HR: 1340h
AN: B43D-1596    [Abstracts]
TI: Annual CO2 flux Across Moisture and Vegetation Gradients in the Amazon.
AU: * Baker, I T
EM: baker@atmos.colostate.edu
AF: Colorado State University, 1371 Campus Delivery, Fort Collins, CO 80523-2371, United States
AU: Prihodko, L
EM: lara@nrel.colostate.edu
AF: Colorado State University, 1371 Campus Delivery, Fort Collins, CO 80523-2371, United States
AU: Denning, A S
EM: denning@atmos.colostate.edu
AF: Colorado State University, 1371 Campus Delivery, Fort Collins, CO 80523-2371, United States
AB: The Amazon region is important to global climate both due to its large size and the large fluxes of energy, moisture and carbon exchanged there between the atmosphere and terrestrial biosphere. The spatial extent and large flux magnitude in the region firmly couple both the global circulation of the atmosphere and carbon flux to the region. Landsurface models have a poor record for simulating the annual cycle of exchange of carbon in the Amazon basin. In general, models have predicted uptake of carbon during the wet season and efflux during dry months, while observations show the opposite. Observational research has suggested a number of biogeophysical mechanisms to explain all or part of this annual cycle, including: 1) increased canopy phenological response to increased insolation during dry season 2) ability of deep roots to maintain transpiration as surface soil dries 3) Hydraulic redistribution of soil moisture by roots to bring deep water to surface. Using the Simple Biosphere model we were able to show that a control simulation has an erroneous response consistent with previous modeling efforts. We were also able to show that, when the above mechanisms were included in the model physics, a much more realistic simulation of the annual cycle of CO2 flux (NEE) at the Tapajos River km83 site was possible. We now conduct a regional analysis across 8 tower sites throughout Amazonia across multiple climactic regimes. Annual precipitation ranges from less than 1000 mm to more than 2000 mm, and length of dry season (defined as a month with <100 mm precipitation) ranges from none to 6 months or more. Vegetation types consist of tropical forest, pasture, and savanna. We find that by including the aforementioned mechanisms into the model we remove stress and obtain more reasonable annual cycles of NEE in the forest sites, but in the pasture and savanna sites the modified model removes vegetation stress in an unrealistic manner. Regional simulations require realistic input information on soil and rooting depth to perform realistically when confronted with data. When we include these data in the simulations the model carbon flux is comparable to observed across moisture and vegetation gradients in Amazonia.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting