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| Titel |
High temporal frequency measurements of greenhouse gas emissions from soils |
| VerfasserIn |
K. Savage, R. Phillips, E. Davidson |
| 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. 10 ; Nr. 11, no. 10 (2014-05-21), S.2709-2720 |
| Datensatznummer |
250117419
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| Publikation (Nr.) |
 copernicus.org/bg-11-2709-2014.pdf |
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| Zusammenfassung |
Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)
are the most important anthropogenic greenhouse gases (GHGs). Variation in soil
moisture can be very dynamic, and it is one of the dominant factors
controlling the net exchange of these three GHGs. Although
technologies for high-frequency, precise measurements of CO2 have been
available for years, methods for measuring soil fluxes of CH4 and
N2O at high temporal frequency have been hampered by lack of appropriate
technology for in situ real-time measurements. A previously developed
automated chamber system for measuring CO2 flux from soils was
configured to run in line with a new quantum cascade laser (QCLAS) instrument
that measures N2O and CH4. Here we present data from a forested
wetland in Maine and an agricultural field in North Dakota, which provided
examples of both net uptake and production for N2O and CH4. The
objective was to provide a range of conditions in which to run the new system
and to compare results to a traditional manual static-chamber method.
The high-precision and more-than-10-times-lower minimum detectable flux of
the QCLAS system, compared to the manual system, provided confidence in
measurements of small N2O uptake in the forested wetland. At the
agricultural field, the greatest difference between the automated and manual
sampling systems came from the effect of the relatively infrequent manual
sampling of the high spatial variation, or "hot spots", in GHG fluxes.
Hot spots greatly influenced the seasonal estimates, particularly for
N2O, over one 74-day alfalfa crop cycle. The high temporal frequency of
the automated system clearly characterized the transient response of all
three GHGs to precipitation and demonstrated a clear diel pattern related to
temperature for GHGs. A combination of high-frequency automated and
spatially distributed chambers would be ideal for characterizing hot
spots and "hot moments" of GHG fluxes. |
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