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| Titel |
Water stable isotope shifts of surface waters as proxies to quantify evaporation, transpiration and carbon uptake on catchment scales |
| VerfasserIn |
Johannes Barth, Robert van Geldern, Jan Veizer  , Ajaz Karim, Heiko Freitag, Hayley Fowlwer |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140743
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| Publikation (Nr.) |
 EGU/EGU2017-4172.pdf |
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| Zusammenfassung |
| Comparison of water stable isotopes of rivers to those of precipitation enables separation of
evaporation from transpiration on the catchment scale. The method exploits isotope ratio
changes that are caused exclusively by evaporation over longer time periods of at least one
hydrological year. When interception is quantified by mapping plant types in catchments, the
amount of water lost by transpiration can be determined. When in turn pairing transpiration
with the water use efficiency (WUE i.e. water loss by transpiration per uptake of CO2) and
subtracting heterotrophic soil respiration fluxes (Rh), catchment-wide carbon balances can
be established. This method was applied to several regions including the Great
Lakes and the Clyde River Catchments ...(Barth, et al., 2007, Karim, et al., 2008). In
these studies evaporation loss was 24 % and 1.3 % and transpiration loss was 47
% and 22 % when compared to incoming precipitation for the Great Lakes and
the Clyde Catchment, respectively. Applying WUE values for typical plant covers
and using area-typical Rh values led to estimates of CO2 uptake of 251 g C m−2
a−1 for the Great Lakes Catchment and CO2 loss of 21 g C m2 a−1 for the Clyde
Catchment. These discrepancies are most likely due to different vegetation covers.
The method applies to scales of several thousand km2 and has good potential for
improvement via calibration on smaller scales. This can for instance be achieved by
separate treatment of sub-catchments with more detailed mapping of interception
as a major unknown. These previous studies have shown that better uncertainty
analyses are necessary in order to estimate errors in water and carbon balances. The
stable isotope method is also a good basis for comparison to other landscape carbon
balances for instance by eddy covariance techniques. This independent method
and its up-scaling combined with the stable isotope and area-integrating methods
can provide cross validation of large-scale carbon budgets. Together they can help
to constrain relationships between carbon and water balances on the continental
scale.
References
.Barth JAC, Freitag H, Fowler HJ, Smith A, Ingle C, Karim A (2007) Water
fluxes and their control on the terrestrial carbon balance: Results from a stable
isotope study on the Clyde Watershed (Scotland). Appl Geochem 22: 2684-2694 DOI
10.1016/j.apgeochem.2007.06.002
Karim A, Veizer J, Barth J.A.C. (2008) Net ecosystem production in the great
lakes basin and its implications for the North American missing carbon sink: A
hydrologic and stable isotope approach. Global and Planetary Change 61: 15-27 DOI
10.1016/j.gloplacha.2007.08.004 |
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