title: Plant functional diversity increases grassland productivity-related water vapor fluxes: an Ecotron and modeling approach.
abstract: The impact of species richness and functional diversity of plants on ecosystem water vapor fluxes has been little investigated. To address this knowledge gap, we combined a lysimeter setup in a controlled environment facility (Ecotron) with large ecosystem samples/monoliths originating from a long-term biodiversity experiment (The Jena Experiment) and a modeling approach. Our goals were (1) quantifying the impact of plant species richness (four vs. 16 species) on day- and nighttime ecosystem water vapor fluxes; (2) partitioning ecosystem evapotranspiration into evaporation and plant transpiration using the Shuttleworth and Wallace (SW) energy partitioning model; and (3) identifying the most parsimonious predictors of water vapor fluxes using plant functional-trait-based metrics such as functional diversity and community weighted means. Daytime measured and modeled evapotranspiration were significantly higher in the higher plant diversity treatment, suggesting increased water acquisition. The SW model suggests that, at low plant species richness, a higher proportion of the available energy was diverted to evaporation (a non-productive flux), while, at higher species richness, the proportion of ecosystem transpiration (a productivity-related water flux) increased. While it is well established that LAI controls ecosystem transpiration, here we also identified that the diversity of leaf nitrogen concentration among species in a community is a consistent predictor of ecosystem water vapor fluxes during daytime. The results provide evidence that, at the peak of the growing season, higher leaf area index (LAI) and lower percentage of bare ground at high plant diversity diverts more of the available water to transpiration, a flux closely coupled with photosynthesis and productivity. Higher rates of transpiration presumably contribute to the positive effect of diversity on productivity.
authors.affiliation: CNRS, Ecotron (UPS-3248), Campus Baillarguet, F-34980, Montferrier-sur-Lez, France.|Centre d'Ecologie Fonctionnelle et Evolutive, CEFE-CNRS, UMR 5175, Université de Montpellier, Université Paul Valéry, EPHE, 1919 route de Mende, F-34293, Montpellier Cedex 5, France.
authors.forename: Alexandru
authors.identifier: http://orcid.org/0000-0002-2889-1234
authors.initials: A
authors.lastname: Milcu
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092, Zurich, Switzerland.
authors.forename: Werner
authors.initials: W
authors.lastname: Eugster
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092, Zurich, Switzerland.
authors.forename: Dörte
authors.initials: D
authors.lastname: Bachmann
authors.affiliation: Institute of Geoscience, Friedrich Schiller University Jena, Burgweg 11, 07749, Jena, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Guderle
authors.affiliation: UFZ, Helmholtz Centre for Environmental Research, Department of Community Ecology, Theodor-Lieser-Strasse 4, 06120, Halle, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Roscher
authors.affiliation: Institut für Biologie II, Geobotanik, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104, Freiburg, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Gockele
authors.affiliation: CNRS, Ecotron (UPS-3248), Campus Baillarguet, F-34980, Montferrier-sur-Lez, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Landais
authors.affiliation: CNRS, Ecotron (UPS-3248), Campus Baillarguet, F-34980, Montferrier-sur-Lez, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Ravel
authors.affiliation: Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knoell-Strasse 10, 07745, Jena, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Lange
authors.affiliation: Institute of Ecology, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743, Jena, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Ebeling
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, 85354, Freising, Germany.
authors.forename: Wolfgang W
authors.initials: WW
authors.lastname: Weisser
authors.affiliation: CNRS, Ecotron (UPS-3248), Campus Baillarguet, F-34980, Montferrier-sur-Lez, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Roy
authors.affiliation: Institute of Geoscience, Friedrich Schiller University Jena, Burgweg 11, 07749, Jena, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Hildebrandt
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092, Zurich, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Buchmann
mesh_terms: D044822:Biodiversity; D004463:Ecology; D017753:Ecosystem; D065948:Grassland; D008962:Models, Theoretical; D010944:Plants; D013227:Steam; D014867:Water
chemical_list: D013227:Steam; D014867:Water
keywords: Ecotron; Shuttleworth and Wallace model; The Jena Experiment; biodiversity-ecosystem functioning; ecosystem evaporation; ecosystem transpiration; evapotranspiration; functional traits; leaf area index; lysimeter; plant species richness