HR: 1340h
AN: B33D-1582    [Abstracts]
TI: A Study of Water Uptake by a Mature Amazonian Rainforest.
AU: * Ivanov, V Y
EM: ivanov@umich.edu
AF: University of Michigan, Department of Civil and Environmental Engineering, 1351 Beal Avenue, 105 EWRE, Ann Arbor, MI 48105, United States
AU: Hutyra, L
EM: lrhutyra@u.washington.edu
AF: University of Washington, Urban Ecology Research Laboratory, 3949 15th Avenue NE, Box 355740, Seattle, WA 98195, United States
AU: Wofsy, S C
EM: swofsy@deas.harvard.edu
AF: Harvard University, School of Engineering and Applied Science / Department of Earth and Planetary Science, 29 Oxford St., Cambridge, MA 02138, United States
AB: Approximately half of the Amazon evergreen forests is subjected to seasonal droughts of at least 3 months duration. Nonetheless, several plot-scale studies have shown that rainforests do not seem to exhibit a significant water stress during dry seasons. Moreover, recent analysis of remotely sensed spectral indices indicates an increased green leaf area and photosynthetic activity associated with these periods. These studies suggest both a specific phenology pattern and physiological water uptake adaptations to prolonged episodes of dry conditions. Several mechanisms have been proposed to support observations, including deep root function and hydraulic redistribution. In this study, we further investigate possible explanatory mechanisms. A vegetation-hydrology model that parameterizes the essential water-energy processes using a simplified three-leaf representation of canopy vertical structure is constructed. Deep 35 m profile is used to explicitly resolve the propagation of wet and dry cycles into the soil column. We focus on a site in Tapajós National Forest near km 67 of the Santarém- Cuiabá highway (BR-163), which was a part of the Brazilian-led Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-ECO). Meteorological data for the period of 2002-2005 are used as forcing. Land- surface fluxes, phenology, soil water, soil texture and water retention properties as well as observed profiles of root biomass are used to constrain the model. In a set of numerical experiments, we explore the implications of phenology pattern, soil texture effects in moisture redistribution, and possible niche separation in root water uptake among plant types.
DE: 0495 Water/energy interactions (1878)
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: 2007 Fall Meeting