 |
| Titel |
The exchange of carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia |
| VerfasserIn |
L. Kutzbach, C. Wille, E.-M. Pfeiffer |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 5 ; Nr. 4, no. 5 (2007-10-18), S.869-890 |
| Datensatznummer |
250001967
|
| Publikation (Nr.) |
 copernicus.org/bg-4-869-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| The exchange fluxes of carbon dioxide between wet arctic polygonal tundra
and the atmosphere were investigated by the micrometeorological eddy
covariance method. The investigation site was situated in the centre of the
Lena River Delta in Northern Siberia (72°22' N, 126°30' E). The study
region is characterized by a polar and distinctly continental climate, very
cold and ice-rich permafrost and its position at the interface between the
Eurasian continent and the Arctic Ocean. The soils at the site are
characterized by high organic matter content, low nutrient availability and
pronounced water logging. The vegetation is dominated by sedges and mosses.
The micrometeorological campaigns were performed during the periods
July–October 2003 and May–July 2004 which included the period of snow and
soil thaw as well as the beginning of soil refreeze. The main CO2
exchange processes, the gross photosynthesis and the ecosystem respiration,
were found to be of a generally low intensity. The gross photosynthesis
accumulated to −432 g m−2 over the photosynthetically active period
(June–September). The contribution of mosses to the gross photosynthesis was
estimated to be about 40%. The diurnal trend of the gross photosynthesis
was mainly controlled by the incoming photosynthetically active radiation.
During midday, the photosynthetic apparatus of the canopy was frequently
near saturation and represented the limiting factor on gross photosynthesis.
The synoptic weather conditions strongly affected the exchange fluxes of
CO2 by changes in cloudiness, precipitation and pronounced changes of
air temperature. The ecosystem respiration accumulated to +327 g m−2
over the photosynthetically active period, which corresponds to 76% of
the CO2 uptake by photosynthesis. However, the ecosystem respiration
continued at substantial rates during autumn when photosynthesis had ceased
and the soils were still largely unfrozen. The temporal variability of the
ecosystem respiration during summer was best explained by an exponential
function with surface temperature, and not soil temperature, as the
independent variable. This was explained by the major role of the plant
respiration within the CO2 balance of the tundra ecosystem. The wet
polygonal tundra of the Lena River Delta was observed to be a substantial
CO2 sink with an accumulated net ecosystem CO2 exchange of −119 g
m−2 over the summer and an estimated annual net ecosystem CO2
exchange of −71 g m−2. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|