LIGHT REFLECTANCE CHARARACTERISTICS AND AERIAL PHOTOGRAPHIC IMAGE RELATIONS AMONG CHIHUAHUAN DESERT PLANT SPECIES IN WEST TEXAS

摘要

Radiometric ground reflectance measurements were made on several common plant species on two range sites (limestone hill and canyon sites) near Alpine, in the Chihuahuan Desert of west Texas. Measurements were made on two dates: July and October 1999. Reflectance measurements were made at the visible blue (0.45 - 0.52 mum), visible green (0.52 - 0.60 mum), visible red (0.63 - 0.69 mum), and near-infrared (NIR) (0.76 - 0.90 mum) wavelengths. Reflectance values differed significantly (P=0.05) among the plant species at all four wavelengths and on both dates. Differences in reflectance among the plant species were attributed to variable foliage coloration, phenology, and vegetative density. Color-infrared (CIR) and conventional color aerial photographs obtained of the study sites on the two dates showed that several plant species could be differentiated. More species could be distinguished in the October photographs than in the July photos. Some species were more distinguishable in the CIR film, while others could be better delineated in the conventional color film. Reflectance measurements of several species were related to their image tonal responses on the aerial photographs. Textural image response, growth form, and geometric shape of some species were important in their discrimination on aerial photos.