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| Titel |
Soil Greenhouse Gas Flux Measurements in a Pacific Northwestern Douglas-fir Forest |
| VerfasserIn |
I. Hawthorne, M. S. Johnson, R. Jassal, T. A. Black, C. Webster |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250071057
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| Zusammenfassung |
| Forests and forest soils are dynamic sources and sinks for greenhouse gases (GHG). Climate
and management practices can impact the GHG balance of a forest. Motivated by
the contemporary scientific understanding of climate change, carbon (C) cycle
studies to date have largely been concerned with carbon dioxide (CO2) fluxes.
Methane (CH4) and nitrous oxide (N2O) are less abundant trace gases, but with large
greenhouse warming potentials and differing lifetimes in the atmosphere, CH4 and N2O
are also significant global warming contributors, warranting careful consideration
when trying to determine complete GHG balances. Soil fluxes of CO2, CH4 and
N2O were measured at a Pacific Northwestern Douglas-fir forest on Vancouver
Island, BC, Canada (49o 52’ N, 125o 20’ W). Samples were syringe collected (0, 3,
10, 20, 30 min) and transferred to pre-evacuated 12-ml vials (Exetainers, Labco
Limited, Buckinghamshire, UK) once a month (Oct-Dec, 2011) from each of 16
closed-chambers in order to determine soil GHG flux rates. Samples were analysed using
an Agilent 7890A Gas Chromatography (GC) system for CO2 and CH4 using a
Flame Ionisation Detector (FID) with methanizer, and for N2O using an Electron
Capture Detector (ECD). Resulting data were analysed using the HMR package
implemented with the R language for statistical computing to determine the best
fit for flux estimation considering linear and non-linear Hutchinson and Mosier
models. The presence of outliers and questionable features in the data resulted in the
need for careful data screening. Initial results suggest that the CH4sink strength
of these soils decrease during the cooling and increasingly wet autumn to winter
months (3.6-2.6 μmol m-2hr-1). Low concentrations of N2O made it difficult to
quantify any emissions (0.15-0.05 μmol m-2hr-1), while CO2 was emitted to
the atmosphere (2.05-0.75 μmol m-2s-1). Monthly results for Jan-Mar 2012 will
be included. Results of CO2 fluxes measured by GC using the closed-chambers
compared with a portable flow-through (4 L min-1) chamber with a LI-COR Inc LI 840
infrared gas analyzer using collars installed in close proximity will be presented.
Developments made on a flow-through chamber design for CH4 will be discussed. |
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