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| Titel |
Greenhouse gases dissolved in soil solution - often ignored, but important? |
| VerfasserIn |
Daniel Weymann, Nicolas Brueggemann, Thomas Puetz, Harry Vereecken |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093644
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| Publikation (Nr.) |
 EGU/EGU2014-8558.pdf |
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| Zusammenfassung |
| Flux measurements of climate-relevant trace gases from soils are frequently undertaken in
contemporary ecosystem studies and substantially contribute to our understanding of
greenhouse gas balances of the biosphere. While the great majority of such investigations
builds on closed chamber and eddy covariance measurements, where upward gas
fluxes to the atmosphere are measured, fewest concurrently consider greenhouse gas
dissolution in the seepage and leaching of dissolved gases via the vadose zone to the
groundwater.
Here we present annual leaching losses of dissolved N2O and CO2 from arable,
grassland, and forest lysimeter soils from three sites differing in altitude and climate. We aim
to assess their importance in comparison to direct N2O emission, soil respiration, and further
leaching parameters of the C- and N cycle. The lysimeters are part of the Germany-wide
lysimeter network initiative TERENO-SoilCan, which investigates feedbacks of climate
change to the pedosphere on a long-term scale. Soil water samples were collected weekly
from different depths of the profiles by means of suction cups. A laboratory pre-experiment
proved that no degassing occurred under those sampling conditions. We applied the
headspace equilibration technique to determine dissolved gas concentrations by gas
chromatography.
The seepage water of all lysimeters was consistently supersaturated with N2O and CO2
compared to water equilibrated ambient air. In terms of N2O, leaching losses increased in
the ascending order forest, grassland, and arable soils, respectively. In case of the
latter soils, we observed a strong variability of N2O, with dissolved concentrations
up to 23 μg N L-1. However, since seepage discharge of the arable lysimeters
was comparatively small and mostly limited to the hydrological winter season,
leached N2O appeared to be less important than direct N2O emissions. In terms of
dissolved CO2,our measurements revealed considerable leaching losses from the
mountainous forest and grassland soils, based on concentrations up to 24 mg C L-1 and
high seepage discharge. Such losses turned out to be similarly important like soil
respiration, particularly during winter when temperature-dependent soil respiration
declined.
In conclusion, the results of the first year of our measurements provide evidence that
dissolved greenhouse gases should be considered in studies which aim to assess full
greenhouse gas balances, particularly in ecosystems where hydrological conditions favour
microbial activity and high leaching losses. |
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