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| Titel |
The physical origins of rapid soil CO2 release following wetting |
| VerfasserIn |
Stanislaus Schymanski, Lina Grahm, Dani Or |
| 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 |
250149722
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| Publikation (Nr.) |
 EGU/EGU2017-14101.pdf |
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| Zusammenfassung |
| A rainfall event after an extended dry period is known to produce large spikes in CO2
release from soil, a phenomenon referred to as the "Birch effect". The Birch effect is
commonly attributed to biological factors, such as the rapid activation of dormant
microbial populations and stimulation of soil organic carbon turnover. Evidence
suggests that CO2 emissions set in at time scales too short for microbial activation
and growth (seconds to minutes after onset of wetting). We conducted controlled
wetting experiments on sterilized soil in the lab showing CO2 efflux dynamics
that are consistent in magnitude with those reported in field studies (up to 4 mmol
m−2 s−1 per mm of precipitation). The explanation proposed is purely physical,
involving desorption of CO2 from soil surfaces as it is replaced by the more polar
water during wetting. We present experimental results and a CO2 adsorption and
desorption model that lend credence to the notion that a large fraction of the early
soil CO2 emission during wetting (minutes to an hour) is associated with physical
processes independent of microbial activity. This suggests that a significant amount of
atmospheric CO2 becomes bound to soil surfaces during dry seasons and is rapidly
released at the onset of wet seasons world-wide, irrespective of the soil organic carbon
cycle. |
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