HR: 0800h
AN: B11D-0764    [Abstracts]
TI: Simulated Response of Conterminous United States Ecosystems to Climate Change at Different Levels of Fire Suppression, CO2,and Growth Response to CO2
AU: * Lenihan, J
EM: lenihan@fsl.orst.edu
AF: USDA Forest Service, PNW Research Station 3200 SW Jefferson Way, Corvallis, OR 97330, United States
AU: Bachelet, D
EM: dbachelet@tnc.org
AF: The Nature Conservancy, 120 East Union, Olympia, WA 98501, United States
AU: Neilson, R
EM: rneilson@fs.fed.us
AF: USDA Forest Service, PNW Research Station 3200 SW Jefferson Way, Corvallis, OR 97330, United States
AU: Drapek, R
EM: drapek@fsl.orst.edu
AF: USDA Forest Service, PNW Research Station 3200 SW Jefferson Way, Corvallis, OR 97330, United States
AB: The impact of fire management, CO2 levels, and the growth response to CO2 on the response of ecosystems to climate change scenarios produced by three different General Circulation Models (GCMs) was simulated for the conterminous United States by the MC1 Dynamic Global Vegetation Model (DGVM). Distinct regional trends in response to projected climatic change were evident across all combinations of the experimental factors. In the eastern half of the U.S., the average response to relatively large increases in temperature and decreases in precipitation was an 11 percent loss of total ecosystem carbon. In the West, the response to increases in precipitation and relatively small increases in temperature was an 5 percent increase in total carbon stocks. Simulated fire suppression reduced average carbon losses in the East to about 6 percent, and preserved forests which were largely converted to woodland and savanna in the absence of fire suppression. Across the west, unsuppressed fire maintained near constant carbon stocks despite increases in vegetation productivity. With fire suppression, western carbon stocks increased by 10 percent and most shrublands were converted to woodland or even forest. With a relatively high level of growth sensitivity to CO2, total ecosystem carbon pools at the end of the century were on average about 9-10 percent larger in both regions of the U.S. compared to a low level of CO2 sensitivity . The western U.S. gained enough carbon to counter losses from unsuppressed fire only with the high CO2 sensitivity, especially in conjunction with the higher CO2 level. In the eastern U.S., fire suppression was sufficient to produce a simulated carbon sink only with both the high CO2 level and high CO2 sensitivity. Considerable uncertainty exists with respect to the impacts of global warming on the ecosystems of the conterminous U.S., some of which resides in the future trajectory of atmospheric CO2, in the direct response of vegetation to increasing CO2, and in future tradeoffs among different fire management options, as illustrated in this study.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1630 Impacts of global change (1225)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting