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Grazingland landscapes are often a complex mosaic of geology, topography, soils, plants, and climate. Organizing this information into sites with some common ecological basis is the precursor to formulating ecological sites. The USDA-Natural Resources Conservation Service develops Ecological Sites and Description reports which are based on physical and biotic factors. Ecological dynamics, primarily disturbance regimes (grazing, fire, drought, management actions, and all resulting interactions) are integral factors related to the formation of ecological sites. ESDs function as a primary repository of ecological knowledge and are maintained on the NRCS Ecological Site Information System (ESIS), which is the repository for information associated with ESDs and the collection of all site data. The classification of rangeland Ecological Sites and pastureland Forage Suitability Groups are based on different criteria. Rangeland ESD's are a classification concept based on stands of native plants with similar climate, soils, and hydrology that occurs in a relatively repeated fashion across a landscape. In contrast, FSG's are based on landscape, soil, and environmental properties. Adaptable forage species are correlated with these groups. Why use multivariate tools for ESD development? When many variables are to be evaluated e.g., plant species composition, soils, climate, and environmental, multivariate tools are necessary to simultaneously analyze multiple variables that may be related.