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| Titel |
Subterranean ventilation: a key but poorly known process affecting the carbon balance of semi-arid ecosystems |
| VerfasserIn |
Ana López Ballesteros, Enrique P. Sánchez Cañete, Penélope Serrano Ortiz, Andrew S. Kowalski, Cecilio Oyonarte, Francisco Domingo |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121691
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| Publikation (Nr.) |
 EGU/EGU2016-502.pdf |
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| Zusammenfassung |
| Subterranean ventilation, conceived as the advective transport of CO2-rich air from the
vadose zone to the atmosphere through a porous media (i.e. soil or snow; Sánchez-Cañete et
al., 2013), has arisen as an important process contributing to the carbon (C) balance of
Mediterranean ecosystems (Kowalski et al., 2008; Sánchez-Cañete et al., 2011; Serrano-Ortiz
et al., 2014), apart from other well-known biotic processes (i.e. plant photosynthesis,
autotrophic and heterotrophic respiration). Recent studies have linked this subterranean CO2
release to fluctuations in the friction velocity or wind speed under drought conditions when
water-free soil pores enable air transport (Rey et al., 2012a, 2013), however, barometric
pressure variations has been suggested as another important driver (Sánchez-Cañete et al.,
2013).
In this study, we investigate this process in newly studied semi-arid grassland located in SE
Spain, as the ideal ecosystem to do so given the great length of the dry season and the
slight biotic activity limited to the winter season. Preliminary results, based on
unpublished analyzed eddy covariance data and subterranean CO2 molar fraction
measurements, confirm the presence of ventilation events from May to October
for seven years 2009-2015. During these events, increases in the friction velocity
correlates with sizeable CO2 emissions of up to ca.10 μmol m−2 s−1, and CO2 molar
fraction regularly drops 2000-3000 ppm just after the turbulence peak, at several
depths below the soil surface (0.15 and 1.5 m). Additionally, during the driest period
(July-August), the friction velocity explains from 37% to 57% of the net C emission
variability. On the other hand, the model residuals do not show a significant relationship,
neither with air pressure nor with soil water content. Overall, the results found in
this newly monitored site demonstrate, as shown by past research, the relevance
of subterranean ventilation as a key process in the C balance of Mediterranean
ecosystems. |
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