HR: 17:30h
AN: B34A-07    [Abstracts]
TI: Nitrogen Deposition, Nitrogen Saturation and Carbon Interactions in Mid-Atlantic Forest Ecosystems
AU: * Pan, Y
EM: ypan@fs.fed.us
AF: USDA Forest Service, Northern Global Change Program, 11 campus blvd, Newtwon Square, PA 19073, United States
AU: Hom, J
EM: jhom@fs.fed.us
AF: USDA Forest Service, Northern Global Change Program, 11 campus blvd, Newtwon Square, PA 19073, United States
AU: Birdsey, R
EM: rbirdsey@fs.fed.us
AF: USDA Forest Service, Northern Global Change Program, 11 campus blvd, Newtwon Square, PA 19073, United States
AU: McCullough, K
EM: kmccullough@fs.fed.us
AF: USDA Forest Service, Northern Global Change Program, 11 campus blvd, Newtwon Square, PA 19073, United States
AB: Scientists have long debated whether anthropogenic inputs of nitrogen deposition over the decades have caused N saturation in northeastern forests. Although regulations for NOx emissions reductions have been implemented, N deposition showed limited change during the 1990s for much of the eastern United States until recent trends showing steady reduction of N deposition. In this study, we investigated how forest ecosystems respond to long term N deposition in terms of changing productivity and function for retaining inputs of nitrogen deposition. We applied our GIS variant of the PnET-CN model for this analysis. Besides modeling forest productivity, N retention and losses associated with N deposition trends over last few decades, we also predicted and evaluated responses of forest ecosystems into 2050 under five future nitrogen deposition scenarios: N deposition before regulations, holding emissions steady at 1998 levels, and three scenarios that extend the national EPA nitrogen deposition trends data from 1995-2005 to simulate possible trajectories of nitrogen reduction levels. The model results show that the increased N deposition has increased forest productivity in the region by 18%, but may reduce carbon accumulation in growing stock as forests saturated with N inputs. The predictions for the future N deposition scenarios up to 2050 attested that forests have approached N saturation under current N deposition level. The model estimates indicate insignificant increases in forest NPP with additional N inputs above 2000 levels, but show different forest N losses under different N deposition scenarios. Additional N inputs will only cause more N exports from forests to aquatic systems in the region, which could range from double to more than tenfold dependent on regulation strength of N deposition.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0478 Pollution: urban, regional and global (0345, 4251)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting