Abstract ID: 356

Relating carbon and water exchange over an intensive agriculture field in the Amazon crop to locally and remotely sensed phenological measurements.

We present analysis of 5 years of micrometeorological data made in an agricultural field in the eastern Amazon. We develop relationships between remotely-sensed observations (enhanced vegetation index, EVI) and in situ measurements such as the radiometric and turbulent fluxes. There are clear differences that appear in the turbulent fluxes (CO2, H2O, and sensible heat), and radiative parameters (albedo and PAR albedo, the photosynthetically active radiation albedo) due to the landscape changing from pasture to crop field. Since September 2000, agricultural practices in Santarém, Pará, have changed rapidly from cattle grazing, to upland (non-irrigated) rice cultivation, and then to soybean cultivation. Seasonal changes in greenness and reflectivity measured in situ follow the patterns of daytime evaporation and carbon uptake, which depend on crop type. For instance, the lowest values of the Bowen ratio were observed during the wet season during rice plantation. Changes in the albedos depend on crop type, and they not only indicate changes in the net radiation regime, but they also mirror changes in the energy partition and CO2 fluxes. Dataset from MODIS, collection 5, indicates that the enhanced vegetation index (EVI) can detect seasonal and crop changes, but it cannot clearly distinguish the crop type. Also remote sensing and in situ radiative parameter PAR albedo does not yield a unique pattern for each crop (rice or soil). The relationship between net ecosystem exchange (NEE) and PAR albedo resulted in different relationships each year, indicating that other parameters than radiative fluxes must be included in parameterizations.

Session:  Carbon - What has been learned and what further can be learned from a network of eddy covariance towers in Amazonia?.

Presentation Type:  Oral