52 Cold-Temperate Forests and Woodlands 2.4 Great Basin Conifer Woodland David E. Brown Arizona Game and Fish Department This cold-adapted evergreen woodland is characterized by the unequal dominance of two conifers-juniper (Juniperus) and pinyon (Pinus). These trees rarely, if ever, exceed min height and are typically openly spaced (woodland), except at higher elevations and other less xeric sites where interlocking crowns may present a closed (forest) aspect. The shorter, bushier junipers ("cedars") are generally more prevalent than pinyons, but either may occur as an essentially pure stand. Structurally, these juniper-pinyon woodlands are among the simplest communities in the Southwest. This woodland has its evolutionary center in the Great Basin and is one of the most extensive vegetative types in the Southwest. It extends southward through Colorado, Utah, Nevada, southeastern California, northern Arizona, and New Mexico to mountainous area in Trans-pecos Texas, southern New Mexico, central Arizona, and northern Baja California Norte. Juniper-pinyon woodland covers extensive areas here between 1,500 and 2,0 m (extremes are 1,050 and 2,00 m) and reaches its greatest development on mesas, plateaus, piedmonts, slopes, and ridges. Several species of juniper may assume or share dominance in the Southwest. Rocky Mountain Juniper (Juniperus scopulorum) is an important constituent in the higher and colder woodlands in Colorado, northern New Mexico and Arizona, and more locally in southern Nevada and Utah (Fig. ). In northwestern New Mexico, western Colorado, Utah, northern Arizona, Nevada, and eastern California, the Great Basin, Utah Juniper (1. osteospenna) may be the more common. One-seed Juniper (1. monosperma) is the prevalent species in juniper-pinyon woodlands in west Texas, central and southern New Mexico, and much of sub-mogollon Arizona (Fig. ), as is the closely related 1. californica in southern California and Baja California Norte. Rocky Mountain Pinyon (Pinus edulis) is the common pinyon pine almost throughout (Fig. ) except that west of ca. longitude 3.5 it is largely replaced by the single needled form (P. monophylla) or farther south in Baja California Norte by the Four-leaved Pinyon (P. quadrifolia) (Fig. ). Not included as Great Basin conifer woodland species are Alligator-bark Juniper and Mexican Pinyon. Although the former species may be present in juniper-pinyon woodland with One-seed Juniper and Rocky Mountain Pinyon in central and southeastern Arizona and west-central New Mexico, both trees are species of the Madrean evergreen woodland farther south; they normally occur in the communities of oaks (encinal) and oaks and pine (oak-pine) that have their center of distribution in Mexico. This is also the case with Pinchott and Drooping Juniper east of the Sierra Madre Occidental and in the Big Bend region of Texas. Precipitation ranges from 0 to 500 mm per year with extremes of 0 and 560 mm (Table 4). This sparse rainfall is more or less evenly spread throughout the year, and much of the winter precipitation falls as snow. Summer precipitation is of more importance in eastern juniper-pinyon woodlands than in the western portions where more than 80% of the precipitation falls during the late fall and winter. The unifying climatic feature of all these arid woodlands is cold winter minimum temperatures; freezing temperatures can be expected to occur about 0 or more days a year, precluding the participation of evergreen oaks and other warm-temperate forms. Habitats tend to be rocky, with thin soils predominating. In
. Brown Great Basin Conifer Woodland 53 Figure. Extensive juniper-pinyon woodland of Rocky Mountain lunipets (Juniperus scopulorum) with some Pinyon (Pinus edulis) and Alligatorbark lunipet (Juniperus deppeana) south of the Mogollon Rim, Coconino National Forest, Arizona, ca. 2,000 m elevation. This southern [asciatioti of Great Basin conifer woodland gives way to interior chaparral and semidesert grassland immediately downslope to the south. the central and eastern areas of the Southwest, the principal contact with Great Basin conifer woodland is grassland, and extensive landscapes there are characterized by parkland and savanna-like mosaics. The openness of these "cedar glades" depends on soil type, range history and condition. Here the understory is typically composed of grasses [e.g., Bouteloua gracilis) and.iuubs, e.g. Threadleaf Groundsel jsenecio longilobus) and Snakeweed jgutierrezia sarothrae) of the Plains grassland. Also well represented in many of these grass understories are Galleta Grass jhilaria jamesii), Indian Ricegrass joryzopsis hymenoides), Western Wheatgrass jagropyron smithii) and other grasses of the Plains grassland Great Basin grassland transition. Other grasses locally common to abundant include several muhleys jmuhlenbergia spp.), dropseeds jsporobolus spp.], and Junegrass jkoeleria cristata). Junipers have invaded large areas of former grassland [Humphrey, 62). That this is also true for pinyons is less certain, and woodlands well stocked with pinyons are not to be considered as disclimax grassland-as numerous futile attempts to "reconvert" these areas to grass will attest. Junipers tend to be at lower elevations than pinyons' and normally occupy the deeper soil sites below 2,000 m. In the Great Basin, conifer woodland occurs on the mountain gradient above and within Great Basin desertscrub. Here Big Sagebrush is the principal and often the almost exclusive understory plant. Indeed, Big Sagebrush continues to be an important subdominant in juniper-pinyon woodlands
54 Cold-Temperate Forests and Woodlands Figure. Series of One-seed Juniper (Juniperus monosperma' and Rocky Mountain Pinyon (Pinus edulis) near Aurora, San Miguel County, New Mexico ca. 1,80 m elevation. An eastern [asciatioti with understory of Blue Grama (Bouteloua gracilis). south-westward to the Sierra Juarez in Baja California Norte. Other more or less Great Basin Desert associates of general or regional importance are rabbitbrush (Chrysothamnus spp.i, Winterfat (Ceratoides lanata), Shadscale (Atriplex confertifolia), and Black Sagebrush (Artemisia arbuscula spp. nova). On those mountain ranges over 1,500 m elevation in and adjacent to the Mohave Desert, Blackbrush (Coleogyne ramosissima) is a common major understory component of the pinyon-juniper woodlands present there. In northwestern and central Arizona understory species of adjacent interior chaparral and even Sonoran desertscrub (Arizona Upland subdivision) may be important in the makeup [e.g., Quercus turbinella, Rhamnus crocea, Garrya wngbtii, Catiotia holacantha). Chaparral also intergrades with Great Basin conifer woodland in southern California and Baja California Norte. In the Sacramento, Guadalupe, Organ, Burro, Peloncillo, and other southern New Mexico mountains, in sub-mogollon Arizona, and the Trans-Pecos region of Texas, Great Basin conifer woodland phases into the more southerly derived Madrean evergreen woodland. This transition is marked by the disappearance of Juniperus osteosperma, f. scopulorum., and Pinus edulis, and the appearance of f. deppeana, Quercus emoryi, Q. gtisea, Q. arizonica, and Pinus cembroides with their respective floral and faunal associates. This replacement may be gradual or abrupt and is much influenced by slope exposure, elevation, and edaphic situation. Generally the warm-temperate and more moisture-requiring Madrean species first make their appearance on south slopes, pro-
Brown Great Basin Conifer Woodland 55 Figure. Pinyon {Pinus edulis} dominated Great Basin conifer woodland on Fish Tail Mesa, Kaibab National Forest, Arizona ca. 1,585 m elevation. The maiot understory species on this ungrazed site is Big Sagebrush (Artemisia tridentatal The shrub in right center of photo is Cliffrose (Cowania mexicana), a common constituent in Great Basin conifer woodlands and an important winter browse species for Mule Deer (Odocoileus hemionus). tected hillsides, and in drainages; the southernmost conifer woodlands are to be found on high north slopes and mesas. Also, particularly at lower elevation, there may be integration with interior chaparral, e.g., in the Organ and Burro mountains in New Mexico and in the Apache and other mountain ranges in Arizona. The upslope contact with Great Basin conifer woodland is montane conifer forest, except north of Parallel (and locally elsewhere as in the Sandia and Manzano mountains I where Great Basin montane scrubland makes its appearance. Here, and not uncommonly elsewhere at higher elevations within the conifer woodland, important plant associates are "Gambel Oak (Quercus gambelii-in shrub form I, mountainmahoganies (Cercocarpus montanus, C. ledifolius, C. intricatusl, Skunkbush Sumac (Rhus trilobatal, Saskatoon Serviceberry (Amelanchier alnifolial, snowberries (Symphoricarpos spp.l, and currants (Ribes spp]. Other shrubs generally important as subdominant associates in juniper-pinyon woodland include Cliffrose (Cowania mexicsnc], Apache Plume (Fallugia paradoxa I, Mormon-tea (Ephedra viiidis and others], Barberry or Algerita (Berberis {remonti and B. haematocarpa I, Fourwing Saltbush (Atriplex canescens], Small Soapweed (Yucca glaucal, and Datil (Yucca baccatal: other associated species as Buffalo-berry (Shepherdia spp.], Antelope Bitterbrush (Purshia tridentatal, and Fernbush (Chamaebatiaria millefoliuml are of more local occurrence. Herbs and grasses commonly encountered throughout much of the conifer woodland include gilias (Cilia spp.1
S6 Cold-Temperate Forests and Woodlands Figure. Great Basin conifer woodland of Four-leaved Pinyon (Pinus quadrifolia), Singleleaf Pinyon (P. monophylla), and California lunipet (Juniperus californica) in the Sierra luatez; Baia California Norte, ca. 1,0 m elevation. The sunlit shrub in lower right center is Big Sagebrush (Artemisia tridentata) and these woodlands possess a surprising physiognomic and biotic similarity through a number of widespread fasciations. buckwheats (Eriogonum spp.i, Sego-lily (Calochortus nuttallil, penstemons (Penstemon spp.], several globemallows (Sphaeralcea digitate, S. matgitiata, S. coccinea, and others I, Louisiana Sagebrush (Artemisia ludovicianal, lupines (Lupinus spp.i, and bromes (Bromus spp.]. Several cacti have Great Basin conifer woodland as their center of distribution or are otherwise well represented here. Among these are the Red Hedgehog Cactus (Echinocereus tiiglochidiatus var. melanacanthusl and the hedgehogs E. engelmanii var. variegatus and E. fendleri var. fendleri; the prickly-pears Opuntia etinacea, O. basilatis var. aurea, O. pbaeacantha, O. macrorhiza, O. polyacantha, O. fragilis; the chollas O. whipplei and 0. imbticata; Sclerocactus whipplei var. intermedius; Mammillaria wiigbtii; Pediocactus papytacanthus, P. simpsonii; Coryphantha vivipara var. aiizotiica and C. missouriensis. Only a few vertebrates are closely tied to Great Basin conifer woodland [e.g., Pinyon Mouse (Peromyscus truei], Pinyon Jay (Gymnorhinus cvanocepbalusi, Gray Flycatcher (Empidonax wrightii)) or are centered here [e.g., Bushy-tailed Woodrat (Neotoma cinerea arizonael, Gray Vireo (Vireo vicinior), Black-throated Gray Warbler (Dendroica nigrescens], Scott's Oriole (Icterus parisoruml, and the Plateau Whiptail (Cnemidophorus velox)). A somewhat larger number of the more adaptable, and, therefore, more widely distributed species also may be found in these relatively recent environments. Furthermore, juniper-pinyon woodlands are more or less seasonal habitats for a number of montane and subalpine animals; as such they are often of great importance as winter range for Rocky Mountain Elk and Mule Deer.
. Brown Great Basin Conifer Woodland 5 Table 4. Precipitation within and adjacent to Great Basin Conifer Woodland Elevation M_ea_n_M_on_t_hl_y_P_re_ci_p_ita_t_io_n_in_m_m _ Station (inm) F M A M A S o N D Total Orderville, UT ' llr' Mesa Verde N.P., CO 2,5 ' 8 ' Trinidad FAA CO 1,51 ' 4 ' Conchas Dam, NM 1,4 35 ' 4 ' Santa Rosa, NM 1,8 5' 4 41' Elk, NM 3E 1, 56' 5 ' Mesacalero, NM 2,068 ' 5 48' Santa Fe, NM 2, 35 41' 5 56' Mountainaire, NM 1,8 ' 6 ' Cuba, NM 2, 36 02' 6 58' Fort Bayard, NM 1,82 48' 8 0' Zuni R.S., NM 1,66 35 06' 8 ' Blue, AZ 1,56 ' 06' Lukachukai, AZ 1,8 36 ' l4' Klagetoh, AZ 1,4 36 ' ' Pinedale, AZ 1,81 ' 1 ' Cibecue, AZ 1,50 03' 1 ' Betatakin, AZ 2,2 36 41' 1 ' Pleasant Valley 1,53 R.S.,AZ 06' 1 56' Walnut Can. 2,0 N.M,AZ 35 ' 1 31' Sedona R.S., AZ 1,3 52' III 46' Grand Canyon, AZ 2,5 36 03' 1 08' Drake, AZ 1,4 58' 1 ' Walnut Creek, AZ 1,551 56' 1 4' Ml Trumbull, AZ 1,0 36 ' 3 ' 1,658 45 3 35 31 368 44 8 35 48 4 42 3 3 13 3 44 42 31 31 6 6 35 41 8 13 45 65 6 4 54 0 45 6 53 60 3 62 48 68 54 48 3 81 60 83 53 2 53 81 2 88 61 54 62 8 52 36 58 55 50 6 3 42 46 55 6 65 45 31 450 13 3 3 4 0 362 8 350 536 8 2 4 4 1 51 41 48 448 44 4 366 35 0 36 34 8