Environmental Covariates for Digital Soil Mapping in the Western USA

Abstract

Unlikemost of the USA, thewestern region still lacks initial soilmapping on many private and public lands. Spatially explicit soil data are needed to support a variety of land uses including energy development, mining, grazing, agriculture, forest products, recreation, wildlife habitat, species conservation and urban develop- ment. The wide diversity of lithology, geomorphology, climate, and vegetation and the vast, difficult-to-access terrain of western landscapes facilitated the develop- ment of digital soil mapping. Environmental covariates used in digital soil mapping in the western USA include derivatives of digital elevations models (DEM) and remotely sensed spectral data (RS). DEM-derived data are often used to represent climate and relief (geomorphology,microclimate). The lowvegetation cover of arid, semiarid, and seasonally dry climates typical of the West facilitates the use of RS data and its derivatives. Landsat and ASTER data are the most common sources of RS data, and are used to represent organisms (vegetation type and density), parent material (lithology, mineralogy), and soil (mineralogy, wetness, other surface char- acteristics). Spatially explicit, digital environmental covariates have improved sev- eral aspects of soil survey in the western USA including pre-mapping, developing efficient and targeted field sampling plans, and implementation of spatial prediction models.