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| Titel |
Continent-wide increase of water-use efficiency in vegetation during severe droughts of the recent decade |
| VerfasserIn |
Wouter Peters, Ivar van der Velde, John. B. Miller, Pieter P. Tans, Bruce Vaughn, James W. C. White |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108833
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| Publikation (Nr.) |
 EGU/EGU2015-8640.pdf |
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| Zusammenfassung |
| Recent severe droughts in Europe, Russia, China, and North America have caused
widespread decline of agricultural yield and reduction of forest carbon uptake during the past
decade. During droughts plants limit their water-loss at the expense of carbon uptake by
partially closing their stomata, which increases the intrinsic water-use efficiency defined as
the ratio of gross primary production to stomatal conductance. Here we present new evidence
on this drought response of terrestrial vegetation derived from year-to-year changes in the
13C:12C stable isotope ratio in atmospheric CO2 (δ13C). Observations from more than 50,000
flask samples from a global monitoring network show a strong increase in water-use
efficiency over continent-wide scales during severe droughts in Europe (2003, 2006), Russia
(2010), and the United States (2002). This large-scale area-integrated vegetation drought
response can not be measured from laboratory experiments or local-scale field studies
and the atmospheric δ13C record thus offers a unique perspective on large-scale
vegetation drought dynamics. Independent evidence from multiple eddy-covariance sites
supports our inverse model interpretation of the observed global atmospheric δ13C
record. With the parameterized stomatal conductance and soil moisture response
used in our study, as well as many current climate models, our vegetation model
underestimates this increase in water-use efficiency during severe droughts. We
therefore suggest minor modifications to better reproduce the observations. We
conclude that the global δ13C record provides a new opportunity to test and improve
interannual drought dynamics in coupled biosphere-atmosphere models for CO2. |
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