Attempts to estimate LAI using airborne flashlamps and lasers

Two aircraft instruments, one a flashlamp/spectrometer - AVIS, and the other a ranging laser - SLICER, were used to collect data in conjunction with ground measurements of leaf area index (LAI). The second derivatives of the AVIS spectral reflectance curves, radius of curvature, distance ratios, and NDVIs were calculated and compared to various ground LAI and canopy closure measures. All relationships between AVIS spectral reflectance curve surrogates and ground LAI measures on 30 forested stands were random. SLICER estimates of average canopy height, median height canopy-ground power return ratios, canopy power return, and other transformations of the laser data were used to model ground-measured LAI and crown closure. Statistically significant relationships were found between four laser variables and LAI and crown closure. However R/sup 2/ values were low, 0.17-0.38. These linear and implicitly linear models were of little practical utility for prediction of LAI on the 24 stands considered.