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| Titel |
Assessing water-use-efficiency from stable isotopes and eddy covariance data |
| VerfasserIn |
A. Knohl, M. Barthel, W. L. Kutsch, Y. Salmon, P. Sturm |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026956
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| Zusammenfassung |
| The water and carbon cycles in terrestrial ecosystems play an essential role in the earth
system by modifying the atmospheric carbon dioxide and water vapor composition and by
partitioning energy at the land surface. Carbon uptake during photosynthesis and water
release during transpiration are closely linked through stomatal conductance. The
efficiency of carbon uptake versus water loss is called water-use-efficiency and is a key
factor for agricultural irrigation practices and species competition in water limited
ecosystems.
Here we review various concepts to assess water-use-efficiency at plant and
ecosystem scale and present results from different biomes. We will show that inherent
water-use-efficiency (estimated from eddy covariance measurements as the ratio of gross
primary productivity over evapotranspiration times vapor pressure deficit) is a fairly
conservative ecosystem property and only changes under sever drought conditions. Another
approach to assess water-use-efficiency is the stable carbon isotope composition (δ13C) of
plant material. Typically, in a first approximation a simply linear relationship between
leaf δ13C and intrinsic water-use-efficiency (the ratio of assimilation to stomata
conductance) is assumed. More recent studies, however, show that various factors influence
leaf δ13C independently of the exchange through the stomata leading to incorrect
water-use-efficiency estimates. Based on laboratory and field experiments using stable
carbon isotopes in various plant components as well as recently developed laser
spectroscopy for continuous stable isotope measurements we discuss possibilities and
limitations of using stable carbon isotopes to approximate plant water-use-efficiency. |
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