As moist air from the Pacific Ocean rises over the Cascade Mountains, most of the moisture falls on their western slope. This casts a "rain shadow" over central Washington, creating a landscape with very little rainfall. Where the Columbia Basin lies in rain shadow, the climate of hot, dry summers and cold winters does not support forest communities, except along rivers and on the highest ridges. Most of the natural vegetation of the Columbia Basin was once a vast expanse of steppe communities. Steppe communities consist of low, wiry shrubs that are widely spaced among clumps of grasses. They are found typically in relatively dry environments and often have wide gaps of bare ground between the bunches of grass and shrubs. If you drive east of the Cascade Mountains to the Columbia River, you can see vast expanses of steppe communities.

Broad expanse of steppe with widely spaced shrubs near the Columbia River.	Many low shrubs produce brilliant flowers among the grasses and sagebrush of steppe.

An important plant community in the dry landscape of the Columbia Basin of central Washington is the sagebrush steppe. Along our transect, the hillsides of Ginkgo State Park, which is near the Columbia River north of Vantage, are covered by sagebrush steppe. Trails in Ginkgo State Park provide the opportunity to walk through and explore sagebrush steppe. The hillsides here are dotted by the characteristic shrub of sagebrush steppe: big sagebrush (Artemisia tridentata). Other shrubs, including bitter-brush (Purshia tridentata), parsnip-flowered eriogonum (Eriogonum heracleoides), and gray ball sage (Salvia dorrii), are scattered among the sagebrush. Bunch grasses are also an important part of sagebrush steppe. These are grasses in which the stems are clumped. The main bunchgrass on the hillsides at Ginkgo State Park and in many other steppe communities of Washington is bluebunch wheatgrass (Agropyron spicatum).

Sagebrush steppe community covers the landscape in Ginkgo State Park.	Big sagebrush

Bluebunch wheatgrass	Bitter-brush	Gray ball sage

William O. Douglas, a former Justice of the U.S. Supreme Court, explored the sagebrush steppe of central Washington while growing-up. He wrote of that area in Of Men and Mountains: "The earliest of the wild flowers was the pepper-and-salt, the diminutive member of the lomatiums. . . A soft carpet of violets, buttercups, yellow bells, and eye grasses would appear. But these were fragile flowers that hardly had a chance to taste the sweetness of life before they died. . . The lupine, dwarf sunflowers, sage pinks, and blue bells were hardier specimens and lingered longer. But they too were usually gone by June, leaving some relics behind. . . Later came the purple and white asters; the ever present yarrow; the sedum with its starry flowers of bright yellow; the wild onion, one of the loveliest of all the filigrees of nature, its six petals of deep purple set off by anthers of pale yellow; and the exquisite bitterroot." Douglas's description captures well the rapid sequence of flowering, which is concentrated during spring and early summer, in the sagebrush steppe. Summers in the steppe region of eastern Washington are very hot and dry, and only the shrubs flower during that season. The grasses and other herbaceous plants dry quickly in the summer heat and their leaves and above-ground stems begin to die-back.

Common yarrow	Yellow fritillary
Rocky mountain helianthella	Purple-eyed grass
Large-fruited lomatium

Historically, the Washington sagebrush steppe was dominated by sagebrush interspersed with perennial bunchgrasses. Bunchgrasses look like they sound: they tend to form clumps, rather than spreading out in mats across the ground, such as we find in lawn grasses. When you look at a bunchgrass prairie you see tufts of grass with bare space between them, rather than a continuous cover of grass. Unlike the tallgrass prairies of the Great Plains, neither fires nor extensive grazing by large herbivores (like bison) were historically part of the Washington steppe ecology. When European settlers moved into the area at the turn of the twentieth century, they brought with them both fire and grazers. These two influences had a tremendous impact on the native plants. In particular, neither sagebrush nor perennial bunchgrasses are resistant to heavy grazing, and, after it was introduced by settlers to Washington, grazing led quickly to the colonization of disturbed steppe by plants, typically annual grasses and herbs, better-adapted to it. One such grass is Bromus tectorum, downy cheatgrass, an introduced European grass that has become a dominant member of communities across Washington and outcompetes the perennial native grasses.

Downy cheatgrass