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The Great Basin Desert is part of the Great Basin between the Sierra Nevada and the Wasatch Range. The desert is a geographical region that largely overlaps the Great Basin shrub steppe defined by the World Wildlife Fund, and the Central Basin and Range ecoregion defined by the U.S. Environmental Protection Agency and United States Geological Survey. It is a temperate desert with hot, dry summers and snowy winters.〔(【引用サイトリンク】title=What is the Great Basin? )〕 The desert spans a large part of the state of Nevada, and extends into western Utah, eastern California, and Idaho. The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.〔 Basin and Range topography characterizes the desert: wide valleys bordered by parallel mountain ranges generally oriented north-south. There are more than 33 peaks within the desert with summits higher than , but valleys in the region are also high, most with elevations above . The biological communities of the Great Basin Desert vary according to altitude: from low salty dry lakes, up through rolling sagebrush valleys, to pinyon-juniper forests. The significant variation between valleys and peaks has created a variety of habitat niches, which has in turn led to many small, isolated populations of genetically unique plant and animal species throughout the region. According to Grayson,〔 more than 600 species of vertebrates live in the floristic Great Basin, which has a similar areal footprint to the ecoregion. Sixty-three of these species have been identified as species of conservation concern due to contracting natural habitats (for example, ''Centrocercus urophasianus'', ''Vulpes macrotis'', ''Dipodomys ordii'', and ''Phrynosoma platyrhinos'').〔〔 The ecology of the desert varies across geography, also. The desert’s high elevation and location between mountain ranges influences regional climate: the desert formed by the rain shadow of the Sierra Nevada that blocks moisture from the Pacific Ocean, while the Rocky Mountains create a barrier effect that restricts moisture from the Gulf of Mexico.〔 Different locations in the desert have different amounts of precipitation, depending on the strength of these rain shadows. The environment is influenced by Pleistocene lakes that dried after the last ice age: Lake Lahontan and Lake Bonneville. Each of these lakes left different amounts of salinity and alkalinity. ==Definition and boundaries== The Great Basin Desert is defined by its animals and plants,〔 yet the boundaries are unclear.〔 Scientists have different definitions of the Great Basin Desert, which are often defined by negatives. J. Robert Macey defines the "Great Basin scrub desert as lacking creosote bush."〔 The Great Basin Desert includes several arid basins lacking ''Larrea tridentata'' (chaparral) such as the "Chalfant, Hammil, Benton, and Queen valleys," as well as all but the southeast portion of the Owens Valley. Conversely, the "Panamint, Saline, and Eureka valleys" have creosote bush, unlike the Deep Springs Valley which includes part of the Great Basin scrub desert. The study and definition of ecoregions can also indicate the boundaries of the Great Basin Desert. In 1987, J.M. Omernik defined a desert ecoregion between the Sierra Nevada and Wasatch Range, naming it the "Northern Basin and Range" ecoregion. In 1999, the U.S. EPA renamed the "Northern Basin and Range" to "Central Basin and Range" and the "(Snake River) High Desert" to the "Northern Basin and Range". The World Wildlife Fund adopted the Basin and Range ecoregions from Omernik, but excised a small region of high-altitude areas which contain Holocene refugia, from the former "Northern Basin and Range" ecoregion and renamed it the "Great Basin Shrub Steppe".〔〔 Although the EPA had refined the boundaries of the Central Basin and Range ecoregion by 2003,〔 when USGS geographer Christopher Soulard wrote his reports on the region, his maps used the 1999 boundary for the "Central Basin and Range",〔 which is essentially the same as the "Great Basin Shrub Steppe". He states that the Great Basin Desert is "encompassed within" that area.〔 This article describes the general ecology of the region, including the high-elevation areas, and does not rely on minor differences in the definitions of the ecoregion or desert. See Great Basin montane forests for more specific details on the high-elevation ecoregion. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Great Basin Desert」の詳細全文を読む スポンサード リンク
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