User:Hike395/ecoGreatBasin

Communities

The pattern of basin and range after basin and range in this region results in incredible biological diversity. Across the high desert there are numerous sub-climates correlating to the varied elevations. Heading from the valley bottoms to the mountain peaks, one will encounter constantly changing combinations of plant and animal species making up some 200 distinct biological communities. These communities can be generally grouped into six general communities or “life zones”.

Shadscale zone

Valley bottom at Ash Meadows National Wildlife Refuge

In the lower valley bottoms, where mountain run off evaporates to create saline soils, is the shadscale zone. Plants in this community are adapted to living with very little precipitation, high heat, and saline conditions. The amount of water and the soil type in any one area will determine exactly which plants will live there. Certain areas of the valley floors may harbor no life. These parched areas that flood periodically are called playas. On the shores of the playas, shadscale is the dominant plant, but is kept company by spiny hopsage, winterfat, four-winged saltbrush, and green rabbitbrush. Trees are not found in this community. Big greasewood is the dominant shrub in more saline areas or where the water table is high. These shrubs and associated grasses typically produce abundant small seeds that are harvested by rodents and insects. Ranches and irrigated alfalfa fields form mesic habitats for some non-desert species.

Sagebrush community

Sagebrush in the Virgin Mountains, Nevada

Up from the valley bottoms on the lower mountain slopes and alluvial fans and bajadas, the annual precipitation increases and the shadscale community gives way to the sagebrush community. Areas in this community that have wetter and less saline soils are dominated by big sagebrush. Low sagebrush or black sagebrush dominate areas with steep rocky slopes and shallow soils. Bunchgrasses such as wheatgrass and blue grass usually co-dominate with sagebrush or play a secondary role. Bunchgrass seems to dominate over sagebrush in areas that receive more moisture. Other shrubs commonly found in the sagebrush zone are rabbitbrush, bitterbrush, snowberry and Mormon tea (ephedra).

Pinyon-Juniper community

Pinyon-Juniper woodland in Elko County, Nevada

Continuing up in elevation, you reach the pinyon-juniper community. The main plants in this community are singleleaf pinyon pine and Utah juniper, often with a sagebrush understory. The elevational range of this zone varies, but it is usually found between 6,000 and 8,000 feet (1,800 and 2,400 m), with lower limits determined by lack of moisture and the upper limits determined by temperature. The pinyon-juniper community consists of short evergreen trees that rarely grow over 20 feet in height.

The trees are widely spaced and have an understory of a mixture of shrubs and herbaceous plants, often with nearly bare ground. These characteristics have led this zone to be named the “pygmy forest” by many scientists. The lower end of this zone is dominated by juniper; the middle is a combination of both species, and the upper end is dominated by pinyon.

Montane community

The taller ranges of the Great Basin have a montane community. Due to the great distances created by basins between these small forest habitats, various rock substrates, and local climates, montane forests are tremendously varied across the Great Basin.

A grove of Great Basin bristlecone pines

Isolated from one mountain range to the next, montane communities inthe region have long individual histories, each one affected differently by chance factors of migration over vast expanses of desert. Smaller communities are also vulnerable to adverse affects of climate change and to genetic drift.

White fir, Douglas fir, and ponderosa pines are found in the middle elevations of some mountain ranges, while limber pine, subalpine fir, Engelmann spruce, and bristlecone pines occupy the higher elevations, continuing to the upper tree line. Mountain mahogany often dominates drier, warmer south-facing slopes.

The Bristlecone pine is an important species that is indicative of the Great Basin. Bristlecones live a long time, some for thousands of years. The harsh areas they occupy are often devoid of other plant life, so there is little competition and reduced risk of fire. The trees grow very slowly, producing very dense, disease-resistant wood. These factors contribute to the Bristlecone’s long life.

Alpine community

Some mountain ranges in the Great Basin are high enough to have an alpine community; a community of low growing plants above the treeline. Tree line is generally found above 10,000 feet in the Great Basin, moving downslope with higher latitudes. The plants that grow above treeline are separated from other such areas by miles of foothills and valleys. This “island” phenomenon produces many endemic species - species that have evolved while isolated on a particular mountain peak or range and are found only in that one place. Grasses, sedges, low perennial herbs, and wildflowers grow above tree line.

Riparian community

The riparian communities of the Great Basin cut across all elevations and life zones. In the Great Basin, water is rapidly lost either to the earth or the sky. However, areas around streams where plant life is abundant constitute a riparian area. Water-loving plants like willow, narrowleaf cottonwood, choke cherry, wild rose, and aspen are found along these wet areas. The willow has a spreading root network that allows it to reach all around for water and it also helps streams by slowing erosion.

Endangered species

The topography of the Great Basin (“island” mountain tops separated from one another by vast expanses of desert valleys) renders it vulnerable to extinctions. Populations that occupy the high peaks are isolated from one another; therefore, they cannot interbreed. Small populations are more vulnerable to the forces of extinction - generally small populations have less genetic diversity and therefore a lesser ability to adapt to changing conditions. Groundwater pumping, road and home construction, grazing, and mining are all activities that alter habitat; as more habitat is affected, the threat of extinction increases. The Great Basin is home to many threatened and endangered species:

• Fish
  • Ash Meadows Amargosa pupfish (Cyprinodon nevadensis mionectes)
  • Pahrump kilifish (Empetrichthys latos)
  • Desert dace (Eremichthys acros)
  • Lahontan cutthroat trout (Oncorhynchus clarki henshawi)
• Birds
  • Least tern (Sterna antillarum athalassos)
• Mammals
  • Ash Meadows montane vole (Microtus montanus nevadensis)
• Plants
  • Sodaville milkvetch (Astragalas lentiginosus var. sesquimetralis)
  • Ash Meadows blazing star (Mentzelia leucophylla)
  • Amargosa niterwort (Nitrophila mohavensis)
  • Ute lady’s tresses (Spiranthes diluvialis)