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| Titel |
A downward CO2 flux seems to have nowhere to go |
| VerfasserIn |
J. Ma, R. Liu, L.-S. Tang, Z.-D. Lan, Y. Li |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 22 ; Nr. 11, no. 22 (2014-11-17), S.6251-6262 |
| Datensatznummer |
250117679
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| Publikation (Nr.) |
 copernicus.org/bg-11-6251-2014.pdf |
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| Zusammenfassung |
| Recent studies have suggested that deserts, which are a long-neglected
region in global carbon budgeting, have strong downward CO2 fluxes and
might be a significant carbon sink. This finding, however, has been strongly
challenged because neither the reliability of the flux measurements nor the
exact location of the fixed carbon has been determined. This paper shows,
with a full chain of evidence, that there is indeed strong carbon flux into
saline/alkaline land in arid regions. Based on continuous measurement of net
ecosystem CO2 exchange (NEE) from 2002 to 2012 (except for 2003), the
saline desert in western China was a carbon sink for 9 out of 10
years, and the average yearly NEE for the 10 years was −25.00 ± 12.70 g C m−2 year−1.
Supporting evidence for the validity of these NEE
estimates comes from the close agreement of NEE values obtained from the
chamber and eddy-covariance methods. After ruling out the possibility of
changes in C stored in plant biomass or soils, the C uptake was found to be
leached downwards into the groundwater body in the process of groundwater
fluctuation: rising groundwater absorbs soil dissolved inorganic carbon
(DIC), and falling groundwater transports the DIC downward. Horizontal
groundwater flow may send this DIC farther away and prevent it from being
observed locally. This process has been called "passive leaching" of DIC,
in comparison with the active DIC leaching that occurs during groundwater
recharge. This passive leaching significantly expands the area where DIC
leaching occurs and creates a literally "hidden" carbon sink process under
the desert. This study tells us that when a downward CO2 flux is
observed, but seems to have nowhere to go, it does not necessarily mean that
the flux measurement is unreliable. By looking deeper and farther away, a
place and a process may be found "hidden" underground. |
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