HR: 0800h
AN: B11A-0131    [Abstracts]
TI: The Interplay Between the Carbon and Water Cycles Along a Successional Gradient in the Southeastern US
AU: * Stoy, P C
EM: pcs3@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: * Stoy, P C
EM: pcs3@duke.edu
AF: Graduate Program in Ecology, Duke University, P.O. Box 90329, Durham, NC 27708
AU: Katul, G G
EM: gaby@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Katul, G G
EM: gaby@duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, P.O. Box 90287, Durham, NC 27708-0287
AU: Juang, J
EM: jj19@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Siqueira, M B
EM: mbs4@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Palmroth, S
EM: sari.palmroth@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Kim, H
EM: hk11@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: McCarthy, H R
EM: hrm@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Oishi, A C
EM: acoishi@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Oishi, A C
EM: acoishi@duke.edu
AF: Graduate Program in Ecology, Duke University, P.O. Box 90329, Durham, NC 27708
AU: Uebelherr, J M
EM: jmu@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AU: Uebelherr, J M
EM: jmu@duke.edu
AF: Graduate Program in Ecology, Duke University, P.O. Box 90329, Durham, NC 27708
AU: Oren, R
EM: ramoren@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Levine Science Research Center, P.O. Box 90328, Durham, NC 27708-0328
AB: We measured net ecosystem exchange of CO$_{2}$ (NEE) and evapotranspiration (ET) for three years at adjacent old-field (OF), {\it Pinus taeda} dominated planted pine forest (PP) and mature oak-hickory forest (HW) ecosystems in the southeastern US (SE). The ecosystems serve as a model for post-agricultural succession, represent dominant ecosystem types in the SE, and experience identical edaphic and climatic conditions, which during the measurement period included severe drought. We present a sensitivity analysis on NEE estimates using eddy-covariance measurements alone, then constrain NEE using independent estimates of soil and ecosystem respiration and canopy carbon assimilation. Annual NEE differed greatly among ecosystems during mild drought (2001), with +150 (i.e., C source), -500 and -250 g C m$^{-2}$ y$^{-1}$ at OF, PP, and HW, respectively. During the severe drought of 2002, the magnitude of annual NEE was reduced by 350 g C m$^{-2}$ y$^{-1}$ (70%) at PP, but differed by less than 50 g C m$^{-2}$ y$^{-1}$ at the other two ecosystems. During the wetter-than-average year (2003), OF became a slight C sink, NEE at PP recovered slightly to -250 g C m$^{-2}$ y$^{-1}$, and the magnitude of NEE at HW decreased by 50 g C m$^{-2}$ y$^{-1}$ due in part to light limitation. Thus, we observed a progressive decoupling of the carbon and water cycles along the successional gradient. Over the next 40 years, the land cover area of pine plantations in the SE is predicted to double, and the land cover area of upland hardwood forests, to decline. Our results suggest that increasing the fractional cover of pine plantation will make variability in the SE C sink more sensitive to variability in the hydrologic cycle.
DE: 1803 Anthropogenic effects
DE: 1812 Drought
DE: 1851 Plant ecology
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting