evapotranspiration; global warming; grassland species; species richness; water use efficiency
Abstract :
[en] 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 m(2) ground area) in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3 degrees 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.
Allen LH Jr, Pan D, Boote KJ, Pickering NB, Jones JW (2003) Carbon dioxide and temperature effects on evapotranspiration and water use efficiency of soybean. Agron J 95:1071-1081
Bruun HH, Ejrnæs R (2000) Classification of dry grassland vegetation in Denmark. J Veg Sci 11:585-596
Carter EB, Theodorou MK, Morris P (1997) Responses of Lotus corniculatus to environmental change. I. Effects of elevated CO2, temperature and drought on growth and plant development. New Phytol 136:245-253
Cernusca A (1976) Energy exchange within individual layers of a meadow. Oecologia 23:141-149
Chaves MM, Pereira JS, Maroco J, Rodrigues ML, Ricardo CPP, Osorio ML, Carvalho I, Faria T, Pinheiro C (2002) How plants cope with water stress in the field. Photosynthesis and growth. Ann Bot 89:907-916
Ciais P, Reichstein M, Viovy N, Granier A, Ogee J, Allard V, Aubinet M, Buchmann N, Bernhofer C, Carrara A, Chevallier F, De Noblet N, Friend AD, Friedlingstein P, Grunwald T, Heinesch B, Keronen P, Knohl A, Krinner G, Loustau D, Manca G, Matteucci G, Miglietta F, Ourcival JM, Papale D, Pilegaard K, Rambal S, Seufert G, Soussana JF, Sanz MJ, Schulze ED, Vesala T, Valentini R (2005) Europe-wide reduction in primary productivity caused by the heat and drought in 2003. Nature 437:529-533
De Boeck HJ, Nijs I, Lemmens CMHM, Ceulemans R (2006) Underlying effects of spatial aggregation (clumping) in relationships between plant diversity and resource uptake. Oikos 113:269-278
De Boeck HJ, Lemmens CMHM, Gielen B, Bossuyt H, Malchair S, Carnol M, Merckx R, Ceulemans R, Nijs I (2006) Combined effects of climate warming and plant diversity loss on above- and below-ground grassland productivity. Environ Exp Bot (in press)
Eatherall A (1997) Modelling climate change impacts on ecosystems using linked models and a GIS. Clim Change 35:17-34
Ejrnæs R, Bruun HH (2000) Gradient analysis of dry grassland vegetation in Denmark. J Veg Sci 11:573-584
Gielen B, De Boeck H, Lemmens CMHM, Valcke R, Nijs I, Ceulemans R (2005) Grassland species will not necessarily benefit from future elevated air temperatures: a chlorophyll fluorescence approach to study autumn physiology. Physiol Plant 125:52-63
Haith DA, Shoemaker LL (1987) Generalized watershed loading functions for stream-nutrients. Water Resour Bull 23:471-478
Hooper DU, Chapin FS, Ewel JJ, Hector A, Inchausti P, Lavorel S, Lawton JH, Lodge DM, Loreau M, Naeem S, Schmid B, Setala H, Symstad AJ, Vandermeer J, Wardle DA (2005) Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecol Monogr 75:3-35
Houghton JT, Ding Y, Griggs DJ, Noguer M, van der Linden PJ, Dai X, Maskell K, Johnson CA (2001) IPCC 2001. Climate change 2001: the scientific basis. Contribution of working group I to the second assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge
Larcher W (2003) Physiological plant ecology, 4th edn. Springer-Verlag, Berlin
Lemmens CMHM, De Boeck HJ, Gielen B, Bossuyt H, Malchair S, Carnol M, Merckx R, Nijs I, Ceulemans R (2006) End-of-season effects of elevated temperature on ecophysiological processes of grassland species at different species richness levels. Environ Exp Bot 56:245-254
Llorens L, Penuelas J, Estiarte M (2003) Ecophysiological responses of two Mediterranean shrubs, Erica multiflora and Globularia alypum, to experimental drier and warmer conditions. Physiol Plant 119:231-243
Loreau M, Hector A (2001) Partitioning selection and complementarity in biodiversity experiments. Nature 412:72-76
Mahmoud A, Grime JP (1976) An analysis of competitive ability in three perennial grasses. New Phytol 77:431-435
Marchand FL, Nijs I, De Boeck HJ, Kockelbergh F, Mertens S, Beyens L (2004) Increased turnover but little change in the carbon balance of high-arctic tundra exposed to whole growing season warming. Arc Antarct Alp Res 36:298-307
Myneni RB, Keeling CD, Tucker CJ, Asrar G, Namani RR (1997) Increased plant growth in the northern high latitudes from 1981 to 1991. Nature 386:698-702
Naeem S, Thompson LJ, Lawler SP, Lawton JH, Woodfin RM (1994) Declining biodiversity can alter the performance of ecosystems. Nature 368:734-737
Reichstein M, Tenhunen JD, Roupsard O, Ourcival JM, Rambal S, Miglietta F, Peressotti A, Pecchiari M, Tirone G, Valentini R (2002) Severe drought effects on ecosystem CO2 and H2O fluxes at three Mediterranean evergreen sites: revision of current hypotheses? Global Change Biol 8:999-1017
Rodrigues ML, Pacheco CMA, Chaves MM (1995) Soil-plant water relations, root distribution and biomass partitioning in Lupinus albus L. under drought conditions. J Exp Bot 46:947-956
Sala OE, Chapin FS III, Armesto JJ, Berlow E, Bloomfield J, Dirzo R, Huber-Sanwald E, Huenneke LF, Jackson RB, Kinzig A, Leemans R, Lodge DM, Mooney HA, Oesterheld M, Le Roy Poff N, Sykes MT, Walker BH, Walker M, Wall DH (2000) Global bio-diversity scenarios for the year 2100. Science 287:1770-1774
Saleska SR, Harte J, Torn MS (1999) The effect of experimental ecosystem warming on CO2 fluxes in a montane meadow. Global Change Biol 5:125-141
Thornley JHM, Cannell MGR (1997) Temperate grassland responses to climate change: an analysis using the Hurley pasture model. Ann Bot 80:205-221
Van Peer L, Nijs I, Reheul D, De Cauwer B (2004) Species richness and susceptibility to heat and drought extremes in synthesized grassland ecosystems: compositional vs physiological effects. Funct Ecol 18:769-778
van Ruijven J, Berendse F (2005). Diversity-productivity relationships: initial effects, long-term patterns, and underlying mechanisms. Proc Nat Sci USA 102:695-700
Walther G-R (2003) Plants in a warmer world. Perspect Plant Ecol Evol Syst 6:169-185
Xu ZZ, Zhou GS (2005) Effects of water stress and nocturnal temperature on carbon allocation in the perennial grass, Leymus chinensis. Physiol Plant 123:272-280
