Vascular Flora of the Upper Rock Creek Watershed, Eastern Sierra Nevada, California

The upper Rock Creek watershed is located on the east slope of the Sierra Nevada in Inyo and Mono counties. It is ca. 36.5 square miles (94.5 square km) in area and varies in elevation from 7360 to 13,750 ft (2243 to 4191m). Quaternary glacial erosion and deposition produced striking landscape features, including alpine fellfields and numerous small lakes. Previous floristic inventories in Rock Creek recorded a combined 396 minimum-rank taxa (species, subspecies, varieties, named hybrids) but were restricted to Little Lakes Valley and the surrounding high areas. An updated, annotated checklist of vascular plants is presented, based on preexisting specimens and new collections. I conducted intensive fieldwork from 2012 through 2016, resulting in 1506 collections (including two collections from a brief 2018 visit). More than 1000 historical collections were examined. The resulting checklist contains 591 taxa, of which 25 (4.2%) are nonnative to California and 32 (5.4%) are special-status plants. My fieldwork resulted in 128 taxa previously undocumented for the watershed. Eighty-one species historically collected were not rediscovered and are noted as such in the checklist. Nine taxa are new county records. The flora is represented by 77 families, 248 genera and 572 species. For each taxon, the checklist cites at least one collection and indicates the vegetation type(s) where it has been documented and its abundance in the watershed. A brief review of botanical exploration in the watershed during the past century is presented, along with geology, climate, vegetation and history of human activity.

introduction Floristic inventories that utilize herbarium collections as their basis serve as important baselines of information about plants and the environments in which they occur. Studies of local floras are crucial to our understanding of biodiversity amid the realities of climate change and human impacts to the environment. With growing digitization of collections data, floristic datasets are proving to be increasingly useful and especially rich due to their breadth of information at spatial and temporal scales (Wolf et al. 2016).
The upper Rock Creek watershed is situated on the east slope of the Sierra Nevada mountain range (Inyo and Mono counties, California, USA) in the Inyo National Forest. Historical collections from Rock Creek contributed several additions to the California flora: four new taxa were described in the previous century, including Tonestus peirsonii (as Haplopappus eximius H.M. Hall subsp. peirsonii D.D. Keck) (Asteraceae), Draba sierrae (Brassicaceae), Castilleja peirsonii (Orobanchaceae) and Festuca brachyphylla subsp. breviculmis (Poaceae).
In spite of the great number of collections from the upper Rock Creek watershed prior to this study (>1000), and two previously published floristic checklists-F. W. Peirson (1938Peirson ( , 1942 and J. T. Howell (1946)-no collections-based floristic work had ever focused on the entire geographic area forming the upper watershed, i.e., Rock Creek Canyon (Fig. 1). The earlier checklists were restricted to the Little Lakes Valley area.
The main goal of the present study was to produce an updated vascular flora of the watershed combining pre-existing herbarium specimens and new collections.
physical setting

Location and Features
The upper Rock Creek watershed ( Fig. 1, 2-5) is located ca. 25 road miles (40 km) northwest of Bishop and ca. 19 miles (30 km) southeast of the town of Mammoth Lakes, California. A single paved road, Rock Creek Road, enters the canyon mouth ca. 1 mile (1.6 km) southwest of the road's junction with U.S. Route 395 (US-395) at Tom's Place. A secondary entry route, Sand Canyon Road (Forest Rd 5S08/30E302), is a four-wheel-drive (4WD) road accessible from the community of Swall Meadows that enters the area from the northeast. Two additional access points into the watershed are via hiking/pack trails traversing Mono Pass and Morgan Pass. The watershed is ca. 36.5 square miles (94.5 square km; 23,360 acres) in area, ca. 56% of which lies within the John Muir Wilderness (Fig. 1). The elevation ranges from 7360 to 13,750 ft (2243 to 4191 m).
The study boundary is the nearly continuous ridgeline that encompasses Rock Creek Canyon on the east, west and south (Fig. 1). Its northern boundary is the canyon mouth at the 7360 ft (2243 m) contour (37.5508 N, 118.6833 W), which is ca. 500 m north-northeast of the water tank along Rock Creek Road, near French Campground. Rock Creek continues its course downstream from this point, outside the study area, for ca. 1 mile (1.6 km) to Tom's Place before it turns sharply east into lower  Rock Creek and eventually, farther southeast, into the Owens River. Hereafter my use of the name Rock Creek implies the upper watershed, i.e., Rock Creek Canyon, unless otherwise noted.
Numerous high peaks are situated along the rim of the watershed, including 13,704 ft (4177 m) Mount Abbot on the south rim ( Fig. 1, 4) and 12,835 ft (3912 m) Mount Starr on the west (Fig. 1). The highest point in the study area is the summit of Mount Morgan at 13,748 ft (4190 m) (Fig. 1, 3). Northwest of Mount Morgan is Transverse Ridge, which runs crosswise to the long axis of the watershed and is a collection locality on some F. W. Peirson herbarium specimens (Fig. 1). Wheeler Ridge (Fig.  1, 2) is a long, north-south ridge that divides the watershed from the Owens Valley. Mono Mesa (Pointless Peak) (Fig. 1, 5), ca. 12,256 ft (3736 m), is an unglaciated plateau above and west of Rock Creek Lake (Fig. 1).
Lakes and pools are abundant; the largest, Rock Creek Lake ( Fig. 1), is nearly 59 acres (34 ha) in size. Little Lakes Valley ( Fig. 1, 3-4) contains eight named lakes or groups of lakes; there are 12 additional named lakes in the watershed and several unnamed lakes. Rock Creek has two main divisions: a primary channel that flows northward from headwaters at ca. 13,000 ft (3962 m) above Little Lakes Valley, and the East Fork that orig-inates near 12,200 ft (3718 m) above the Tamarack Lakes (

Geology and Geomorphology
Rock types.-The bedrock of the study area is primarily Mesozoic granite with a scattering of small Paleozoic metamorphic outcrops, as mapped by several studies (Bateman et al. 1965;Lockwood and Lydon 1975;Langenheim et al. 1982;Bateman 1992). Light-colored biotite granite and granodiorite are the most abundant rock types, followed by older formations of quartz monzonite. Secondary, infrequent plutonic outcrops include diorite, quartz diorite and gabbro: these dark, gray-colored rocks are common in the Tamarack Lakes area (Fig. 1, 11). Metasedimentary rock is uncommon and occurs only as small outcrops on the east side of the canyon along ridges between Mount Morgan and the north terminus of Wheeler Crest ( outcrop at the northeast base of Mount Morgan. The oldest metamorphic rocks in the study area occur around the heavily weathered summit of Sherwin Peak (Fig. 1). These outcrops are biotite quartz hornfels, calc-hornfels and mixed calcareous rocks (Langenheim et al. 1982). Although the region immediately north, east and west of Rock Creek Canyon was heavily modified by Cenozoic volcanism which produced vast tablelands of lava flows and tuff (Birman 1964;Hildreth and Fierstein 2016), no volcanic formations occur within the study area.
Sierra Nevada uplift.-Relief in the watershed is largely a product of Late Cenozoic uplift of the Sierra Nevada caused by tectonic movements. Westward tilting and uplift of the Sierra batholith began in the Tertiary period about five million years ago and continues today, in concert with downward frontal faulting along the western edge of the Basin and Range floor where it meets the Sierra block (Wakabayashi and Sawyer 2001). The magnitude of uplift is dramatically exemplified by the precipitous eastern escarpment of Wheeler Ridge ( Fig. 1, 2) above the Owens Valley floor.
Glaciation.-Thousands of years of Quaternary glacial erosion and deposition have markedly influenced landforms in the study area. There is general consensus that at least seven glaciations occurred in the Sierra Nevada with multiple advances and retreats (Birman 1964;Phillips et al. 2009;Hildreth and Fierstein 2016). These glaciations deposited successive moraines in Rock Creek Canyon. Two examples of lateral moraines from the Tahoe glaciation are the Tamarack and Hilton benches along the east and west shoulders of Rock Creek Canyon ( Fig. 1, 2, 5) (Putnam 1960;Birman 1964;Bateman et al. 1965). Small remnant glaciers have been found on the northeast slopes of Mount Abbot and Mount Mills ( Fig. 4) (Birman 1964;Lockwood and Lydon 1975). Some talus fields, including one at the northwest base of the ridge dividing Little Lakes Valley from the Tamarack Bench, are rock glaciers with reservoirs of slowly melting ice (Birman 1964;Bateman et al. 1965). Sedimentary deposits of alluvium by glacial meltwaters are abundant across the canyon floor and just outside its mouth.
Topography and soils.-The landforms of the study area are typical of eastern Sierra Nevada canyons heavily modified by glacial activity and faulting. The watershed descends in elevation from south to north. Steep rugged escarpments form the walls of Rock Creek Canyon which, in contrast to most major canyons in the Sierra Nevada, is oriented north-south. Smaller ridges and benches are scattered in the interior, creating a variety of orographic contours and elevational heterogeneity. The majority of the principal ridgeline is 11,000-13,000 ft (3353-3962 m) in elevation and is dominated by jagged, crumbling parent material routinely subjected to seasonal frost shattering (Putnam 1960 Precipitation.-The eastern slope of the Sierra Nevada is subject to the rain shadow effect, receiving significantly less precipitation than the western Sierra as prevailing air masses from the west release the bulk of their moisture on the cismontane slopes (Holland and Keil 1995). The majority of precipitation in the study area falls as snow in December, January and February. One recent study estimated an annual precipitation average of 22.1 in. (562 mm) in the Rock Creek watershed between 1971 and 2000 (Millar et al. 2012). Snowpack accumulated throughout the winter typically attains peak depths in April, but snowfall amounts can be highly variable between years (MCCDDPD 2007). Patches of snow often persist on high north-facing slopes through summer, but most of the study area is usually snow-free by the middle of June. Thundershowers are common in July and August; however, these events generally contribute a very low percentage of the annual precipitation total, according to hydrological studies from the nearby Convict Creek drainage (Orr and Howald 2000). During the five-year span of the present study (2012)(2013)(2014)(2015)(2016), California experienced significant drought coupled with record  (Table 1).
Wind and air temperature.-Based on the experience of the author, the majority of the watershed is not subject to strong winds during summer. Wind on exposed ridgelines can be gusty, especially during the night, and in May and June it can be mildly to moderately windy down canyon, usually below 9000 ft (2740 m). In winter, passing storms presumably create windy conditions. Air temperature in the watershed fluctuates widely on a seasonal and daily basis. Daytime highs during winter often remain below freezing. Nighttime lows can drop below 32°F (0°C) any time of year, though uncommon in summer (MCCDDPD 2007). January tends to be the coldest month and July the warmest. Historical temperature records for the study area are limited, but daily air temperature data from two weather stations-one within the study area and one just outside-were obtained for a recent ten-year period ( Table 2). Temperature ranges at elevations above 9700 ft (2960 m) in the study area during the same period in January and July were not available, but are expected to have been cooler than those recorded at lower elevations.
Growing season.-In North America, the annual growing season is defined as the period between the last spring date and first autumn date on which temperatures below 32°F (0°C) are experienced (Walsh et al. 2014). This frost-free period is negatively correlated with elevation; consequently, the growing season in the study area, as in other areas near the Sierra Nevada crest, is relatively short and varies with elevation. Plants occurring above 12,000 ft (3658 m) have only a few weeks to complete their annual growth cycle. It is important to note that freezing temperatures can occur any time of the year in the high Sierra Nevada but are less common in summer. In Rock Creek and nearby drainages of the region, consistently freezing temperatures typically begin in October with the arrival of snowfall and persist until April (MCCDDPD 2007).
On 21 May 2012 in the study area, Ruby Lake at 11,100 ft (3380 m) was completely covered with surface ice, and shoreline vegetation had not yet leafed out, while some shrubs and herbaceous species on south-facing slopes below 9000 ft (2740 m) were flowering (J. England, pers. obs.). The growth period of plants in the study area varies widely depending on aspect: species on south-facing aspects begin flowering weeks earlier than those on north aspects at similar elevation. It is not uncommon for snow to linger into July on north aspects above 11,000 ft. During 2012-2016, peak flowering in the study area began in June at the lowest elevations and progressed along an upward elevation gradient, peaking in August at elevations above treeline (J. England, pers. obs.).

Wildfire and Other Landscape Disturbances
Numerous small wildfires have been recorded in the watershed since 1950, the majority from natural causes (U.S. Geological Survey 2017b). In July 2002, the Birch Fire burned a large area near the northern part of the study area (MCCDDPD 2007). Over 2500 acres (1012 ha) of National Forest were burned in this human-caused fire, from the west side of lower Rock Creek across Birch Creek, Whiskey and Sand canyons, to Rock Creek Road. The western edge of the fire burned ca. 300 acres (121 ha) of the study area on a steep, west-facing slope above the canyon mouth. I observed severe impacts to pinyon pine woodland vegetation on the hillsides within the burn; hundreds of Cercocarpus ledifolius plants did not survive, nor the majority of Pinus monophylla trees. Table 2. Daily air temperature ranges in the upper Rock Creek watershed region. Recordings from two weather stations were obtained from the California Department of Water Resources data portal (CDEC 2017). "RKC" and "RCK" are the station names provided by the CDEC. The RKC station is located outside the study area, ca. one air mile (1.6 air km) northeast of the study boundary; the RCK station is located within the study area. Summary of typical minimum and maximum temperature ranges for January and July is based on station recordings during 2006-2016. No January or July recordings at RKC were available for 2012-2014. No July data were available for RCK in 2016. Fire suppression in the canyon dates to the early twentieth century, at least in the more accessible and developed areas. Presuppression wildfires presumably occurred on a somewhat regular basis historically as a result of lightning strikes.
In addition to fire, historic natural causes of disturbance in forested areas of the region include insects and disease (Millar 1996), rock slides (J. England, pers. obs. 2012England, pers. obs. -2016 and avalanches such as the February 1986 snow slides (Birkeland and Mock 2001) which felled dozens of trees and destroyed a campground near Mosquito Flat (Jim King, pers. comm.).

Floristic Provinces
The watershed is geographically situated at the confluence of two floristic provinces circumscribed by the Jepson Flora Project (2018) that represent major biogeographical transitions: the California Floristic Province and the Great Basin Province. Floristic elements of both are evident in the study area. The Great Basin component, part of the East of the Sierra Nevada floristic region, is the smaller of the two in terms of species composition in the study area. The remainder of the study area is within the California Floristic Province, specifically the High Sierra Nevada floristic region.

Vegetation and Habitats
Describing vegetation is challenging. Efforts have been made to classify California's vegetation at a statewide level (e.g., Holland and Keil 1995;Sawyer et al. 2009). These treatments use terms such as communities and/or alliances to describe associations of species often found growing together which form repeated patterns of vegetation. The challenge of using such a classification system to describe a local flora is that vegetation can resemble a blended mixture of types across the landscape. This is certainly true of the upper Rock Creek watershed, which varies greatly in elevation and topography. Therefore, no attempt is made here to describe all of the plant associations and habitats encountered during fieldwork for this study. However, some vegetation types widely recognized by authors (e.g., Holland and Keil 1995) were encountered: Jeffrey pine forest; pinyon pine woodland; sagebrush scrub; riparian woodland; lodgepole pine forest; meadows, lake and stream margins, seeps; whitebark pine forest; and alpine. In addition, I call attention to aspen groves, which are frequent in the study area. Transitions between types are rarely abrupt, and usually occupy a fairly extensive area exhibiting a blended species composition with elements of both types. Microhabitat variation within and between types is presumably a result of environmental factors such as moisture regime, exposure, nutrient availability and elevation. I ascribe an elevation range to each vegetation type based on personal observations; these ranges are estimates only: Following is a brief description of vegetation and habitats in the study area, including the dominant species and common shrubs, trees and herbaceous plants.
Jeffrey pine forest.-Pinus jeffreyi forms the backbone of the scarcest vegetation type in the study area. It is open in structure and has a woody understory dominated by sagebrush (Artemisia tridentata subsp. vaseyana). It covers the canyon bottom for a distance of roughly 1.5 miles (2.4 km) near the canyon mouth, in a narrow belt along both sides of the riparian woodland, and can best be seen between French Campground and "third crossing" (Fig. 1)  The understory and open areas between individual trees are typically inhabited by scattered woody and herbaceous species growing in decomposing granitic soils. Pinyon pine woodland is best represented on rocky slopes along Rock Creek Road between "first crossing" and "third crossing" (Fig. 1 Riparian woodland.-This vegetation dominates the stream banks of the main channel of Rock Creek (which runs more or less parallel to Rock Creek Road) along a corridor extending from the canyon mouth up to Mosquito Flat, where the riparian tree canopy phases out. The presence of a fairly dense tree canopy distinguishes the riparian woodland from streamside vegetation above Mosquito Flat, which is associated with the more openly structured whitebark pine forest. The riparian woodland canopy is occasionally broken, and in these places the vegetation intergrades with that of streamside meadows (Fig. 14). Species composition is highly transitional within the riparian woodland due to the sharp elevation gradient, and is best divided into two sections of dominant woody species: below 8500 ft (2591 m) and above 8500 ft. The lower riparian woodland is dominated by Salix species (willows) and other deciduous trees, and also includes Water Birch Riparian Scrub, a State-listed Rare vegetation type dominated by Betula occidentalis (CNDDB 2018). It is best observed along the creek between "first crossing" and Aspen Campground (Fig. 1) Aspen groves.-Populus tremuloides is found in a variety of mesic habitats throughout the study area from lower to middle elevations, becoming less common above 10,200 ft (3110 m). Aspen trees are common associates in the riparian woodland and lodgepole pine forest, and the species can be co-dominant with Pinus contorta subsp. murrayana in wetter areas. In places where moisture is abundant, it is not unusual for aspens to form dense stands of tall trees and provide habitat for other plant species. Populus tremuloides tolerates a range of exposures and substrates in the study area, and exhibits different growth forms depending on habitat. Tall upright forms occur in canyon bottoms, but on steep, exposed slopes the species typically has a dwarfish, shrubby appearance. Aspen groves are best represented along the canyon bottom be- Lodgepole pine forest.-At middle elevations along the canyon bottom and on mesic slopes, Pinus contorta subsp. murrayana is the dominant species (Fig. 12, 14). Occasionally, P. contorta forms dense stands, but frequently the forest is patchy and interspersed with other vegetation/habitats, such as riparian woodland, meadows, seeps, aspen groves, and dry rocky slopes vegetated by sagebrush scrub and scattered conifers such as Juniperus grandis and Pinus flexilis. Meadows, lake and stream margins, seeps.-A profusion of mesic habitats in the study area contain a highly variable association of species due to differences in elevation and other microenvironmental factors. Meadows in the lodgepole pine forest, for example, have different species associations than meadows in the whitebark pine forest. Lakeside vegetation at Rock Creek Lake differs from that of lake margins in Little Lakes Valley. Therefore the reader should take note that describing a single vegetation type each for meadows, lake and stream margins, and seeps is not practical in the context of this study.
Meadows in the watershed are patchy in distribution and have different associations of species depending on moisture regime, but are typically dominated by grasses, sedges, and rushes (Fig. 6,10,14). Willows and other scattered shrubs occasionally occur in meadows. Meadow margins at lower to middle elevations are often densely vegetated by willows, aspen groves, lodgepole pine forest and riparian woodland (Fig. 14). DOMINANT: Carex spp., Juncus spp., Poaceae spp. SHRUBS AND TREES: Artemisia cana subsp. bolanderi, Kalmia polifolia, Phyllodoce breweri, Salix spp., Vaccinium spp. HERBA-CEOUS: Achillea millefolium, Agrostis idahoensis, Antennaria spp., Calamagrostis muiriana, Carex abrupta, C. aurea, C. microptera, Castilleja spp. including C. peirsonii (Fig. 19) Lakes are widely scattered in the study area from 9400 ft (2865 m) and higher, commonly encountered in the John Muir Wilderness (Fig. 1, 3-4 (Fig. 6). The forest has a very open structure with scattered trees and shrubs. Dry rocky slopes with large boulders and loose, decomposing granite soils characterize much of the whitebark pine forest (Fig. 9), but there are extensive patchworks of mesic vegetation-especially in Little Lakes Valley-such as meadows and margins of streams, lakes and pools that support taxa not found in the drier areas of the forest. Whitebark pine forest is well represented in the John Muir Wilderness from Little Lakes Valley (Fig. 3-4) (Fig. 28), Selaginella watsonii, Trisetum spicatum.
Alpine.-The transition from subalpine to alpine vegetation in montane areas of California has been helpfully discussed by authors such as Sawyer and Keeler-Wolf (2007). Ruby Lake is an example of a location in the study area where this ecotone occurs. The delimitation of the alpine vegetation zone is all areas above tree line (timberline). Less than one percent of Califor-nia is above tree line, the majority of it along the Sierra Nevada crest (Holland and Keil 1995). Alpine habitat in the study area is a heterogeneous patchwork of fellfields (Fig. 8), dry slopes of decomposing granite soils, crumbling talus, mesic lake margins (Fig. 6, 11), pools, seeps and moist depressions. Vegetative cover is relatively low compared to other communities. Environmental conditions are harsh and the growing season is extremely short, typically two months long. High exposure to sunlight and wind, along with significant water runoff owing to typically shallow, poorly developed soils, collectively contribute to a relatively xeric environment.
Woody and annual species are uncommon; most alpine plants in the watershed are perennials with low cushion-or mat-like forms. Pinus albicaulis, where present, is in small isolated stands of highly stunted plants (Fig. 6). Talus-covered ridgetops and peaks above 12,000 ft (3660 m) do not support many species but do provide habitat for certain plants not typically found below that elevation, including Hulsea algida and Polemonium eximium (Fig. 13, 27). Alpine vegetation occurs in all areas above 11,100 ft (3380 m) and as high as 13,750 ft (4190 m

Plant Geography
A helpful synthetic discussion of various studies that address the origin of the High Sierra Nevada flora was provided by Sawyer and Keeler-Wolf (2007). Stebbins (1982) hypothesized four origins of the high montane, subalpine and alpine flora of the High Sierra Nevada south of Donner Summit, which he termed Old Cordilleran (39% of the flora), Circumboreal (26%), Lowland Cismontane California (19%) and Great Basin (16%). Stebbins' analysis, informed in part by fossil flora records, generally aligns with previous work by Smiley (1921), Chabot and Billings (1972) and Raven and Axelrod (1978). Of the four floristic sources, one-Lowland California-consists of an endemic element that evolved in California. The other elements are said to have arrived via migration from areas pre-dating the Sierra Nevada, outside the state. The most commonly proposed route for the majority of the Old Cordilleran invaders is from the north along the Cascade-Sierra Nevada axis; most of these species' relatives are found in North America. The presence of Rocky Mountain disjuncts in the Sierra has led some to propose a westward migration route for certain taxa associated with the Old Cordilleran group (e.g., Major and Bamberg 1963). The Circumboreal group is composed of cosmopolitan species believed by Stebbins to have had multiple migration pathways; this group contains a large number of woody taxa including Salix. He proposed that the Great Basin element originated from the desert and Basin and Range floras east of the Sierra. This generalized way of thinking about how California's flora originated has provided a useful groundwork for discussion. However, growing use of molecular phylogenetic data and genomic tools to explore what have been longstanding biogeographical questions are showing that the story is much more complex than can be summarized here (Baldwin 2014).

human activity
Prior to the Twentieth Century Indigenous groups.-Relatively little information is known about the presence of prehistoric humans in the high Sierra Nevada, but there is evidence that alpine sites in the Sierra were traversed during early hunting and gathering forays, and for commerce between human groups (Arkush 1993;Stevens 2005). Artifacts from "Paleoindian" encampments in nearby Long Valley date to the early Holocene (Basgall 1989). The only evidence of indigenous people in Rock Creek Canyon is documentation by archaeological surveyors of obsidian flake detritus indicative of historical tool making and at least one projectile point (MCCDDPD 2013).
European-American settlers.-By the middle of the nineteenth century, Euro-Americans had begun to lay claim to the valleys adjacent to the study area, settling and making a livelihood from cattle and sheep ranching as well as farming. Basque sheep herders made their mark (quite literally, as discussed below) in the eastern Sierra Nevada during the peak of the state's wool industry in the 1880s and 1890s (Busby et al. 1980). Herders typically brought flocks over the Sierra from the west side, moving the animals to summer forage in eastern montane meadows. Numerous arborglyphs were carved by the Basque on treesusually aspen, occasionally pines-depicting humans and other figures. There are a number of glyphs on trees in Rock Creek Canyon, some with dates from the late 1800s (McNeill 2016), suggesting that the herders brought sheep on multiple occasions into the study area for grazing.

Twentieth Century Until Present
Road construction.-Sand Canyon Road (Forest Rd 5S08/ 30E302) is a 4WD road that is accessible from the community of Swall Meadows and enters the study area from the northeast. It runs south, along the base of Wheeler Ridge, for ca. 5 miles (8 km) and terminates near the Wilderness boundary on Tamarack Bench (Fig. 1, 2). The road was originally constructed in 1918 as a route to transport mining equipment to Morgan Pass and the Pine Creek prospects just outside the study area, and served as the primary route up the canyon until Forest Highway 89/Rock Creek Road was built shortly thereafter (Kurtak 1998).
Rock Creek Road winds ca. 10.5 miles (16.9 km) up the canyon and now terminates at the Mosquito Flat trailhead (the old section of the road from Mosquito Flat to Morgan Pass was permanently closed to vehicles following the Wilderness Act in the 1960s). The Little Lakes Valley hiking trail follows the route of the old road to Morgan Pass, and remnants of discarded mining equipment are evident along the trail.
Nine miles (14.5 km) of Rock Creek Road underwent construction for improvements in 2014 and 2015, including the addition of a bicycle lane (MCCDDPD 2013). The only other vehicle-accessible road within the study area is Wheeler Ridge Mine Road (Forest Rd 30E301), a steep east-west 4WD route between Sand Canyon Road and the crest of Wheeler Ridge (Fig. 1).
Recreation.-Tourism and recreation in Inyo and Mono counties began to grow substantially in the 1930s, and by the 1960s had become the mainstay of the region's economy (Busby et al. 1980). Two resorts, a pack station and 12 developed campgrounds were constructed in Rock Creek Canyon (Fig. 1) (MC-CDDPD 2013). Horseback riding (sometimes with pack mules), hiking, backpacking, cross-country skiing, fishing and camping are among the recreational activities popular in the watershed. Commercial and residential use.-The author's research yielded no evidence of historical commercial timber harvesting and mining within the study area, although as noted above, a road was built through the study area to access the Pine Creek mines in the adjacent watershed. Two resorts and a pack guide outfit have been operating in Rock Creek Canyon since the early twentieth century, and presumably rely on local water sources for necessary operations. A small number of private cabins are used for seasonal residences; all cabins today are outside the Wilderness.

Previously Published Checklists
The first known collections in the watershed were made in 1930 by Frank W. Peirson in the Little Lakes Valley area. Peirson made a total of eight collecting trips to "Rock Creek Lake Basin" between 1930 and 1940, resulting in 822 collections that I was able to locate through searches of online databases, the majority of which are housed at RSA/POM (SEINet Portal Network [SEINet] 2016; Consortium of California Herbaria [CCH] 2018). The earliest day and month Peirson recorded in his journal for any of those trips was July 17, and the latest was August 22. Peirson published the first checklist for the watershed in 1938: Plants of Rock Creek Lake Basin, Inyo County, followed by a short addendum list in 1942. Both lists were restricted to Little Lakes Valley and the surrounding high areas, from 10,500 ft (3200 m) and above. His highest documented collection locality was above Mono Pass at 12,500 ft (3810 m) (Carex helleri, Peirson s.n., 15 Aug 1933, CAS). A total of 344 minimum-rank taxa (species, subspecies, varieties, named hybrids) were reported.
A second inventory was carried out during a Sierra Club trip led by John T. Howell in July 1946. Howell's publication, Base Camp Botany, 1946, in which he presents his species checklist, does not provide exact dates of that trip. However, his specimen labels for those collections-housed at CAS/DS and other herbaria-are dated from July 14 to July 29 (SEINet 2016; CCH 2018). Howell's checklist for Rock Creek was restricted to the same general region that Peirson documented but extended downstream to Mosquito Flat, at the 10,300 ft (3139 m) contour. His highest collections in the study area were from Mono Mesa at 12,200 ft (3718 m) (e.g., Cystopteris fragilis, Howell 22752, CAS). Howell (1946) reported 313 taxa for the Rock Creek "basin," including 52 species not recorded by Peirson, which he noted were mostly found in the Mosquito Flat vicinity, not surveyed by Peirson. All together, Peirson and Howell recorded 396 minimum-rank taxa for the study area.

Other Collections
Sporadic botanical documentation by others from the 1930s to the early 2000s resulted in over 400 additional herbarium records that I was able to locate (SEINet 2016; CCH 2018). Significant contributions, in order of earliest to most recent, were made by R. Woglum, A. Crafts & M.
Halperin, E. Robinson, C. Sharsmith, R. Ferris, J. Thomas and G. Wallace. Except for the last two, the collections were made before 1950.

Type Localities
Type specimens I encountered from the watershed include

project objectives and methods
The primary objective of the study was to produce a vascular plant checklist based on preexisting and new collections. I spent 89 days in the study area from 2012 to 2016 and made 1506 collections (including two collections made during a short visit in 2018). An effort was made to document as many taxa as possible by surveying as much of the watershed as time, resources and accessibility allowed. Early and late season taxa were documented in 2012 and 2013, the two years that fieldwork was conducted at regular intervals throughout the growing season (May-Sep). Areas targeted for fieldwork include those poorly documented based on records in the SEINet and CCH data portals (SEINet 2016; CCH 2018) ( Fig. 1: left inset). Examples of undercollected areas were the high peaks, the eastern half of the watershed and areas below 10,000 ft (3048 m).
Locality data were recorded in the field at each collection site, including coordinates obtained from a Global Positioning System (GPS) unit, elevation, abundance, habitat description and associated taxa. Duplicates were collected for later distribution to herbaria, with a full set deposited at RSA. I examined, verified and annotated more than 1000 pre-existing collections housed in the following herbaria: ASC, CAS/DS, CDA, GH, LA, NMC, NY, PASA, RSA/POM, SBBG, SD, UC/JEPS, UCD and UCR. Taxonomy follows the Jepson Flora Project (2018) with the following exceptions: family classification for Boraginales is according to the Boraginales Working Group (2016); recent treatments in Cryptantha (Hasenstab-Lehman and Simpson 2012) and Luzula (Zika et al. 2015a) were also followed. Additional resources were consulted for help with identification, including Flora of North America (FNA Editorial Committee 1993+) and Intermountain Flora (Cronquist et al. 1972(Cronquist et al. -2012 for various plant groups, Correll and Correll (1975) for aquatic plants and Isely (1998) for Fabaceae. The author relied heavily on the RSA collection for identifying plants in challenging taxonomic groups, especially specimens recently annotated by taxonomic specialists. The determinations of some specimens were confirmed by experts in the groups as needed.
The remarkably rich composition of grasses (65 native taxa) is noteworthy when comparing the Rock Creek flora with several other floras in the eastern Sierra Nevada region (Table  4), as is the relatively high diversity of Rosaceae (33 taxa) and Carex (47). Rock Creek is the only one of these floras to have Rosaceae among the five largest families represented. Rock Creek shares notable similarities with the two study areas closest in geographic distance-the Glass Mountain Region flora (Honer 2001) and the San Joaquin Roadless Area flora (Constantine-Shull 2000)-in having Carex, Boechera and Eriogonum as the three largest genera represented. It should be noted that these two study areas are geologically dissimilar to Rock Creek in having primarily volcanic substrates in contrast to granitic.
Thirty-two taxa (5%) in the study area are rare (specialstatus) plants recognized by California and/or the California  (Table 5). Nineteen taxa are endemic to the High Sierra Nevada region, representing 3% of the total flora (Table 6). Twenty-five non-native taxa constitute 4% of the flora. Seventy-four taxa are annuals or short-lived perennials (13%); 57 (77%) of these are obligate annuals and 11 (15%) are non-native (Jepson Flora Project 2018). Twenty (35%) of the obligate annuals were documented as high as the whitebark pine forest (10,200-11,100 ft/3110-3380 m). Only one obligate annual-Rorippa curvisiliqua (Brassicaceae)-was found above treeline, where it was seen at one locality at 11,624 ft (3543 m).

Taxa Omitted From the Catalog
Collections historically identified as Lupinus gracilentus Greene were determined to be misidentifications (Butler s.n., Jul 1931, PASA1662; Peirson s.n., 11 Aug 1933, UC511825; Peirson 9055, RSA). Lupinus gracilentus (slender lupine; Fabaceae) is a special-status species (Rank 1B, CNPS 2018) that is known to occur on the west slope of the central Sierra Nevada in Yosemite National Park. The extent of its distribution, especially for collection records east of the Sierra crest, is in need of study (Sholars and Riggins 2012). All collections from the Rock Creek watershed historically identified as L. gracilentus were examined by the author and determined to be L. lepidus var. confertus (Kellogg) C.P. Sm., based in part on examination of original material of L. gracilentus collected from Tuolumne Co. by Chestnut & Drew in 1889 (NDG).
A specimen of Salix nivalis Hook. (Peirson 11207, RSA) was mislabeled with the locality of Ruby Lake. It was actually collected outside the study area in the Virginia Lakes watershed of Mono County, as evidenced by Peirson's collection notebook entry for his number 11207, and by correctly labeled duplicates in other herbaria (HSC, NY, SBBG, SD, POM). Salix nivalis is not likely to occur in the watershed, as it appears to be restricted to metamorphic substrates at locations elsewhere in the Sierra Nevada (Moore and Johnson 2011).
Several species have been infrequently reported from the Rock Creek watershed that unfortunately lack an herbarium voucher (CCH 2018) (e.g., Pterospora andromedea Nutt. [Ericaceae; Rose 2015]). The vascular plant inventory presented in this study only includes taxa based on at least one representative herbarium specimen.

Noteworthy Collections
New records for the Sierra Nevada.-According to online database collection records (SEINet 2016; CCH 2018), two taxa collected during this study are evidently the first records for the Sierra Nevada; both are special-status species listed in the CNPS Inventory of Rare and Endangered Plants (online edition, v8-03, 2018) (Table 5).
Carex stevenii (Steven's sedge; Cyperaceae) previously had only been documented from the White Mountains (the species is also found outside California, in the southern Rocky Mountains [Zika et al. 2015b]). In the study area there is a single known occurrence of C. stevenii-a small population was found in 2012 near Rock Creek Lodge (Fig. 1).
Penstemon cinicola (ash beardtongue; Plantaginaceae) was documented in 2012 and 2013 at several sites above 9800 ft (2987 m) in the study area. It was previously known to occur only on volcanic soils, at locations north of the study area such as the Glass Mountain region, Modoc Plateau, Warner Mountains and southern Cascade Range (Wetherwax and Holmgren 2012). The nearest known population is in the Glass Mountain area ca. 25 miles (40 km) to the north. There is a collection record (Woodland 2627, NY) (CCH 2018) of P. cinicola from the west slope of the Sierra Nevada in El Dorado County, a likely misidentification.  (Peirson 1938(Peirson , 1942Howell 1946). These   (Table 5). Herbarium searches (SEINet 2016; CCH 2018) revealed one additional perennial dicot (Gentianopsis simplex, Gentianaceae) not recorded in earlier checklists. Elizabeth Butler documented this species from Heart Lake in the 1930s (s.n., Jul 1931, PASA187) during the same year and month that Peirson made one of his visits to Heart Lake. Butler's remains the only known collection from the watershed.

Special-Status Species and Taxa of Limited Distribution
Rare taxa.-Thirty-two taxa in the study area are listed in the CNPS Inventory of Rare and Endangered Plants (v8-03, 2018) ( Table 5). The inventory employs a ranking system based on degree of rarity. Five taxa in the study area are Rank 1B: they are California endemics and rare throughout their ranges. Ten taxa are Rank 2: they are rare throughout their range in California but are more common elsewhere. Seventeen are Watch List taxa (Rank 4).
Two legumes, Astragalus monoensis and Lupinus padrecrowleyi, are officially listed as Rare under the California Endangered Species Act (CESA) (CNDDB 2018). No federally listed taxa are known from the watershed; however, as of April 2018, Pinus albicaulis is a candidate species (i.e., under review) for listing under the Federally Endangered Species Act (FESA) due to its rapid decline throughout its range in North America (U.S. Department of the Interior, Fish and Wildlife Service 2018).

Narrowly distributed taxa.-Thirty-seven taxa in the Rock
Creek flora have relatively narrow ranges as circumscribed by Baldwin et al. (2012) (Table 6). Known distributions of these taxa are limited to the High Sierra Nevada region, or extend only to the East of Sierra Nevada region and/or the White and Inyo mountains.
Sensitive species.-Taxa recognized as sensitive by the State of California (CNDDB 2018), CNPS (2018) and/or the Inyo National Forest due to threats and/or extreme rarity warrant a brief discussion. Botrychium crenulatum (scalloped moonwort; Ophioglossaceae), a diminutive fern, is only known in the watershed from a single population on a wet slope along the margin of a horse pasture near Rock Creek Lodge, at ca. 9500 ft (2895 m) elevation. This species (CNPS List 2 [endangered in CA; more common elsewhere]) is listed as threatened by grazing and trampling within its range. Horses were observed in the pasture during fieldwork for this study. It is possible that B. crenulatum occurs in suitable habitat elsewhere in the watershed; the species is inconspicuous even to a trained botanical eye, and could be easily overlooked.
Boechera tularensis (Tulare rockcress; Brassicaceae) (CNPS List 1B [rare, threatened, or endangered in CA or elsewhere]) is possibly threatened by recreational activities and vehicles within its range. In the study area it is only known from a single historical collection (Alexander, Bailey & Urban 847A, B [NMC]). It was documented in 2008 at ca. 10,500 ft (3200 m) along the trail between Mosquito Flat and Ruby Lake. It was not rediscovered during the present study.
Calyptridium pygmaeum (Fig. 18) (pygmy pussypaws; Montiaceae) (CNPS List 1B [rare, threatened, or endangered in CA or elsewhere]) is possibly threatened by recreational activities and vehicles within its range. In the eastern Sierra Nevada, it has only been recorded from the Rock Creek and Cottonwood Creek watersheds. Statewide there are 27 collections I am aware of (although I have not verified the determinations for all), that represent ca. 15 occurrences (CCH 2018). The species was first documented in the study area at Heart Lake in the 1930s (Peirson 13457, RSA) but wasn't recorded again until the present study. It was found at Heart Lake and Rock Creek Lakes Resort in 2013, and at Rock Creek Lake in 2015. All sites where C. pygmaeum has been documented in the watershed receive considerable impact from human traffic. The latter two locations are noteworthy in that they are developed sites-at Rock Creek Lake the species was found growing in a road pavement crack and at the Resort it was found in a dirt parking area. It is likely that C. pygmaeum occurs elsewhere in the study area-there appears to be plenty of suitable habitat-but the plants are small, ephemeral and easily overlooked.
Lupinus padre-crowleyi (Father Crowley's lupine; Fabaceae) (CNPS List 1B [rare, threatened, or endangered in CA or else-where]; State List Rare) is a very rare Sierra Nevada endemic only known from Inyo, Mono and Tulare counties. This species is known in the study area from a single occurrence, found in 2013 on Wheeler Ridge at ca. 11,000 ft (3353 m). This locality is currently the northernmost known occurrence of the species (CCH 2018).
Astragalus monoensis (Mono milkvetch; Fabaceae) (CNPS List 1B; State List Rare) is threatened by road maintenance, vehicles and sheep grazing within its range. Interestingly, the Rock Creek plants are disjunct-the closest occurrence is ca. 14 air miles (22.6 air km) northwest, near Hot Creek at the edge of the species' primary area of distribution, where it occurs on volcanically derived soils. It is unclear whether the Rock Creek plants are a natural population, or perhaps arrived via human-mediated transportation, e.g., seeds mixed with gravel brought in for road work, or lodged in the cracks of automobile tire treads. The author only found the species along Rock Creek Road (ca. 13 plants observed; England 260, 291) and at the Palisades day parking area (Fig. 1) Creek in 1992 and1994 (Fredendall 6355, 6413, RSA). Both collections, annotated during the present study, were originally determined as A. lemmonii A. Gray). The locality data are vague for these collections; the provided elevation of 9400 ft (2865 m) would place them uproad from the Palisades population (8885 ft /2708 m).
The Palisades site was used as a staging area for road maintenance in 2014 and 2015, when Rock Creek Road was widened to accommodate a bicycle lane. Temporary negative impacts to roadside vegetation were anticipated by the planning agencies, but the long-term viability of the Palisades population of A. monoensis was determined not to be threatened by the project (MCCDDPD 2013). However, in June 2012, the author documented 13 plants along the road shoulder between Big Meadow and Palisades, near a pullout (England 260, RSA). Unfortunately, the Biological Assessment conducted in July 2012 to assess potential impacts to rare species from the planned road work reported that A. monoensis was not present along the roadway. The plants documented along the road during this study were growing within four feet (ca. 1 m) of the west pavement edge and the majority did not survive the bicycle lane addition-in August 2018 I resurveyed the collection site and found only three individuals.

Regional Endemism
Although no taxa were found to be restricted to the study area, 19 taxa in the Rock Creek flora are endemic to the High Sierra Nevada bioregion (Baldwin et al. 2012) (Table 6). The Sierra Nevada has been recognized as a hot spot of botanical diversity within California (Raven and Axelrod 1978;Thorne et al. 2009). Burge et al. (2016) reported 299 minimum-rank taxa endemic to the Sierra Nevada. Shevock (1996) estimated as many as 405 Sierra Nevada endemics, but his geographical boundaries for the region were broader than those of Baldwin et al. (2012), which were used by the Burge et al. (2016) study. Shevock noted that more than half of all Sierra endemics are considered rare by governmental agencies and/or conservation organizations. He also observed that among eastern Sierra Nevada river drainages, the Owens River Basin is noteworthy for its relatively high species diversity and numbers of endemic and rare taxa. Raven and Axelrod (1978) suggested that major climatic change at high elevations during the Pleistocene drastically limited the opportunities for plant speciation during that time period; therefore, endemics that occur in the high Sierra are of relatively recent origin and special interest. The Pleistocene period in the Rock Creek watershed, as in much of the Sierra Nevada, was marked by repeated glacial advances and retreats (Hildreth and Fierstein 2016).

Non-Native Taxa
Twenty-five taxa are not native to the study area (Jepson Flora Project 2018). All non-native taxa documented previously were encountered except for Festuca myuros (Poaceae), which was recorded from a single collection at Rock Creek Lake in 1947 (Benson 12577, POM). It may still be present in the study area but, if so, it is likely uncommon. The most widespread and abundant naturalized species is Bromus tectorum (cheat grass; Poaceae), which is common up to ca. 9500 ft (2890 m) along roadways and in frequently disturbed areas adjacent to roads. I documented B. tectorum as high as Rock Creek Lake (9800 ft/2990 m) and it may infrequently occur higher along the road. A collection of B. tectorum from Ruby Lake at 11,150 ft (3400 m) (Peirson 11308, RSA) is correctly identified but appears to be an anomaly; no evidence of cheat grass in the Wilderness Area was found during the present study. The Wilderness appears to be little impacted by non-natives; only two were documented: Taraxacum officinale (Asteraceae; fairly common, usually along trails and in small numbers) and Phleum pratense (Poaceae; rare). There are several historical collections of Poa pratensis subsp. pratensis (Poaceae) from the study area, all from 1946 or earlier (Halperin 515, CAS; Howell 22374, CAS; Peirson 10817, RSA). However, I did not encounter this species.
Perhaps most noteworthy with regard to non-natives is the unusually high elevations at which some were recorded. Elymus ponticus (Poaceae; 9400 ft/2865 m), Matricaria discoidea (Asteraceae; 9700 ft/2960 m), Plantago lanceolata (Plantaginaceae; 9900 ft/3020 m), Portulaca oleracea (Portulacaceae; 9750 ft/2970 m) and the aforementioned B. tectorum (9800 ft/2990 m and 11,150 ft/3400 m) have no previous collections in California from such high elevations (SEINet 2016; CCH 2018). All of these records except for Peirson's are along Rock Creek Road, apparently the highest paved road (10,240 ft/3121 m) in the Sierra Nevada and undoubtedly a corridor for plant dispersal, natives and non-natives alike. Undocumented weeds probably exist in the campgrounds along Rock Creek Road (I was not permitted to make collections within campgrounds). Trails presumably are also natural corridors for dispersal of non-natives such as Taraxacum officinale.

Taxa Not Rediscovered
Eighty-one taxa vouchered by previous collections were not rediscovered. There are several possible explanations for this. First, below-average precipitation was recorded in all years the author conducted fieldwork. Some taxa not rediscovered may be more abundant in wetter years. Second, although I attempted to achieve excellent geographic coverage during field surveys, it was not possible to search the entire area. Evanescent plants or those that were present in only one year may have been missed. Some taxa may have been present but were overlooked, particularly those very small in stature, and those such as sedges, rushes and grasses that tend to "blend in" with similar-looking species. Lastly, some taxa present historically in the watershed may no longer be present; taxa that were rare in the 1930s would have been especially vulnerable. Many of the taxa not rediscovered are known from a single historical collection, which suggests that they may have been uncommon in the watershed when they were collected. A question is whether or not climate change, recreational activities, and/or other impacts have led to the disappearance of previously documented species.

Noteworthy Absences
Red fir, Abies magnifica A. Murray var. magnifica (Pinaceae) and white fir, A. concolor (Gordon & Glend.) Lindl. ex Hildebr., have not been recorded in the study area to my knowledge. Collections of Abies on the east slope of the central Sierra Nevada are relatively sparse (CCH 2018); many records of A. magnifica exist from the east slope of the northern Sierra and for A. concolor on the east slope of the northern and southern Sierra. However, A. magnifica is a common forest species on the slopes of Mammoth Mountain, ca. 15 air miles (24 km) northwest of Rock Creek, and Abies concolor has also been documented both in the Mammoth area (Howald 2000) and at several sites in the Glass Mountain region ca. 22 air mi. (36 km) north of Rock Creek (Honer 2001). The presence of Abies in the Mammoth region might be attributed in part to the relatively wetter conditions around Mammoth Pass (ca. 9370 ft/2866 m) which sits low on the Sierra crest, allowing more moisture from winter storms to reach the east slopes (Sawyer and Keeler-Wolf 2007).

Threats to the Flora
Climate change.-Warming annual temperatures are likely the greatest medium-to long-term threat to the flora, especially to taxa that grow on mountaintops as they have "nowhere to go" (Loarie et al. 2009). Podistera nevadensis (Apiaceae), Draba sierrae ( Fig. 22) (Brassicaceae), Astragalus kentrophyta var. danaus and Lupinus padre-crowleyi (Fabaceae) are rare, narrowranging taxa that are uncommon and limited to ridgetops within the watershed. Suitable habitat for these species may contract in the future if climate change projections come to pass. A century ago, the alpine region of the Sierra Nevada was observed by Smiley (1921) to be fragmentary in its distribution. One could postulate that alpine-restricted species such as Hulsea algida (Asteraceae) and Polemonium eximium (Fig. 13, 27) (Polemoniaceae) will suffer population decline if alpine habitats are altered by warming. The topographic and micro-climatic heterogeneity within the watershed, however, could provide refugia for some taxa (Loarie et al. 2009). Warming temperatures may increase the amount of suitable habitat for some natives and also for non-natives, leading to potential range shifts if other climatic variables are relatively stable. Bromus tectorum, well established along Rock Creek Road below 9500 ft (2895 m), could potentially advance farther up the canyon if present temperature barriers are relaxed (Griffith and Loik 2010). Many non-native species from lower areas in California have already moved higher in elevation over the past century in response to climate change, with ca. 27% of non-native taxa exhibiting sig-nificant range shifts toward higher elevations (compared to ca. 12% of endemic taxa showing a similar pattern) (Wolf et al. 2016).
Drought and wildfire.-A span of dry years in the past decade has resulted in significant impacts to the forests (Inyo National Forest 2014). I observed significant mortality of Pinus albicaulis (Pinaceae) at its lower elevations, particularly in the Tamarack Bench and Hilton Bench areas. Millar et al. (2012) conducted surveys of P. albicaulis stands in the Rock Creek watershed containing dead trees, and attributed high mortality rates in the plot sites to mountain pine beetle (Dendroctonus ponderosae) infestations associated with successive years of drought during the first decade of the current century. Large wildfires such as the 2002 Birch Fire that burned part of the study area are potentially grave threats to the flora. Conversely, the practice of fire suppression in the more accessible areas of the watershed, especially near the resorts and campgrounds, has potentially changed forest composition and fuel structure in those areas, perhaps increasing the risk of catastrophic fire (Inyo National Forest 2014).
Recreation.-Increased recreational use on the Inyo National Forest is projected, based on rising urban populations in southern California (Inyo National Forest 2014). This is a matter of concern for sensitive ecosystems in the study area such as wetlands and meadows adjacent to hiking trails and campgrounds. Overnight camping in the John Muir Wilderness is restricted by a limited number of Wilderness entry permits per day. However, day hiking in the Wilderness is not presently regulated by permit nor limited to maximum number of visitors per day.
I observed some habitat degradation along the edges of trails and lakes due to trampling from foot traffic, horses and mules. The most popular destinations in Little Lakes Valley are the easily accessible lakes such as Heart Lake, Long Lake and Gem Lakes. Shorelines and meadow areas along these and other lakes have already received a moderate level of disturbance. The Inyo Forest has attempted to dissuade repeated trampling of some meadow areas by posting signage such as "Restoration Area" at a few sites. Streamside vegetation in the riparian zone near campgrounds was also observed to have received a significant amount of disturbance from fishermen and campers. It is recommended that the Inyo National Forest monitor these impacts toward control, reduction and mitigation. The following 591 minimum-rank vascular plant taxa were documented from the upper Rock Creek watershed. This catalog is a result of intensive fieldwork conducted from 2012 through 2016 (two collections were made during a one-day visit in 2018), and herbarium searches using the Consortium of California Herbaria (CCH) and SEINet Portal Network databases (accessed on multiple occasions 2012-2018). A full set of specimens collected during this study is housed at Rancho Santa Ana Botanic Garden (RSA). Specimens cited are housed at RSA unless otherwise indicated. More than 1000 pre-existing collections were examined, verified, and annotated from the following herbaria: ASC, CAS/DS, CDA, GH, LA, NMC, NY, PASA, RSA/POM, SBBG, SD, UC/JEPS, UCD and UCR. Identifications were made by the author or by an expert in the taxonomic group. For each taxon, the catalog cites at least one collection and indicates the vegetation type(s) where it has been documented and its abundance in the watershed.
Family classification for Boraginales is according to the Boraginales Working Group (2016); other authorities followed include recent treatments in Cryptantha (Hasenstab-Lehman and Simpson 2012) and Luzula (Zika et al. 2015a). All other taxonomy follows the Jepson Flora Project (2018).
Abundance terms are defined typically as follows: rare = a single collection site, not observed elsewhere; uncommon = narrowly distributed, seldom observed; occasional = variably distributed, infrequently observed; locally common = narrowly distributed, commonly observed within its range; common = broadly distributed, commonly observed.
Non-native taxa are denoted by an asterisk (*) and may include waif occurrences of California natives. Special-status taxa listed in the CNPS Inventory of Rare and Endangered Plants (online edition, v8-03) and State Listed taxa are denoted by a dagger ( †). CNPS rarity ranks: 1B: Plants rare, threatened, or endangered in California or elsewhere; 2: Plants rare, threatened or endangered in California but more common elsewhere; 4: Plants of limited distribution (watch list). Plants designated Rare by the California Fish and Game Commission (CNDDB 2018): CA-Rare.
Taxa identified from previous collections but not rediscovered during fieldwork for this study are denoted by a diamond (♦). New collections from areas previously surveyed by Peirson (1938;1942) and/or Howell (1946) but not recorded in those checklists are noted. See Fig. 1 Peirson (1938Peirson ( , 1942 or Howell (1946 Peirson (1938Peirson ( , 1942 or Howell (1946