The Inversion of the Great Soil Zones in Western Washington

A LARGE portion of eastern WVashington is occupied by the dark-colored soils of the Palouse and closely related series. These soils belong to the chernozem group. The development of the chernozems is a mass effect of a certain natural combination of definite climatic conditions, grass vegetation, and topographical configuration of the general landscape. The great geographical unit known as the northern horizontal zone of chernozems, famous for its fertile and productive black soils, is a broad belt throughout which such a combination of physiographic conditions remains relatively uniform. This belt does not stretch entirely across the continents, being interrupted in various places by the mountainous regions and the coastal regions strongly affected by the influence of a marine climate, in neither of which normal chernozems can be developed. It may be assumed that in the western United States chernozem soils would occupy most of W;ashington and Oregon but for the Cascade Range. The Cascades, standing as a barrier across the path of the prevailing westerly winds from the Pacific Ocean, create on their western slopes and foothills an independent, exceedingly humid west-coast natural province and cast a dry climatic shadow over the part of Washington and Oregon east of the mountains. The exceedingly high humidity of the humid province, which stretches from British Columbia into the northern part of California, coupled with a luxuriant forest vegetation composed mainly of evergreens, creates an environment that has caused the development of a group of soils fundamentally and strikingly different from the chernozems. On the other hand, a meridional belt of arid semidesert reaching far northward extends through the entire region covered by the dry climatic shadow east of the Cascades. This is a northward peninsulalike protrusion of another great horizontal zone, south of the chernozem zone. If the Cascade Range and the coastal mountains did not exist, this zone would hardly extend as far north as the northern boundary of Utah and Nevada and would reach the coast only in the southernmost part of California. This region is occupied by the very light gray, grayish-brown, or brown soils similar to those of Ritzville, Wheeler, and many other series, which form another great group of light-gray and brown soils of the semidesert serozems and burozems. This geographical distribution of the principal soil groups of Wtash

Archaeology · Earth science · Geography · Geology · Rangeland and Wildlife Management · Soil and Environmental Studies