A Vascular Flora of the San Rafael Swell, Utah

Great Basin Naturalist Volume 43 Number 1 Article 6 1-31-1983 A vascular flora of the San Rafael Swell, Utah James G. Harris Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Harris, James G. (1983) "A vascular flora of the San Rafael Swell, Utah," Great Basin Naturalist: Vol. 43 : No. 1 , Article 6. Available at: https://scholarsarchive.byu.edu/gbn/vol43/iss1/6 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]. A VASCULAR FLORA OF THE SAN RAFAEL SWELL, UTAH' James G. Harris^ Abstract.— The vegetation of the San Rafael Swell in southeastern Utah is examined based on personal field col- lections and previously collected herbarium specimens in the Brigham Young University Herbarium (BRY). An annotated checklist includes information on frequency of occurrence and habitat preference for each entity. Treated are 491 vascular plant taxa from 59 families. The San Rafael Swell is the eroded rem- (1981), Welsh (1978, 1980a, 1980b), Welsh massive in nant of a domal anticline, oval and Atwood (1981), Welsh and Moore (1973), shape, stretching along northeasterly axis a Welsh and Reveal (1977), Welsh et al. (1981); in from Capitol Reef National Park northern monocotyledons, Cronquist et al. (1977). Wayne County to the foot of the Tavaputs The checklist includes 478 vascular plant Plateau in Carbon County. Folding of the taxa found in the study area and an addition- earth's crust, which formed the domal anti- al 13 taxa known to occur on lands immedi- cline, and the subsequent erosion of the cen- ately adjacent to the study area and to be ex- tral dome left a huge area of concentric stone pected in the San Rafael Swell. These 13 taxa rings, each progressively younger from the are listed below: innermost to the outermost. One of these Allionia incarnata L. rings, the Ferron Sandstone Member of the Cordylanthus wrightii Gray Mancos Shale Formation, encloses approx- Descurainia pinnata (Walter) Britt. var. filipes (Gray) Peck imately L4 million acres of land and forms Eriogonum smithii Reveal the boundary of this study. In some cases, Euphorbia micromera Boiss. where the Ferron Sandstone has been com- Haplopappus drummondii (T. & G.) Blake pletely eroded from the structural confines of Helianthus petiolaris Nutt. Hymenopappus Hook. var. lugens (Greene) the swell, artificial boundaries have been fol- filifolius Jeps. lowed (Fig. 1). Lupinus pusillus Pursh var. rubens (Rydb.) Welsh Throughout the field seasons of 1979 and Phacelia demissa Gray var. heterotricha Howell 1980, I attempted to collect representatives Physocarpus alternans (Jones) Howell of all vascular plant species growing in the Sphaeralcea munroana (Dougl.) Spach Sporobolus giganteus Nash San Rafael Swell. A voucher specimen from flora of the Rafael Swell is not each collection has been placed in the Brig- The San particularly rich in of species. This ham Young University Herbarium (BRY). In- numbers is part, the relatively nar- cluded in the checklist are species not found due, at least in to by me, but collected by others and vouched row elevational range in the area. Although rich in of species, the flora is for by specimens in the Brigham Young Uni- not numbers rather rich in numbers of unique and geo- versity Herbarium. The checklist is not defin- graphically restricted species. The following itive; additional taxa will undoubtedly be dis- to the San covered in the swell. eight species are strictly endemic Swell: The following sources were used for identi- Rafael fication and nomenclature: lower vascular Astragalus rafaelensis Jones Cryptantha johnstonii Higgins plants and gymnosperms, Cronquist et al. Cryptantha pnesiana (Payson) Payson (1972); dicotyledons, Neese and Welsh Erigeron maguirei Cronquist 'Part of a master's thesis, originally submitted to the Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602. 'Department of Botany and Range Science, Brigham Young University, Prove, Utah 84602. Present address: Department of Botany, University of Alberta, Edmonton, Alberta T6G 2E9. 79 80 Great Basin Naturalist Vol. 43, No. 1 Emery County Fig. 1. Map of the San Rafael Swell study area. Pediocactus despainii Welsh & Goodrich Vegetative Zones Sclerocactus wrightii Benson Sphaeralcea psoraloides Welsh The vegetation of the San Rafael Swell can Thelypodiopsis harnebyi Welsh & Atwood be divided into five major zones: the Sand An additional seven species are endemic to Desert Shrub Zone, the Salt Desert Shrub the San Rafael Swell and the adjacent lands Zone, the Mixed Desert Shrub Zone, the Pin- in close proximity to the swell. They are list- yon-Juniper Zone, and the Ponderosa Pine- ed as follows: Mountain Brush Zone. These zones are con- Astragalus pardalinus (Rydb.) Barneby Astragalus woodruffii Jones trolled principally by elevation, precipi- Hoffmanseggia repens (Eastw.) Cockerell tation, and local edaphic factors. Although in Hymenoxys depressa (T. & G.) Welsh & Reveal some areas the zones are clear and well de- Lomatium junceum Barneby & Holmgren fined, in most areas they interfuse consid- Psorothamnus polyadenius (Torr.) Rydb. var. jonesii Barneby erably and it becomes difficult to draw a Townsendia apnea Welsh & Reveal sharp boundary line between them. January 1983 Harris: San Rafael Swell Flora 81 Sand Desert Shrub Zone.— The San Ra- 7800 ft (1766-2377 m). Within this altitudin- fael Desert, in the southeastern region of the al range Juniperus osteosperma is dominant at San Rafael Swell, ranges from an elevation of the lower elevations and Pinus edulis is domi- about 4200 ft (1280 m) at the lowest point to nant at the higher elevations. Intermediate about 5000 ft (1524 m) at the highest point. elevations yield a heterogeneous mixture of It is a sandy desert with moving dunes in both species. some areas. Common shrubs in this zone in- Dense stands have almost no understory, clude: Artemisia filifolia. Ephedra torreyana. but more open or scattered stands will in- Yucca hatrimaniae, Poliomintha incana, Ti- clude almost all the species found in the quilia latior, and Coleogyne ramosissima. Mixed Desert Shrub Zone. PoNDEROSA Pine-Mountain Abronia elliptica, Oenothera pallida, Hoff- Brush Zone.— highest point in manseggia repens, and Oryzopsis hymenoides The the San Rafael Swell is the San Rafael Knob at 7921 ft are characteristic herbaceous plants of this (2414 m) in elevation. The area surrounding the zone. knob and the summit of Cedar Mountain rep- Salt Desert Shrub Zone.— In the San resent the highest vegetative zone in the Rafael Swell the Salt Desert Shrub Zone is swell. Pinus edulis continues to remain domi- widespread, occurring mainly on alkaline nant even at the highest elevations, but above clay soils between 4500 and 5800 ft 7500 ft (2286 m) plants characteristic of the (1372-1766 m) in elevation. Communities in Ponderosa Pine-Mountain Brush Zone be- this zone are characteristically dominated by come increasingly common. Some common Atriplex interspersed with any of confertifolia species in this zone are: Pinus ponderosa, Ar- the following subdominant species: Hilaria temisia nova, Cowania mexicana, Mahonia jamesii, Oryzopsis hymenoides, Enceliopsis fremontii, Populus tremuloides, Amelanchier nudicaulis, Aristida purpurea, Eriogonum in- utahensis, Cercocarpus montanus, Ribes lep- flatum, Salsola iherica or Ceratoides lanata. tanthum, Juniperus scopulorum, Hymenoxys Highly alkaline flood plains in this zone richardsonii, Symphoricarpos longiflorus and are often covered by nearly pure stands of Philadelphus microphyllus. Sarcobatus vermiculatus, which may at times In addition to these five major vegetative be accompanied by thick clumps of Tamarix zones, smaller communities dependent on ramosissima. unique local habitats are scattered through- Heavy clay soils of the Mancos Shale For- out the area. These include plants distributed mation are often dominated by Atriplex cu- along seeps and streams, along washes and neata and Atriplex corrugata. During wet roadsides where runoff collects, in hanging springs these areas may be blanketed by an- gardens, on rocky outcrops, and on disturbed nual species such as Cleome lutea, Lupinus sites. pusillus, Malcolmia africana, Camissonia sca- Annotated Checklist poidea, and Camissonia eastwoodiae. Mixed Desert Shrub Zone.— Deep, well- Following each species entry in the checklist (with the exception of the 13 taxa from drained soils between 4500 and 5800 ft area) a designa- (1372-1766 m) in elevation are often domi- lands adjacent to the study nated by one or several of the following tion is given concerning the frequency of occurrence and habitat preference of the taxon. shrubby species: Artemisia tridentata, Arte- Plants of broad distribution that are not lim- misia bigelovii, Artemisia spinescens, Xantho- ited to a specific zone or community type are cephalum sarothrae or Chrysothamnus vis- listed as widespread. The following abbrevia- cidiflorus. These may be intermingled with tions are used: an understory of herbaceous plants including: C—common Hilaria jamesii, Stipa comata, Boutehua gra- O— occasional cilis. Astragalus spp., Sphaeralcea spp., and U—uncommon Leucelene ericoides. R— rare SnD— Sand Desert Shrub Zone Pinyon-Juniper Zone.— Pinus

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