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San Juan Series, San Juan National Historic Park, Washington
The San Juan soil series is an example of a native prairie soil with relatively high amounts of organic carbon within the soil profile. Prairie vegetation is naturally incorporated into the soil profile year after year, creating a zone that is enriched in carbon and visually striking for its dark color. Carbon stored in a soil profile naturally improves soil health, productivity, and stability as well as enhancing water quality.
The San Juan series consists of very deep, somewhat excessively drained soils formed in eolian sands over glacial outwash. San Juan soils are on dunes, hillslopes, and glacial outwash plains with slopes of 0 to 60 percent. Average annual precipitation is about 20 inches and average annual air temperature is about 50 degrees Fahrenheit.
The Hoypus soil series is an example of a native forest soil with the majority of its organic carbon stored at the top of the soil profile in the forest litter layer. Although visually much different than the San Juan soil, the Hoypus soil shares nearly identical physical properties and serves an equally important ecological role. Although these two soils have formed under different vegetative cover, they have both formed in the sand and gravel of glacial outwash. Pictured above, an oblique aerial view of Mount Finlayson illustrating where the Hoypus and San Juan soil series are mapped adjacent to each other, distinguished by vegetative cover. Numbers on the map correspond to general soil map unit numbers found in the Soil Survey of San Juan Island National Historical Park.
Last Updated: December 09, 2011