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
