ELSEVIER Multivariate Statistical Classification of Soil Spectra Alicia Palacios-Orueta* and Susan L. Ustin* The purpose of this work was to evaluate whether A VIRIS (Advanced Visible Infrared Imaging Spectrome- ter) bands can be used to discriminate between soils having similar properties, as well as to compare A VIRIS spectra with those from laboratory measurements. Multi- variate analysis techniques show that two soils belonging to the same series and a third soil belonging to a different, but related series can be discriminated at a high level of accuracy using reflectance data from A VIRIS or from laboratory measurements. It is also shown that wave- lengths important in discriminating soils were highly correlated between AVIRIS and laboratory data. The distribution of variance and weighting functions also show consistent patterns between these data sets. INTRODUCTION The monitoring of soils is a major challenge to soil scientists. Soils exhibit continuous variation in space and time. Both natural and anthropogenic processes, such as agriculture or grazing practices, can change soil properties in ways that produce cumulative environmen- tal impacts. Studies of spatial and temporal changes are needed for identifying environmental problems and for developing mitigation strategies. Monitoring small changes are difficult because of the high spatial variabil- ity. It is likely that most soil changes will be small on decadal time scales relative to the large spatial heteroge- neity existing in the pedisol even on a local scale. Nonetheless, the potential significance of biogeochemi- cal feedbacks onto the climate system make such mea- surements important. We have examined the application of high spectral resolution remote sensors as a means * Department of Land, Air, and Water Resources, University of California, Davis Address correspondence to Alicia Palacios, Dept. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616. Received 5 July 1995; revised 13 November 1995. REMOTE SENS. ENVIRON. 57:108-118 (1996) ©Elsevier Science Inc., 1996 655 Avenue of the Americas, New York, NY 10010 to provide spatial information on the properties and conditions of soil surfaces and to evaluate its potential to detect small differences in soil properties. The soils chosen for this study exhibit a range of variation compa- rable to potential decadal scale temporal changes that result from altered surface processes. Spectrometry has been used for 25 years to differ- entiate highly divergent soil types. Researchers have shown that soils having dissimilar properties can be discriminated using reflectance measurements. Condit (1972) classified 160 soil spectra into three types based on their spectral shapes, the first type corresponding to chenozern soil, the second to pedalfer, and the third type to a red quartz and calcite sand. In an analysis of 485 soils, representing the major orders of the globe, Stoner and Baumgardner (1981) distinguished five dis- tinct reflectance forms, based on curve shapes and ab- sorption bands. These soils had different physical and chemical characteristics; however, spectral differences were mainly due to organic matter and iron oxide con- tent. Other recent studies have supported these findings (Csillag et al., 1993; Henderson et al., 1992; Zhang et al., 1992). Satellite multispectral data has been used as well to discriminate between soil types (Lee et aI., 1988; Lewis et al., 1975; Smith et al., 1990; Suet al., 1989, 1990; Thompson et al., 1981, 1984; Wright and Birnie, 1986). Agbu et al. (1990) used Systeme Pour I' Observa- tion de la Terre (SPOT) data and found that some soil properties like organic matter content, particle size distribution, and color could be used to predict satellite reflectance. Coleman et al. (1993) used the Thematic Mapper (TM) to differentiate surface soils with high accuracy and found significant correlations between ra- diance data and organic matter, iron content, and parti- cle size distribution. The development of imaging spectrometry makes it possible to obtain observations at a much higher spectral resolution. De Jong (1992) investigated the use 0034-4257 / 96 ! $15.00 SSDI 0034-4257(95)00250-2