THE CLASSIFICATION, DISTRIBUTION, AND EXTENT OF SOILS WITH A XERIC MOISTURE REGIME IN THE UNITED-STATES

Soils with cool, moist winters and relatively warm, dry summers, a Med iterranean climate, are recognized as having a xeric moisture regime i n Soil Taxonomy. These soils are classified mostly in taxa that use th e formative element ''xer'' in the name. Soil series with either a xer ic moisture regime or an aridic regime bordering on a xeric moisture r egime make up more than 48,640,000 hectares in the western part of the United States. They are classified in the orders of Mollisols (20,080 ,000 ha), Aridisols (11,200,000 ha), Alfisols (5,320,000 ha), Inceptis ols (4,800,000 ha), Entisols (4,400,000 ha), Vertisols (1,520,000 ha), Andisols (960,000 ha), and Ultisols (960,000 ha).