Modelling Spatial Patterns of Gross Primary Productivity in the Tapajós Region
Luiz
Eduardo Oliveira Cruz de
Aragão, INPE, aragao@ltid.inpe.br
(Presenting)
Yosio
Edemir
Shimabukuro, INPE, yosio@ltid.inpe.br
Mathew
Williams, University of Edinburgh, mat.williams@ed.ac.uk
The aim of this work was to generate gross primary productivity (GPP) surfaces for the Tapajós region, using the Aggregate Canopy Model (ACM), to evaluate the effects of land cover and of atmospheric CO2 increase over carbon assimilation by vegetation. We used a multi-scale methodology, involving field, GIS and remote sensing techniques, to create the GPP surfaces. After the implementation of the ACM in a GIS, we calculated the GPP surfaces, at 270 m spatial resolution, for 4 dates, 20/03/2001, 03/04/2001 (wet season), 22/08/2001 and 05/10/2001 (dry season). We also estimated the spatial GPP pattern at different atmospheric CO2 levels (from 250 ppm to 550 ppm). The results showed that GPP range from 4 g C m-2 to 15 g C m-2, in a clear day. Primary forests located in areas with an altitude between 100 m and 200 m high, associated to the “platô” formation, are more productive than primary lowland forests. Old secondary forest has an assimilation pattern quite similar to that observed for lowland forests. During the wet season irradiance limits the GPP process, reducing around 2 times the CO2 assimilation of the more productive locations. According to the model, an increase of 55% in the atmospheric CO2 concentration can lead to an assimilation increment of ~3 g C m-2 for the forests located in the “platô” region and ~2 g C m-2 for the lowland and the secondary forests. However, this positive feedback can be limited by temperature range oscillations. We concluded that GPP process is spatially variable over Tapajós at the regional scale, due to differences in land cover types, and this information can improve the accuracy of large scale studies to understand carbon budget in the tropics.
Submetido por Luiz Eduardo Oliveira Cruz de Aragão em 18-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)