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Ecoregions

Lakes Basin Ecosystem Diversity

The arid, sagebrush-dominated landscape of the Lakes Basin may not seem ecologically diverse, but in fact it is home to a wide range of plants and animals, including some found nowhere else in Oregon. The habitats on and around Steens Mountain exemplify this diversity. The mountain's east side rises gradually from 4,200 feet to its summit at just over 9,700 feet. This range of elevation creates distinct precipitation and temperature zones that allow diverse plant communities to thrive in relatively close proximity. In the book Flora of Steens Mountain, author Donald Mansfield describes these zones, which are described here.

Shadscale-Marsh Zone (1300 m or 4270 ft)

This zone includes the alkaline playa of the Alvord Desert, which lies east of Steens Mountain. This desert is the driest location in Oregon, receiving less than seven inches of precipitation annually. Like other closed basin playas in the Lakes Basin, salt- tolerant plants, such as saltbush, greasewood and salt grass, are characteristic of this zone. To the west of Steens Mountain but within the same zone is the Malheur Marsh. Like other wetlands in the Lakes Basin, this marsh hosts a wide diversity of birds. Over 320 species of birds and 58 mammal species have been observed on the Malheur National Wildlife Refuge. The refuge is nationally recognized by bird watching enthusiasts.

The Sagebrush Zone (1300-1650 m or 4270-5410 ft)

This elevation zone hosts the sagebrush plant communities typical in much of the Lakes Basin. These communities consist of an overstory of sagebrush and an understory of forbs and perennial grasses such as bluebunch wheatgrass and Idaho fescue. Even within the sagebrush communities there is diversity - different types of sagebrush are adapted to specific precipitation and soil conditions. Moisture-loving woody plants can also occur in riparian areas within this zone, including willow, mountain alder, black cottonwood, cherry, and red osier dogwood. One characteristic wildlife species of this zone is the greater sage grouse. This large, ground-dwelling bird depends on sagebrush for food, shelter and protection from predators. Sage grouse is considered an indicator species that can be used to track the health of many other sagebrush- dependent wildlife species and is a focus for many conservation and restoration efforts.

Juniper Zone (1650-2000 m or 5410-6560 ft)

Mansfield describes a juniper zone on Steens Mountain that includes patches of sagebrush and mountain mahogany. Juniper woodlands are common throughout the Lakes Basin, and their extent has expanded dramatically since European settlement. For more information about juniper encroachment, visit Fanning the Flames: Restoring the Fire Regime in the Great Basin.

Aspen-Upper Sagebrush-Grass Zone (2000-2400 m or 6560-7870 ft)

Mansfield describes this zone as a mosaic of aspen woodlands, sagebrush steppe, and grassy meadows. Mountain big sagebrush dominates drier areas, while aspen and gooseberries are common in sheltered areas. Meadows host sedges and grasses such as Wheeler's bluegrass and perennial forbs. Steens thistle, a type of thistle endemic to Steens mountain, occurs in this zone.

Alpine Bunchgrass-Tundra Zone (less than 2400 m or 7870 ft)

The plants in this zone must survive the harsh weather conditions of an alpine climate. Steens is known for its wet meadows that occur in glacially-carved basins where snow accumulates and melts. Common plants include American bistor, cinquefoils, speedwells, elephantheads, sedges, rushes and bentgrasses. Many of the high elevation plants found on Steens are more typical of the Rocky Mountains or the Sierra Nevadas, and occur nowhere else in Oregon.

Sources

Mansfield, Donald H. 2000. Flora of Steens Mountain. Oregon State University Press.

The Unique Botany of Steens Mountain: The Rare and Endemic Plants by Mansfield in the journal of the Native Plant Society of Oregon.

Oregon Department of Fish and Wildlife. 2006. Oregon Conservation Strategy. Oregon Department of Fish and Wildlife, Salem, Oregon.

Authored by Maria Wright, Faculty Research Assistant, Institute for Natural Resources and Caitlin Bell, Science Writer, Oregon Explorer

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