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| Titel |
Pronounced short-term temporal dynamics of methane fluxes during the snowmelt period at a boreal peatland in NW Russia |
| VerfasserIn |
M. Gažovič, L. Kutzbach, P. Schreiber, C. Wille, M. Wilmking |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027210
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| Zusammenfassung |
| Peatlands are one of the major natural sources of methane (CH4), but the quantification of
efflux is uncertain especially during winter, fall and the highly dynamic spring thaw period.
Here we report unexpected diurnal variations in methane fluxes as measured using the eddy
correlation technique lasting several days during the snow thawing period at a boreal peatland
in NW Russia. The beginning of snowmelt in 2008 was characterized by moderate CH4
fluxes of ~0.5-1.8 mg m-2 h-1. However, we found unexpected pattern in CH4 fluxes from
21.04-3.05.2008 when fluxes showed strong diurnal variability apparently controlled by
changes in the surface temperature. Hourly CH4 fluxes were ~0.5 mg m-2 h-1
during night and reached as much as ~5 mg m-2 h-1 during midday. An empirical
model based on linear reduced major axis regression was used to gap-fill the time
series with surface temperature as a predictor. There was a lag of one hour between
the diurnal maxima of surface temperature and CH4 flux, respectively. The fluxes
started to decrease earlier than the surface temperature reached its maximum. The
most likely explanation is that thawing and refreezing of an ice layer at the wet
peatland micro-sites due to oscillating surface temperatures above 0 Ë C during the
days and below 0 Ë C during the nights, which was observed during this period of
the year, led to a pronounced diurnal variability of the resistance for gas diffusion
from the soil and open water bodies to the atmosphere. Apparently, physical factors
influencing the gas transport processes have a stronger effect on CH4 efflux than
microbiological ones during the spring whereas the control of CH4 efflux is dominated by
biological processes during the vegetation period. The evidence of strong temporal
variation on an hourly time scale is important when estimates of cold season fluxes
are made to quantify seasonal or annual CH4 emissions, especially when static
chambers are applied under climatic conditions favouring these events to prevent
over or underestimation of CH4 fluxes depending on sampling time during the day. |
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