Annual carbon cost of stem CO2 flux in an old growth tropical forest
Evilene
Lopes, Complex System Research Center, Institute for the Study of Earth, Ocean and Space, University of New Hampshire, Durham, NH, USA, evilene@kaos.sr.unh.edu
(Presenting)
Patrick
Michael
Crill, Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden, patrick.crill@unh.edu
Michael
M.
Keller, USDA Forest Service, International Institute of Tropical Forestry, Rio Piedras, Puerto Rico, michael.keller@unh.edu
Ruth
Varner, Complex System Research Center, Institute for the Study of Earth, Ocean and Space, University of New Hampshire, Durham, NH, USA, Ruth.varner@unh.edu
In woody stems, CO2 is a product of metabolism in the living cells of the xylem parenchyma, cambium and phloem. Stem CO2 efflux is an important component of the carbon balance of an ecosystem. Total respiration, including the foliage and soil components, would be expected to nearly equal photosynthesis in a mature forest. Stem CO2 flux was measured at the Tapajos National Forest (TNF) using dynamic chambers and an infrared gas analyzer (IRGA) system. The average efflux of stem CO2 for the Tapajos National Forest (TNF) was 1.72 (+/- 1.36) umol m-2 (wood) s-1. Stem respiration was scaled to a ground area basis using wood surface area. Surface area was estimated during the dry season of 2003 on selectively logged trees at the km 83 site of TNF. We measured 90 fallen trees with diameter at breast height varying between 15 and 150 cm. We approximated the area of bole to a frustum of a cone and used diameter of the tree base, top, and height of tree bole. For the trees selected wood surface area resulted in a wood area index of 0.7 m-2 wood/ m m-2 ground. The above-ground woody-tissue CO2 flux estimated for the TNF is 456 gC m-2 (ground) yr-1 using stem surface to extrapolate the fluxes. This represents between 15% - 20% of the gross photosynthesis in this ecosystem.
Submetido por Evilene Bowley em 19-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)