Remote sensing of mangrove wetlands: Relating canopy spectra to site-specific data

Remote sensing was examined as a tool to describe the spectral and structural changes within and between mangrove species and community types. To accomplish this goal, high-resolution canopy reflectance spectra were obtained at 21 mangrove sites in southwest Florida. This was in addition to leaf spectra, canopy closure, height, and species composition from a number of these sites. High relative variability typified measurements of canopy reflectance spectra, canopy height, and percent species composition, while leaf reflectance variances within species (black or red, about 0.04 to 0.06 percent) were higher than between species (about 0.02 percent). A transformed canopy closure variable - Leaf Area Index (LAI) - was low with little variance, and it was significantly correlated to canopy height but not to species composition. Mean reflectances were generated for the blue, green, red, and near-infrared (NIR) wavelength regions from the obtained canopy reflectance spectra by using either user-defined bandwidths or bandwidths defined for the Advanced Very High Resolution Radiometer, Thematic Mapper, and XMS (SPOT) sensors. Results from these sets of reflectances in combination with correlation analyses suggest blue and red reflectances were redundant as were SPOT panchromatic and green reflectances and all normalized difference vegetation indexes derived for each set of NIR and red reflectances. Eighty-four percent of the LAI variance was explained by using any generated normalized difference vegetation index; however, species composition was not correlated to any combination of reflectance bands or vegetation index.