Great Basin Naturalist Volume 47 Number 2 Article 15 4-30-1987 Flora of the Orange Cliffs of Utah L. M. Shultz Utah State University E. E. Neely University of Wyoming, Laramie J. S. Tuhy The Nature Conservancy, Wellsville, Utah Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Shultz, L. M.; Neely, E. E.; and Tuhy, J. S. (1987) "Flora of the Orange Cliffs of Utah," Great Basin Naturalist: Vol. 47 : No. 2 , Article 15. Available at: https://scholarsarchive.byu.edu/gbn/vol47/iss2/15 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. FLORA OF THE ORANGE CLIFFS OF UTAH L. M. Shultz', E. E. Neely-. and j. S. Tuhy' Abstract. —The vascular flora of tht- Orange Cliff's area, defined here as part of the Colorado Plateau floristic province, harbors approxiniateh- 209 species in 123 genera and 49 families. A species checklist is proxided with a discussion of physical and floristic aspects of the region. The flora is compared statistically to the San Rafael Swell flora, which is also a subset of the Colorado Plateau. We define si.x vegetation types and three edaphic communities; these are described and mapped. Of eleven endemic plant species in the Orange Cliffs, three are local and rare. Sites for Astragalus nidularius, A. moencoppensis, and Xylorhiza ^lahritiscula var. lincarifolia are discussed and mapped. Local floras are essential for assessment of counties for more than 95% of the taxa listed. biological diversity and for making biogeo- Additionally, we identified and described graphic comparisons. Unfortunately, they are nine vegetation types for the area (Fig. 2). available for few areas in the intermountain These include big sagebrush, blackbrush, region. A review by Bowers (1982) shows only grassland types, three pinyon-juniper associa- eight local checklists for Utah and Nevada, tions, and three edaphically defined types respectively, and most are unpublished re- designated as Chinle-shale, slope, and ports. While several floras cover broader ar- ephemeral wash types. eas within the state (Arnow et al. 1980, Cron- We were able to compare the flora of the quist et al. 1972, 1977, 1984, Holmgren and Orange Cliffs area to the flora of the San Rafael Reveal 1966, Shaw 1981, Welsh 1986), the Swell by using the recent publication by Har- less ambitious florula, or local checklist, has ris (1983). The San Rafael Swell is a massive the advantage of showing floristic similarities domal upwarp which lies northwest of the as well as discontinuities within broader floris- study area in Emery County and northern tic provinces. Wayne County. Both areas are included Recent attention has been drawn to the within the Canyonlands floristic section Orange CliflFs area because of its unusually (Holmgren 1972). Because the two areas are rich reserves of tar sands. Access is difficult in close proximity but differ in geology and and attained with a drive of over 100 kilome- topography, this study presents a special op- ters on unimproved roads. Because of this portunity to compare two subsets of the Colo- inaccessibility, the area has been poorly rado Plateau flora, the San Rafael portion on known floristically. In 1980 we began a com- the west and Orange Cliffs portion in the cen- prehensive inventory of the Orange Cliffs ter of the Plateau. (Fig. 1) within the Glen Canyon recreational area. Our work in the area was coordinated by Description of Study Area U.S. National Park Service personnel and was concurrent with the inventory of the Glen Southwest of the confluence of the Green Canyon National Recreation Area bv Welsh River and Colorado River, the Orange Cliffs (1983). rise above the Colorado River in a regional The species list presented here is based on transition between the San Rafael Desert to three years of field work and provides the first the west and the Canyonlands to the east. published checklist for the area. From an ex- Encompassing much of eastern Wayne and amination of herbarium records, we deter- Garfield counties, the Orange Cliffs lie within mined that our collections represent the first the Canyonlands floristic section of the Colo- record from eastern Wavne and Garfield rado Plateau Division, a section which is the 'Department olBiologN. Utah State University, Logan, Utah 84.322, ~Rock\ Mountain Herbarium, University of Wyoming, Laramie, Wyoming. *rhe Nature Conservancy, Wellsville, Utah 84a39. 287 288 Great Basin Naturalist Vol. 47, No. 2 •^-^- Wa^'"- 1 ^.N7?;F* Segment of Southeast Utah showing Orange Cliffs region and San Rafael Swell iff San Rafael Swell San Rafael Desert Cliffs Fig. 1. Map of Utah from satellite image. The Canyonlands section of southeastern Utah is roughly bounded by the dark line. The San Rafael Swell boundary encompasses the flora described b\' Harris (1983), with the San Rafael desert shown as an area transitional to the Orange Cliffs. (Base map reproduced by permission from Weber State College, Ogden, Utah.) richest area for endemism in the intermovin- Canyon (heads of tributaries of the Dirty tain region (Hohngren 1972). Devil River), to French Spring on the north. The Orange ChfFs area hes primarily within The area encompasses appro.ximately 218 km" the Glen Canyon National Recreation Area. (84 mi") with elevations ranging from 1,675 m Small portions are administered by the Bu- to 2, 135 m. reau of Land Management or the state of The Orange Cliffs region consists primarily Utah. The area extends from Big Ridge and of gently dipping sedimentary strata of Trias- Sunset Pass on the south, northward across sic and Jurassic age (Huntoon et al. 1982). The parts of the South and Main forks of Happy oldest rock exposed within the study area is April 1987 Shultz et al. : Orange Cliffs Flora 289 VEGETATION COMMUNITIES Big Sagebrush Blackbrush Grassland & Ephedra/Grassland Pinyon-Juniper/Sagebrush-Rabbitbrush Pinyon-| uniper/Ash-Serviceberry I Pinyon-)uniper/Blackbru5h-shrubs I Slope ] Chinle Shale Ephemeral Washes Seeps Area Boundary \ c s L Kilometers 1:62.500 Fig. 2. Vegetation map of the Orange Cliffs area. Types A-F are defined by the dominant vegetation. The slope, Chinle shale, and ephemeral wash types are defined by physical factors. the Moenkopi Formation, comprised of ma- layers. Above the Moenkopi is the Chinle roon to reddish brown sandstones, mud- Formation, composed of a lower sandstone stones, shales, and lighter-colored carbonate and conglomerate member and an upper 290 Great Basin Naturalist Vol. 47, No. 2 PLANTS/NARROW ENDEMICS Locations with Astragalus nidularius populations. A Astragalus nidularius X Xylorhlza glabrluscula var. linearlfolla m Astragalus moencoppensis • Seep areas 1970 Magnetic Declination Fig. 3. Narrowly distributed soil endemics of the Orange Cliffs. Although the plant species mapped are rare, none are protected by the Endangered Species Act. shale member. The overlying Wingate Sand- cliffs (up to 100 m high) for which the Orange stone forms the striking orange-red vertical Cliffs are named. The Wingate is usually April 1987 ShULTZ ETAl,.: OrANCE ClIPFS FlOIU 291 Table 1. Average annual precipitation and temperatures for one station within the Orange Cliffs region (Hans F'lat), one for Canyonlands (The Neck), and one for the southeast edge of the San Rafael Desert (Hanksvillc). Data are from NOAA (1982) and Gaylon Ashcroft, Office of the State Climatologist (personal eomnnmication). Rainfall Temperature (inches) (F) Mt: Minimum Mean Hans Flat Ranger Station* (2,012 m elevation) 11.6 (no data available) The Neck** (1,808 m elevation) 9.2 63.4 41.8 52.7 Hanksville*** (1,283 m elevation) 5.2 69.4 36.7 53.1 four-year mean (1981-84) twenty-year mean (1965-84) thirty-year mean (19.51-80) capped by the Kayenta Formation, in turn in two areas (Mueller-Dombois and Ellenberg overlain by the Navajo Sandstone, which is 1974), and the Otsuka Index, whose prefer- the youngest exposed formation in the region. ence is explained in a recent factor analysis The Navajo is eroded from the southern part (McLaughlin 1986). Formulas for similarities of the study area but is extensively exposed to (S) are as follows: the north on mesa tops. S (j) = c / a + b - c Qaccard Index) The climate of the Orange Cliffs area is S (s) = c/ (a + b)" X .5(Sorenson Index) typical of the Colorado Plateau. Rainfall peaks S (o) = c / (a X b)''' (Otsuka Index) are in spring, midsummer, and fall (Gaylon Ashcroft, Office of Utah State Climatologist, where c = number of species common to both personal communication). Average annual floras, a ^ number of species in flora one, h = precipitation and temperatures are reported number of species in flora two. for the three meteorological stations closest to The classification of vegetation types began the Orange Cliffs (Table 1). with a review of references dealing with vege- tation types in the general area (Cronquist et Methods al. 1972, Loope 1977). Reconnaissance on ground and by fixed-wing aircraft verified that Intensive surveys were made throughout major vegetation types of the Orange Cliffs the study area over three successive field sea- are similar to those of Canyonlands National sons from 1981 through 1983. Comprehensive Park. Sites in each major vegetation type were collections were made of vascular plant spe- sampled for species composition, cover, den- cies with voucher specimens identified and sity and frequency of species; soil profiles deposited in herbaria of Utah State University were described on at least one site in each (UTC), Brigham Young University (BRY), and major type. Data are reported by Tuhv and University of Colorado (COLO).