A Correlation and Regression Analysis of Percent Canopy Closure Versus TMS Spectral Response for Selected Forest Sites in the San Juan National Forest, Colorado

This investigation tested the correlation of canopy closure with the signal response of individual Thematic Mapper Simulator (TMS) bands for selected forest sites in the San Juan National Forest, Colorado. Ground truth consisted of a photointerpreted determination of percent canopy closure of 0-100 percent for 32 sites. The sites selected were situated on plateaus at an elevation of approximately 3 km with slope < 10 percent. The predominant tree species were ponderosa pine and aspen. The mean TMS response per band per site was calculated from data acquired by aircraft during mid-September, 1981. A correlation analysis of TMS response versus canopy closure resulted in the following correlation coefficients for bands 1-7, respectively: -0.757, -0.663, -0.666, -0.088, -0.797, -0.597, -0.763. Two model regressions were applied to the TMS data set to create a map of predicted percent forest canopy closure for the study area. Results indicated precent predictive accuracies of 71, 74, and 57 for percent canopy closure classes of 0-25, 25-75, and 75-100, respectively.