346
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
30 mg CO2*m- 2 *h- 1 and 300 mg CO2*m-2*h- 1 (Figure. 3b). The average CO 2 -losses were
about 170 mg CO2*m- 2 *h- 1 and thus some 40 % higher than at the polygon depression.
CO2-emmissions from soil at both sites revealed a strong diurnal course with an amplitude of
as much as 160 mg CO2*m- 2 *h- 1 over less than 24 h. The emmissions showed best
correlation with soil temperature at 2 cm depth (Table 3). Also, the total magnitude of
emmissions were modified by watertable position, especially at the polygon depression. CO 2 -
emissions increased with falling watertable, especially pronounced if the change of watertable
occured close to the soil surface.
In the polygon depressions carbon dioxide emmissions from soils ranged from 20 to
260 mg CO 2 *m- 2 *h- 1 over the field season, showing an average of 120 mg CO 2 *m-2*h- 1
(Figure.3a). Carbon dioxide emissions of the polygon apex showed a minimum of
30 mg CO2*m- 2 *h- 1 and a maximum of 300 mg CO2*m-2*h- 1 (Figure.3b). The average CO 2 -
losses were about 170 mg CO2*m- 2 *h- 1 and thus some 40 % higher than in the polygon
depression.
CO2-emmissions from soil at both sites revealed a strong diurnal course with a maximum of
about 160 mg CO2*m- 2 *h- l • The best temperature correlation of the emmissions could be
obtained with soil temperatures at 2 cm depth (Table 3). Also, the total magnitude of
emmissions were modified by watertable position. CO2-emissions were increasing with falling
watertable.
Methane emissions
The methane emission rates from the polygon depression ranged between 1.8 and
5.2 mg CH4 *m- 2 *h- 1 (mean: 3.1 mg CH4 *m- 2 *h- 1 , compare Figure. 3a). The emmissions
varied in dependence of the water table position. Falling of the water table below the soil
surface caused a decrease of methane emissions. After heavy rainfalls in the first days of
August the water table rose up to 6 cm above the ground. With a delay of 4 days the methane
emission rates also rose from about 2.1 up to 3.1 mg CH4 *m- 2 *h- 1 in the polygon
depression.
The methane emissions from the dry apex part of the investigated polygon ranged between
o and 0.2 mg CH4 *m- 2 *h- 1 (mean: 0.1 mg CH4 *m-2*h- 1 , Figure.3b), sometimes the
emmissions were negative, thus the apex became a sink for methane.
Magnitude of methane emissions decreased during the summer period. The methane
emissions showed no diurnal variations. The mean methane emmissions of the whole polygon
area is 2.2 mg CH4 *m- 2 *h- 1 between middle of July until beginning of September (see also
Samarkin et aI., 1997, Samarkin et aI., 1997, this volume).
Discussion
The results of this study indicate that CO2-emmissions from soils of polygon depression and
polygon apex differ as a result of microclimatical differences as well as water regime. The
higher temperature in 2 cm depth observed at the polygon apex compared to the polygon
depression, as well as the permanently about 8 cm lower watertable at the polygon apex lead to
CO2-emissions of an average of 60 % more at the apex than at the depression site. In total,
CO 2 -emmissions presented here were higher than those measured by Bunnel et al. (1975) in the
wet sedge tundra of Barrow (60-140 mg CO2*m- 2 *h- 1 ), but within the same range than values
from a wet sedge tundra in the southern tundra belt of Taymyr Peninsula measured during
summer of 1995 (Sommerkorn, unpublished data). Previous studies have indicated that factors
controlling the ecosystem and soil emmissions are complex and site specific, but frequently, as
in the present paper, the temperature was identified as the primary environmental factor (e.g.
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
30 mg CO2*m- 2 *h- 1 and 300 mg CO2*m-2*h- 1 (Figure. 3b). The average CO 2 -losses were
about 170 mg CO2*m- 2 *h- 1 and thus some 40 % higher than at the polygon depression.
CO2-emmissions from soil at both sites revealed a strong diurnal course with an amplitude of
as much as 160 mg CO2*m- 2 *h- 1 over less than 24 h. The emmissions showed best
correlation with soil temperature at 2 cm depth (Table 3). Also, the total magnitude of
emmissions were modified by watertable position, especially at the polygon depression. CO 2 -
emissions increased with falling watertable, especially pronounced if the change of watertable
occured close to the soil surface.
In the polygon depressions carbon dioxide emmissions from soils ranged from 20 to
260 mg CO 2 *m- 2 *h- 1 over the field season, showing an average of 120 mg CO 2 *m-2*h- 1
(Figure.3a). Carbon dioxide emissions of the polygon apex showed a minimum of
30 mg CO2*m- 2 *h- 1 and a maximum of 300 mg CO2*m-2*h- 1 (Figure.3b). The average CO 2 -
losses were about 170 mg CO2*m- 2 *h- 1 and thus some 40 % higher than in the polygon
depression.
CO2-emmissions from soil at both sites revealed a strong diurnal course with a maximum of
about 160 mg CO2*m- 2 *h- l • The best temperature correlation of the emmissions could be
obtained with soil temperatures at 2 cm depth (Table 3). Also, the total magnitude of
emmissions were modified by watertable position. CO2-emissions were increasing with falling
watertable.
Methane emissions
The methane emission rates from the polygon depression ranged between 1.8 and
5.2 mg CH4 *m- 2 *h- 1 (mean: 3.1 mg CH4 *m- 2 *h- 1 , compare Figure. 3a). The emmissions
varied in dependence of the water table position. Falling of the water table below the soil
surface caused a decrease of methane emissions. After heavy rainfalls in the first days of
August the water table rose up to 6 cm above the ground. With a delay of 4 days the methane
emission rates also rose from about 2.1 up to 3.1 mg CH4 *m- 2 *h- 1 in the polygon
depression.
The methane emissions from the dry apex part of the investigated polygon ranged between
o and 0.2 mg CH4 *m- 2 *h- 1 (mean: 0.1 mg CH4 *m-2*h- 1 , Figure.3b), sometimes the
emmissions were negative, thus the apex became a sink for methane.
Magnitude of methane emissions decreased during the summer period. The methane
emissions showed no diurnal variations. The mean methane emmissions of the whole polygon
area is 2.2 mg CH4 *m- 2 *h- 1 between middle of July until beginning of September (see also
Samarkin et aI., 1997, Samarkin et aI., 1997, this volume).
Discussion
The results of this study indicate that CO2-emmissions from soils of polygon depression and
polygon apex differ as a result of microclimatical differences as well as water regime. The
higher temperature in 2 cm depth observed at the polygon apex compared to the polygon
depression, as well as the permanently about 8 cm lower watertable at the polygon apex lead to
CO2-emissions of an average of 60 % more at the apex than at the depression site. In total,
CO 2 -emmissions presented here were higher than those measured by Bunnel et al. (1975) in the
wet sedge tundra of Barrow (60-140 mg CO2*m- 2 *h- 1 ), but within the same range than values
from a wet sedge tundra in the southern tundra belt of Taymyr Peninsula measured during
summer of 1995 (Sommerkorn, unpublished data). Previous studies have indicated that factors
controlling the ecosystem and soil emmissions are complex and site specific, but frequently, as
in the present paper, the temperature was identified as the primary environmental factor (e.g.