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.
Highlights
Many results from experimental biodiversity research support the hypothesis that increased plant species richness has positive effects on several aspects of ecosystem functioning [1,2,3,4], PLOS ONE | DOI:10.1371/journal.pone.0116367 January 14, 2015No Complementary Water Use in Temperate GrasslandONE, but this does not alter the authors0 adherence to PLOS ONE policies on sharing data and materials.such as plant biomass production aboveground [5,6,7,8], whereas the underlying mechanisms for these positive effects are not yet fully understood [9]
The Jena Experiment consists of 82 plots with different plant species number (1, 2, 4, 8, 16 and 60 species) and functional group richness (1, 2, 3 and 4 functional groups), from a species pool of 60 species assigned to four plant functional groups
We tested if plant communities of increased species or functional group richness exhibit increased spatial or temporal complementarity in water use compared to low diverse communities
Summary
Many results from experimental biodiversity research support the hypothesis that increased plant species richness has positive effects on several aspects of ecosystem functioning [1,2,3,4], PLOS ONE | DOI:10.1371/journal.pone.0116367 January 14, 2015No Complementary Water Use in Temperate GrasslandONE, but this does not alter the authors0 adherence to PLOS ONE policies on sharing data and materials.such as plant biomass production aboveground [5,6,7,8], whereas the underlying mechanisms for these positive effects are not yet fully understood [9]. Many results from experimental biodiversity research support the hypothesis that increased plant species richness has positive effects on several aspects of ecosystem functioning [1,2,3,4], PLOS ONE | DOI:10.1371/journal.pone.0116367. ONE, but this does not alter the authors0 adherence to PLOS ONE policies on sharing data and materials. Such as plant biomass production aboveground [5,6,7,8], whereas the underlying mechanisms for these positive effects are not yet fully understood [9]. One frequently proposed explanation is niche complementarity [10, 11], assuming that partitioning of resources such as light, nutrients or water reduces competitive interactions among the species of a mixture. Experimental evidence, for the resource water, is still sparse
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