Pinyon-Juniper Woodlands

General Information

Tree Species—These coniferous woodlands are below the ponderosa pine forests, at elevations between 4,500 to 7,500 ft. Colorado pinyon (Pinus edulis) is found throughout, with singleleaf pinyon (Pinus monophylla) occurring on limited areas. North of the Mogollon Rim, Utah juniper (Juniperus osteosperma), Rocky Mountain juniper (J. scopulorum), and one-seed juniper (J. monosperma) are intermixed with pinyon, while alligator juniper and Utah juniper are south of the Mogollon Rim. Annual and perennial grasses and grass-like plants, forbs, and half-shrubs and shrubs abound beneath the woodland overstories.

Precipitation—There are wide fluctuations in weather patterns throughout the pinyon-juniper woodlands. Annual precipitation varies from 12 to 24 inches. Winter precipitation is usually rain with occasional snow. Evapotranspiration rates are relatively high in the growing season. Only during the coldest months of December through February is precipitation greater than the evapotranspiration rates. Also see: water yield and potential increase.

Fifty percent of more of the annual precipitation occurs during the winter season and is the major source of runoff --80 percent of the annual streamflow. Most stream channel originating in the pinyon-juniper woodland type are ephemeral, flowing only during the spring snowmelt period. Because winter precipitation normally occurs as low intensity rain or snow, and runoff is the product of either low intensity rainfall or snowmelt, erosion potential is energy limited and the dominant parent materials further limit the supply of sediment (e.i., heavy clay soil characteristic of volvanic-derived soil) or the transport of the dominant sediment size (e.i., coarse textured soils derived from sedimentary and granitic parent materials) unless runoff is substantially concentrated.

Resources and Activities—Recreation, a resource of these woodland areas, is limited by summer temperatures and the relative lack of water. These woodlands are also an important source of firewood. Livestock, which spend their summers at higher elevations, graze in the woodlands in winter. These woodlands are also seasonal and yearlong habitats for many wildlife species.

Soils—Soils are derived from basalt, limestone, and sandstone parent material. Pinyon-juniper woodlands generally occupy extensive areas of gently rolling topography. With the exception of steep canyon walls, few slopes exceed 20% to 25%.

Images Available

There are currently over 300 images available in the image database illustrating various aspects and conditions found in pinyon-juniper ecosystems in southwestern United States. These can be accessed after getting into the database by using the key words pinyon-juniper. Additional key words are available for searching the images in a drop down list within the database.