title: Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments.
abstract: Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Kevin R
authors.identifier: 0000-0001-6829-1148
authors.initials: KR
authors.lastname: Wilcox
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Shi
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors.forename: Laureano A
authors.initials: LA
authors.lastname: Gherardi
authors.affiliation: Department of Biology & Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Lemoine
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL, USA.
authors.forename: Sally E
authors.initials: SE
authors.lastname: Koerner
authors.affiliation: U.S. Department of Agriculture, Agriculture Research Service, Fort Collins, CO, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Hoover
authors.affiliation: Agricultural, Food & Nutritional Science, University of Alberta, Edmonton, AB, Canada.
authors.forename: Edward
authors.initials: E
authors.lastname: Bork
authors.affiliation: Department of Environmental Science and Management, Humboldt State University, Arcata, CA, USA.
authors.forename: Kerry M
authors.initials: KM
authors.lastname: Byrne
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: James
authors.initials: J
authors.lastname: Cahill
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Collins
authors.affiliation: Department of Integrative Biology, Department of Microbiology and Molecular Genetics and Kellogg Biological Station, Michigan State University, Hickory Corners, MI, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Evans
authors.affiliation: Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
authors.forename: Anna K
authors.initials: AK
authors.lastname: Gilgen
authors.affiliation: Global Change Research Institute, Czech Academy of Sciences, Brno, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Holub
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Lifen
authors.identifier: 0000-0002-1546-8189
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Biology & Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA.
authors.forename: Alan K
authors.initials: AK
authors.lastname: Knapp
authors.affiliation: U.S. Department of Agriculture, Agriculture Research Service, Fort Collins, CO, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: LeCain
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Junyi
authors.initials: J
authors.lastname: Liang
authors.affiliation: Área de Biodiversidad y Conservación, Departamento de Biología, Geología, Física y Química Inorgánica, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Móstoles, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Garcia-Palacios
authors.affiliation: CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain.|CREAF, Cerdanyola del Vallès, Catalonia, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Peñuelas
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Pockman
authors.affiliation: Department of Biology & Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA.
authors.forename: Melinda D
authors.initials: MD
authors.lastname: Smith
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, China.
authors.forename: Shanghua
authors.initials: S
authors.lastname: Sun
authors.affiliation: Environment and Parks, Government of Alberta, Edmonton, AB, Canada.
authors.forename: Shannon R
authors.initials: SR
authors.lastname: White
authors.affiliation: Facultad de Agronomía, Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Laura
authors.initials: L
authors.lastname: Yahdjian
authors.affiliation: Department of BioSciences, Rice University, Houston, TX, USA.|Department of Biology, University of Texas, Arlington, TX, USA.
authors.forename: Kai
authors.identifier: 0000-0003-1587-3317
authors.initials: K
authors.lastname: Zhu
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Luo
mesh_terms: D057231:Climate Change; D017753:Ecosystem; D065948:Grassland; D006109:Poaceae; D011891:Rain
keywords: aboveground net primary productivity; belowground net primary productivity; biomass allocation; climate change; grasslands; meta-analysis; root biomass