The present work delimited the main littoral vegetations of the Pará State through the differences in the reflectance levels obtained by Landsat images and in situ by a spectrophotometer. This study indicated that the mangrove leaves present lower values of reflectance than others vegetations, mainly in the visible interval of the electromagnetic spectrum.This may be related to the strong absorption developed by the photosynthesis pigments of the mangrove trees. Among its leaves, the Avicennia presented higher reflectance values than Rhizophora. Besides, the reflectance of mangrove leaves changed between the studied areas, mainly the Rhizophora that in Curuçá presented higher values. This can be associated to the stress conditions found in the Bragança and Mosqueiro, since the environmental changes affects the spectral reflectance of leaves. In the case of the mangrove, adverse salinity conditions may hinder the plants development. The tidal water salinity in Mosqueiro presents low values. This factor allows a wider ecological competition between the mangrove species and others vegetations that together with the sediment type, may produce an increase in the stress to the mangrove. It may justify the low height of the trees, and the relatively high reflectance values. Thus, the relationship between the tree height and spectral values of the Rhizophora and Avicennia indicates an inverse relation. This may be attributed to the development of chlorophyll in the initial periods of vegetation growth that allows a elevated amount of energy reflected in the visible interval until the leaves reach its typical green color with relatively lower reflectance. Based on the reflectance data was possible to elaborate maps with the following vegetation units: mangrove, terra firme vegetation, tidal varzea, transition zones mangrove/varzea and herbaceous field.
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