How do climate warming and plant species richness affect water use in experimental grasslands?
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Climate warming and plant species richness loss have been the subject of numerous experiments, but studies on their combined impact are lacking. Here we studied how both warming and species richness loss affect water use in grasslands, while identifying interactions between these global changes. Experimental ecosystems containing one, three or nine grassland species from three functional groups were grown in 12 sunlit, climate-controlled chambers (2.25 m2 ground area) in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3°C (heated). Equal amounts of water were added to heated and unheated communities, so that warming would imply drier soils if evapotranspiration (ET) was higher. After an initial ET increase in response to warming, stomatal regulation and lower above-ground productivity resulted in ET values comparable with those recorded in the unheated communities. As a result of the decreased biomass production, water use efficiency (WUE) was reduced by warming. Higher complementarity and the improved competitive success of water-efficient species in mixtures led to an increased WUE in multi-species communities as compared to monocultures, regardless of the induced warming. However, since the WUE of individual species was affected in different ways by higher temperatures, compositional changes in mixtures seem likely under climatic change due to shifts in competitiveness. In conclusion, while increased complementarity and selection of water-efficient species ensured more efficient water use in mixtures than monocultures, global warming will likely decrease this WUE, and this may be most pronounced in species-rich communities.
KeywordsEvapotranspiration Global warming Grassland species Species richness Water use efficiency
Analysis of co-variance
General linear model
- h (subscript)
- mix (subscript)
- mono (subscript)
- res (subscript)
Soil water content
- u (subscript)
Water use efficiency
This research was funded by the Fund for Scientific Research—Flanders (Belgium) as project “Effects of biodiversity loss and climate warming on carbon sequestration mechanisms in terrestrial ecosystems”, contract # G.0434.03N. H.J. De Boeck holds a grant from the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen). H. Bossuyt is a post-doctoral research associate of the Fund for Scientific Research - Flanders. We thank B. Gielen for help with harvesting above-ground biomass, and F. Kockelbergh for technical assistance.
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