Pinyon–juniper woodland

Both pinyon pine and juniper species reproduce exclusively through seed production, and produce most of their seeds during mast years, which occur about every three to five years. These birds are the only species capable of re-establishing pinyon pines after major disruptions like fires and beetle infestations, and according to Audubon are critical to the ecosystem's survival. Pinyon-juniper woodlands support a number of native species including the pinyon mouse and the pinyon jay. The woodlands also serve as refuges for desert and mountain animals attempting to escape heat or cold; few animals other than the pinyon jay stay in the ecosystem year-round. However, it serves as important habitat for a number of endangered species, including Woodhouse's scrub jay and the gray vireo. == Subtypes ==

Pinyon–juniper woodland has three major subtypes based on vegetation: pinyon-juniper savannah, pinyon-juniper wooded shrubland, and pinyon-juniper persistent woodland. Pinyon-juniper savannah Pinyon-juniper savannahs are dominated by grasses and forbs, with dense undergrowth and savannah-like sparser trees. Monsoon summer rains are common in pinyon-juniper savannahs, since they favor the growth of warm-season grasses. Common grass species are blue grama, other species of grama grass, new mexico muhly, curlyleaf muhly, and needle and thread grass. Pinyon-juniper persistent woodlands Pinyon-juniper persistent woodlands are dominated by trees, with a variety of tree ages, often in areas with winter or bi-modal precipitation. Persistent woodland sites are usually unproductive, with thin soils and sparse ground or shrub cover, often occurring on rocky or rugged terrain. Pinyon-juniper wooded shrublands Pinyon-juniper wooded shrublands are transition zones where pinyon-juniper woodland is expanding or contracting, often bordering other vegetation types. In absence of fire, they shift from grass and forb-dominated, to shrub-dominated, to tree-dominated communities over time. Common shrub species are big sagebrush, other species in that genus, antelope bitterbrush, rabbitbrush, mountain mahogany, and snakeweed. == Range and species composition ==

Today, pinyon–juniper woodland range spans from New Mexico, to the eastern Sierra Nevada, the Colorado Plateau, the Great Basin, and higher elevations of Mountain ranges of the Mojave Desert. The woodland's range includes the Mogollon Rim in the south, to its northern extent in the Snake River Plain. It typically occurs at between . Historically, however, the range and elevations of pinyon-juniper woodland have shifted based on differences in climate. On the order of 10,000 years ago during the Wisconsin glaciation, pinyon-juniper woodlands occurred in areas that today are the Chihuahuan, Mojave, and Sonoran desert lowlands, and since then pinyon-juniper altitude ranges have continued to change based on changing moisture and temperature ranges over time. Due to its temperature tolerance, pinyon generally does not naturally grow north of northern Utah, as well as some portions of southern Wyoming and Idaho. In Arizona the great basin woodland species are Juniperus arizonica, Juniperus californica in western Arizona, Juniperus deppeana, Juniperus monosperma, Juniperus osteosperma, Juniperus scopulorum at higher elevations, Pinus monophylla var. fallax below the Colorado plateau, and Pinus edulis on the Colorado plateau. In Arizona the great basin woodland includes many species of oaks: Quercus turbinella, Quercus gambelii at higher elevations, Quercus grisea, Quercus arizonica, and Quercus emoryi. In Southern Arizona, Pinus discolor, Juniperus deppeana, and Pinus leiophylla make up the conifer woodland with many oak species. California In California, pinyon-juniper woodland is mainly found in pockets on the eastern side of the Sierra Nevada, and also somewhat in the Transverse Ranges and Peninsular Ranges, as well as several isolated patches on desert mountaintops. Mojave Desert In the steppes adjoining the Mojave Desert, this vegetation type can be found in areas receiving inches of annual precipitation, and between . Associates include bitterbrush (Purshia glandulosa), Apache plume (Fallugia paradoxa), desert sagebrush (Artemisia tridentata), green ephedra (Ephedra viridis), mountain mahoganies (Cercocarpus spp.), and buckwheats (Eriogonum spp.). By Major Land Resource Area Part, though not all, of the range of pinyon-juniper woodlands occurs interspersed with sagebrush throughout the D-region Major Land Resource Areas, including in D-35, D-36, D-38, and D-39, as well as in the two E-region areas E-49 and E-51. D-35 (Colorado Plateau) In the D-35 (Colorado Plateau) region, pinyon-juniper appears in a mosaic with sagebrush ecosystems extending across the region. Understories generally include galleta (Hilaria rigida), blue grama (Bouteloua gracilis), black grama (Bouteloua eriopoda), and western wheatgrass (Pascopyrum). However, differences exist based on soil composition and elevation. Alkaline regions at lower elevations include alkali sacaton (Sporobolus airoides), Indian ricegrass (Oryzopsis hymenoides), needled grasses (Stipa spp.), four-wing saltbush (Atriplex canescens), and winterfat (Krascheninnikovia lanata). Regions with more saline soil include greasewood (Adenostoma fasciculatum) and shadescale (Atriplex confertifolia). D-36 (Southwestern Plateaus, Mesas, and Foothills) In the D-36 (Southwestern Plateaus, Mesas, and Foothills) region, pinyon-juniper woodland appears in a mosaic gradient with other ecosystems based on elevation. Gambel Oak (Quercus gambelii), mountain muhly (Muhlenbergia montana), and snowberry (Symphoricarpos spp.) are interspersed throughout the lower-elevation pinyon-juniper woodlands. D-38 (Mogollon Transition) In the D-38 (Mogollon Transition) region, pinyon-juniper woodland is also distributed in an elevation gradient. The pinyon is predominantly Mexican pinyon pine (Pinus cembroides). Trees and shrubs associated with the ecosystem include Mexican blue oak (Quercus oblongifolia), New Mexico locust (Robinia neomexicana), buckbrush (Ceanothus cuneatus), and manzanita (Arctostaphylos spp.). Present in the understory are a diverse range of grass and forb species, including grama, needle-grasses and jojoba. D-39 (Arizona and New Mexico Mountains) In the D-39 (Arizona and New Mexico Mountains) region, pinyon-juniper woodland is distributed in an elevation gradient where pinyon-juniper woodlands are present at mid-elevations, over (in areas with deep soils) areas of grassland. The woodlands dominate north-facing slopes, but on north-facing slopes are intermixed with oak species and an understory of fescues, blue-grasses, and brome species. Higher elevations are dominated by firs and spruces. E regions In the E-49 (Southern Rocky Mountain Foothills) region, pinyon-juniper woodlands are found exclusively in lower elevations in the south. They are mixed with sagebrush, mountain mahogany (Cercocarpus spp.), grama and needled grasses, and western wheatgrass. In the E-51 (High Intermountain Valleys) region, pinyon-juniper woodlands occur in a mosaic with shrub-grasslands extending across the region. Patches of pinyon-juniper systems are present in E-47 (Wasatch and Uinta Mountains) and E-48A (Southern Rocky Mountains). ==See also==