Humboldt Ecological Province

 

 

 
 
 

Location

Humboldt Province is in southeastern Oregon. This province and High Desert Province represent the portion of Oregon that lies within the huge western Great Basin that extends south into Mexico and east into west Texas.24 In Oregon, Humboldt Province covers about 1.8 million acres in southeastern Harney County and southwestern Malheur County. It extends south into Humboldt County, Nevada.

 
 

Description

Humboldt Province is characterized by long, generally north–south mountain ranges such as Pueblo and Trout Creek mountains in Oregon and the Pine Forest range and Bilk Creek Mountains in northern Nevada. Long, north–south closed valleys, technically called grabens, lie between these mountain ranges; they include Pueblo Valley in Oregon and Kings Valley and Desert Valley in Nevada. Between the valley floor and the mountain range are immense, continuous ancient-lake terraces and fans that constitute a more or less foothill formation below about 4,500 feet elevation. The upper elevation of these terraces denotes the extent of inundation by ancient lakes. Elevations in Oregon’s portion of Humboldt Province range from 4,025 feet at Alvord Desert to 8,545 feet on Pueblo Mountains (Fig. 22). (Elevations are from USGS 1:250,000 topographic maps, Adel, Oregon.)

Figure 22: Immense sodic bottomlands and mountain ranges in Humboldt Province near the Oregon-Nevada border. Continuous ancient-lake terraces and fans appear as a lighter-color formation between the bottomlands and the mountains.

Humboldt Province is significantly more arid at lower elevations than is High Desert Province. In Oregon’s portion of the Humboldt, this difference is reflected by the increasing incidence from north to south of sites that support stands of vegetation including bud sagebrush, shadscale, winterfat, and similar arid-site species (Fig. 23). Another feature that helps to characterize Humboldt Province is the common “desert varnish,” which is a shiny black coating on the exposed surfaces of stones and gravel on very arid sites. The coating is manganese dioxide. It occurs only under very arid conditions in which indicator species, such as those previously mentioned, also grow.

Figure 23: Managed natural desert shrub range on very stony ancient lakeshore terraces and fans that typify Humboldt Province, Oregon

 
 

Soils

Soils of Humboldt Province in Oregon are related to basaltic uplands and ancient lakebeds. Basaltic upland soils are generally shallow to very shallow with loamy surface layers and clayey subsoils. They are very stony or rocky. Very steep slopes are essentially rockland. The soils, formed in ancient lakebeds, occur as bottomlands at the lowest elevations below 4,200 feet and as lakeshore terraces and fans below about 4,500 feet elevation.

Two major areas of bottomland soils are in Humboldt Province in Oregon: the Alvord basin, which is about 65 miles long north to south; and, about 12 miles to the east, the Coyote Lake basin, which extends about 28 miles north to south. Alvord basin contains Alvord Lake, which fluctuates in size over the years and receives its water through Wildhorse Creek to the north. Coyote Lake basin drains into the playa Coyote Lake.

Bottomland soils in Alvord basin occupy about 143,000 acres and extend from the north boundary of Alvord Desert south nearly to the Nevada border, a distance of about 50 miles. This area of bottomland soils varies in width, east to west, from about 1 mile to 10 miles; the widest area is just south of Alvord Desert. The long, relatively narrow bottomlands in Alvord basin are typical of Humboldt Province physiography.

Bottomland soils of Alvord basin occupy about 4,000 acres in Alvord lakebed, about 29,000 acres in Alvord Desert, and about 8,000 acres in other playas within the basin. These lakebed soils are poorly drained and clayey. About 31,000 acres of bottomlands are loamy, well-drained soils, and about 9,000 acres are silty and very poorly drained, but these areas are not wetlands because of insufficient moisture. About 58,000 acres of bottomlands are poorly drained silty to clayey soils that are strongly alkaline but are not wetlands. About 4,000 acres within the bottomlands are shallow silty soils overlying lacustrine sediments.92

Bottomland soils in Coyote Lake basin occupy about 63,000 acres of which about 3,000 acres are Coyote Lake playa and about 4,500 acres are other playas in the basin. These soils are poorly drained and clayey. About 12,000 acres of the bottomlands are loamy well-drained soils, and about 1,500 acres are clayey poorly drained soils. About 26,000 acres of bottomlands are strongly alkaline soils, and about 16,000 acres are shallow silty soils over lacustrine sediments. None of these bottomlands are wetlands.92, 94

 
 

Climate

There are no official weather stations in Oregon’s portion of Humboldt Province.17, 28 However, the 1941 Yearbook of Agriculture provides climatic data for three stations less than 30 miles south of the Oregon border which are very likely in Humboldt Province in Nevada. All three stations are near major highways in huge north–south valleys.

A precipitation map53 shows that a sizable portion of Humboldt Province in Oregon, such as around Alvord Lake, receives less than 10 inches annual precipitation. This map also shows about 15 inches annual precipitation on Pueblo Mountains and about 25 inches annual precipitation on Trout Creek Mountains, both in Humboldt Province in Oregon.

These data substantiate that, based on plant communities and soils, Humboldt Province in Oregon is significantly more arid than High Desert Province in Oregon, although both are components of the western Great Basin.

 
 

Vegetation

In Oregon, vegetation on uplands in the Humboldt Province is typified by both desert shrub and shrub–grassland climax types according to unpublished field studies.47, 49 A natural grassland climax type also occurs but only on bottomland sites that receive run-on water; however, some shrubs naturally occur in the plant communities of these bottomland sites. A deciduous tree climax type, which consists of aspen groves, occurs in scattered areas at higher elevations on some mountains.

Prominent shrubs that grow on sites in the desert shrub climax type include black greasewood, spiny hopsage, shadscale, bud and Wyoming sagebrushes, winterfat, and spiny horsebrush. Prominent grasses on sites in the desert shrub climax type include Indian ricegrass, squirreltail, basin wildrye, inland saltgrass, sand dropseed, and desert needlegrass.

Prominent shrubs that grow on sites in the shrub–grassland climax type include Wyoming, mountain, threetip, and low sagebrushes; green rabbitbrush; spiny hopsage; shrubby buckwheat; and mountain snowberry. Prominent grasses that grow on sites in the shrub–grassland climax type, which includes the mountainous uplands, include bluebunch wheatgrass, Sandberg and Cusick bluegrasses, Idaho fescue, squirreltail, Thurber and western needlegrasses, basin wildrye, and Indian ricegrass.

Prominent shrubs that grow on lower bottomland sites, which are alkaline, include black greasewood, basin big sagebrush, gray and green rabbitbrushes, golden currant, silver buffaloberry, and willow. Prominent grasses that grow on lower bottomland sites include basin wildrye, inland saltgrass, Lemmon alkaligrass, alkali bluegrass, and alkali sacaton.

Dry meadows and wet mountain meadows occur in Humboldt Province in Oregon but have not been sampled sufficiently to characterize them. They probably resemble equivalent sites in High Desert Province because of the cold, wet nature of these sites.

Plant species recorded in Humboldt Province, Oregon but not in High Desert Province in Oregon include alkali sacaton, desert needlegrass, sand dropseed, silver buffaloberry, green ephedra, and pickleweed (iodine bush).

 
 

Management Implications

Livestock ranching is the dominant economic enterprise in Humboldt Province in Oregon. The physical and ecological nature of Humboldt 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.

Potential production of forage per acre on Humboldt 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 science and technology in Humboldt 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 Humboldt Province. Therefore, to attain a verified upward trend, by itself, is a commendable achievement and should be the goal of contemporary resource management programs.

 
 

Province Demarcation

Humboldt and High Desert Demarcation

Beginning at the southwest corner of Humboldt Province in Oregon, which is at the Oregon–Nevada border about 15 air miles west of Denio community, the line of demarcation between Humboldt and High Desert provinces heads northwest and northerly along the west side of Rincon Creek watershed to the southeast end of Catlow Valley and then north along the rimrocks east of the valley. The line veers east through the pass between Pueblo Mountains, in Humboldt Province, and Steens Mountain which is in High Desert Province. The line goes north along the footslopes of Steens Mountain at about 4,500 feet elevation, passing west of Alvord Lake, Alvord Desert, Mann Lake, and Tudor Lake, which are in Humboldt Province (Fig. 24).

Figure 24: Ancient-lake terraces along the eastern footslopes of Steens Mountain, in High Desert Province, and Alvord Lake basin, which is in Humboldt Province, Oregon

From the vicinity of Tudor Lake, the line goes south, east, and north at about 4,500 feet elevation around the footslopes of Sheepshead Mountains, which are in High Desert Province. From this location, the line veers east to cross Highway 78 about 7 miles southeast of Folly Farm. It continues northeast along the northern border of extensive lava fields that are west of Owyhee River in this vicinity.39, 42, 52 Here, about 20 miles down the Owyhee River from Rome on Highway 95 and on the canyon’s west rim, is the juncture of Humboldt, High Desert, and Snake River provinces.

Humboldt and Snake River Demarcation

From that juncture, the line of demarcation between Humboldt and Snake River provinces travels southerly along the west rim of Owyhee River canyon and the breaks of drainages into the river. It crosses Highway 95 about 3 miles east of Burns Junction, where highways 78 and 95 merge. From there the line runs east along the south breaks of Owyhee River canyon to about 7 miles north of Jackie’s Butte and the juncture of Humboldt, Snake River, and Owyhee provinces at about 4,000 feet elevation.

Humboldt and Owyhee Demarcation

From the juncture of Humboldt, Snake River, and Owyhee provinces, the line of demarcation between Humboldt and Owyhee provinces wanders around the western slopes of Jackie’s Butte, which is in Owyhee Province, at about 4,000 feet elevation and then south along the west edge of the plateau where it butts into hilly uplands such as Battle Mountain. The line continues south to the Nevada border along the western boundary of the sloping basaltic plateau where it butts up against the hilly uplands.