Water-use efficiency and transpiration across European forests during the Anthropocene

作者：Frank, D. C.; Poulter, B.; Saurer, M.; Esper, J.; Huntingford, C.; Helle, G.; Treydte, K.; Zimmermann, N. E.; Schleser, G. H.; Ahlstrom, A.; Ciais, P.; Friedlingstein, P.; Levis, S.; Lomas, M.; Sitch, S.; Viovy, N.; Andreu-Hayles, L.; Bednarz, Z.; Berninger, F.; Boettger, T.; D'Alessandro, C. M.; Daux, V.; Filot, M.; Grabner, M.; Gutierrez, E.; Haupt, M.; Hilasvuori, E.; Jungner, H.; Kalela-Brundin, M.; Krapiec, M.; Leuenberger, M.; Loader, N. J.; Marah, H.; Masson-Delmotte, V.; Pazdur, A.

来源：Nature Climate Change, 2015, 5(6): 579-+.

DOI：10.1038/nclimate2614

• CARBON-ISOTOPE DISCRIMINATION
• CO2 FERTILIZATION
• GAS-EXCHANGE
• RISING CO2
• TREE-RING
• CLIMATE
• RUNOFF
• RESPONSES
• INCREASE
• TRENDS

The Earth's carbon and hydrologic cycles are intimately coupled by gas exchange through plant stomata(1-3). However, uncertainties in the magnitude(4-6) and consequences(7,8) of the physiological responses(9,10) of plants to elevated CO2 in natural environments hinders modelling of terrestrial water cycling and carbon storage(11). Here we use annually resolved long-term delta C-13 tree-ring measurements across a European forest network to reconstruct the physiologically driven response of intercellular CO2 (Ci) caused by atmospheric CO2 (Ca) trends. When removing meteorological signals from the delta C-13 measurements, we find that trees across Europe regulated gas exchange so that for one ppmv atmospheric CO2 increase, C-i increased by similar to 0.76 ppmv, most consistent with moderate control towards a constant C-i/C-a ratio. This response corresponds to twentiethcentury intrinsic water-use efficiency (iWUE) increases of 14 +/- 10 and 22 +/- 6% at broadleaf and coniferous sites, respectively. An ensemble of process-based global vegetation models shows similar CO2 effects on iWUE trends. Yet, when operating these models with climate drivers reintroduced, despite decreased stomatal opening, 5% increases in European forest transpiration are calculated over the twentieth century. This counterintuitive result arises from lengthened growing seasons, enhanced evaporative demand in a warming climate, and increased leaf area, which together oppose effects of CO2-induced stomatal closure. Our study questions changes to the hydrological cycle, such as reductions in transpiration and air humidity, hypothesized to result from plant responses to anthropogenic emissions.

• 出版日期2015-6
• 单位中国地震局