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Abstract

In Central Amazonian white-water floodplains (várzea), different forest types become established in relation to the flood-level gradient. The formations are characterized by typical patterns of species composition, and their architecture can be quantified using large-scale aerial photography. Crown sizes, tree heights, the projected crown area coverage and the gap frequencies influence the light reflectance in the upper canopy, and provide information which facilitates a classification of different forest types by satellite imagery. Results of ground analysis indicate that at the average flood-level of 3 m, species diversity and architecture of the forests changes, thus justify the classification into the categories of low várzea (várzea baixa) and high várzea (várzea alta). The structure of low várzea depends on the successional stage, and species diversity increases with increasing age of the formations. Within the early successional stages of low várzea, a homogeneous, nonstratified canopy is developped, with uniform tree heights and crown extensions, resulting in a smooth canopy surface. Gap frequency is low. Therefore, these forests show a simple behaviour pattern in pixel distribution and are easy to detect, when scanned by TM images. In subsequent successional stages, tree heights and crown areas increase, and an initial stratification is developed. Gap frequency tends to increase with increasing age of the formations. In high várzea, only one successional stage was found and species diversity is higher than in all low-várzea formations. Tree heights reach 45 m and stratification is well defined. The more complex architecture of the high várzea results in the most diffuse behaviour patterns of pixel distribution, when scanned by TM image data