Spectral reflectance and soil morphology characteristics of Santa Rita Experimental Range soils

Abstract

The Santa Rita Experimental Range (SRER) soils are mostly transported alluvial sediments that occur on the piedmont slope flanking the Santa Rita Mountains in Arizona. The major geomorphic land forms are alluvial fans or fan terraces, but there are also areas of residual soils formed on granite and limestone bedrock, basin floor, stream terraces, and flood plains. The soils range in age from recent depositions to soil material one to two million years of age. We sampled A and B horizons of soil series from different geomorphic surfaces, and measured the dry spectral reflectance (0.4 to 2.5 μm wavelength) on the sieved less than 2-mm-size fraction. Soil color (measured with a Chroma Meter), texture, organic carbon, calcium carbonate content, and effervescence properties were determined and correlated to spectral reflectance in selected wavelengths. The Munsell soil color value component was most positively correlated to reflec- tance. Soil effervescence and calcium carbonate content, percent sand and clay, and the Munsell soil color hue component and redness rating were also significantly correlated to soil reflectance. Energy reflected from soil surfaces represents the interaction between many soil properties, and soil color is an integrated expression of many soil properties. It is the best soil morphology property to measure to predict the spectral reflectance of soils, particularly in the visible and near infrared parts of the electromagnetic spectrum. Acknowledgments: The Soils Map GIS data for the Santa Rita Experimental Range (SRER) were completed by Debbie Angell and Dr. M. McClaran, and the manipulation of this data to prepare the geomorphic land form map was prepared by Dawn Browning and Mamadou Niane, University of Arizona, School of Renewable Natural Resources (SRNR). The SRNR Advanced Resource Technology (ART) Laboratory facilities were utilized to create the geomorphic land form map of the SRER. Special thanks are extended to Mary Kay Amistadi and Dr. Jon Chorover, Department of Soil, Water and Environmental Science, University of Arizona, for determining the organic carbon and calcium carbonate content of the SRER soils. We also thank Dr. M. S. Moran, the USDA Agricultural Research Service, Tucson, AZ, for allowing us to use her Analytical Spectral Device to measure spectral reflectance.