Aridic and torric (L. aridus, dry, and L. torridus, hot and dry) moisture regimes.--These terms are used for the same moisture regime but in different categories of the taxonomy.

In the aridic (torric) moisture regime, the moisture control section is, in 6 or more out of 10 years,

1. Dry in all parts for more than half the cumulative days per year when the soil temperature at a depth of 50 cm from the soil surface is above 5°C; and

2. Moist in some or all parts for less than 90 consecutive days when the soil temperature at a depth of 50 cm is above 8°C.

Soils that have an aridic or a torric moisture regime normally occur in arid climates. A few are in semiarid climates and either have physical properties that keep them dry, such as a crusty surface that virtually precludes infiltration of water, or they are very shallow over bedrock. There is little or no leaching in these moisture regimes, and soluble salts accumulate in the soil if there is a source of them.

The limits set for soil temperature exclude from these moisture regimes the very cold and dry polar regions and high elevations. The data available on the soils of those regions are so fragmentary that no provision is made for their moisture regimes in this taxonomy.

7/15/98