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| Titel |
Deep CO2 soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe |
| VerfasserIn |
E. P. Sánchez-Cañete, A. S. Kowalski, P. Serrano-Ortiz, O. Pérez-Priego, F. Domingo |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-18), S.6591-6600 |
| Datensatznummer |
250085368
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| Publikation (Nr.) |
 copernicus.org/bg-10-6591-2013.pdf |
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| Zusammenfassung |
Knowledge of all the mechanisms and processes involved in soil CO2
emissions is essential to close the global carbon cycle. Apart from
molecular diffusion, the main physical component of such CO2 exchange
is soil ventilation. Advective CO2 transport, through soil or snow, has
been correlated with the wind speed, friction velocity or pressure (p). Here
we examine variations in subterranean CO2 molar fractions
(χc) over two years within a vertical profile (1.5 m) in a semiarid
ecosystem, as influenced by short-timescale p changes.
Analyses to determine the factors involved in the variations in subterranean
χc were differentiated between the growing period and the dry
period. In both periods it was found that variations in deep χc
(0.5–1.5 m) were due predominantly to static p variations and not to wind or
biological influences. Within a few hours, the deep χc can vary
by fourfold, showing a pattern with two cycles per day, due to p oscillations
caused by atmospheric tides. By contrast, shallow χc (0.15 m)
generally has one cycle per day as influenced by biological factors like
soil water content and temperature in both periods, while the wind was an
important factor in shallow χc variations only during the dry
period. Evidence of emissions was registered in the atmospheric boundary
layer by eddy covariance during synoptic pressure changes when subterranean
CO2 was released; days with rising barometric pressure – when air
accumulated belowground, including soil-respired CO2 – showed greater
ecosystem uptake than days with falling pressure. Future assessments of the
net ecosystem carbon balance should not rely exclusively on Fick's law to
calculate soil CO2 effluxes from profile data. |
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