The pinyon-juniper ecosystem ranges from southern Idaho and southeast Oregon southward throughout the mountainous areas of the west. Like other mountain ecosystem, it is found at a particular elevation in a given region. Pinyon-juniper is generally bounded by the northern desert shrub, desert plains grassland, or shortgrass plains at the lower part of its elevation range and by Montane forest at its upper limits. Acreage of pinyon-juniper type is higher among the western mountain range types.

Climate. Precipitation ranges from 30 to 40 centimeters with a major portion coming in the warmer months in the more extensive southern areas. The frost free period is 120 days in the north to 200 days or more in the south.

Soils. The soils of the pinyon-juniper include aridisols, mollisols, and entisols. The aridisols and mollisols tend toward well developed horizons, while the entisols have little soil development.

Vegetation. The pinyon-juniper type is characterized by an open stand of small, xeric shrubby trees, earning it the name, "pygmy forest". The principal tree species are the pines, pinyon pine (Pinus edulis), Mexican pinyon pine (P. cembroides), and the junipers, oneseeded juniper (Juniperus monosperma), rocky mountain juniper (J. scopulorum), and other juniper species. The open nature of the stands allows for a substantial grass cover, which includes blue grama, black grama, curlymesquite, needlegrasses, and muhlys.

Management. About 80% of the pinyon-juniper type is grazed. Livestock carrying capacities range from 2 to 8 hectares per animal-unit-month of grazing. Much of the area is overgrazed, and in some areas livestock consume the tree growth. Normally, livestock on good condition range will not graze tree growth. One primary reason for reduced grazing value of the pinyon-juniper type is due to fire protection. There is a marked reduction in woody species in pinyon-juniper type in New Mexico due to wildfire. This vegetation type represents one of the more important deer habitats of the southwestern United States.