HR: 1340h
AN: B23A-0929    [Abstracts]
TI: Quantifying Terrestrail Carbon Trends in the Conterminous U.S. - Overall Approach and Results From the Appalachian Forests
AU: * Liu, J
EM: jxliu@usgs.gov
AF: NRC Research Associate Program, EROS Data Center , Sioux Falls, SD 57198 United States
AU: Liu, S
EM: sliu@usgs.gov
AF: SAIC, EROS Data Center, Sioux Falls, SD 57198 United States
AU: Loveland, T R
EM: loveland@usgs.gov
AF: USGS, EROS Data Center, Sioux Falls, SD 57198 United States
AB: Estimating dynamic terrestrial ecosystem carbon (C) sources and sinks over large areas is crucial for C management, but it is complicated due to the variations of climate, soil, vegetation, and disturbances. The scaling of C sources and sinks from field to regional level has been challenging. As part of the U.S. Carbon Trends Project, we simulated the forest ecosystem C sequestration of the Appalachians region for the period of 1972 to 2000 using the General Ensemble biogeochemical Modeling System (GEMS). Land cover change was detected using sequential Landsat imagery within seventy-two sample blocks across the region. GEMS used the 60-meter resolution land cover change maps to capture stand-replacing events and used forest inventory data to estimate non-stand-replacing events that was not captured in those maps. GEMS also used Monte Carlo approaches to deal with spatial scaling issues such as initialization of forest age and soil properties. Ensemble simulations were performed to incorporate the uncertainties of input data. Simulated results show that from 1972 to 2000 the net primary productivity (NPP), net ecosystem productivity (NEP) and net biome productivity (NBP) ranged from 481 to 731(average 595), 97 to 329 (average 173), and 50 to 308 (average 136) g C m$^{-2}$ yr$^{-1}$, respectively. The inter-annual variability was mostly driven by climate. The inter-ecoregion variability showed the impacts from soil and land cover change. Model test revealed that without dynamic land cover change the annual C sink strength for this region would be over-estimated about 20 to 70 percent of the normal condition C sink. This over-estimated C sink was close to the amount of forest harvesting C in the normal condition. Detailed C budgets for the year 2000 were also analyzed. Within a total 148,000 km$^{2}$ forested area, average forest ecosystem C density was 161 Mg C ha$^{-1}$ , of which 81 Mg C ha$^{-1}$ was in biomass and 80 Mg C ha$^{-1}$ was in litter and soil. The total C stock of the Appalachian forests was estimated to be 2,375 Tg C including 1,191 Tg C in living biomass and 1,184 Tg C in litter and soil. The total net C sink of the forest ecosystem in 2000 was 13 Tg C y$^{-1}$.
DE: 9350 North America
DE: 4805 Biogeochemical cycles (1615)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting