Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) data

Abstract

Multispectral measurements collected by Landsat Thematic Mapper (TM) were correlated with field measurements, direct soil loss estimates, and Universal Soil Loss Equation (USLE) estimates to determine the sensitivity of TM data to varying degrees of soil erosion in pinyon-juniper woodland in central Utah. TM data were also evaluated as a predictor of the USLE Crop Management C factor for pinyon-juniper woodlands. Correlation analysis showed that TM Band 4 (near infrared) accounted for 78 % of the variability in percent trees ( r = − 0.88). In multiple regression, percent trees, total soil loss, and percent total nonliving cover together accounted for nearly 70 % of the variability in TM Bands 2, 3, 4, and 5. TM spectral data were consistently better predictors of soil erosion factors than any combination of field factors. TM data were more sensitive to vegetation variations than the USLE C factor. USLE estimates showed low annual rates of erosion which varied little among the study sites. Direct measurements of rate of soil loss using the SEDIMENT (Soil Erosion Direct measureMENT) technique, indicated high and varying rates of soil loss among the sites since tree establishment. Erosion estimates from the USLE and SEDIMENT methods suggest that erosion rates have been severe in the past, but because significant amounts of soil have already been eroded, and the surface is now armored by rock debris, present erosion rates are lower. Indicators of accelerated erosion were still present on all sites, however, suggesting that the USLE underestimated erosion within the study area. These findings indicate that remotely sensed multispectral data should be considered as input to future models designed to estimate soil loss within pinyon-juniper woodlands and probably other vegetation types distributed over broad geographic regions.