This layer contains the delineations of the soil landtype mapping units defined in the 1992 update to the SRI (Soil Resource Inventory)
The mapping units are derived and defined on the basis of soil, landform, geology and vegetation characteristics. The average delineation size for each mapping unit is 50 to 600 acres. This data was originally mapped at the 1:24000 scale. Due to the reconnaissance nature of this survey, it lacks detail for use in high-intensity, small-area projects. These projects require additional on-site study by various technical specialists, including soil scientists.
The dominant landtype of the mapping unit is described in the mapping unit description and identified by the same number as used for the mapping unit. Within the mapping unit, other landtypes occur. Those most commonly associated with the dominant landtype of the mapping unit are included in the descriptions as inclusions. These inclusions of other landtypes account for no more than 30 percent of the mapping unit. (for further descriptions of mapping unit symbology see SOIL RESOURCE INVENTORY" Willamette National Forest, Basic Soil Information and Interpretive Tables
Rosana A. Costello, Theresa J. Valentine
For use with the HJ Andrews GIS database.
Many symbols shown on the maps have three digits and are called "Mapping Unit Complexes." These are mapping units used in areas where two or more defined mapping units are present in an arrangement too complex to separate at the one-inch per mile scale. The Legend of Complexes indicates the mapping unit components of the complex and the approximate percentage of each component.