High Desert Ecological Province

 

 

 
 
 

Location

The High Desert Ecological Province in south-central Oregon is the northernmost segment of the huge western Great Basin that extends south into Mexico and east into west Texas.24 In Oregon, the province covers about 7.8 million acres, mainly in Lake and Harney counties with small portions in Malheur, Deschutes, and Crook counties. It extends south into northwestern Washoe County, California and northwestern Humboldt County, Nevada.

 
 

Description

The High Desert Province is characterized by innumerable large and small closed basins surrounded by extensive terraces formed in ancient lakes. Interspersed in this pattern of closed basins and terraces are low basaltic ridges, hilly uplands, isolated buttes such as Glass, Paiute, and Beattys; mountains such as St. Patrick, Wagontire, and Warner; and block-faulted igneous formations such as Steens Mountain, Abert Rim, and Poker Jim Ridge. Elevations range from 4,030 feet at Harney Lake to 9,670 feet on Steens Mountain. (Elevations are from USGS 1:250,000 topographic maps.) The terrace and basin portion of the province is flat to gently sloping; intermediate hills, buttes, and mountains are steep to very steep. Ecological sites range from arid low-lying terraces to subalpine mountain tops and from lakebeds that are nearly always dry to permanent wetlands and marshes (Fig. 17).

Figure 17: Overview of extensive closed basins typifying High Desert Province, Oregon. Wagontire Mountain is on the horizon at right

This is the portion of Oregon that apparently was largely inundated by ancient lakes. Evidence of extensive inundation exists in exposed shoreline terraces, such as on the highway roadcut northwest of the Horse Ranch near Fort Rock, and in wave-action beachlines on uplands, such as southeast of Summer Lake and the east side of Warner Valley. These shoreline terraces are at about 4,500 feet elevation (Fig. 18).

Figure 18: Ancient shoreline of Warner Valley along the west side of Poker Jim Ridge on Hart Mountain National Antelope Refuge in High Desert Province, Oregon

Beachlines and shoreline terraces are not in a continuous band around the perimeter of this province because they have been superseded by other geologic formations in various locations. For example, in the area from Fort Rock north to Brothers, the ancient shoreline terrace is obscured by a mantle of pumice and/or lava flows from Mazama, Paulina, and probably other volcanoes. In this area, the boundary between High Desert and Mazama provinces is a belt rather than a distinct line. Field observations indicate that, where the pumice mantle is more than 8 to 10 inches thick over buried soils, herbaceous vegetation resembles the arid portion of Mazama Province, which is typified by bluebunch wheatgrass and Idaho fescue. Where less than 8 to 10 inches of pumice mantle are over buried soil, herbaceous vegetation resembles the High Desert Province’s, which is typified by bluebunch wheatgrass and Thurber needlegrass.32

 
 

Soils

Soils in the terrace and basin portions of High Desert Province were formed mainly from parent materials through water action. They range from deep loam to deep clayey soils in basins and from deep sandy to shallow clayey soils on terraces and fans where weak to strong hardpans are common. On some terraces and fans, the soil surface may be extremely stony, which might be related to thin surface flows of basalt that have fractured or to colluvial action. These soils may be strongly alkaline, calcareous, or neutral.

An upland terrace formation occurs in the vicinity of some igneous mountains such as Hart Mountain. The sloping upland terrace landform represents an outflow of igneous tuffaceous material which characteristically weathers into dense clay. Usually, these upland clayey terraces have a surface cover of basalt stones but soil beneath the surface stones is not stony. This suggests that a thin layer of basalt was deposited on the surface after the tuffaceous underlying material had formed the upland terrace landform. The upland clayey terraces usually support a stand of low sagebrush.

Soils developed on basaltic uplands generally are moderately deep to very shallow and stony or gravelly, and they may be extremely rocky. They are generally slightly acidic in surface layers to slightly alkaline in the subsoil.

Soils in the vicinity of Christmas Valley and Fort Rock Valley have sandy surface layers which likely are related to the nearby, upwind tuffaceous ancient lakeshore terraces. Areas of deep sands, which are probably dunes formed over time, are common. The northwest part of High Desert Province was settled and dry farmed in about 1910. However, settlement quickly dwindled before 1914 when drought began. Extensive stands of gray rabbitbrush in this area indicate previously farmed lands.

Along the north and east boundary of High Desert Province in Oregon, which is mainly in Harney and Malheur counties, available soil data do not suffice to produce groups of soil series to illustrate the soils contrasts that are known to exist between High Desert Province and contiguous provinces—John Day, Snake River, and Humboldt. This is because available soil maps of Harney and Malheur counties show reconnaissance mapping units on nonfarmed lands that merely represent different kinds of soils, e.g., basins/plains, shallow/not shallow, well-drained/less well drained, loamy/clayey. The drainage basin surveys were made primarily to identify areas that might be suitable for irrigation, if feasible.,72, 73, 92, 94 This deviation from general soil maps for other Oregon counties and river basins, where associations of soil series were mapped, hinders using soil data to help clarify ecological differences between provinces.

 
 

Climate

The High Desert Province in Oregon is uniformly dry as illustrated by 16 official weather stations. 17 All stations, except for Hart Mountain Antelope Refuge, are in or near the bottom of closed basins between 4,100 and 4,500 feet elevation.

Average annual precipitation for the province is about 10 inches. The deviation ranges from 8 inches at Plush to about 12 inches at Diamond and Frenchglen, which are in the vicinity of Steens Mountain. A precipitation map53 shows several sizable basins in the province that receive less than 10 inches annually, a few prominent uplands that receive about 15 inches annually, about 25 inches annually on top of Hart Mountain, and over 50 inches annually on top of Steens Mountain. In some instances, these differences occur within a few air miles of each other.

High Desert Province in Oregon also is uniformly cold. Average maximum and minimum temperatures during the normal growing season, April through June, are about 68 and 35°F, respectively. Frosts can occur any week of the year. Such relatively low temperatures during the growing season effectively change the net effective environment on a site 5 which, in turn, significantly influences the kinds of species that naturally occur in the plant community as well as the amount of herbaceous growth produced. Cold springs mean minimum temperatures can offset or minimize benefits derived from favorable moisture conditions. When monitoring responses to climate and/or resource management strategies, mean minimum temperatures in spring are especially significant for evaluating results.

Vegetation on top of large mountains in High Desert Province in Oregon reflects the frigid temperatures and fierce winds there. For example, sagebrush plants on top of Hart Mountain have hedged canopy tops that slant up from west to east, like a roof, away from prevailing westerly winds. Furthermore, rough fescue, which is native to more northern latitudes (primarily north of 47°N latitude in eastern Washington, in western Montana, and in British Columbia and Alberta) occurs on both Hart and Steens mountains at about 7,000 feet elevation. This suggests the climatic conditions there may be comparable to the more northern latitudes where rough fescue is a common component of native plant communities.6

Throughout High Desert Province, climate varies widely from locality to locality at any given time, both seasonally and from year to year, even though in general it is a uniformly dry climate with extremes of cold and hot.

 
 

Vegetation

According to the 1936 Forest Type Map of Oregon,54 stands of western juniper were at that time on upland areas scattered across High Desert Province in Oregon. In the area north and northwest of Silver Lake community, juniper stands collectively covered an estimated 18,000 acres in 1936. From the vicinity of Cougar Mountain, about 20 air miles north of Silver Lake, scattered juniper stands existed eastward nearly to Wagontire Mountain and collectively covered an estimated 185,000 acres in 1936. On the western and northern slopes of Steens Mountain, an estimated 80,000 acres of scattered juniper stands existed in 1936.

Natural stands of western juniper in High Desert Province in Oregon usually are associated with rocky or very stony uplands, lava flows, and ridges where understory vegetation, when burning, is insufficient to help create crown fires. In the vicinity of Christmas Lake Valley, some natural juniper stands are on areas of moderately deep sands. Natural stands of juniper are characterized by the presence of very old trees and of uneven-age classes.

An ecological oddity, the Lost Forest, is northeast of Christmas Lake Valley. In 1936 it covered an estimated 2,500 acres and consisted of huge old-growth ponderosa pine with some juniper growing on sandy soils at about 4,500 feet elevation. The pine has been partially harvested by a BLM timber sale. The isolated stand lies about 25 air miles east of the nearest pine forest, which is in Mazama Province. Another isolated 60-acre grove of ponderosa pine is on the Hart Mountain National Antelope Refuge. It is at about 6,000 feet elevation in a location known as Blue Sky on the east slopes of Warner Peak near Post Meadows, south of the refuge headquarters.

Specimens of white fir, which grow in protected spots at high elevations, are rare in High Desert Province in Oregon.

The 1936 Forest Type Map of Oregon also shows scattered stands of hardwoods, probably aspen, in drainages and on north and northwest slopes of Steens Mountain; collectively the stands covered an estimated 5,000 acres in 1936. Similar stands of aspen on Hart Mountain are too small and scattered to be shown on the 1936 map.

The huge number of closed basins that typify High Desert Province in Oregon include perpetually dry lakebeds, lakebeds that are inundated infrequently and for short periods, perpetual lakes that fluctuate in size over time, and wetlands and marshes that are reasonably perpetual. Vegetation on the bottomlands varies according to the frequency, depth, and duration of inundation.

For example, perpetually dry lakebeds usually are vegetated with drought-tolerant upland species such as big sagebrushes, rabbitbrushes, needlegrasses, ricegrasses, and squirreltail. Lakebeds that are inundated infrequently and for short periods vary from being essentially barren—playas—to those that grow such plant species as silver sagebrush, mat muhly, streambank wheatgrass, basin wildrye, and a variety of forbs. Larger perpetual lakes that fluctuate in size over time include Silver, Summer, and Abert in Lake County and Silver, Harney, and Malheur in Harney County. They also may vary over time from being essentially barren to being perpetually vegetated by such plants as sedges, rushes, squirreltail, rabbitbrushes, greasewood, and a wide variety of forbs, all of which are affected by soil chemistry.

A good example of how vegetation varies according to duration of standing water can be seen on a shallow lakebed in southeastern Hart Mountain Refuge. On this lakebed were at least four distinct bands of vegetation between the deepest area and the shoreline. The area of longest inundation was vegetated primarily by spikesedge. The next band, where inundation was of shorter duration, was vegetated by wedgeleaf dock. The next-driest band was vegetated by mat muhly, and the outside, driest band on the lakebed was streambank wheatgrass. The beachridge, formed by soil blowing off the dry lakebed in summer and which was never inundated, was vegetated by needlegrass and green rabbitbrush. All the variations on this single lakebed are related to frequency, depth, and duration of inundation (Fig. 19).

Figure 19: Concentric bands of vegetation on a shallow lakebed in Hart Mountain National Antelope Refuge, in High Desert Province, Oregon. The vegetation bands are related to the frequency, depth, and duration of inundation.

In the Harney County lake basin near Burns, the 1974 General Soil Map of Harney County92 shows several kinds of bottomland associated with the three main sources of water flowing into Silver, Harney, and Malheur Lakes: Silver Creek, Silvies River, and Donner and Blitzen River.

In this system of streams and lakebeds, deep well-drained loamy and sandy soils on nearly flat alluvial fans and flood plains were mapped on an estimated 29,000 acres. The native vegetation on the bottomlands probably was a good stand of basin wildrye and other species.

Deep, poorly drained silty and clayey soils on flood plains were mapped on an estimated 188,000 acres. The native vegetation probably consisted of a good stand of mixed meadow grasses, forbs, and shrubs including such species as basin wildrye, streambank wheatgrass, Cusick bluegrass, sedges, rushes, big sagebrush, and green rabbitbrush. Much of this area is currently being used for hay production and pasture and is more or less irrigated.

Deep, poorly drained, strongly alkaline soils on flood plains were mapped on an estimated 184,000 acres. The native vegetation probably included such species as saltgrass, sedges, rushes, greasewood, and rabbitbrushes.

The three lakebeds—Silver, Harney, and Malheur—occupied about 2,000 acres, 27,000 acres, and 28,000 acres, respectively, for a total of about 57,000 acres in 1974. These lakes are more or less perpetual but fluctuate in size over time.

The 1971 General Soil Map of Lake County 84 shows that Paulina Marsh, north of Silver Lake community, occupied an estimated 21,000 acres at that time. Soils of the marsh are poorly drained and clayey. The native vegetation probably included tufted hairgrass, bluegrasses, sedges, and rushes and was a natural grassland. The marsh is more or less irrigated and used for hay production and pasture.

Silver Lake, about 5 miles east of Silver Lake community, occupied an estimated 9,600 acres in 1971. The entire lake was mapped as a playa, indicating that at that time the lake must have been dry. However, circa 1960s, Silver Lake was inundated to the tops of fenceposts between the highway and the north boundary of the lakebed, which illustrates the wide fluctuation in the degree of inundation over time. When the lakebed is partially inundated, it is vegetated with plant species such as squirreltail in drier areas and sedges and rushes in moist or wet areas. The lakebed currently is used primarily for pasture; however, portions of it have been cultivated and farmed in past years.

Summer Lake in 1971 occupied an estimated 19,000 acres, and the contiguous playa occupied an estimated 22,000 acres, none of which even now is vegetated to any extent. At the north end of Summer Lake is a marsh that occupied an estimated 4,500 acres in 1971. This marsh is maintained by water from the Ana River, which originates at a large spring gushing out of the base of Winter Rim near Summer Lake community. This marsh is managed as part of the Summer Lake State Wildlife Management Area. The native vegetation varies from bluegrasses, sedges, and rushes on drier areas to cattails and bulrushes around the edges of ponds, some of which were constructed and maintained as part of the wildlife management program.

According to the 1971 General Soil Map of Lake County,84 the Chewaucan Marsh, which is fed by Chewaucan River, occupied an estimated 42,000 acres between Paisley and Valley Falls community. The core of this marsh, an estimated 25,000 acres, consists of two areas of poorly drained silty soils that in native condition probably produced meadow plants such as tufted hairgrass, redtop, sedges, and rushes. The area currently is being managed for hay and pasture under extensive water-control systems. These two core areas are separated at The Narrows and nearly surrounded by a contiguous belt of loamy, poorly drained, strongly alkaline soils that occupy an estimated 17,000 acres. In native condition, this area probably produced greasewood, rabbitbrushes, saltgrass, squirreltail, basin wildrye, and similar alkali-tolerant plants. Some of this sodic area currently is being farmed under irrigation.

Lake Abert north of Valley Falls community occupied an estimated 34,000 acres in 1971.84 The water comes from the outlets of Chewaucan Marsh and Crooked Creek. Contiguous to the north end of the lake is a 12,000-acre playa. The shoreline of Lake Abert is not conducive to wetland vegetation. North of Lake Abert are a number of perpetual playas such as Alkali Lake and North Alkali Lake which do not produce wetlands.

The group of lakes collectively known as Warner Lakes in southeastern Lake County consists of nine major lakes which vary as to size and duration of inundation over time. Based on the 1971 General Soil Map of Lake County, these lakebeds and their estimated acreages are, from south to north: Crump, 7,400 acres; Hart, 5,400 acres; Anderson, 500 acres; Swamp, 770 acres; Flagstaff, 3,200 acres; Lower Campbell, 830 acres; Campbell, 2,400 acres; Stone Corral, 1,300 acres; and Bluejoint, 8,300 acres.

Numerous smaller lakes, ponds, and sloughs are in the wetlands of Warner Valley. The valley consists of poorly drained silty soils that in native condition probably produced meadow plants such as tufted hairgrass, redtop, sedges, and rushes. The wetlands occupy an estimated 34,000 acres within the Warner Lakes basin. Some of this area is being managed for hay and pasture under extensive water-control systems. Contiguous to these wetlands in this huge valley, mainly in the southwest and northeast portions, are areas of loamy, poorly drained, strongly alkaline soils that occupy an estimated 90,000 acres. In native condition, these areas probably produced greasewood, rabbitbrushes, saltgrass, basin wildrye, squirreltail, and similar alkali-tolerant plants. Much of the area of lakes and wetlands is included in the BLM Warner Lakes Management Plan.

Probably the most significant and valuable wetlands in High Desert Province, from a total ecosystem viewpoint, are those associated with isolated springs and streams scattered over the arid landscape. No matter how small, each provides the nucleus habitat for a wide variety of birds, mammals, reptiles, and other life which could not exist except for the water and special plant communities there. These wetlands consist of grassland meadows, patches of shrubs, aspen groves, and combinations of the first three. The variety of shrubs, grasses, and forbs present depends on the degree and duration of wetness and shade at each location.

The High Desert Province in Oregon is almost entirely a natural shrub–grassland on uplands. Sagebrushes strongly dominate among a wide variety of shrub species commonly growing in this province. Sagebrush species are reasonably site-specific in where they grow. For example, Wyoming big sagebrush is the most prominent shrub in the province: it is almost ubiquitous throughout the uplands of the province. Basin big sagebrush grows mainly on sites having moderately deep loamy soils such as are on droughty bottomlands and fans. Mountain big sagebrush is dominant above about 5,500 feet elevation on gravelly or stony upland soils. Low sagebrush is strongly dominant on shallow to very shallow stony upland soils, but also occurs mixed among other sagebrush species on moderately deep, very gravelly mountain slopes. Silver sagebrush is on some but not all intermittent lakes. Bud sagebrush occurs only on the most arid uplands in the province, which are very shallow, very stony soils.

Other shrubs in High Desert Province in Oregon include bitterbrush, mountain snowberry, and lanceleaf green rabbitbrush which grow on certain mountains on moderately deep, gravelly upland soils generally above 5,500 feet elevation. Such shrubs as hopsage, littleleaf and spiny horsebrushes, bud sagebrush, shadscale, threadleaf green rabbitbrush and winterfat typify the most arid sites in the province, which are usually shallow and stony. These most arid sites are minor in extent in High Desert Province but are widespread in the contiguous Humboldt Province.

Chokecherry and bittercherry, snowbrush, Utah serviceberry, viscid green rabbitbrush, and aspen grow on areas immediately below where snowdrifts normally form in winter. Curlleaf mountain-mahogany grows mainly on rocky ridges and bedrock outcrops above 6,000 feet on some mountains. It usually is in small groves or in elongated strips interspersed with other kinds of vegetation.

About 30 shrub species have been recorded consistently on upland sites and 15 shrub species on bottomland sites in High Desert Province in Oregon. This is obviously an incomplete record.

Predominant grass species in the arid shrub–grasslands include bluebunch wheatgrass, Idaho fescue, Thurber needlegrass, squirreltail, and Sandberg and Canby bluegrasses. The most arid sites may include Indian and Webber ricegrasses and, on sandy soils, needle-and-thread and thickspike wheatgrass.

Rough fescue grows on Hart and Steens mountains above about 6,000 feet on north exposures and above about 7,000 feet on the undulating mountain tops. This occurrence of rough fescue in High Desert Province in Oregon is an ecological oddity. The natural range of rough fescue is in northeastern Washington, western Montana, southeastern British Columbia, and southwestern Alberta. The rough fescue on Hart and Steens mountains is likely the most southern occurrence of this species in United States. No other sightings have been reported in Oregon 6 (Fig. 20).

Figure 20: Stand of rough fescue in a managed natural shrub grassland at about 7,000 feet elevation on Hart Mountain in High Desert Province, Oregon

The most moist uplands in High Desert Province in Oregon apparently are where snowdrifts normally form during winter on north-facing slopes. These areas are typified by stands of tall shrubs and aspen and certain grass species including big and Wheeler bluegrasses, mountain brome, Columbia and western needlegrasses, oniongrass, bearded and slender wheatgrasses, and basin wildrye.

About 35 major grass and grasslike species have been recorded consistently on uplands and about 40 species on bottomlands in High Desert Province in Oregon. Obviously, this is an incomplete record.

The High Desert Province in Oregon is relatively rich in perennial forb species because habitats range from marshes to arid uplands and the climate varies from arid cold desert at about 4,000 feet elevation to over 50 inches annual precipitation with fierce winds and temperatures at nearly 10,000 feet elevation. Some forb species are widespread in this province; however, a few are specifically oriented to local situations. Identification of forb species can be troublesome in this portion of Oregon because the most commonly used plant manuals in the Pacific Northwest do not adequately apply to this area. However, Peck’s manual of higher plants of Oregon 23 has been a reliable reference. Peck’s descriptions of uncommon local species and their habitats are surprisingly accurate which indicates that he actually was there and personally observed the species. This certainly cannot be said about some other authors’ manuals which apparently were assembled using work by other taxonomists. Another useful plant identification manual for this portion of Oregon is “A Manual of the Flowering Plants of California.”15

 

 
 

Management Implications

Livestock ranching is the dominant economic enterprise in High Desert Province. Agricultural crop alternatives are severely restricted due to adverse climate and scarcity or cost of water for farming. Almost all cropland production is oriented toward livestock ranching. Tourism and outdoor recreation is a growing enterprise; however, its potential is somewhat curtailed by immense distances, topographic features, few all-weather roads, weather restrictions, limited kinds of recreational activities, distance from populated areas, and the seasonal nature of recreational activities such as hunting.

The physical and ecological nature of High Desert Province historically has been a basis for huge ranches and large herds of livestock. These ranches are so complicated and extensive as to defy quick acquaintance with the resources, problems, needs, options, and opportunities. Not just any rancher or manager can operate these ranches successfully at first tenure.

Long-time resource management programs in High Desert Province are hindered by the ever-changing field personnel of public agencies who are routinely transferred and replaced by newcomers. Yet, the huge preponderance of public lands in the province essentially gives government officials and programs a strong impact on management of all the land, private and public.

Potential production of forage per acre on High Desert rangelands is inherently low except on meadows and in the higher-precipitation zones. A viable ranching unit requires many acres. Overall, these rangelands have been improving in ecological status, slowly but surely, for several decades. Currently, there is much evidence that proper application of modern rangeland science and technology in High Desert grazing strategies will produce an upward trend in ecological status while at the same time benefitting watershed health, wildlife habitat, aesthetics, and quality and quantity of forage for herbivores, both wild and domestic. An upward trend in ecological status is the most significant criterion on which to judge progress. Upward trend in ecological and soil status occurs very slowly, especially in early stages, on arid rangelands such as in High Desert Province. Therefore, to attain a verified upward trend is a commendable achievement and should be the goal of contemporary resource management programs (Fig. 21).

Figure 21: Managed natural shrub-grassland dominated by bluebunch wheatgrass and Thurber needlegrass in the vicinity of Glass Buttes, High Desert Province, Oregon

 
 

Province Demarcation

High Desert and Klamath Demarcation

Beginning at the southwest corner of the High Desert Province in Oregon, which is at the Oregon–California border about 15 air miles southwest of Adel in Lake County, the line of demarcation between High Desert and Klamath provinces lies at about 6,000 feet elevation south of the dry Big Lake. The line goes north at about that elevation to cross Parsnip Creek west of Adel, up Drake Creek to cross the Plush cutoff road going east of Drake Peak and on north across Twelvemile and McDowell creeks. At Honey Creek, the line turns west to the south end of Abert Rim, then south to Sherman Valley from where it follows north along the west side of Abert Rim escarpment nearly to Lake Abert. From there, it veers southwest to the vicinity of Valley Falls, which is in High Desert Province. From the vicinity of Valley Falls, the line meanders northwest at about 4,500 feet elevation along the western boundary of Chewaucan Valley, around Tucker Hill, southward up Moss Creek about 6 miles, then northwesterly along the valley at the base of Winter Ridge. The communities of Paisley and Summer Lake are in High Desert Province.

About 3 miles north of the community of Summer Lake, the line of demarcation between High Desert and Klamath provinces turns west along the headwaters of various drainages that drain north into Silver Lake basin. It continues west about 5 miles south of Silver Lake community into the headwaters of Bridge Creek. Here is the juncture of High Desert, Klamath, and Mazama provinces.

The line of demarcation between High Desert and Klamath provinces is based on soil lines between Booth–Bluejoint and Woodcock–Mound soils associations, which typify the Klamath Province, and Floke–Olson, Harriman–Hager, Crump–Ozamis, and Hart–Plush soil associations, which typify the High Desert Province.84

High Desert and Mazama Demarcation

From the juncture of High Desert, Klamath, and Mazama provinces, the line of demarcation between High Desert and Mazama provinces goes north across Buck Creek at about 4,900 feet elevation and on to the vicinity of Halfway Lake. To the north, it almost parallels Highway 31 for about 10 miles, about 1 to 2 miles west of the highway. The line of demarcation crosses Highway 31 northwest of the Horse Ranch about 7 miles west of Fort Rock community. Where the line crosses Highway 31 below the rimrocks, the highway roadcut reveals an ancient lakeshore terrace of stratified lacustrine materials, which signifies the boundary of High Desert Province in this area.

From the highway crossing near Horse Ranch, the belt of demarcation between High Desert and Mazama provinces meanders northeast by Hole-in-the-Ground, which is in Mazama Province, on by Cabin Lake Ranger Station, which is very near the line of demarcation, and on to the north portion of Devils Garden, which is in High Desert Province. From north of Devils Garden, the belt of demarcation between High Desert and Mazama provinces runs northeast to cross Highway 20 about 8 miles northwest of Hampton community at about 4,500 feet elevation. It continues on to the southwest slopes of Hampton Butte and the juncture between High Desert, Mazama, and John Day provinces.

The belt of demarcation between High Desert and Mazama provinces is supported by soils such as Gardone, Floke, and Olson soil series, which typify High Desert Province in this area, and Shanahan and Lapine soil series which typify Mazama Province.84

High Desert and John Day Demarcation

From the juncture of High Desert, Mazama, and John Day provinces at about 4,500 feet elevation on the southwest slopes of Hampton Butte in eastern Deschutes County, the line of demarcation between High Desert and John Day provinces goes southeast along the base of uplands near Hampton community. Then it meanders north for about 20 miles along the headwaters of drainages eastward into the South Fork Crooked River, which is the basin where GI ranch headquarters are. The line crosses the South Fork easterly at about 4,500 feet elevation and then southerly along the east side of North Fork basin to near where Crook, Deschutes, and Harney counties join and on south to near where Deschutes, Lake, and Harney counties join. From this area, the demarcation line between High Desert and John Day provinces travels east at about 4,500 feet elevation to the vicinity of Hines, Burns, and Harney, all in High Desert Province. This line of demarcation is where ancient lake terraces of the High Desert Province adjoin the uplands to the north, which are in John Day Province.

From the vicinity of Harney community, the line of demarcation lies at about 4,500 feet elevation around the eastern border of Harney basin to the community of Crane. The juncture of High Desert, John Day, and Snake River provinces is near Crane.

From near Hampton eastward to Harney Basin and Crane, the line of demarcation between High Desert and John Day provinces is the ancient-lake shoreline at about 4,500 feet elevation. It is reflected on general soil maps.70, 72

High Desert and Snake River Demarcation

Just east of Crane, the line of demarcation between High Desert and Snake River provinces begins at about 4,250 feet elevation in the gap at Crane. At this point one might speculate that the ancient lake in which terraces of Snake River Province were formed at one time might have been connected to the ancient lake in which terraces of High Desert Province were formed. For this to have happened, the lakes would have had to exist simultaneously. But this is a matter of conjectural paleontology and has no current significance in differentiating between the two provinces. Obviously, the terraces and basins in High Desert Province suggest quiet-water abatement, which seems logical for such closed basins that would have no strong currents escaping to the ocean. In contrast, the terraces of Snake River Province are typified by strong geologic erosion and sharp dendritic drainage patterns which suggest that the water receded in strong currents, possibly out through the Snake River to the ocean. Consequently, the kinds of ecological sites, soils, plant communities, and especially the management implications are markedly different between Snake River and High Desert provinces.

Demarcation between the provinces south and east from Crane to the vicinity of Folly Farm and northeast toward Crowley is likely a belt. There is no readily apparent line of demarcation anywhere within this belt; therefore, the line becomes a matter of field-experienced judgment.42

Based on the fact that ancient terrace lines are extensive and consistently visible at about 4,500 feet elevation around the perimeter of the geologic basin that forms High Desert Province, and that Snake River Province line west of Warm Springs Reservoir is at about 4,500 feet elevation, the belt of demarcation between High Desert and Snake River provinces has been placed at about 4,500 feet elevation from the vicinity of Crane southeast to just north of Folly Farm, then northeast to just north of Crowley. From there it runs east around the south side of Cedar Mountains to the rim of the Owyhee River canyon, which is at 4,000 feet elevation. This demarcation belt places the dry lakebeds and closed basins south of Crowley in High Desert Province, which is typified by similar closed-basin topography; whereas Snake River Province to the north is typified by landscape dissected by dendritic drainages into the Snake River system.

High Desert and Humboldt Demarcation

About 20 miles down the Owyhee River from Rome on Highway 95, on the west rim of the canyon is the juncture between High Desert, Snake River, and Humboldt provinces. From this juncture, the line of demarcation between High Desert and Humboldt provinces travels southwest to the eastern footslopes of Sheepshead Mountains, then south and west around Sheepshead at about 4,500 feet elevation. The line wanders north of the basin in which Alvord Desert lies to the eastern footslopes of Steens Mountain and then south along the base of Steens Mountain at about 4,500 feet elevation. Sheepshead Mountains and Steens Mountain are in High Desert Province. Pueblo Mountains and Trout Creek Mountains are in Humboldt Province. Alvord Desert and Alvord Lake are in Humboldt Province.

From the vicinity southwest of Alvord Lake, the line of demarcation between High Desert and Humboldt provinces runs west through the gap between Steens Mountain and Pueblo Mountains on to the southeastern rim of Catlow Valley. From there it goes south at about 6,000 feet elevation along the ridge that separates drainages to the west from drainages eastward into Rincon Creek watershed. The demarcation line crosses into Nevada about 15 air miles west of the community of Denio.

The line is fairly sharp in the northeast corner of Sheldon National Wildlife Refuge in Nevada. It lies at the summit on Highway 140 which is north of Thousand Creek Ranch. Railroad Point and Jackass Flats are in Humboldt Province; Duferrena is in High Desert Province.