Drought stress and carbon uptake in an Amazon forest measured with spaceborne imaging spectroscopy

20 de abril de 2004

abr 20, 2004

Gregory P. Asner, Daniel Nepstad, Gina Cardinot, David Ray

Amazônia contains vast stores of carbon in high-diversity ecosystems, yet this region undergoes major changes in precipitation affecting land use, carbon dynamics, and climate. The extent and structural complexity of Amazon forests impedes ground studies of ecosystem functions such as net primary production (NPP), water cycling, and carbon sequestration. Traditional modeling and remote-sensing approaches are not well suited to tropical forest studies, because (i) biophysical mechanisms determining drought effects on canopy water and carbon dynamics are poorly known, and (ii) remote-sensing metrics of canopy greenness may be insensitive to small changes in leaf area accompanying drought.

New spaceborne imaging spectroscopy may detect drought stress in tropical forests, helping to monitor forest physiology and constrain carbon models. We combined a forest drought experiment in Amazônia with spaceborne imaging spectrometer measurements of this area. With field data on rainfall, soil water, and leaf and canopy responses, we tested whether spaceborne hyperspectral observations quantify differences in canopy water and NPP resulting from drought stress. We found that hyperspectral metrics of canopy water content and light-use efficiency are highly sensitive to drought.

Using these observations, forest NPP was estimated with greater sensitivity to drought conditions than with traditional combinations of modeling, remote-sensing, and field measurements. Spaceborne imaging spectroscopy will increase the accuracy of ecological studies in humid tropical forests.

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PEC 215: Threat to Rights and to the Environment

PEC 215: Threat to Rights and to the Environment

In addition to enforcing the fundamental rights of indigenous peoples, Indigenous Lands (ILs) are crucial for the maintenance of important ecosystem services. However, this role is under threat. If the Proposed Constitutional Amendment 215 of 2000 (PEC 215/00), currently under discussion in the Brazilian National Congress, is approved, it can cause serious legal insecurity for Indigenous Lands.