Shrubs Of The Great Basin: A Natural History

The Great Basin

THE GREAT BASIN JOHN C. FREMONT, the explorer, coined the name Great Basinfor that vast series ofnorth~south, parallel mountain ranges and basins extending from the Wasatch Range in Utah to the Sierra Nevada of Nevada and California. Northward the boundary lies along the Snake River drainage area, including much ofsoutheastern Oregon. On the west the boundary follows the crest of the Sierras and, at the southern extremity of the White Mountains, swings eastward to exclude the southern part of Nevada. The accompanying maps indicate primarily, though not entirely, a somewhat smaller area called the hydrographic Great Basin, an area into which all streams flow and from which no river exits to the sea. Obviously, Fremont should have made his appel~ lation plural, since there are at least seventy~five separate basins, rather than a single basin. And, in reality, the Great Basin has a domed rather than a concave profile-the highest valley floors at the center range from 5,500 to 6,J00 feet in elevation, while those to the east and west may be as low as 3,800 feet. Many of the ranges are 6,000 to 7,000 feet high, and a few exceed 10,000 feet, with the highest being the White Mountains at an elevation of over 14,000 feet. Dwight Billings divided the Great Basin into a number ofvegetation zones, which we should note in passing, albeit not in any detaiL Except for the extreme saline areas, desert playas, and some lava fields which have no higher plants, the lowest zone is the shadscale zone, named after its most abundant 1 f-._.__._._._._._._._._. i Ariz;ona i The Great Basin, showing principal mountain ranges, rIvers, and lakes. GREAT BASIN SHRUBS 3 shrub. Common companions of the shadscale are green rabbitbrush, bud sagebrush, four-winged saltbush, spiny hopsage, Bailey's greasewood, and littleleafhorsebrush. The more saline areas within the shadscale zone include big greasewood as the dominant shrub, along with desert blite and green molly. Sand dunes are likely spots for smokebush and cotton horsebrush. The sagebrush zone is slightly higher than the shadscale in elevation, with a resultant greater annual precipitation and a lower rate ofevaporation. This zone is, in reality, a sagebrush-grass zone, although in many areas grass has largely disappeared because of overgrazing. Along with big sagebrush are found green and rubber rabbitbrushes, blackbrush in the southern part of the Great Basin, green ephedra, bitterbrush, spiny hopsage, and snowberry. Some sagebrush communities extend upward even to mountaintops and elevations over 10,000 feet high. Above the sagebrush zone, the pinyon-juniper zone is dominated by these two trees. The shrubs within this zone commonly include big sagebrush, snakeweed, bitterbrush, plateau gooseberry, western serviceberry, snowberry, and green and rubber rabbitbrushes. Still higher is a series of coniferous forest zones: the yellow pine-white fir zone, the lodgepole pine-mountain hemlock zone, and so on. Some shrubs occur in all these zones, including such species as greenleaf manzanita, sierra coffeeberry, various currants and gooseberries, and bush chinquapin. For the reader interested in a more detailed summary of our vegetation zones, the best place to start is volume I of Intermountain Flora, by Arthur Cronquist, Arthur Holmgren, Noel Holmgren, and James Reveal. In the discussions to follow, some of the ecological preferences ofour shrubs will be considered, along with some of the reasons why certain species are found where they are. ...