Flussi di energia e di carbonio di un ecosistema di tundra umida siberiana
Author(s)
Corradi, Chiara Assunta Riccarda
Date Issued
November 23, 2007
Type
Doctoral Thesis
Abstract
Carbon dioxide, energy flux measurements and methane chamber measurements were carried out in an arctic wet tussock grassland located on a flood-plane of the Kolyma river in NE Siberia over a summer period of 104 days in 2002, 167 days in 2003 and 164 days in 2004.
The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 13 °C (max. temperature at midday: 28 °C by end July), dry air (max. vapour pressure deficit at midday: 25 to 40 hPa) and low rainfall of 50 to 80 mm during summer (July to September). Summer evaporation (July to September: 103 mm in 2002, 160 mm in 2003 and 135) exceeded rainfall by a factor of 2. The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be -38 g C m-2 yr-1 from July 2002 to June 2003 and -17 g C m-2 yr-1 from July 2003 to June 2004 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 10 to 13gCm-2 measured over 60 days) was about 30 % of C-uptake during the same period of time (end July to end September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 versus CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200 gCequivalent m-2 yr-1). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2-C sink. These results add to knowledge of trace gas fluxes from arctic vegetation. There is no direct socio-economic impact of such results, but the data have policy implications within the Kyoto agreement, because they show that the arctic vegetation is a trace gas source even if it is a CO2 sink. Carbon dioxide, energy flux measurements and methane chamber measurements were carried out in an arctic wet tussock grassland located on a flood-plane of the Kolyma river in NE Siberia over a summer period of 104 days in 2002, 167 days in 2003 and 164 days in 2004. The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 13 °C (max. temperature at midday: 28 °C by end July), dry air (max. vapour pressure deficit at midday: 25 to 40 hPa) and low rainfall of 50 to 80 mm during summer (July to September). Summer evaporation (July to September: 103 mm in 2002, 160 mm in 2003 and 135) exceeded rainfall by a factor of 2. The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be -38 g C m-2 yr-1 from July 2002 to June 2003 and -17 g C m-2 yr-1 from July 2003 to June 2004 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 10 to 13gCm-2 measured over 60 days) was about 30% of C-uptake during the same period of time (end July to end September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 versus CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200 gCequivalent m-2 yr-1). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2-C sink. These results add to knowledge of trace gas fluxes from arctic vegetation. There is no direct socio-economic impact of such results, but the data have policy implications within the Kyoto agreement, because they show that the arctic vegetation is a trace gas source even if it is a CO2 sink.
The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 13 °C (max. temperature at midday: 28 °C by end July), dry air (max. vapour pressure deficit at midday: 25 to 40 hPa) and low rainfall of 50 to 80 mm during summer (July to September). Summer evaporation (July to September: 103 mm in 2002, 160 mm in 2003 and 135) exceeded rainfall by a factor of 2. The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be -38 g C m-2 yr-1 from July 2002 to June 2003 and -17 g C m-2 yr-1 from July 2003 to June 2004 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 10 to 13gCm-2 measured over 60 days) was about 30 % of C-uptake during the same period of time (end July to end September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 versus CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200 gCequivalent m-2 yr-1). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2-C sink. These results add to knowledge of trace gas fluxes from arctic vegetation. There is no direct socio-economic impact of such results, but the data have policy implications within the Kyoto agreement, because they show that the arctic vegetation is a trace gas source even if it is a CO2 sink. Carbon dioxide, energy flux measurements and methane chamber measurements were carried out in an arctic wet tussock grassland located on a flood-plane of the Kolyma river in NE Siberia over a summer period of 104 days in 2002, 167 days in 2003 and 164 days in 2004. The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 13 °C (max. temperature at midday: 28 °C by end July), dry air (max. vapour pressure deficit at midday: 25 to 40 hPa) and low rainfall of 50 to 80 mm during summer (July to September). Summer evaporation (July to September: 103 mm in 2002, 160 mm in 2003 and 135) exceeded rainfall by a factor of 2. The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be -38 g C m-2 yr-1 from July 2002 to June 2003 and -17 g C m-2 yr-1 from July 2003 to June 2004 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 10 to 13gCm-2 measured over 60 days) was about 30% of C-uptake during the same period of time (end July to end September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 versus CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200 gCequivalent m-2 yr-1). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2-C sink. These results add to knowledge of trace gas fluxes from arctic vegetation. There is no direct socio-economic impact of such results, but the data have policy implications within the Kyoto agreement, because they show that the arctic vegetation is a trace gas source even if it is a CO2 sink.
File(s)![Thumbnail Image]()
Name
ccorradi_tesid.pdf
Size
8.89 MB
Format
Adobe PDF
Checksum (MD5)
d4cab47c52bd6c50116bc15857b4c919