title: Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship.
abstract: Well-defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid.
authors.affiliation: Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Vallès, Catalonia, E-08193, Spain.|CREAF, Cerdanyola del Vallès, Barcelona, Catalonia, E-08193, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Estiarte
authors.affiliation: Department of Biology, University of Antwerp, 2610, Wilrijk, Belgium.
authors.forename: Sara
authors.initials: S
authors.lastname: Vicca
authors.affiliation: Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Vallès, Catalonia, E-08193, Spain.|CREAF, Cerdanyola del Vallès, Barcelona, Catalonia, E-08193, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Peñuelas
authors.affiliation: Institute of Ecology, University of Innsbruck, Sternwarte str. 15, 6020, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Bahn
authors.affiliation: Department of Geoscience and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958, Frederiksberg C, Denmark.|NIVA, Center for Catchments and Urban Water Research, Oslo, NO-0349, Norway.
authors.forename: Claus
authors.initials: C
authors.lastname: Beier
authors.affiliation: Center for Ecology and Hydrology, Environment Centre Wales, Bangor, Gwynedd, LL57 2UW, UK.
authors.forename: Bridget A
authors.initials: BA
authors.lastname: Emmett
authors.affiliation: USDA-ARS, 808 E Blackland Rd, Temple, TX, 76502, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Fay
authors.affiliation: Oak Ridge National Laboratory, Climate Change Science Institute, Oak Ridge, TN, 37831-6301, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Hanson
authors.affiliation: Institute of Ecology, University of Innsbruck, Sternwarte str. 15, 6020, Innsbruck, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Hasibeder
authors.affiliation: Institute for Plant Sciences and Genetics, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Jaime
authors.initials: J
authors.lastname: Kigel
authors.affiliation: Institute of Ecology and Botany, MTA Centre for Ecological Research, Vacratot, H-2163, Hungary.
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Kröel-Dulay
authors.affiliation: Department of Geoscience and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958, Frederiksberg C, Denmark.
authors.forename: Klaus Steenberg
authors.initials: KS
authors.lastname: Larsen
authors.affiliation: Institute of Ecology and Botany, MTA Centre for Ecological Research, Vacratot, H-2163, Hungary.
authors.forename: Eszter
authors.identifier: 0000-0002-9654-6934
authors.initials: E
authors.lastname: Lellei-Kovács
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive CEFE, UMR5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, 1919 Route de Mende, 34293, Montpellier, Cedex 5, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Limousin
authors.affiliation: CREAF, Cerdanyola del Vallès, Barcelona, Catalonia, E-08193, Spain.
authors.forename: Romà
authors.initials: R
authors.lastname: Ogaya
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive CEFE, UMR5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, 1919 Route de Mende, 34293, Montpellier, Cedex 5, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Ourcival
authors.affiliation: NIVA, Center for Catchments and Urban Water Research, Oslo, NO-0349, Norway.
authors.forename: Sabine
authors.initials: S
authors.lastname: Reinsch
authors.affiliation: School of Life Sciences and School of Sustainability, Arizona State University, Tempe, AZ, 85287, USA.
authors.forename: Osvaldo E
authors.initials: OE
authors.lastname: Sala
authors.affiliation: Department of Geoscience and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958, Frederiksberg C, Denmark.
authors.forename: Inger Kappel
authors.initials: IK
authors.lastname: Schmidt
authors.affiliation: Department of Molecular Biology & Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Sternberg
authors.affiliation: Department of Biology, Plant Ecology Group, University of Tübingen, Auf der Morgenstelle 3, 72076, Tübingen, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Tielbörger
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94240, 1090 GE, Amsterdam, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Tietema
authors.affiliation: Department of Biology, University of Antwerp, 2610, Wilrijk, Belgium.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Janssens
mesh_terms: D002980:Climate; D004463:Ecology / Q000379:methods*; D017753:Ecosystem; D011891:Rain; D014867:Water
chemical_list: D014867:Water
keywords: aboveground productivity; drought; precipitation; precipitation-reduction experiments; spatial fit; temporal fit