The soils of the C. Hart Merriam elevation gradient are typically well-drained, shallow to deep, and have diverse compositions that reflect the rock types associated with their formation. Their composition and characteristics also reflect the precipitation levels and vegetation types that occur within the elevation ranges where the soils are found, as well as the inclination of the slopes on which they are found. The following soil descriptions incorporate this information.

FH2 (Sponseller-Ess-Gordo): This map unit is made up of soils from the Sponseller, Ess, and Gordo soil series. It is made up of approximately 25% of each, plus an additional 25% of minor associated soils, rock outcrop, and talus. These soils are well-drained and form in residuum and colluvium weathered from basalt, rhyolite, andesite, cinders, ash flow tuff, and related volcanic rocks. They occur in high mountain areas at elevations ranging from 6,600 to 12,500 ft. (2,000 to 3,790 m) where the mean annual precipitation is about 18-30 inches (46-76 cm) or more. Plant cover includes ponderosa pine, Douglas fir, spruce, quaking aspen, juniper, Gambel oak, Arizona fescue, pine dropseed, junegrass, wheatgrass, mountain muhly, squirreltail, and brackenfern.

MA1 (Badland-Torriorthents-Torrifluvents): This map unit is made up of 40% Badlands, 25% Torriorthents, and 25% Torrifluvents, in addition to 10% minor associated soils and rock outcrop. This unit consists of Badland and shallow, well-drained soils formed on shale and sandstone and deep, well-drained soils formed in recent alluvium derived from sedimentary rocks. They occur at elevations ranging from 4,600 to 6,000 ft. (1,400 to 1,820 m) where mean annual precipitation is about 6-12 inches (15-30 cm). Plant cover is sparse and consists mostly of fourwing saltbush, shadscale, Mormon tea, alkali sacaton, galleta, blue grama, Indian ricegrass, and annuals. The Badlands contribute to the characteristic scenery of the Painted Desert, Monument Valley, and Petrified Forest National Monument.

MA2 (Moenkopie-Shalet-Tours): These well-drained soils form in residuum and alluvium weathered from sandstone, shale, and conglomerates. They occur on plateaus and floodplains at elevations ranging from 4,400 to 6,500 ft. (1,340 to 1,970 m) where mean annual precipitation is about 6-10 inches (15-25 cm). Moenkopi soils make up about 60%, Shalet soils 15%, and Tours soils 15%. There is an additional 10% of associated minor soils. Plant cover includes alkali sacaton, galleta, fourwing saltbush, blue and black grama, sand dropseed, Mormon tea, and some sagebrush and juniper.

MS2 (Winona-Boysag-Rock Outcrop): This unit is described as shallow, medium, and fine-textured, undulating to rolling soils and rock outcrop on plateaus and plains. It consists of well-drained soils and rock outcrop on broad limestone and sandstone plateaus and plains. These soils form in residuum on limestone and calcareous sandstone. They occur at elevations ranging from 4,600 to 6,600 ft. (1,400 to 2,000 m) where mean annual precipitation is about 10-16 inches (25-41 cm), with exceptional precipitation levels of up to 20 inches (50 cm) in higher areas. Winona soils make up 60%, Boysag soils 15%, rock outcrop 15%, and minor associated soils make up the remaining 10%. Plant cover includes juniper, pinyon pine, cliffrose, ceanothus, big sagebrush, blue and black grama, Indian ricegrass, pine dropseed, spike muhly, and galleta.

MS4 (Rudd-Bandera-Cabezon): This unit is described as shallow, gravelly, cobbly and stony, medium and fine-textured, undulating soils on plains and mesa tops and gently rolling to steep soils on cinder cones. It consists of well-drained and somewhat excessively drained soils formed in residuum and alluvium weathered from basalt, andesite, ash flow tuffs, cinders, and related volcanic rock. They occur at elevations ranging from 5,000 to 7,400 ft. (1,520 to 2,250 m) where mean annual precipitation is about 10-16 inches (25-41 cm), with as much as 20 inches (50 cm) in some areas. Rudd soils make up about 40%, Bandera soils about 25%, Cabezon soils 20%, and minor associated soils and rock outcrop 15%. Plant cover includes blue, black, and sideoats grama, galleta, western wheatgrass, juniper, shrub live oak, big sagebrush, cliffrose, some Mormon tea, and some pinyon and ponderosa pine.

MS5 (Roundtop-Boysag): This unit is described as shallow and moderately deep, gravelly, fine-textured, undulating to moderately steep soils on plains and mountains. It consists of well-drained soils formed in residuum weathered from limestone and calcareous sandstone. Roundtop soils make up about 60%, Boysag soils 25%, and minor associated soils 15%. They occur at elevations ranging from 6,200 to 7,200 ft. (1,880 to 2,180 m) where mean annual precipitation is about 12-18 inches (30-46 cm). Plant cover includes pinyon and some ponderosa pine, juniper, Gambel oak, mountain mahogany, cliffrose, beargrass, ring muhly, squirreltail, pine dropseed, Indian ricegrass, rabbitbrush, big sagebrush, and blue, black, and sideoats grama.

Reference:

Hendricks, D.M. Arizona Soils. University of Arizona College of Agriculture (Tucson, Arizona), 1985.