Land Resource Regions in Washington

Appendix 2  -  Washington Soils Atlas

Land Resource Regions in Washington

Land Resource Region A

Land Resource Region A is the largest Land Resource Region in Washington. It includes steep mountains and narrow to broad, gently sloping valleys and plains characterize this region. Two major mountain systems are in this region. One, the Coast Range, parallels the coast. The Cascade Mountains is the other major mountain system in the region. This area has a rich agricultural areas because of a mild coastal climate, high rainfall, and deep soils that formed in alluvium and glacial drift. The annual precipitation in the mountains is typically more than 100 inches, but it can exceed 250 inches on the highest peaks. This region is dry in summer. The average annual temperature is 45 to 55 degrees F. in most of the region. The frost-free period is more than 200 days in most of the valleys, and only 40 to 70 days on mountain slopes. Some areas on the highest mountains are covered by glaciers. The ground is permanently frozen in these areas. The dominant soil orders in this region are Alfisols, Andisols, Entisols, Inceptisols, Spodosols, and Ultisols.

A large part of this region is Federal land, mostly in national forests. The mountains are heavily forested, and timber production is the major industry. Dairy farming is an important enterprise in the valleys that receive abundant rainfall. Grain crops, grass and legume seeds, fruits, and horticultural specialty crops are grown extensively in the drier valleys.

Land Resource Region B

Land Resource Region B is on the lee side of the Cascade Mountains in Washington. It is an area of smooth to deeply dissected plains and plateaus. Most of this region is underlain by basalt flows from the Columbia and Idaho Batholiths. The basalt is covered with a veneer of loess and volcanic ash in most areas. The region has a few isolated mountain ranges. The average annual precipitation is 6 to 20 inches in most of the region. It is lowest in the Columbia Basin area in central Washington. The average annual precipitation can be as much as 45 to 85 inches in the mountains. Summers are dry. The average annual temperature is 40 to 49 degrees F. In most areas the frost-free period ranges from 125 to 220 days. It is typically 40 to 70 days in the mountains. Irrigation is a dominant use of water in the region. The dominant soil orders in the region are Mollisols and Aridisols. Other soil orders that occur are Alfisols, Andisols, Entisols, and Inceptisols.

About 29 percent of the land is federally owned grazing land, rangeland and cropland. A few very small areas are forested. Wheat, grown without irrigation, is the major crop in the region, but oats, barley, lentils, and peas also are important. Fruits, mainly apples, are a major crop in the western part of the region. Potatoes, sugar beets, beans, and forage crops are grown under irrigation in the central Columbia basin in Washington. A variety of specialty crops are grown in local areas, including vegetables, vegetable seeds, mint, and hops. Grazing is the major land use in the drier parts of the region. This region is primarily a mixture of grazing land and cropland.

Land Resource Region E

Land Resource Region E is characterized mainly by rugged mountains, but it has some broad valleys and remnants of high plateaus . The average annual precipitation ranges from 9 inches in some of the valleys to 63 inches on some of the mountain peaks. The average annual temperature ranges from 32 to 50 degrees F. The frost-free period is 65 days or less in the high mountains, where freezing temperatures occur every month of the year. Some areas on the highest mountains are covered by glaciers. The ground is permanently frozen in these areas. The freeze-free period on the foothills in the southern part of the region is as long as 190 days. The soils in this region are dominantly Alfisols, Entisols, Inceptisols, and Mollisols.

About 60 percent of the land in this region is federally owned. The mountain slopes generally are forested, and the valleys are dominated by shrubs and grasses. Grazing is the leading land use in the valleys and mountains, but timber production is important on some of the forested mountain slopes. Recreation is an important use throughout the region. Some of the valleys are irrigated. Grain and forage for livestock are the main crops. Beans, sugar beets, peas, and seed crops are grown in areas where soils, climate, and markets are favorable.
 

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