Owyhee Upland

Malheur Experiment Station

Information for Sustainable Agriculture

Wild horses leaving a water hole

Environmental context of the Owyhee uplands*

Myrtle Pearl Shock

The Owyhee uplands are located in the southeastern-most corner of Oregon, in Malheur County. The Owyhee uplands are part of the Columbia Plateau drainage system, however the vegetation and animal life closely resemble that found in the northern Great Basin. The Owyhee uplands are bounded by the Idaho border to the east, Nevada to the south and the Steens Mountain range and high lava plains on the west. The region is immense. Malheur County is 6.35 million acres in size, larger than Vermont with 6.15 million acres. The Owyhee uplands cover about the southern two-thirds of the county, or approximately 4 million acres. The watershed of the Owyhee River extends into extreme southwestern Idaho and northern Nevada.

The identification of natural variables is an important facet in describing the environmental landscape. With such an extensive area to cover, the sections which follow refer to general trends of the mesas and canyons. The mountain environments are not included.

Geological setting

The Owyhee uplands are part of the Basin and Range physiographic province. The Basin and Range is an area of fault-block topography, mountain ranges running north to south separated by broad basins.

"The Owyhee uplands lie in the northwest corner of the Great Basin. This region differs from the rest of the province in that it is a flat deeply dissected plateau with little interior drainage where fault-block topography is less pronounced. The drainage basin of the Owyhee River encompasses the uplands. Originating in Nevada, the Owyhee River flows northerly through Idaho and Oregon to join the Snake River near Adrian, Oregon. In spite of low rainfall in the area, steep gradients give the the [sic] river and its tributaries well-defined drainage patterns and deep canyons. Cutting through the uplands over 6,000 feet above sea level, the river drops to approximately 2,000 feet where it joins the Snake. Small streams flowing in from the hills are largely intermittent." (Orr E. L. and W. N. Orr. 1999. Geology of Oregon. Kendall/Hunt Publishing Co., p 79)

The geological background of this province is based in volcanic activity which started in the Miocene. There are deep volcanic deposits of basalts, tuffs and tuffaceous sediments. While basalt is prevalent, other features include rhyolite, diatomaceous deposits, new sedimentary deposits and new surface lava. The episodes of deposition affecting the Owyhee uplands include the Owyhee Basalts that erupted onto the plateau 13-12 million years ago and the ash-flow tufts from the Steens mountains around the same time. In a few areas there has been relatively recent volcanism, of special note is Jordan Craters.

The Jordan Craters lava flow is located in the Owyhee uplands on the plateau. It is a 75 square kilometer olivine basalt flow that is extremely recent by geological time. Potassium argon (K-Ar) dating shows that it is no older than 30,000 years. However, "studies based on growth rates of lichen and weathering rates of exposed and unexposed basalt suggest that the flow may be between 4,000 and 9,000 years old". "Additionally the southeasterly flowing lava altered ancestral drainage patterns, giving rise to a natural dam and the formation of two small lakes (Upper and Lower Cow Lakes)" (Wood and Kienle 1990. Volcanoes of North America: United States and Canada. Cambridge University Press, p 211).

Soils

Overlying the geological foundation is the soil. In general desert soils vary widely in chemistry as well as pH. Important in soil formation are fluvial and eolian processes. Deeper soils have accumulated along river terraces. Soils on the mesas are generally shallow and some areas are stripped to bare rock by wind and water. A more detailed description of soils would depend upon the existence of a regional soil survey. As of December 2000, the majority of Malheur County, Oregon had not been surveyed. "Soils on the plains are moderately sloping, clayey, very stony or rocky, and shallow to very shallow over basalt bedrock or hardpans. On the buttes and mountain slopes, soils are relatively steep, loamy, stony and moderately deep" (Anderson, E.W., M.M. Bormarn and W.C. Krueger. 1998. The Ecological Provinces of Oregon: A treatise on the basic ecological geography of the state. Oregon Agricultural Experiment station, p 94)

Climate

The climate of the Great Basin is semiarid, characterized by an mean annual temperature of 9°C (48.2°F) and between 100 and 200 mm (3.94-7.88 in.) of precipitation annually. The majority of this precipitation comes during the winter and spring. The current climatic conditions of Rome, OR on the Owyhee River at 3400 feet (1036 m) of elevation best reflect recent climatic conditions of the Owyhee uplands. Average annual precipitation over the last 50 years is 8.21 inches (20.85 cm). The average daily maximum temperature in the hottest month, which is July, is 92.0°F (33.3°C). The average daily minimum temperature for January, the coldest month of the year, is 18.1°F (-7.7°C). Data from further to the south at weather station McDermitt 26N (located 26 miles to the North of the Oregon/Nevada border along US 95) reflects similar conditions at 4500 feet (1371 m) of elevation. Average annual precipitation is 9.43 inches (23.95 cm). The temperature ranges from an average daily maximum of 91.1°F (32.8°C) in the month of July and the average daily minimum for Jan of 18.9°F (-7.3°C). The averages for this station are for the last 45 years (Western Regional Climate Center).

The environment of the Owyhee uplands is comparable to that of the Great Basin. The main difference between the two is hydrological. While the Owyhee uplands have drainage into the Pacific Ocean by way of streams and rivers, the Great Basin has internal drainage. These two areas indeed have many similarities. The plant communities which can be found in the two regions are similar. In turn animal communities are similar with the notable exception of different varieties of fish that inhabit the Owyhee River in comparison to inland lakes.

Local wind patterns

High winds come up in the morning and evening across the plateau regions of the Owyhee uplands. These winds, anabatic and katabatic, are driven by gravity and the heating and cooling associated with morning and evening, respectively. In the evening as layers of the surface cool, the cold surface air is denser and sinks, moving down slope across the mesa. The downward movement is called a katabatic wind. The reverse happens in the morning as the air at lower elevations warms and rises, pushing air the opposite direction across the mesa as an anabatic wind.

Vegetation complexes

Most of the North American deserts fall within the Basin and Range province, the most northern of which is the cold desert or Basin and Range. The cold desert is primarily semiarid with steppe vegetation. The plant community is dominated by the evergreen Artemisia spp. (sagebrush) complex.

"This complex segregates out along moisture, temperature, soil depth and chemistry, and soil-texture gradients. Important associates with Artemisia include shrubs such as Purshia tridentata [bitterbrush],Chrysothamnus nauseosus [gray rabbitbrush], Chrysothamnus viscidiflorus [green rabbitbrush] and bunchgrasses of the genera Pseudoroegneria [wheatgrass], Elymus [wildrye, wheatgrass, bottlebrush], Festuca, Leymus [wildrye], Oryzopsis [ricegrass] and Stipa [needlegrass]." (Smith, S. D., R. K. Monson and J.E. Anderson. 1997. Physiological Ecology of North American Desert Plants. Springer, p 22)

Throughout the desert environment, there is high spatial variability of plants, in other words, species appear in patches and these can abruptly change to another patch with a different species composition.

The Owyhee uplands are dominated by big sagebrush scrub. Grasses which are associated with big sagebrush, in the area of study, include bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg bluegrass (Poa sandbergii), bottlebrush squirreltail (Sitanion hystrix) and Idaho fescue (Festuca idahoensis) (Anderson et al. 1998). "The Idaho fescue will usually be found in slightly higher and moister spots; the wheat grass is able to tolerate drier environments" (Hatton, R. R. 1988. Oregon's Big Country. Maverick Publications, p 23). Within this range of the Artemisia steppe, the economically important species, all of which have edible parts, include: basin wildrye (Elymus cinereus), biscuitroot (Lomatium spp.),camas (Camassia quamash), bitterroot (Lewisia rediviva), cattail roots (Typha latifolia), chokecherry (Prunus virginiana), wild rose (Rosa spp.), wild onions (Allium spp.) and currants (Ribes spp.). The plant community has changed in recorded history with the invasion by exotic species, including Russian thistle (Salsola kali) and cheatgrass (Bromus tectorum). Western juniper (Juniperus occidentalis), a native species, is expanding from higher elevations onto the steppe due to fire suppression (Miller, R. F. and J. A. Rose. 1995. Historic expansion of Juniperus occidentalis (Western juniper) in southeastern Oregon. Great Basin Naturalist 55(1):37-45).

Within the Artemisia complex, there are three subspecies of Artemisia tridentada; these are associated with different elevations, soils and edible plants. The mountain big sagebrush (Atremesia tridentada vaseyana) are found at elevations of over 5000 feet (1500 m) where the annual precipitation exceeds 12 inches (30 cm); these areas in the Owyhee uplands are the Mahogany, Spring and Trout Creek Mountains. The other two subspecies are Wyoming big sagebrush (Artemesia tridentada wyomingensis) and basin big sagebrush (Artemesia tridentada tridentata), both of which are found in the lower elevations. Wyoming big sagebrush is found on the shallow soils. Basin big sagebrush is found in deeper soils; associated with it are basin wildrye (Elymus cinereus), yellow currants (Ribes aureum) and squaw currants (Ribes cerium).

Outside of the Artemisia complex, some other important vegetation groups are found in the Owyhee uplands. In clay soils with standing water the low sagebrush, or Artemisia arbuscula, thrives. It is a key to the locations where bitterroot (Lewisia rediviva), biscuitroot (Lomatium spp.) and often onions (Allium spp.) are found. Additionally, Indian rice grass (Oryzopsis hymenoides), which has a large, heavy seed, grows on sandy soils throughout the Owyhee uplands. Riverside vegetation is marked by a narrow band of willow (Salix spp.), rushes (Juncus spp.), sedges (Carex spp.) and riparian grasses. In some locations along the rivers edible plants can be found: yellow and red currants (Ribes aureum and cereum), wild rose (Rosa spp.), hackberry (Celtis spp.), and chokecherries (Prunus virginiana).

Camas (Camassia quamash) only grow along the Cow Creek drainage in the Owyhee uplands. Cow Creek is one of two bottomlands in the Owyhee uplands, the other is Jordan Creek. "Originally, these bottomlands likely produced a dense, vigorous stand of basin wildrye" (Anderson et al. 1998:95). Cow Creek's drainage pattern has been altered by volcanic activities. Jordan Craters now covers the wide valley through which Cow Creek used to run from the mountains of Idaho, westward until it reached the Owyhee River. Cow Creek is now confined in the Cow Lakes before the drainage turns south to join Jordan Creek. Jean Findley, Vale BLM biologist, believes that because of the low gradient across what is now the Jordan Craters, Cow Creek used to pass through a wetland, rich in camas and basin wildrye.

Paleobotanical research provides a record of the environment in the Great Basin desert. The dominant vegetation reflects the climatic conditions which are favorable for its growth. The following time periods are noted by differences in the dominant vegetation (Smith et al. 1997, 27): Late Wisconsin - subalpine coniferous forest (21,000 - 11,000 BP); Early Holocene - Pinus-Juniperus woodland (11,000 - 8,000 BP); Middle Holocene - Juniperus woodland / Artemisia steppe (8,000 - 4,000 BP); Late Holocene - Artemisia steppe / Atriplex desert scrub (< 4,000 BP). This change from juniper woodland to sagebrush steppe has yet to be confirmed for the Owyhee uplands.

Animal community

Large mammals of the Owyhee uplands today include pronghorn (Antilocapra americana), white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), elk (Cervus elaphus), bighorn sheep (Ovis canadensis) and cougar (Felis concolor). Some smaller animals are cottontails (Sylvilagus spp.), jackrabbits (Lepus spp.), badgers (Taxidea taxus), rattlesnakes (Crotalus viridis), gopher snakes (Pituophis catenifer), chipmunks (Eutamis spp.), sagebrush voles (Lagurus curtatus) and coyotes (Canis latrans). Some of the birds of the area are sage grouse (Centrocercus urophasianus), hawks (Buteo spp.), and migratory birds like ducks (Anatidae spp.) and geese (Branta canadensis). These animals are routinely observed in the area.

The Owyhee uplands are semi-arid and have been so for most of the last millenia. Precipitation is low and water is scarce in most locales. Paleobotanical research reflects an environment which has supported Artemisia steppe / desert scrub communities for the last 8000 years. The dominate vegetation of the area currently is big sage scrub which includes a number of plants which have edible parts. This vegetation supports several types of large and small mammals, particularly the pronghorn.

*The material here is excerpted from Rock art and settlement in the Owyhee uplands of southeastern Oregon, a Bachelor of Philosophy Thesis for the University of Pittsburgh University Honors College by Myrtle Pearl Shock.

For local vegetation see the local vegetation database.
Links to other information:Lower Owyhee Watershed Assessment.