Formation of the Soils
Climatic factors that influence the soils in the park are precipitation, temperature, and wind patterns. The park is located at high elevations in the Cascade Mountains; therefore, snowfall is a major factor in soil development. The average annual snowfall is about 500 inches, and the snowpack routinely remains through July or August. Precipitation in summer is light, and it generally is limited to a few scattered thunderstorms. The average annual precipitation averages about 60 to 70 inches on the western side and at the crest of the Cascade Range, but it decreases to an average of about 30 inches on the eastern side. The soil moisture regime along the eastern and northeastern edges, where elevation is relatively low, in the southern “panhandle” area, and in the southwestern corner of the park is the drier xeric regime. The remainder of the survey is in the moist udic regime.
The winters in the park are cold, and the summers are cool. The soil temperature regime throughout the park is cryic except on the glacial valley sidewall at the extreme southwestern corner, where it is frigid. The cryic soil temperatures inhibit soil development. Soil development occurs at a faster rate when temperatures are warm and moisture is present in the soil; however, this favorable environment for soil development exists for only a short period of time each year in the park.
The wind patterns affect the soils by causing drifting of snow and rapid drying of soils in areas unprotected by forest cover and the associated layer of duff (O horizon). This is most noticeable in the treeless open areas throughout the park, where there are sites that support desert vegetation because of early melting of the snowpack and subsequent drying of the soils as a result of wind blowing across the open areas. This rapid drying of the soil surface, the lack of layers of duff on the surface, and the prevalent winds that move soil particles create a poor environment for the survival and growth of tree seedlings, thus resulting in open meadow areas such as the “Pumice Desert.” Smaller areas have snowdrifts that are so deep and remain so long into the year that vegetation does not have enough time to grow and reproduce before the next winter.