Document: ANN-3-34-52

Carbon storage and flux in a salt marsh exposed to elevated CO₂ .

MARSH, A.S.* ¹, J.P.MEGONIGAL ² and B.G.DRAKE ¹

Smithsonian Environmental Research Center ¹
George Mason University ²

Abstract:
The objective of our study was to identify the fate of 5.6 kg C m^-2 of 'excess' carbon assimilated over a 12-year period (1988-1999) by a C3 salt marsh exposed to elevated CO₂. We focused on three potential carbon sinks in a community dominated by the C3 plant Scirpis olneyi: Winter ecosystem respiration, hydrologic export, and the soil carbon pool. Potential carbon sinks were also analyzed in an adjacent C4 community dominated by Spartina patens. Winter whole-system respiration rates were not effected by the CO₂ treatment in either community. Hydrologic export may account for as much as 23% of the 'excess' carbon in the Scirpus community as plots exposed to elevated CO₂ showed a consistent increase in dissolved inorganic carbon of 6 to 27% compared to ambient levels. There was no increase in dissolved inorganic carbon in the interstitial waters of the Spartina community with elevated CO₂, or of dissolved organic carbon in the interstitial waters of either community. We are currently analyzing soil samples to determine the size and recalcitrance of the soil carbon pool.

Keywords: elevated CO₂, carbon sequestration

This abstract is being presented at: 1:00 PM in session:
Oral Session #52: Carbon Storage in Ecosystems.