Historically there have been various approaches to mapping and describing terrestrial ecosystems. Ecological descriptions and maps have been based mainly on vegetation or have been compiled from data of various independently conducted vegetation surveys, soil surveys and other resource efforts. Commonly, soil surveys are used as the baseline polygon map to which Ecological Site Descriptions (ESD) are assigned. ESDs tend to be a soil map unit component interpretation. Historically there has been minimal vegetation input during the soil mapping process. An ESD has typically been assigned to a soil map unit component based on a typical soil pedon location selected by a soil scientist. The vegetation specialist is not always involved in site selection. It is assumed that the ESD and soils were consistently mapped together in the soil survey project area and that the site reflects the ESD potential. The USDA Forest Service, Southwestern Region, uses an integrated approach that has been formally in place since 1986. Ecological types are mapped and described along a climatic gradient. Climate classes have been established and described along a climatic gradient. Soil temperature and moisture regimes have been established for each climate class through monitoring and interpretation from weather station data. Indicator plant species have been correlated to climate classes and various soil properties. PC ord is being used to verify the correlation. Scientists who describe and map these ecological types are soil scientists with skills in plant taxonomy, ecology, geology and geomorphology. They are also skilled in the associated protocols for data collection. Botanists, geologists, ecologists and geomorphologists are consulted and part of the quality assurance process. The resulting ecological type is the associated soil, plant, climate and landform data collected. Data are collected by the same person(s), at the same location, at the same time, resulting in a more consistent and accurate ecological description and map.