Thornthwaite annual P-E index ranges from 25 to about 35. These are the competing Yologo and Zavco series and the Olmos and Valco series. Olmos and Yologo soils occur in similar positions. Olmos and Valco soils have petrocalcic horizons and are calcareous throughout. Valco and Zavco soils occur at lower elevations.
Permeability is moderately slow.
Runoff is negligible on 0 to 1 percent slopes, very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 12 percent slopes. Native vegetation consists of mid grasses, a few short grasses, about 25 percent woody shrubs and 5 percent perennial forbs. With retrogression woody plants dominate, mostly blackbrush, and form a dense canopy. Other increasers and invaders are threeawn, hairy grama, and red grama. The series is of moderate extent.