Tree SpeciesThese 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.
PrecipitationThere 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 ActivitiesRecreation, 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.
SoilsSoils 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 around 350 images available in the image
database illustrating various aspects and conditions found in chaparral
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.