Pinyon is a minor component of the following forest cover types (61):  Bristlecone Pine (Society of American Foresters (Type 209), Interior  Douglas-Fir (Type 210), Rocky Mountain Juniper (Type 220), Interior  Ponderosa Pine (Type 237), Arizona Cypress (Type 240), and Western Live  Oak (Type 241). It is an integral component in Pinyon-Juniper (Type 239)  over a large area. However, as the type extends westward, pinyon is  replaced by singleleaf pinyon (Pinus monophylla) in Nevada and  some localities in western Utah and northwestern Arizona (4,67). Southward  along the Mexican border, Mexican pinyon (P. cembroides var. bicolor),  recently given separate species status as border pinyon (P.  discolor), becomes the dominant tree in the woodlands (6,48,49).

    Common associates of pinyon over most of its range are oneseed juniper  (Juniperus monosperma) and Utah juniper (J. osteosperma); redberry  juniper (J. erythrocarpa), also a one-seeded juniper, is confined  to the southern portion. Alligator juniper (J. deppeana) and Rocky  Mountain juniper (J. scopulorum) are also found in some localities  (1,4,67). Oneseed juniper predominates in east-central Arizona and most of  New Mexico, and extends into western Texas and south-central Colorado.  Rocky Mountain juniper is also a common component in northern New Mexico  and the western half of Colorado, but it is found over most of the  woodlands as well. It usually grows at higher elevations and is seldom  dominant in the stand. Utah juniper is the codominant associate in Utah,  northern Arizona, western Colorado, and northwestern New Mexico. At  higher, more mesic elevations in southern and western New Mexico and  westward into central Arizona, alligator juniper commonly forms a  component of stands.

    Although pinyon-juniper woodlands consist of relatively few tree  species, stands exhibit considerable diversity in appearance and  composition (4). Some have nearly closed canopies of a single tree species  with little or no understory vegetation. Others are open, with widely  scattered pines, junipers, or both among grasses and shrubs. A typical  pinyon-juniper woodland, with its many-branched trees resembling shrubs,  has the appearance of a stunted coniferous forest.

    Any particular stand usually contains only a few different plant  species, but because of the wide distribution of the type, the total flora  associated with woodlands is quite varied (4,67,73). Common tree and shrub  associates include: Gambel oak (Quercus gambelii), gray oak (Q.  grisea), shrub live oak (Q. turbinella), true  mountain-mahogany (Cercocarpus montanus), curlleaf  mountain-mahogany (C. ledifolius), antelope bitterbrush (Purshia  tridentata), big sagebrush (Artemisia tridentata), black  sagebrush (A. nova), serviceberry (Amelanchier spp.),  rabbitbrush (Chrysothamnus spp.), Mexican cliffrose  (Cowania mexicana), Apache-plume (Fallugia paradoxa), skunkbush  (Rhus trilobata), Mormon-tea (Ephedra spp.), yucca  (Yucca spp.), opuntia (Opuntia spp.), broom  snakeweed (Gutierrezia sarothrae), and buckwheat (Eriogonum  spp.).

    Some of the more important herbaceous plants are goosefoot (Chenopodium  graveolens), rock goldenrod (Solidago pumila), gilia (Gilia  spp.), penstemon (Penstemon spp.), segolily  (Calochortus nuttallii), globemallow (Sphaeralcea spp.),  white aster (Aster hirtifolius), hymenopappus (Hymenopappus  filifolius var. lugens), Indian ricegrass (Oryzopsis  hymenoides), dropseed (Sporobolus spp.), needle-and-thread  (Stipa comata), squirreltail (Sitanion hystrix), Junegrass  (Koeleria pyramidata), galleta (Hilaria jamesii), blue  grama (Bouteloua gracilis), sideoats grama (B. curtipendula),  ring muhly (Muhlenbergia torreyi), western wheatgrass (Agropyron  smithii), bluebunch wheatgrass (A. spicatum), slender  wheatgrass (A. trachycaulum), downy chess (Bromus tectorum),  and threeawn (Arisitada spp.).