Light reflectance characteristics and video remote sensing of pricklypear.

Abstract

This paper describes the use of a black-and-white visible-infrared (0.4-2.4 micromoles) sensitive video camera, filtered to record radiation in the 1.45-2.0 micromoles mid-infrared (MIR) spectral region, for distinguishing the succulent plant species pricklypear (Opuntia lindheimeri Engelm.) on rangelands in southern Texas. Ground-based spectroradiometric plant canopy measurements at 5 sampling dates revealed that pricklypear had significantly lower (p = 0.05) reflectance than that of associated plant species and soil over the 1.50-1.75 micromoles MIR water absorption spectral region. Airborne MIR video imagery of rangeland areas indicated that pricklypear populations could be differentiated from other landscape features. The optimum time for distinguishing the evergreen pricklypear was in January-February because most of the associated woody plant species were deciduous and lost their foliage during this period. Computer-based image analyses of MIR video imagery showed that pricklypear populations could be quantified, indicating that MIR video imagery may be useful for distinguishing and mapping pricklypear populations over large and inaccessible rangeland areas.