title: No evidence of complementary water use along a plant species richness gradient in temperate experimental grasslands.
abstract: Niche complementarity in resource use has been proposed as a key mechanism to explain the positive effects of increasing plant species richness on ecosystem processes, in particular on primary productivity. Since hardly any information is available for niche complementarity in water use, we tested the effects of plant diversity on spatial and temporal complementarity in water uptake in experimental grasslands by using stable water isotopes. We hypothesized that water uptake from deeper soil depths increases in more diverse compared to low diverse plant species mixtures. We labeled soil water in 8 cm (with 18O) and 28 cm depth (with ²H) three times during the 2011 growing season in 40 temperate grassland communities of varying species richness (2, 4, 8 and 16 species) and functional group number and composition (legumes, grasses, tall herbs, small herbs). Stable isotope analyses of xylem and soil water allowed identifying the preferential depth of water uptake. Higher enrichment in 18O of xylem water than in ²H suggested that the main water uptake was in the upper soil layer. Furthermore, our results revealed no differences in root water uptake among communities with different species richness, different number of functional groups or with time. Thus, our results do not support the hypothesis of increased complementarity in water use in more diverse than in less diverse communities of temperate grassland species.
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland.
authors.forename: Dörte
authors.initials: D
authors.lastname: Bachmann
authors.affiliation: Faculty of Biology, Department of Geobotany, University of Freiburg, Freiburg, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Gockele
authors.affiliation: Department of Experimental Plant Ecology; Institute for Water and Wetland Research; Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Janneke M
authors.initials: JM
authors.lastname: Ravenek
authors.affiliation: UFZ, Helmholtz Centre for Environmental Research, Department of Community Ecology, Halle, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Roscher
authors.affiliation: J. F. Blumenbach Institute of Zoology and Anthropology, Georg August University Göttingen, Göttingen, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Strecker
authors.affiliation: Department of Special Botany and Functional Biodiversity, Institute of Biology, University of Leipzig, Leipzig, Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Weigelt
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Buchmann
mesh_terms: D018533:Biomass; D017753:Ecosystem; D065948:Grassland; D018517:Plant Roots / Q000502:physiology; D006109:Poaceae / Q000502:physiology*; D012987:Soil / Q000737:chemistry*; D014867:Water / Q000032:analysis*; D052584:Xylem / Q000502:physiology
chemical_list: D012987:Soil; D014867:Water