Chapter 46
Ecological Subregions of the United States



Black Hills Coniferous Forest

One Section has been delineated in this Province: The area of this Section, which is located in Wyoming and South Dakota, is about 3,700 mi2 (9,600 km2).

Section M334A--Black Hills

Geomorphology. Slopes range from moderate on some of the high plateaus to very steep along drainage ways and on peaks and ridges. Narrow valleys are mostly gently sloping to strongly sloping. Elevation ranges from 2,950 to 7,220 ft. (900 to 2,200 m). This Section is within Fenneman and Johnson's Great Plains geomorphic physical division.

Lithology and Stratigraphy. The central part of the Section is Precambrian granite and metamorphosed sedimentary and volcanic rocks. The periphery of the North Dakota area of the Section is Paleozoic carbonates and shales. Most of the Wyoming part of the Section is Cretaceous sandstones, siltstones, shales, and Tertiary intrusive igneous rocks.

Soil Taxa. There are mesic, frigid, and cryic temperature regimes. Soils include Alfisols, Inceptisols, and Entisols, including Orthents and Boralfs.

Potential Natural Vegetation. K\"uchler classified vegetation as dominates open to dense forest vegetation. Black Hills ponderosa pine forest.

Fauna. Typical large mammals of this Section are mule deer, white-tailed deer, elk, and mountain lion. Smaller common mammals are jackrabbits, red foxes, swift foxes, porcupines, and bushy-tailed wood rats. Year-round forest dwelling bird species include the pygmy nuthatch, red-breasted nuthatch, black-capped chickadee, and Cooper's hawk. Summer residents include sharp-shinned hawk, belted kingfisher, chipping sparrow, and swallow. Representative herpetofauna are the prairie rattlesnake, wandering garter snake, snapping turtle, spiney softshell turtle, boreal chorus frog, and Great Plains toad.

Climate. Precipitation ranges from 15 to 26 in (370 to 650 mm). Temperature averages 37 to 48 oF (3 to 9 oC). The growing season 80 to 140 days.

Surface Water Characteristics. Perennial streams, springs, and shallow wells are present. Cold Brook Reservoir and Pactolo Reservior are sizable man-made reservoirs in this area. The Belle Fourche and Laramie Rivers, and the South Fork of the Powder River flow through here.

Disturbance Regimes. Fire, insects, and disease are principal natural disturbances.

Land Use. Most of this area is national forest land. A small amount of acreage is in small farms, and ranches. Timber harvest, grazing, mining, and recreation are uses of this Section.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.