Great Basin Naturalist Volume 43 Number 1 Article 8 1-31-1983 Floristics of the upper Walker River, California Matt Lavin University of Nevada, Reno Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Lavin, Matt (1983) "Floristics of the upper Walker River, California," Great Basin Naturalist: Vol. 43 : No. 1 , Article 8. Available at: https://scholarsarchive.byu.edu/gbn/vol43/iss1/8 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]. FLORISTICS OF THE UPPER WALKER RIVER, CALIFORNIA AND NEVADA Matt Lavin' Abstract.— A checklist of the vascular flora of the upper Walker River is presented. Listed are 1078 taxa from this 4000 km^ area. The upper Walker River encompasses a portion of the boundary between the Intermountain and Sierra Nevada floristic regions, and hence displays much floristic diversity within a relatively small area. Due to its location along the east slope of the Sierra Nevada, the Walker River drainage is unique in that it contains much elevational variation eastward into the Intermountain Region. This elevational extension is due to the presence of large mountain ranges including the Sweetwater Mountains, the Bodie Hills, and the Wassuk Range. As a result of this elevational variation, there is much overlapping of the two floristic regions. Additionally, the easternmost expo- sures of the Sierran granodiorites occur within the Walker River basin and may enhance the eastward migration of Sierran plants. The 90 percent floristic similarity (Sorenson's) between the Sweetwater Mountains, lying to the east of the Sierra, and the east slope of the Sierra Nevada (within the Walker River drainage) indicates the Sweetwaters to be more affiliated with the Sierran flora instead of the Intermountain flora. The upper Walker River drainage includes dominates. This vegetation has also been an area of approximately 4000 km 2, located briefly described by Billings (1951). The at the north end of Mono Coimty, California, Sweetwater Mountains, situated between the the southern ends of Douglas and Lyon coun- Intermountain and Sierran floristic regions, ties, Nevada, and the western edge of Miner- display characteristics of both. al County, Nevada. The western boundary of The vascular flora of the upper Walker this drainage generally follows the crest of River is modestly represented in literature. the Sierra Nevada from the Conway Summit- Works such as Hinton (1975), Reveal (1968), Virginia Lakes area, northward to the Topaz Cox (1972), Reveal and Ertter (1980), Hard- Lake-Monitor Pass area. The eastern bound- ham and True (1972), Strother (1974), Munz ary is delimited by the Bodie, Masonic, and (1968), Bameby (1964), Dempster and Ehren- Pine Grove hills and the southwest slopes of dorfer (1965), Halse (1981), and others cite the Pine Nut Range. The Sweetwater Moim- specific collections made within this area. tains and the Wellington hills lie between Davis (1979) compiled a plant list and keys to these hills and the Sierra Nevada. the plants occurring on the east central East slope Sierran vegetation present here Sierra (Owens Lake to Lake Tahoe) and asso- has been generally described by Billings ciated desert ranges. This work was based (1951) and Rundel et al. (1977). The area is solely on distributions given in existing floras. dominated by mixed conifer forests composed Sharsmith (1940) includes the Walker Riv- of Pinus jeffreyi and Abies concolor at the er portion of the Sierra Nevada as the north- low elevations, and Abies magnifica, Tsuga ernmost boundary of the Sierra alpine floris- mertensiana, Pinus monticola, and P. albi- tic region. This area includes Leavitt Peak caulis at the higher elevations. The alpine south to Dunderberg Peak. Thome (1982) de- vegetation of the Sierra is uniquely adapted fines the upper Walker River basin as the for extreme svmimer drought (Chabot and northern boundary of the transmontane Cali- Billings 1972). fornian floristic region. To the east of the Sierra, Intermountain Major and Taylor (1977) conducted a vege- vegetation (high elevation sagebrush steppe tation study of the alpine zone of the Sweet- situated above woodlands composed of Pinus water Mountains. They list 43 species from monophylla and Juniperus osteosperma) pre- the area. Taylor (1977) indicates a 40-50 'Department of Biology, University of Nevada, Reno, Nevada 89557. Present address: P.O. Box 13494, Reno, Nevada 89507. 93 . 94 Great Basin Naturalist Vol. 43, No. 1 percent floristic similarity (Sorenson's) be- Methods tween the Carson Pass area of the Sierra Ne- vada and the Sweetwater Mountains. Since a The checklist (Table 1) was developed 50 percent turnover rate in plant species oc- from collections made during the course of curs every 650 km along the Cascade-Sierran this study: July 1979 to August 1982. Addi- recorded from the axis (Taylor 1977), the Walker River portion tional collections were of Nevada, of the Sierra must have a very high degree of herbaria at the University Reno New York Botanical Garden similarity with Carson Pass, 60 km to the (RENO), The (NY), and the California Academy of Sciences north. An interpretation of this would mean (CAS). Collections from the upper Walker the Walker River portion of the Sierra has River made by Arnold Tiehm and Margaret approximately a 50 percent floristic sim- Williams, Reno, Nevada; Steve Wharff, ilarity to the Sweetwaters. Tonopah, Nevada; Frank Smith, Smithfield, Bell (1980) described the alpine flora of the Utah; Dennis Breedlove, CAS; Joe Robertson, Wassuk Range, located in the lower Walker E. F. Kleiner, Tom Lugaski, Pat and Ham River drainage just west of Walker Lake (50 Vreeland, H. N. Mozingo, and Fred Ryser, all of the Sweetwater Mountains). She km east from the University of Nevada, Reno, were lists 70 vascular plants from the alpine flora also recorded in this checklist. Approximately of this region. Bell has also recently com- 3850 numbers were recorded. Distributional pleted a study of the alpine flora of the information contained within the checklist Sweetwater Mountains, but this information was continually refined while in the field. is unavailable. Various documentary works, mentioned in Messick (1982) completed a flora of the the introduction, were used to determine Bodie Hills, and the results of this work are those plants that have a probable distribution incorporated in Table 1 within the upper Walker River drainage, but The upper Walker River drainage is the were not observed during this study. region of several type collections. The Sweet- Almost all of the taxa listed can be found water Mountains are the type locale for on deposit at the University of Nevada, Reno, Cordylanthus ramosus ssp. setosus, Senecio herbarium and the Toiyabe National Forest pattersonensis and Draba lemmonii var. in- Supervisor's Office, Reno, Nevada. crassata. In the Bodie Hills, we have the type The purposes of the checklist (Table 1) are locale for Draba quadricostata, Pinus mon- to both document the flora present in the up- ophylla, Arabis bodiensis (see Rollins 1982), per Walker River and to document the geo- Streptanthus oliganthus, and Phacelia mon- graphical and altitudinal distribution of each taxon within this area. Nomenclature gener- oensis. A. bodiensis, S. pattersonensis, D. lem- ally follows Kartesz Kartesz monii var. incrassata, and D. quadricostata and (1980). are endemic to the Walker River drainage. The Wellington Hills are the type locale Results and Discussion for Astragalus oophorus var. lavinii, and So- nora Pass for Raillardella argentea, Cymop- Table 1 lists 1078 taxa of vascular plants terus cinerarius, and Wyethia mollis. "A dry from the upper Walker River. The upper near Sonora Pass" is the type rocky mountain Walker River drainage is unique in that it ex- location for Astragalus platytropis, A. lentigi- tends much elevational variation of the east nosus var. ineptus, and A. whitneyi. Bameby slope of the Sierra Nevada eastward into the suggests that the type locale for these three Intermountain Region, due to the presence Astragali may be the Sweetwater Moujitains. and close proximity of such large mountain However, during the course of this in- ranges as the Sweetwater Mountains, the vestigation, all three, including A. platy- Bodie Hills, and the Wassuk Range. Along tropis, were found on Leavitt and Emma any floristic boundary there is bound to be Peak of the Sierra Nevada. Therefore, the some overlap of unique plant species or char- type locale given by Gray could have possi- acteristic vegetation of one flora into anoth- bly referred to the Sierra instead of the er. However, many plants having their center Sweetwaters. of distribution in the Intermountain Region January 1983 Lavin: Walker River Floristics 95 also have outlying populations in the mon- Penstemon bridgesii Phoenicaulis cheiranthoides tane environments of the Sierra Nevada. This Phacelia humilis is discussed Taylor for phenomenon by (1976) Phlox covillei the Carson Pass area of the Sierra. He attri- Plagiobothrys hispidus butes the occurrence of many Intermountain P. kingii var. harknessii Prunus andersonii plants on the east slope of the Sierra to Xero- Purshia tridentata thermic invasion. A list of these plants at the Pinus monophylla headwaters of the