Callow Valley

0Fields

miles

Malheur Marshto Burns

Alvord Desert

5 10 15

DiamondCraters /y\

Riddle Mtn, Folly Fern

•to Burn.

Junction

Fronottglon

I hMann Lak,

kilometers

0Long Hollow

! cord Lake

OREGON

to Demo, Nevada

The Unique Botany of Steens Mountain:The Rare and Endemic Plants

By DONALD MANSFIELD

In southern Harney County the landscape rises from thewest almost imperceptibly to nearly 10,000 ft. and the topof Steens Mountain. Without passing through even a hintof a forest, those traveling the Steens Loop Road soon findthemselves among aspen groves, alpine meadows, cirques, andtams. The vistas of glacial gorges and precipices dropping near-ly 6,000 ft. to the Alvord desert rival any in Oregon. To thebotanist, the excitement and intrigue is only beginning. Fromthe desert scablands and riparian meadows and woodlandsbelow to the alpine meadows, rock outcrops, and talus slopesof the "High Steens:' wildflower displays abound at every turn.Plants abundant here are found nowhere else in the world.Many plants common in the mountains of California or Idahocan he found here as outliers, somehow lost from their relativesto the southwest or northeast, separated by miles of sagebrushdesert.

Steens Mountain is the northern-most fault block mountainrange in the Great Basin. When defined to include the moun-tainous area from Riddle Mountain on the north to the SmithFlat and Long Hollow region near Fields on the south, it oc-cupies an area of approximately 1,000 square miles. The gorgeson the west and north drain gradually into the Malheur Marshand ultimately Harney Lake, while the steep eastern escarp-ment is drained by several streams that find their way to theAlvord Desert or Pueblo Valley. Southeastern Steens Moun-tain drains west into the Catlow Valley.

Steens Mountain is unusual physiographically in two respects.First, large basins, approximately 4,000 ft. in elevation, isolateSteens Mountain from other high mountain ranges. StrawberryMountain in the Blue Mountains, 120 miles to the north, isthe closest mountainous area rising above 9,000 ft. Second,Steens has extensive contiguous area (approximately 75 km 2 )above 8,000 ft. elevation. The nearest ranges with this muchalpine topography are the Cascade-Sierra Range 200 miles tothe west and the Wallowa Range 200 miles to the northeast.The combination of isolation and extensive alpine topographyresults in a unique flora. This article will summarize some ofthe outstanding features of this unique botanical area andhighlight its rare and endemic plant species.

Geologic and Phytogeographic History ofSteens Mountain

A brief geological history of Steens Mountain is relevantto understanding the unique qualities of the sreens flora. Thestory begins about 30 million years ago during the OligoceneEpoch when the area was forested by a tropical flora. Awidespread cooling trend ensued (Wolfe 1978) when theCascade Range began to rise. By 20 to 25 million years ago(early Miocene) eastern Oregon was forested by a deciduousforest flora much like that in present-day Ohio or easternChina (Chaney 1956). Volcanic eruptions that occurred dur-ing this time produced the lowest rocks of what is now Steens

Steens Mountain is located in so flatten! Harney County, Oregon.

Mountain — the red, principally rhyolitic and tuffaceous PikeCreek Volcanic Series (23 million years old). The AlvordCreek Formation of tuffs and plant fossil-bearing lake beddeposits formed approximately 21 million years ago in whatappears today as the light-colored beds above Alvord Ranch.The Alvord Creek fossils tell us that annual precipitation atthis time was about double the current rate and mean annualtemperatures were higher and with less drastic extremes. (Wolfe1978; Ferguson and Ferguson 1978). The andesitic and basalticflows that today form the middle elevations of Steens (theSteens Mountain Volcanic Series) and the Steens MountainBasalt that forms the present-day cliffs above 7,000 ft. flowedover the area from between 13 and 18 million years ago (midMiocene). Roughly 8-10 million years ago (late Miocene)faulting began and the Steens uplift commenced. By this time,

10 Kalmiopsis 1995

the Sierra-Cascade Range had uplifted substantially, providinga rain shadow in southeastern Oregon (Fiero 1986). Together,these geological events resulted in a different regional climateand a greater diversity of habitats than had previously existedin the area. By about the end of the Miocene Epoch, the GreatBasin floristic province had become established (Cronquist

1978).

By 2-3 million years ago (late Pliocene) the climate wasgenerally cool and moist, though drier than in earlier timesand with less summer precipitation. Consequently, theregional flora continued to change as new species emergedthat were adapted to these new climatic conditions (Ravenand Axelrod 1978; Cronquist 1978). The past few million yearshave been characterized by alternating glacial and interglac-ial periods. Three geologically distinct periods of glaciationare evident on Steens Mountain (Lund and Bentley 1976).Initially, glacial ice covered nearly 300 kmZ in the Fish Lakeadvance, filling or carving the major gorges — Big Indian,Little Blitzen, and Kiger. A second period (the Blitzen ad-vance) was restricted to the canyons, covered about 130 kmzand formed the headwalls of the major gorges. During the finaland much smaller glacial advance that ended no later than12,000 to 13,000 years ago (Thompson et al. 1986), the ice

carved the smaller cirques that lie above 8,000 ft. includingSouth Fork Willow Creek and Big Alvord. The past 8,000years in the northern Great Basin have been characterized bya more xeric climate and a corresponding loss of mesic speciesfrom the region (Nowak et al. 1994). On Steens Mountaina roughly twofold increase in sagebrush to grass pollen isobserved between 5,500 and 8,000 years ago, indicating thatthis period was the driest of the Holocene on Steens (Mehr-inger and Wigand 1985).

During alternating glacial and interglacial periods of the pastfew million years, two main processes appear to have produc-ed the modern distribution of plant species in the Great Basin.First, during cool, moist periods of glacial advance, speciesmigrated down in elevation (Thompson 1990) and/or into theregion from the north (Cronquist 1978); during the wanner,drier interglacial periods species migrated to higher elevationsand/or into the region from the south. Second, montane"islands" lost species via local extinctions and gained speciesby immigration according to the predictions of island bio-geography theory (Wells 1983). Based on the current affinityof the flora with Columbia Plateau, Great Basin, and SierraNevada floristic elements (McLaughlin 1989), it appears thatthe present flora of Steens originated with the regional floraprimarily during the Pliocene. That is, most of the plants ofSteens Mountain are distributed throughout the northernIntermountain region. The unique aspects of the Steens flora,those features which distinguish it from the rest of the region,seem to result from the local extinction, migration, and specia-tion peculiarities during the geologically recent QuaternaryPeriod.

Brief History of Botanical Exploration

The history of botanical exploration of Steens can be divid-

ed into three phases.

Early explorations: In the late 1800s, a few collections weremade by William Cusick, John Leiberg, and others. In the

early 1900s Morton Peck, Percy Train, Lila Leach, L.F. Hender-son, and others briefly visited Steens. Of these, Percy Train'scollections were the most extensive and unique, providing theonly record of several of Steens plant species.

Expanding collections and classifying the unique flora:Through the mid-1900s collection trips, mainly from WesternOregon and New York Botanical Gardens by such individualsas Albert Steward, Arthur Cronquist, and Bassett Maguire,increased in frequency. At this time several systematists visitedSteens to examine unique specimens discovered in earlier col-lecting forays. Until my recent survey, the most extensivebotanical collection was done by Charles Hansen in the ear-ly 1950s as part of his doctoral studies on the vertebrates ofSteens Mountain (Hansen 1956).

Continuing exploration through Malheur Field Station(MFS) and the BLM: Botany classes at MFS from the mid1970s to mid 1980s, led separately by Karl Urban and KarlHoke, explored new areas of Steens and continued to con-tribute to new and unusual records. Collections by Dr. Ur-ban, Dr. Hoke, and their students occasionally provide thesole record of Steens' plant species. From the late 1970sthrough the early 1990s, BLM has contracted with botaniststo survey various parts of Steens Mountain and the adjacentAlvord and Malheur basins. Since the late 1980s, 1 have beencollecting extensively (independently, with students throughMFS classes, and in cooperation with BLM) to describe thecomposition, distribution, and variation in the flora and docu-ment historical reports lacking vouchers. We now have an ade-quate sense of the distribution of several species on Steensand in the region and can begin to interpret the original, rela-tionships, and uniqueness of the Steens Mountain flora.

The plant names used in this paper and in the Steens Floraattempt to follow the nomenclature being used in the OregonChecklist project (Scott Sundberg, personal communication).The resources for identification of Steens taxa include, inroughly this order, the Jepson Manual (Hickman 1993), theIntermountain Ft= (Bameby et al. 1990, Cronquist et al. 1972,Cronquist et al. 1977, Cronquist et al. 1984, Cronquist et al.1994), the Flora of North America, volume 2 (Flora 1993), andthe Flora of the Pacific Northwest (Hitchcock and Cronquist1973). Distributional data are also derived from these samesources.

Steens Mountain Flora and Vegetation

At most recent count, the vascular flora of Steens Moun-tain is composed of 91 families, 381 genera. 1,115 species, and1,179 subspecies or varieties. Of the 1,179 taxa, 86 (7.3%) areexotics (post-settlement introductions to the area), six areendemic to Steens Mountain or Steens and nearby ranges,and an additional 57 are currently listed in the Oregon NaturalHeritage Program's Rare, Threatened and Endangered Plantsand Animals or Oregon (ONHP 1993) — see Table 1). SteensMountain represents well the estimated 4,400 plant taxa inOregon (Scott Sundberg, personal communication). Thisdiversity is largely attributed to the variety of habitats span-ning its 6,000 ft. of relief.

To understand the distribution of rare plants on Steens Moun-tain, vegetation can be divided into three zones — the lowdesert (below 4,200 ft., or 4,600 ft. in the Catlow Valley),

Kalmiopsis 1995 11

Ell.lik

IttAt.

5

9

2Steens Mountain thistle(Cirsium peckii)

montane ( 4,200 ft. to 8,200 ft.), and alpine (above 8,200 ft.).Within each of these broad vegetation zones exists a varietyof habitats, each with a unique flora.

Expansive alkaline desert scrub habitats of the Harney Basin,Alvord Desert, and Catlow Valley below about 4,200 ft. to4,600 ft. are dominated by greasewood (Sarcobatus ver-miculatus), spiny hopsage (Grayia spinosa), shadscale (Atripiexconfertifolia), four-winged saltbrush (Arriplex canescens), saltgrass(Distichils spicata var. stricta), and other halophytes (salt-tolerantplants). This bottomland scrub is designated "h" in Table 1.Better drained soils ("s" in Table 1) are dominated by suchspecies as basin big sagebrush (Artemisia tridentata ssp. triden-tata), basin wild rye (Leymus cinereus), or other non-halophyticspecies. Ash or sand ("a" in Table 1), barren clay soils ("c" inTable 1), and a variety of wetlands incuding riparian stream-sides ("wr" in Table 1), ponds, lakes or marshes ("wp" in Table1) are also evident throughout the basin deserts.

The lower flanks of Steens Mountain from about 4,200 ft.to roughly 5,500 ft. are dominated by big sagebrush (Artemisiatridentata ssp. wyomingensis, and A. tridentata ssp. vaseyana),low sagebrush (A. arbuscu1a), gray rabbitbnish (Cirrysotham-nus nauseosus van hololeucus), and a variety of forts and grasses.These sagebrush-dominated slopes ("s" in Table 1) are quiteprevalent. Between about 5,500 ft. and 6,500 ft., sage scrubis intermixed with the overstory dominant species, westernjuniper Ouniperus occidentaii.$). Mountain mahogany (Cercocar-pus ledifikus var. intermontanus), bitterbrush (Purshia tridentata),squaw currant (Ribes cereum), and Lemon's needlegrass(Achnatherum temmonii) often also dominate. Seasonally moistdepressions and vernal pools ("wp" in Table I), clay barrens("c" in Table 1), riparian areas ("wr" in Table 1), and gorge-bottom woodlands and mesic north-facing forested slopes ("f"in Table 1) all contribute to the habitat diversity in the mon-tane zone.

Aspen (Popuiustremtdoides) standsdominate shelteredand mesic sites ofSteens Mountainbetween approx-imately 6,500 ft.and 7,500 ft. ("f" inTable 1). The moreexposed and xericsites between 6,500ft. and 8,000 ft.("s" in Table 1) arefrequently domin-ated by mountainbig sagebrush (Ar-temisia tridentatassp. vaseyana) and avariety of forbs andgrasses includingorange sneezeweed(Hymenoxys hoopesii), Steens Mountain thistle (Cirsium peckii),squirreltail grass (Elymus elymoides ssp. californicus), andCusick's bluegrass (Peat cusickii). In this upper montane areaof Steens Mountain, meadows dominated by gmminoids andperennial forbs ("m" in Table 1) are common. At these elev-a-

dons in the Northern Rocky Mountains or on the east slopeof the Cascades, one would expect to find forests of ponderosapine and Douglas fir giving way to Engelmann spruce, orperhaps subalpine fir and occasional white bark pine or limberpine near timberline. None of these conifers are present onSteens Mountain. In this respect the "subalpine" zone ofSteens Mountain is unique in Oregon. This absence ofsubalpine conifers is evident in several other Great Basinranges but none as large as Steens. The remarkable absenceof subalpine conifers is probably related to Steens isolationand possibly the biology of such seed disposers as the Clark'snutcracker (Wells 1983). Hansen (1956) speculated that NativeAmerican use of fire permanently eradicated conifers that hadbeen present historically. This interesting feature of Steenswarrants future study.

The highest elevations of Steens, above approximately 8,200ft., lack the tundra character of most other ranges. The highestvegetation zone on Steens has been referred to as either"subalpine grassland" (Mairs 1977) or true alpine tundra (Col-lins 1978). Like other alpine areas in the western UnitedStates, the 'High Steens' lacks trees and receives high precip-itation largely in the form of snow, which is irregularlydistributed due to the wind. Furthermore, the area exhibitsevidence of solifluction, the result of freeze/thaw cycles thatmove large quantities of soil (Bentley 1970, Collins 1978).Unlike true alpine areas, the "alpine" zone of Steens apparentlylacks permafrost (Collins 1978) and permafrost-controlledvegetation, such as many common tundra cushion plants, likethe ubiquitous moss campion (Silene acaulis), that typify thealpine zone in the Sierra-Cascade or Rocky Mountains(Zwinger and Willard 1972). Like other Great Basin ranges(Barbour and Major 1977), the alpine vegetation of SteensMountain is developed best in the wetter sites. Within thisalpine belt, several vegetationally distinct habitats can berecognized. The dry, gravelly, windswept summit ridge and thelower lips of the cirques ("dg" in Table 1) come closest to thecushion plant-dominated "fell fields" of the Rocky Mountains.Alpine wet meadows and mesic meadows occur in cirques andpockets where snow accumulates and provides perennial waterin the form of springs and a high water table ("m" in Table1). Talus and scree slopes ("t" in Table 1), rock outcrops ("r"in Table 1), and riparian willow (Sax ssp.) -dominated areas("wr" in Table 1) are evident on Steens as in other alpine areas.Gravelly solifluction zones adjacent to receding snowbanks("wg" in Table 1) provide a final example of unique alpinehabitat on Steens Mountain.

What Makes a Plant Rare?

A plant may be considered rare for one or a combinationof the following reasons: 1) it covers a small geographicalrange, 2) it has very specific habitat requirements, and 3)it exists in small populations or sparsely distributed indivi-duals (Rabinowitz 1981). Clearly, a species will he consideredrare by anybody's definition if it has sparse individuals, requiresli mited and specific symbionts or soils, and is restricted to asmall geograhical area. Furthermore, if such a species isthreatened by any natural or anthropogenic environmentalchange (mining, recreation, invasion by exotic plants, etc.),it may be considered in danger of extinction. Conversely, ifa plant exists in large populations with a large ecologicalamplitude, it may not be considered rare even if its geo-

12 Kalmiopsis 1995

zCC

Steens Mountain draba(Draba sphaeroides var. cusickii)

graphical range is very small, especially if its population sizeis not changing in response to environmental changes. Thereare numerous permutations between these two extremes, sodeciding whether a species is rare is not often a simple matter.

One of the most interesting types of rarity is based on limitedgeographical distribution. A taxon is endemic if it originatedin and its distribution is limited to one area. A plant maybe endemic to a large area (such as western North America)or to a small area (such as Steens Mountain). A species maybe endemic for a variety of reasons that can be consideredto span the range between the two extremes of paleoendemicand neoendemic (Kruckeberg and Rabinowitz 1985, Stebbinsand Major 1965). Paleoendemics are relictual-remnants of taxathat were once more widespread. Neoendemics are newly form-ed taxa that may be in the process of expanding their rangefrom their points of origin.

On Steens Moun-tain there are at leastsix endemic taxa(Table 1), all ofwhich are evidentlyneoendemics forseveral reasons. All(Agastache cusickii,Castdieja pilosa var.steenensis, Cirsiumgecko, Draba spittle-roides var. cusickii,Penstemon davidsoniivar. praeteritis, andPoa sp. nova) arespecies or varietieswith closely relatedcounterparts in rela-tively close geo-graphic proximity.For example, Castilie-ja pilosa var. pi/ma,the ancestor ofSteens' rarest and narrowest endemic (C. pilosa var. steenen-sis), is located below 7,000 ft. on Steens Mountain. All SteensMountain endemics inhabit alpine rock outcrops or gravellysoils. This is an environment which is probably able to retainsufficient moisture during the driest period of the Holocene,yet, no doubt experienced extended periods of drought, im-posing selective pressures that may have driven speciation.Three of these endemics (Agastache cusickii, Cirsium peckii, andPeristemon davidsonii var. praeteritis) have known populationsin other Great Basin mountain ranges (Pueblos Mountains,ranges of northern Nevada, etc.) as well as on Steens Moun-tain. The fact that of these three, two are distinguished fromtheir closest relatives at the species level and that all havepopulations outside of Steens Mountain suggests that theirorigins may be older and/or more geographically distant thanthe other three endemics.

If we are interested in a plant's rarity because we wish to main-tain biological diversity, it matters how genetically diverse rarespecies' populations are and how genetically differentiated arare species is from its close relatives. For example, two specieswith equally small population sizes, habitat requirements, and

geographical ranges may not be considered equally "rare"genetically if one represents a small genetic variation (say, asubspecies or variety) from a widely ranging common speciesand the other represents a large genetic deviation (say, a dif-ferent genus) from its most closely related species. From thisperspective, one would surmise that the endemic plants ofSteens Mountain do not provide the genetic diversity thatpaleoendemic genera (such as Kalmiopsis from the SiskiyouMountains in southwestern Oregon or several of the Califor-nia endemics) contribute.

For the past two decades Oregon has been developing adatabase of rare plants. Plants listed as rare, threatened, orendangered by the Oregon Natural Heritage Program (ONHP1993) can be included for several reasons and those speciesthat may have been considered appropriate to list in 1980 (inthe list that predated the existence of the ONHP) or 1989may not be listed in 1995. For example, some plants previous-ly considered rare by criteria of small range or population sizemay no longer be considered rare as further populations arediscovered and the species is seen to be more widelydistributed. This is the case for several annuals found on SteensMountain, such as Dimersia howellii or Nemacladus rigidus.

Rare Plants on Steens Mountain

The plant taxa found on Steens Mountain that the ONHP(1993) considered rare, threatened, or endangered are sum-marized in Table 1. Though Steens Mountain is a center ofhigh plant species diversity, none of the vascular plant taxaof Steens is listed as either endangered or threatened at eitherthe Federal or State level. Only 2 taxa (Castilleja pilosa var.steenensis and Lupinus birlilie) are candidates (C2 status) forconsideration, meaning that they require "active protectivemeasures to insure their survival" but that informaion on theirbiology and distribution is limited (ONHP 1993). The Steenspaintbrush (C. pilosa var. steenensis) exists in several smallpopulations along the summit ridge from the east Kiger rimto south Steens. Biddle's lupine (L. biddiet) is not a recognizedtaxon by the most recent treatment (Barneby 1990). It inhabitssagebrush-dominated sites in the lowlands.

Taxa on ONHP lists 2, 3 or 4 are either a) endemic but havesufficiently large populations to be considered not threaten-ed with extinction or likely to become threatened under ex-isting conditions (e.g. Agastache cusickii, Draba sphaeruides var.cusickii, Penstenum davidsonii var. praeteritis, or b) rare or well-distributed outside of Oregon but have limited population sizesor disjunct populations in Oregon.

Many Steens Mountain species (e.g. Carex haydeniana, C. nova,Cymoptents nivalis, Llyodia senotina, Sarifraga adscendens, Sedumdebile, Polemonium viscosum) are widely distributed in thenorthern Rocky Mountains but are rare in Oregon. Otherson Steens that are rare in Oregon are disjuncts from the SierraNevada flora (e.g. Allium companulatum, Clayumia nevaden-sis, Salix orestera). Fewer Steens plants with affinity to the floraof the Sierra Nevada are listed as rare (by ONHP) than plantswith Rocky Mountain affinity because many taxa commonto Steens and the Sierra Nevada are also found throughoutthe Southern Cascades and thus are not rare in Oregon. OtherSteens taxa that are rare in Oregon are at the northern end

Kalmiopsis 1995 13

Steens penstemon (Penstemon davulsonii var. praetentis)

of their range in the Great Basin and may not be consideredrare in Nevada, for example. These are typically low eleva-tion taxa such as Chenactis ntacrantha, C. stevoides, Caulan-thus major var. nevadensis, Allenrolfea occidentalis, Phacelia gym-noclada, and Argemone munita ssp. rotundata but also includea smaller number of taxa in the alpine such as Ivesiavar. beneokns and Cryptanzha humilis.

Several taxa on Steens are rare in Oregon because populationstend to be very small and sparse and/or the specific habitatrequired is rare even though the taxa may be more widelydistributed in Oregon (e.g. Botrychium hmaria, B. pinnatum,Gentiana prostrata, Gentianella tenella, Kobresia bellardii, Carexbackii, C. praecepumon, Alhum madidum, Salix arctica). Eachof these has 3 or fewer known populations on SteensMountain.

Perhaps the most distinctive plant of the Steens Mountainflora is the Steens Mountain thistle (Cirsium peckii). To theuntrained eye, the plant appears to be the common, widespread(but allopatric) bull thistle of lower elevations. Steens Moun-tain thistle is not considered rare in Oregon despite itsendemism to Steens Mountain because of its abundance andstatus in the area. The plant is a ruderal species — it thriveson disturbance in an otherwise moderate habitat (see Grimes1979). Like a garden weed whose population increases aftercultivation, Steens Mountain thistle proliferates along opendisturbed roadsides, landslides, etc. throughout the montanezone. This is hardly the behavior one expects of a narrowendemic. However, for some reason related to Steens Moun-tain's isolation and the biology of the plant, the Steens Moun-tain thistle has not yet left the Steens-Pueblo range since itsorigin, probably in the late Pleistocene or Holocene.

A number of species on Steens Mountain are not consideredrare in Oregon but they have limited distributions on Steensand are unusual in some respect that relates to Steens' uni-que botanical history and geography. For example, in 1992 Ifound bog wintergreen (Pyrola asanfolia) in the understory ofthe willows (Salix planifolia ssp. planifolia and S. orestera) of wetcirque bottoms. This plant is found in coniferous forests andshaded wetlands from California to Alaska and east throughCanada. It is a "west slope" plant. The populations on Steensare therefore relicts from when cool, moist, closed-canopywetlands were more continuously distributed from SteensMountain to the Sierra-Cascade cordillera, possibly via the

Wallowa Mountains. Several other taxa are rare on Steens butmore abundant elsewhere in Oregon. Saxifraga debdis and S.caespitosa are found on wet, rimrock cliffs on Steens in onlyone or a few populations, respectively. Similarly, Melica stric-ta and Pelka breweri are rock crevice species that are ratherrare on Steens but not regionally. Other Steens taxa, such asAlopecurus genicalatus and Plagiobothrys hispidus, are mor-phologically different than other Oregon specimens of thesame species (even when observed in the alternating wet anddry years of the 1990s). In the case of the fir (Abies) on Steens(in small isolated populations in both Fir Creek and MoonHill), there is disagreement about the genetic affinity of thetaxon on Steens. Whether it is disjunct from the northernAbies grandis (Flora 1993) or disjunct from the Sierra NevadaAbies concolor var. lowiana, the Sierran white fir (Urban 1981),is unclear. This is the only conifer on Steens Mountain, otherthan western juniper and common juniper. It provides a goodexample of a relict population from the moist Pleistocene, butwhether it is a relict of populations to the southwest or northremains to be determined.

Other taxa are not on the rare plant list because they are intaxonomically difficult groups that are still in the process ofbeing analyzed. An undescribed bluegrass (Poa sp. nova.) oc-curs in the same wet gravels adjacent to receding snowbanksin which we find Alopecurus genicidatus and several other rareplants of Steens. This bluegrass has apparent affinity to severalhigh elevation taxa in the Poa cusickii complex but seems tobe undescribed and is currently under investigation by RobertSoreng (personal communication). Only one record of the bluewillow (Salix glauca var. villosa) is known from Oregon. Hav-ing only recently been identified (George Argus, personal com-munication), this plant from Kiger gorge on Steens will soonbe listed as one of the rarest in Oregon.

In light of the existing disjuncts and endemics, and the isola-tion of Steens, it would not be surprising to find some geneticdifferentiation among other species that may be obscure mor-phologically. At the present time, we know virtually nothingabout the genetic variation between plant taxa on SteensMountain and those of other ranges and can only base discus-sions of rarity on the morphological characteristics we see inherbarium specimens. Even as herbarium specimens are exam-ined, we continue to find novelty in the Steens flora. Furthersystematic studies that include Steens specimens are warranted.

Synopsis

The alpine plants of Steens Mountain most characterize itsunique botany (Table 2). Of the Steens massif, the zone above8,200 ft. is smallest in area but has the largest number of raretaxa. Table 2 also illustrates that the areas most interestingbotanically are the wet areas — wet and subirrigated meadowsand wet gravels by receding snowbanks — and the rock out-crops. The alpine wet meadow species (e.g. the Botrychiums,gentians, and graminoids) are alpine disjuncts that were partof a flora shared by other ranges. These habitats on Steenscontain several other alpine taxa (e.g. Pedicularis attoliens) thatare not rare and hence not considered here. These wet en-vironments probably lost several species to local (and global?)extinction during the Holocene altithermal period (about6,000 to 8,000 years ago on Steens Mountain). By monitor-ing species in these habitats we may have a good biological

14 Kalmiopsis 1995

Table 1. Rare Plants of Steens Mountain.

Taxa from Steens Mountain listed by the Oregon Natural Heritage Program areof general interest due to their rarity on Steens. ONHP (1993) list numbers (1 to4) correspond to the list on which the taxon is currently found. Taxa on previouslists or dropped from consideration are also shown here (P). Endemics are denotedby "". The zones correspond to different alpine (A), montane (M), or desert (D) eleva-tions as defined in the text. Different habitats discusses in the text are:

a—ash or sandb—bottornland salt scrubc—barren, clay soilsdg—dry, gravelly,

windswept ridges

f—forested by aspen orriparian woodlands

m—wet or mesic meadowsr—rock outcrops and crevicess—sagebrush-dominated slopes

t—talus or screewp—wetland ponds, pools,

lakes, and marsheswt.—wetland stream side,

riparianwg—wer gravels

SPECIES

Aquatics, emergents, and

COMMON NAME

vernal pool species

ONHP ZONE HABITAT

Allenrolfea occidentalis Iodine hush 2 D wpDowningia bacigalupii Downingia P M wpDowningia insignis Downingia 4 M wpDowningia [dew Downingia 4 D wpLilaea scilloides Flowering quillwort 3 M wpMyriophyllum sibiricum Water milfoil 3 M wpPotamogeton diversifolius Diverse-leaved pondweed 2 M wpPotamogeton filiformis Slender-leaved pondweed 3 D wpRotala ramosior Toothcup 3 D wp

Ferns and fern alliesBotrychium lunaria Common moonwort 2 ABotrychium pinnatum Northwestern grapefem 2 A mPolystichum kruckebergii Kruckeberg's holly fern 4 A rPolystichum ionchitis Holly fern P APolystichum scopulinum Rock sword fern P APellaea bret.'erii Brewer's cliff brake P MSelaginella watsonii Alpine spikemoss 4 A

ForbsAgastache cusickii Cusick's horsemint 2* A tAllium campanulatum Sierra onion 4 MAllium lemmonii Lemmon's onion 4 MAllium madidum Swamp onion 4 MArgemone munita

ssp. rotundata Prickley poppy 2 D bAstragalus alvordensis Alvord milkvetch 4 D aCastilleja pilosa Steens Mountain

vac steenensis paintbrush 1* A dgCaulanthus major

var. nevadensis Nevada jewelflower 2 M tChaenactis macrantha Mohave pincushion 2 D aChaenactis stevoides Desert pincushion 2 D bCirsium peckii Steens Mountain thistle P* MClaytonia mevadensis Sierran spring beauty 4 A wgCrepis modocensis Modoc hawksbeard 3 MCryPtantha humilis Dwarf cryptanth 3 A dgCymopterus nivalis Hayden's cymopterus 2 ADraba sphaeroides

var. cusickii Steens Mountain draba 4* A rEricameria discoidea Discoid goldenweed 4 AEriogonum caespitosum

var. hauschnecktii Tufted buckwheat P A dgFritillaria atropurpurea Chocolate lily P M fGentians prostrata Pigmy gentian 2 AGentianella tenella Slender gentian 2 A

indicator of the effects of globalwarming on the northern GreatBasin.

At lower elevations, the botanicallyunique areas tend to be the drier sites(Table 2), such as ash bed, sandysoils, and clay depressions in thescablands. These habitats have prob-ably also imposed selective pressures,which, combined with populationfragmentation (due to the patchynature of these environments), mayhave forced speciation throughoutthe Great Basin during thePleistocene and Holocene, resultingin new, rare taxa.

At this juncture it is reasonable toask: What are the effects of juniperencroachment (Miller 1994), grazing,and recreation on the rare flora ofSteens Mountain! Few of the taxalisted in Table 1 are threatened bythe juniper encroachment that is evi-dent on Steens Mountain. Clearly,if encroachment progresses to thepoint of monotypic juniper stands,plant diversity is likely to decrease.Thus, from the perspective of main-taining rare plant habitat, a mosaicof diverse communities is desirableand juniper woodlands should bemanaged accordingly. Most of thealpine zone taxa are fairly secure withcurrent grazing policies that, whenenforced, prevent grazing above8,000 ft. Many of the alpine meadowtaxa may have been more widespreadbefore sheep grazing ravaged Steensearlier this century, but this is con-jecture. At lower elevations, however,grazing may he taking a toll on rareplants in riparian areas. For example,at least 3 low elevation riparian taxa(Juncus capillaris, Juncus tiehmii, andMimulus evanescens (the latter is notlisted in Table 1 because it was onlyrecently described — Meinke 19951)are known from Steens Mountainonly by historical records. It is quitepossible that, as Meinke suggested forM. evanescens, these taxa are rare andthe Steens populations may havebeen decimated as a consequence ofhabitat destruction associated withgrazing. Numerous wetland taxa(Table I) are known from only oneor a few populations on Steens (e.g.Carex backii, Allium madidum, Down-ingia (seta, D. insignis, Myriophyullumsibiricum, Potamogeton diversifolius,Potamogeton filiformis). These are in-deed threatened by any activity that

Kalmiopsis 1995 15

Hackelia patensIvesia baileyi var. beneolensLupinus biddleyilloydia serotinaMalacothrix glahrataMalacothrix torreyiiOT 0 ban c he pinorumPediocactus simpsonii

van robustiorPenstemon davidsonii

var. praeteritisPenstemon janishiaePenstemon pratensisPenstemon seorstISPhaceiia gymnocladaPhysaria chambersiiPoternonium viscosumPyrola asarifoliaPyrrocoma uniflora

var. howeiliiSaxifraga oxiscenziens

var. oregonensisSaxifraga caesPitosa

v-ar. minimaSedum debile

Graminoids

Achnathe-rum speciosumAgrostis huniiiisAlopecurus geniculatusCarex backiiCarex haydenianaCarex novaCarex praeceptorumCarex sheldoniiJuncos bryoidesJuncos capillarisJuncus herniendytus

var. abjectusJunc-u-s tiehmiiKobresia beUardiiMelica strictaPoa sp. nova.

Trees and shrubsAbies grandisPoPulus augustifoliaSalix arctica var. petraeaSalix drummondianaSalix giauca var. vialosaSalix orestera

Pale stickseedOwyhee ivesiaBiddle's lupineAlpine lilyDesert dandelionTimey's malacothrixPine broomrape

Hedgehog cactus

Steens penstemonJanish's penstemonEarly penstemonShort-lobed penstemonThick-leaved phaceliaDouble bladderpodSky pilotBog wintergreen

One-flowered goldenweed

Wedge-leaf saxifrage

Tufted saxifrageWeakstemmed stonecrop

Desert needlegrassAlpine bentgrassWater foxtailBack's sedgeHayden's sedgeNew sedgeTeacher's sedgeSheldon's sedgeMoss rushThin rush

Center basin rushTiehm's rushKobresiaRock melicundescribed bluegrass

Grand firNarrow-leaved cottonwoodArctic willowDrummond's willowBlue willowGray-leaved sierra willow

3 M s

33 A m4 D b4 D b

4

4* A r33 M m3 M s2 D a34

wr

4 A dg

2 A

A4 A

2 D s3 A m

A wg3 M wr4 A wg2 A in3 A m4 M wr3 M wp3 D wr

3 M wp3 q wr2 A m

— A rA wg

4P A4 A wr

A wr3 A wr

Table 2. Distribution of rare plants on Steens Mountain.

The taxa from Table 1 are categorized by devotional distribution and by relativemoisture regime or habitat.

VERNALLY ME-SICWETLAND WET SOIL MOIST TO DRY ROCK TOTAL

Alpine 3 15 0 4 15 37Montane 5 2 5 W 2 24Desert 5 0 1 11 0 17

will disturb plant population pro-cesses, including grazing. Recreationcan impose significant threats to rareplants (Losos 1995) but whetherrecreation threatens rare plants onSteens is largely unstudied. As withgrazing in riparian areas, any distur-bance to plant population processescan be problematic. Thousands ofpeople now visit Steens annually,however, few travel to the sites in-habited by most rare plants. TheSteens paintbrush is perhaps mostthreatened by recreation because itshabitat is one most frequentlyvisited. Because so many of the rareplants exist in only a few popula-tions, it is imperative that all visitors,including botanists, "mad lightly."

Steens Mountain paintbrush(CasaIleja pilosa var. steenensis)

What makes Steens Mountain in-teresting botanically, then, is the uni-que combination of Rocky Mountainand Sierra alpine and, to a lesser ex-tent, montane plants. As a conse-quence of the isolation of Steensfrom these floras, to the northeastand southwest, respectively, some ofthe taxa have differentiated suffi-ciently to produce new species orvarieties that are endemic to eitherSteens (e.g. C. pilosa var. sreeriensisand D. sphaeroides var. cusickii) orSteens and some combination of thesurrounding ranges (e.g. C. peckii andP davidsonii var. praeteritis). Othertaxa simply remain as populationsdisjunct from the rest of their speciesto the northeast or southwest. Beingat the northern limit of the GreatBasin physiographic province alsomeans that the Steens and surround-

16 Kalinlopsis 1995

ing basins are the only Oregon home to several taxa more com-mon to the south. This is particularly true of the desert flora.Though there are several alpine endemics as a consequenceof this unique geographic position, the endemics are all fairlyrecent in origin owing to the relatively recent geologicalhistory of the area and the fairly radical climate change thatthe area has experienced during the Quaternary Period.

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