Nitrous oxide (N2O) is one of several naturally occurring greenhouse gases whose concentration in the atmosphere is increasing. Studies in the American Southwest, Hawaii, Mexico and the Amazon Basin have shown that emissions of N2O (from the soil into the atmosphere) vary among different forests and also as a result of land use change. In Brazil, for example, N2O emissions from forests and forest land converted to pasture differ significantly. Variations in soil nitrogen cycling processes and in physical characteristics of the soil are factors that control that variation.
In order to extrapolate N2O emissions to a regional level from measurements taken at selected sites, it is necessary to know the areal extent of each forest or land cover type. Remote sensing can be used to acquire such information provided that the spectral differences in the land cover types are significant. The multispectral image shown here was compiled from data acquired by a Landsat satellite. The image shows the extent of forest clearing in the area of Manaus, Brazil , through 1986. Although pasture accounts for less than 11% of the 3600 km2 area in the image, 40% of the N2O emissions to the atmosphere from this area are generated by pasture.
One of the conclusions from this research is that N2O emissions to the atmosphere may increase significantly as tropical forest land is converted pasture. The increased emission of a greenhouse gas may contribute to a warming of the earth's atmosphere and surface temperatures.
RESEARCH SITES: Mt. Taylor, NM; Hawaii Volcanoes National
Park; Amazon Basin, Brazil; Chamela, Mexico
COLLABORATORS: CENA, Brazil; Colorado State University, Instituto Nacional de Pesqusas de Amazonia, Brazil; NASA/Goddard I.S.S.; NASA/Langley; Stanford University; University of Wyoming; University of Wisconsin; University of Hawaii; National University of Mexico.
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