THE POLARIZATION OF LIGHT IN A TROPICAL RAIN-FOREST

The light environment within forests presents complex patterns of brig htness and spectral distribution of light. The polarized light field i s no less complex. Using an imaging polarized light analyzer, we exami ned the natural fields of linearly polarized light in the tropical rai n forest of Guatopo National Park, Venezuela. We found that the celest ial polarization pattern remains visible underneath the forest canopy, although cloud and fog coverage may diffuse the light and reduce the polarization signal. We characterized several distinct light environme nts, each having a characteristic polarized light field. Furthermore, objects throughout the forest reflect light that is polarized in a pre dictable fashion depending upon the material, structure, and orientati on of the reflecting surface. As a consequence of these patterns in th e distribution of polarized light, some functions of polarization visi on, such as navigation, must be limited to the spaces exposed to sever al extended portions of the sky, while others, such as remote sensing of surface orientation, object detection, and breaking of camouflage w ould be useful throughout the forest. The polarization of light adds a nother dimension to the complexity of the rain forest photic environme nt.