Carbon dioxide concentrations within a tropical forest canopy in Central Amazon: spatial and temporal variability in a topographic gradient.
Alessandro
Carioca de
Araujo, Vrije Universiteit Amsterdam, arau@geo.vu.nl
(Presenting)
Bart
Kruijt, Alterra, Bart.Kruijt@wur.nl
Antonio
Donato
Nobre, INPA, anobre@ltid.inpe.br
Juliana
Silva de
Souza, INPA, souzajs@hotmail.com
Albertus
Johannes
Dolman, Vrije Universiteit Amsterdam, han.dolman@geo.falw.vu.nl
Maarten
Johannes
Waterloo, Vrije Universiteit Amsterdam, watm@geo.vu.nl
Eddy
Moors, Alterra, Eddy.Moors@wur.nl
Long-term estimates of net ecosystem exchange (NEE) using the eddy covariance method often underestimate the nocturnal emission of CO2 from forest during calm nights. A commonly used approach to limit this underestimation is to add to the eddy CO2 flux a term accounting for the CO2 storage changes in the layer between the ground and the measurement height. This approach can give rise to errors as the storage term is usually evaluated only at one location. Also, it does not take into account the heterogeneity in the source distribution or possible horizontal air movement, such as drainage flows associated with topography. At the LBA K34 site near Manaus, AM, it has been reported that soil respiration differs along a topographical gradient from the plateau to the valley bottom. This together with lateral drainage flows may lead to a heterogeneous storage pool in the flux footprint. It is interesting to investigate whether the vertical [CO2] profiles in a topographic gradient follow the soil respiration pattern. During two consecutive days, in the dry season of 2002, three vertical [CO2] profiles -one for each topographical section- were used to sample canopy air, which was analyzed with an IRGA. Emphasis was given to the nighttime and early morning periods. The vertical [CO2] profiles on the slope and in the valley showed higher concentrations than on the plateau, suggesting a rapid build up in those sections. This may cause differences in the storage pools that seem to be measured by both eddy covariance and storage systems at different times.
Submetido por Alessandro Carioca de Araújo em 17-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)