HR: 1340h
AN: B43A-0130    [Abstracts]
TI: Parameterization of Leaf-Level Gas Exchange for Plant Functional Groups From Amazonian Seasonal Tropical Rain Forest
AU: * Domingues, T F
EM: domingues@biology.utah.edu
AF: University of Utah, 1400 East 257 South, Salt Lake City, UT 84112 United States
AU: Berry, J A
EM: joeberry@biosphere.stanford.edu
AF: Carnegie Institution of Washington, 260 Panama street, Stanford, CA 94305 United States
AU: Ometto, J P
EM: jpometto@cena.usp.br
AF: Centro de Energia Nuclear na Agricultura, Avenida Centenario, 303, Piracicaba, SP 13416-000 Brazil
AU: Martinelli, L A
EM: zebu@cena.usp.br
AF: Centro de Energia Nuclear na Agricultura, Avenida Centenario, 303, Piracicaba, SP 13416-000 Brazil
AU: Ehleringer, J R
EM: ehleringer@biology.utah.edu
AF: University of Utah, 1400 East 257 South, Salt Lake City, UT 84112 United States
AB: Plant communities exert strong influence over the magnitude of carbon and water cycling through ecosystems by controlling photosynthetic gas exchange and respiratory processes. Leaf-level gas exchange fluxes result from a combination of physiological properties, such as carboxylation capacity, respiration rates and hydraulic conductivity, interacting with environmental drivers such as water and light availability, leaf-to-air vapor pressure deficit, and temperature. Carbon balance models concerned with ecosystem-scale responses have as a common feature the description of eco-physiological properties of vegetation. Here we focus on the parameterization of ecophysiological gas-exchange properties of plant functional groups from a pristine Amazonian seasonally dry tropical rain forest ecosystem (FLONA-Tapaj\'{o}s, Santar\'{e}m, PA, Brazil). The parameters were specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, photosynthetic carboxylation capacity, dark respiration rates, and stomatal conductance to water vapor. Our plant functional groupings were lianas at the top of the canopy, trees at the top of the canopy, mid-canopy trees and undestory trees. Within the functional groups, we found no evidence that leaves acclimated to seasonal changes in precipitation. However, there were life-form dependent distinctions when a combination of parameters was included. Top-canopy lianas were statistically different from top-canopy trees for leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and stomatal conductance to water vapor, suggesting that lianas are more conservative in the use of water, causing a stomatal limitation on photosynthetic assimilation. Top-canopy, mid canopy and understory groupings were distinct for specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and photosynthetic carboxylation capacity. The recognition that plant functional groups have distinct impacts on ecosystem-scale gas exchange can increase the accuracy of process-based carbon balance models where structure is known and when logging activities are incorporated into production models.
DE: 9360 South America
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting