Influence of High Temperature on End-of-Season Tundra CO2 Exchange |
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Authors: | Sofie Mertens Ivan Nijs Mark Heuer Fred Kockelbergh Louis Beyens Andy Van Kerckvoorde Ivan Impens |
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Institution: | (1) Research Group of Plant and Vegetation Ecology, Department of Biology, University of Antwerp (UIA), Universiteitsplein 1, B-2610 Wilrijk, Belgium, BE;(2) Polar Ecology, Limnology and Paleobiology Unit, Department of Biology, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium, BE |
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Abstract: | The high-arctic terrestrial environment is generally recognized as one of the world's most sensitive areas with regard to
global warming. In this study, we examined the influence of an isolated warm period on net ecosystem carbon dioxide (CO2) exchange at high latitude during autumn. Using the Free Air Temperature Increase (FATI) technique, we manipulated air, soil,
and vegetation temperatures in late August in a tundra site at Zackenberg in the National Park of North and East Greenland
(74°N 21°W). The consequences for gross canopy photosynthesis, canopy respiration, and belowground respiration of increasing
these temperatures by approximately 2.5°C were determined with closed dynamic CO2 exchange systems. Under current temperatures, the ecosystem acted as a net CO2 source, releasing 19 g CO2-C m−2 over the 14-day study period. Warm soils and senescing vegetation in autumn were unequivocally responsible for this efflux.
Heating enhanced CO2 efflux to 29 g CO2-C m−2. This effect was attributed to a 39% increase in belowground respiration, which was the main component of the carbon (C)
budget. Gross photosynthesis, on the other hand, was not affected significantly by the simulated warming. Although the aftereffects
of an isolated warm period on the C balance in early winter could be significant, simulations with a simple C budget model
suggest that soil carbon pools are not affected to a great extent by such a climatic disturbance. The influence on atmospheric
carbon, however, appears to be significant.
Received 9 June 2000; accepted 20 December 2000. |
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Keywords: | : canopy photosynthesis carbon balance fall warming Free Air Temperature Increase simulation model soil respiration tundra |
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