Response of Tundra Ecosystems to Elevated Atmospheric CO{sub 2}
OAK B188 Response of Tundra Ecosystems to Elevated Atmospheric CO{sub 2}. Atmospheric CO{sub 2} is expected to double by the end of the next century. Global mean increases in surface air temperature of 1.5-4.5 C are anticipated with larger increases towards the poles predicted. Changes in CO{sub 2}...
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| Format: | Report |
| Language: | English |
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University of California (United States)
1990
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| Online Access: | https://doi.org/10.2172/762799 https://digital.library.unt.edu/ark:/67531/metadc723863/ |
| Summary: | OAK B188 Response of Tundra Ecosystems to Elevated Atmospheric CO{sub 2}. Atmospheric CO{sub 2} is expected to double by the end of the next century. Global mean increases in surface air temperature of 1.5-4.5 C are anticipated with larger increases towards the poles predicted. Changes in CO{sub 2} levels and temperature could have major impacts on ecosystem functioning, including primary productivity, species composition, plant-animal interactions, and carbon storage. Until recently, there has been little direct information on the impact of changes in CO{sub 2} and temperature on native ecosystems. The study described here was undertaken to evaluate the effects of a 50 and 100% increase in atmospheric CO{sub 2}, and a 100% increase in atmospheric CO{sub 2} coupled with a 4 C summer air temperature rise on the structure and function of an arctic tussock tundra ecosystem. The arctic contains large stores of carbon as soil organic matter, much frozen in permafrost and currently not reactive or available for oxidation and release into the atmosphere. About 10-27% of the world's terrestrial carbon occurs in arctic and boreal regions, and carbon is accumulating in these regions at the rate of 0.19 GT y{sup -1}. Mean temperature increases of 11 C and summer temperature increases of 4 C have been suggested. Mean July temperatures on the arctic coastal plain and arctic foothills regions are 4-12 C, and mean annual temperatures are -7 to -13 C (Haugen, 1982). The projected temperature increases represent a substantial elevation above current temperatures which will have major impacts on physical processes such as permafrost development and development of the active layer, and on biological and ecosystem processes such as primary productivity, carbon storage, and species composition. Extreme nutrient and temperature limitation of this ecosystem raised questions of the responsiveness of arctic systems to elevated CO{sub 2}. Complex ecosystem interactions with the effects of increasing temperature and CO{sub 2} and changes in the physical environment made a priori predictions impossible. The short stature of the vegetation, the large number of individuals and species encountered in a relatively small area, and the short growing season were advantages which were thought to increase the probability that manipulation of physical conditions would result in short- and moderate-term response. These factors were coupled with an appreciation of the important role of the arctic as a major carbon store, a carbon sink, and the unpredictability of the carbon balance under future global conditions. These factors all contributed to the selection of the arctic as the first ecosystem for in situ manipulation of CO{sub 2} and temperature to determine effects on ecosystem structure and function. |
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