HR: 1340h
AN: H53E-0533    [Abstracts]
TI: Towards a Bottom-Up Scaling Strategy for Regional Carbon and Water Cycling - Field Testing Simple Models for Ecosystem Assimilation and Transpiration
AU: * Novick, K A
EM: kan2@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708 United States
AU: Katul, G G
EM: gaby@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708 United States
AU: Katul, G G
EM: gaby@duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, Box 90329, Durham, NC 27708 United States
AU: Juang, J
EM: jj19@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708 United States
AU: Siqueira, M B
EM: mbs4@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708 United States
AU: Stoy, P C
EM: pcs3@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708 United States
AB: Emerging international strategies to reduce greenhouse gas accumulation will rely on reliable regional- and continental-scale models of carbon and water cycling. To date, most regional estimates of carbon balance use a top-down scaling approach, which provides limited information about vegetative controls on land-atmosphere carbon and water vapor exchange. This study describes a model of ecosystem assimilation and transpiration that can be combined with meteorological Re-analysis data and satellite-derived land cover data to form a novel bottom-up scaling strategy over large land areas to further constrain regional-scale models of carbon and water cycling. Our model uses a Jarvis-type formulation to estimate bulk canopy conductance as a function of photosynthetic active radiation, vapor pressure deficit and soil moisture content. The conductance model is used to estimate Latent Heat Exchange (LE) and is combined with an assumed intercellular carbon dioxide concentration to model assimilation. Ecosystem transpiration is derived as the difference between modeled LE and evaporation as estimated with a simple radiation transfer model. As a logical step in scaling process, the assimilation and evapotranspiration models are field-tested with multiple years of eddy-covariance data from a successional gradient (grassland -- planted pine forest -- hardwood forest) in the Southeastern U.S. The sites have the same soil characteristics and climate, but differ in vegetation cover. Annual precipitation at our study site varied considerably during the study period (Jan 2002 -- Dec 2004), ranging from 260 mm below the long-term mean in 2002, and 150 mm above the mean in 2003. The study ecosystems differed in their response to these hydrologic perturbations, and the impacts of drought conditions on ecosystem assimilation and transpiration are discussed for each vegetation type.
DE: 0428 Carbon cycling (4806)
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
SC: Hydrology [H]
MN: Fall Meeting 2005