Ecophysiological distinction of plant functional groups in Central Amazonian primary forest
Tomas
F.
Domingues, Univ. of Utah, domingues@biology.utah.edu
Françoise
Y.
Ishida, Univ. São Paulo/CENA, yoko@lbaeco.com.br
Jean
P.H.B.
Ometto, Univ. of Utah, Univ. São Paulo/CENA, jpometto@cena.usp.br
(Presenting)
Luiz
Antonio
Martinelli, Univ. São Paulo/CENA, zebu@cena.usp.br
Joseph
A.
Berry, Carnegie Institution of Washington, joeberry@stanford.edu
James
R.
Ehleringer, Univ. of Utah, ehleringer@biology.utah.edu
Plant communities influence carbon and water cycling through ecosystems by controlling photosynthetic and respiratory processes. In order to characterize photosynthetic gas exchange capacity of primary forest in Santarém PA, we have adopted a plant functional type approach consisting of four groupings: lianas at the top of the canopy, top canopy trees, mid canopy trees, and understory trees.
We characterized plants on the basis of different physiological characteristics, including leaf mass to area ratio (SLA), leaf nitrogen content (Narea) and leaf stable carbon isotope ratio (d13C). In addition, we measured leaf photosynthetic characteristics, including the photosynthetic dependence on light, CO2, and relative humidity. These response curves were used to calculate maximum assimilation rates (Amax), stomatal conductance to water vapor (g), the ratio of internal to external carbon dioxide concentration (Ci/Ca). We used a Farquhar-based biochemical model to extract carboxylation rates (Vcmax) from the photosynthetic response curves.
SLA showed that liana and top tree groups are not different, but they differ from both mid trees and understory. SLA also showed that mid tree is different from understory. Identical pattern was obtained for d13C values. Narea showed no difference between liana and up tree, but both were different from mid tree and understory. Narea showed no difference between mid tree and understory groups. Liana was distinct from the other groups based on Ci/Ca values. The only possible distinction based on Vcmax, was top tree and understory. No distinction among functional groups could be made based on Amax and g.
Submetido por Tomas Ferreira Domingues em 18-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)