Great Basin Conifer Woodland

Item Type Article

Authors Brown, David E.

Publisher University of Arizona (Tucson, AZ)

Journal Desert Plants

Rights Copyright © Arizona Board of Regents. The University of Arizona.

Download date 01/10/2021 13:51:34

Link to Item http://hdl.handle.net/10150/550963 52 Cold-Temperate Forests and Woodlands

This cold-adapted evergreen woodland is characterized by 122.4 Great Basin the unequal dominance of two conifers-juniper (Juniperus) and pinyon (Pinus). These trees rarely, if ever, exceed 12 min height and are typically openly spaced (woodland), except at Conifer Woodland 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. David E. Brown Structurally, these juniper-pinyon woodlands are among the in the Arizona Game and Fish Department simplest communities 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 2,300 m (extremes are 1,050 and 2,700 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. 23). 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. 24), 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. 25) except that west of ca. longitude 113.5° 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. 26). 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 com­ munities 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 250 to 500 mm per year with extremes of 180 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 150 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 23. 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 spp.), dropseeds jSporobolus spp.], and Junegrass jKoeleria contact with Great Basin conifer woodland is grassland, and cristata). extensive landscapes there are characterized by parkland and Junipers have invaded large areas of former grassland savanna-like mosaics. The openness of these "cedar glades" [Humphrey, 1962). That this is also true for pinyons is less depends on soil type, range history and condition. Here the certain, and woodlands well stocked with pinyons are not to understory is typically composed of grasses [e.g., Bouteloua be considered as disclimax grassland-as numerous futile gracilis) and .iuubs, e.g. Threadleaf Groundsel jSenecio attempts to "reconvert" these areas to grass will attest. longilobus) and Snakeweed jGutierrezia sarothrae) of the tend to be at lower elevations than and Junipers pinyons' . Plains grassland. Also well represented in many of these grass normally occupy the deeper soil sites below 2,000 m. understories are Galleta Grass jHilaria jamesii), Indian In the Great Basin, conifer woodland occurs on the Ricegrass jOryzopsis hymenoides), Western Wheatgrass mountain gradient above and within Great Basin desertscrub. jAgropyron smithii) and other grasses of the Plains grassland­ Here Big Sagebrush is the principal and often the almost Great Basin grassland transition. Other grasses locally exclusive understory plant. Indeed, Big Sagebrush continues common to abundant include several muhleys jMuhlenbergia to be an important subdominant in juniper-pinyon woodlands 54 Cold-Temperate Forests and Woodlands

Figure 24. Series of One-seed Juniper (Juniperus monosperma' and Rocky Mountain Pinyon (Pinus edulis) near Aurora, San Miguel County, New Mexico ca. 1,890 m elevation. An eastern [asciatioti with understory of Blue Grama (Bouteloua gracilis).

south-westward to the Sierra Juarez in Baja California Norte. California and Baja California Norte. Other more or less Great Basin Desert associates of general or In the Sacramento, Guadalupe, Organ, Burro, Peloncillo, regional importance are rabbitbrush (Chrysothamnus spp.I, and other southern New Mexico mountains, in sub-Mogollon Winterfat (Ceratoides lanata), Shadscale (Atriplex confertifolia), Arizona, and the Trans-Pecos region of Texas, Great Basin and Black Sagebrush (Artemisia arbuscula spp. nova). On those conifer woodland phases into the more southerly derived mountain ranges over 1,500 m elevation in and adjacent to Madrean evergreen woodland. This transition is marked by the Mohave Desert, Blackbrush (Coleogyne ramosissima) is a the disappearance of Juniperus osteosperma, f. scopulorum., common major understory component of the pinyon-juniper and Pinus edulis, and the appearance of f. deppeana, Quercus woodlands present there. In northwestern and central Arizona emoryi, Q. gtisea, Q. arizonica, and Pinus cembroides with their understory species of adjacent interior chaparral and even respective floral and faunal associates. This replacement may Sonoran desertscrub (Arizona Upland subdivision) may be be gradual or abrupt and is much influenced by slope important in the makeup [e.g., Quercus turbinella, Rhamnus exposure, elevation, and edaphic situation. Generally the crocea, Garrya wngbtii, Catiotia holacantha). Chaparral also warm-temperate and more moisture-requiring Madrean intergrades with Great Basin conifer woodland in southern species first make their appearance on south slopes, pro- Brown Great Basin Conifer Woodland 55

Figure 25. 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 intricatusl, Skunkbush Sumac (Rhus trilobatal, Saskatoon Ser­ woodlands are to be found on high north slopes and mesas. viceberry (Amelanchier alnifolial, snowberries (Symphoricarpos Also, particularly at lower elevation, there may be integration spp.l, and currants (Ribes spp]. with interior chaparral, e.g., in the Organ and Burro mountains Other shrubs generally important as subdominant associ­ in New Mexico and in the Apache and other mountain ranges ates in juniper-pinyon woodland include Cliffrose (Cowania in Arizona. mexicsnc], Apache Plume (Fallugia paradoxa I, Mormon-tea The upslope contact with Great Basin conifer woodland is (Ephedra viiidis and others], Barberry or Algerita (Berberis montane conifer forest, except north of Parallel 37° (and {remonti and B. haematocarpa I, Fourwing Saltbush (Atriplex locally elsewhere as in the Sandia and Manzano mountains I canescens], Small Soapweed (Yucca glaucal, and Datil (Yucca where Great Basin montane scrubland makes its appearance. baccatal: other associated species as Buffalo-berry (Shepherdia Here, and not uncommonly elsewhere at higher elevations spp.], Antelope Bitterbrush (Purshia tridentatal, and Fernbush within the conifer woodland, important plant associates are (Chamaebatiaria millefoliuml are of more local occurrence. "Gambel Oak (Quercus gambelii-in shrub form I, mountain­ Herbs and grasses commonly encountered throughout mahoganies (Cercocarpus montanus, C. ledifolius, C. much of the conifer woodland include gilias (Cilia spp.1 S6 Cold-Temperate Forests and Woodlands

Figure 26. 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. 1,400 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, aiizotiica and C. missouriensis. penstemons (Penstemon spp.], several globemallows Only a few vertebrates are closely tied to Great Basin (Sphaeralcea digitate, S. matgitiata, S. coccinea, and others I, conifer woodland [e.g., Pinyon Mouse (Peromyscus truei], Louisiana Sagebrush (Artemisia ludovicianal, lupines (Lupinus Pinyon Jay (Gymnorhinus cvanocepbalusi, Gray Flycatcher spp.I, and bromes (Bromus spp.]. (Empidonax wrightii)) or are centered here [e.g., Bushy-tailed Several cacti have Great Basin conifer woodland as their Woodrat (Neotoma cinerea arizonael, GrayVireo (Vireo vicinior), center of distribution or are otherwise well represented here. Black-throated Gray Warbler (Dendroica nigrescens], Scott's Among these are the Red Hedgehog Cactus (Echinocereus Oriole (Icterus parisoruml, and the Plateau Whiptail tiiglochidiatus var. melanacanthusl and the hedgehogs (Cnemidophorus velox)). A somewhat larger number of the E. engelmanii var. variegatus and E. fendleri var. fendleri; the more adaptable, and, therefore, more widely distributed prickly-pears Opuntia etinacea, O. basilatis var. aurea, O. species also may be found in these relatively recent environ­ pbaeacantha, O. macrorhiza, O. polyacantha, O. fragilis; the ments. Furthermore, juniper-pinyon woodlands are more or chollas O. whipplei and 0. imbticata; Sclerocactus whipplei less seasonal habitats for a number of montane and subalpine var. intermedius; Mammillaria wiigbtii; Pediocactus animals; as such they are often of great importance as winter papytacanthus, P. simpsonii; Coryphantha vivipara var. range for Rocky Mountain Elk and Mule Deer. Brown Great Basin Conifer Woodland 57

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 1,658 45 39 37 29 16 15 23 35 25 30 31 43 368 37°16' llr38' Mesa Verde N.P., CO 2,155 44 37 40 34 25 18 45 54 32 46 28 47 450 37°12' 108°29' Trinidad FAA CO 1,751 10 10 39 33 47 37 47 48 25 23 11 13 343 37°15' 104°20' Conchas Dam, NM 1,294 7 9 14 22 34 38 65 63 36 27 6 11 332 35°24' 104°11' Santa Rosa, NM 1,408 8 10 16 17 33 35 64 73 38 29 7 14 344 34°57' 104°41' Elk, NM 3E 1,737 14 12 13 17 22 41 69 81 58 32 12 18 389 32°56' 105°17' Mesacalero, NM 2,068 25 23 26 15 16 40 94 97 55 30 16 33 470 33°10' 105°48' Santa Fe, NM 2,147 16 20 19 23 31 28 64 60 40 26 18 17 362 35°41' 105°56' Mountainaire, NM 1,987 17 18 17 15 16 21 64 63 34 27 12 24 328 34°32' 106°15' Cuba, NM 2,147 21 19 29 21 21 18 54 63 32 32 16 24 350 36°02' 106°58' Fort Bayard, NM 1,872 21 16 15 7 6 21 70 83 50 24 12 24 349 32°48' 108°09' Zuni R.S., NM 1,966 22 17 23 15 10 10 45 53 29 29 15 21 289 35°06' 108°47' Blue, AZ 1,756 27 25 19 12 6 17 96 122 67 55 25 65 536 33°37' 109°06'

. Lukachukai, AZ 1,987 23 16 32 21 11 8 34 38 24 30 20 21 278 36°25' 109°l4' Klagetoh, AZ 1,949 25 12 19 19 9 15 53 53 17 17 19 14 272 36°30' 109°32' Pinedale, AZ 1,981 35 24 27 18 7 14 63 81 39 47 29 43 427 34°18' 110°15' Cibecue, AZ 1,509 48 30 39 18 9 12 60 72 42 43 29 45 447 34°03' 110°29' Betatakin, AZ 2,221 24 21 22 21 11 12 37 43 24 27 20 29 291 36°41' 110°32' Pleasant Valley 1,539 49 32 44 23 12 12 73 88 43 33 31 51 491 R.S.,AZ 34°06' 110°56' Walnut Can. 2,038 42 29 47 27 16 13 62 64 40 28 32 48 448 N.M,AZ 35°10' 111°31' Sedona R.S., AZ 1,317 43 39 42 30 14 12 48 61 38 29 33 44 434 34°52' III °46' Grand Canyon, AZ 2,125 34 32 37 25 14 12 38 54 32 27 21 40 366 36°03' 112°08' Drake, AZ 1,417 32 28 26 23 9 9 40 62 29 23 14 35 330 34°58' 112°23' Walnut Creek, AZ 1,551 34 28 31 19 9 12 68 78 34 23 22 36 394 34°56' 112°49' Ml Trumbull, AZ 1,707 21 18 26 18 10 11 43 52 24 20 20 25 288 36°25' 113°21'