Soil Resource Inventory
USDA Forest Service Pacific Northwest Region Soil Resource Inventory
The Pacific Northwest Region (Region 6) of the US Forest Service initiated its first survey of forest and rangeland soils in 1967 on the Olympic National Forest. The soil survey effort was initiated specifically in response to the Multiple Use - Sustained Yield Act of June 12, 1960 in which the Forest Service was required to manage the land “without impairment of the productivity of the land”. Understanding the nature and distribution of soils on the landscape and their suitability for different land uses and management activities was necessary to determine how best to meet this requirement (FSM 2550.1).
The resulting Soil Resource Inventory (SRI) was based on a landscape analysis considering the interaction of soils, geology, landform, climate and vegetation. Photo interpretation, field observation, sampling and measurements, laboratory analysis and research results were integrated in developing these relationships. The delineation of mapping units is based on the recognition of the relationships of land patterns and/or characteristics of the soil, geology, vegetation, climate and landforms as they are interpreted for resource use and management. A landtype represents an area of naturally occurring and identifiable land which has certain management requirements and/or interpretations. They are different from any other landtype and, therefore, have reasonable and observable differences, singly or in combination, of one or more soil, geology, landform, climate, or vegetation features or characteristics. The SRI is not limited to the traditional soil classification system of mapping that is based simply on diagnostic soil horizon criteria. Such a system is not compatible with National Forest use because it is restricted to the genetic and morphological characteristics rather than the total characteristics of land; it is not oriented to land management interpretations and is difficult for the user to understand. In contrast, the design of the SRI places its major emphasis on interpretation, behavior, and use of soil resources as related to land management activities. The mapping was done at a nominal scale of one inch to the mile (1:63,360). Note: Soil Resource Inventories are to be used at the scale of Forest Planning and need to be refined by field soil scientists for use in project planning.
About the data
Due to the fact that many Region 6 Forests do not have NRCS SSURGO surveys (at a scale of 1:24,000, these are the highest-resolution soils data generally available), Region 6 initiated a project in 2012 to bring these legacy SRI soils data into digital databases to facilitate their use in regional planning activities. The datasets available on this page are the results of that effort.
The SRI were originally compiled in 20 volumes, with the original year of publication ranging from 1969 to 1979. The Gifford-Pinchot SRI was redone following the eruption of Mt Saint Helens, and that version was published in 1992. The Olympic NF also produced two versions, the original version being published in 1969, with an update in 1982. The Colville National Forest was the only Region 6 forest that did not compile a SRI.
The data are organized into one single regional geodatabase, together with twenty individual forest-level geodatabases. The regional database contains polygons from all twenty SRIs together with a common set of attributes for the two or three soil layers delineated in the individual mapping unit descriptions, such as texture, depth, color, rock content, etc. In general, the regional database contains physical soil attributes that could be compiled more or less completely and consistently across all forests. The individual forest-level databases contain the polygons for each individual SRI, together with various tables of management interpretations and laboratory data, together with a variety of miscellaneous tables. The information contained in these forest-level databases varies widely from forest to forest, which is why they were not merged into a regional view. Full metadata are included with each database, and scans of the original SRI volumes are provided for reference as well. A Forest Service General Technical Report that fully describes the available data is currently in preparation.
The following datasets and scanned PDFs are available: