paper we sought to understandthe global drivers of plant stoichiometry and compare the relative contribution of climatic vs. anthropogeniceffects. We addressed this goal by measuring plant elemental (C, N, P and K) responses toeutrophication and vertebrate herbivore exclusion at eighteen sites on six continents. Across sites, climateand atmospheric N deposition emerged as strong predictors of plot-level tissue nutrients, mediatedby biomass and plant chemistry. Within sites, fertilization increased total plant nutrient pools,but results were contingent on soil fertility and the proportion of grass biomass relative to other functionaltypes. Total plant nutrient pools diverged strongly in response to herbivore exclusion when fertilized;responses were largest in ungrazed plots at low rainfall, whereas herbivore grazing dampenedthe plant community nutrient responses to fertilization. Our study highlights (1) the importance of climatein determining plant nutrient concentrations mediated through effects on plant biomass, (2) thateutrophication affects grassland nutrient pools via both soil and atmospheric pathways and (3) thatinteractions among soils, herbivores and eutrophication drive plant nutrient responses at small scales,especially at water-limited sites.