Great Basin Desert

Source: Wikipedia, the free encyclopedia.
Central Basin and Range
Great Basin shrub steppe
cold semi-arid (BSk)
Conservation
Habitat loss90%[3]
Protected76.62%[2]

The Great Basin Desert is part of the

U.S. Environmental Protection Agency and United States Geological Survey. It is a temperate desert with hot, dry summers and snowy winters.[4] The desert spans large portions of Nevada and Utah, and extends into eastern California.[5] The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.[6]

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.[9] 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

Ecoregions as currently delineated by the Environmental Protection Agency[10] and World Wildlife Fund[3]

The Great Basin Desert is defined by its animals and plants,[4] yet the boundaries are unclear.[11]

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

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.[12]

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.[13] In 1999, the U.S. EPA renamed the "Northern Basin and Range" the "Central Basin and Range" and the "(Snake River) High Desert" the "Northern Basin and Range".[14][a] The World Wildlife Fund adopted the Basin and Range ecoregions from Omernik,[15] but excised a small region of high-altitude areas which contain Holocene refugia,[16] from the former "Northern Basin and Range" ecoregion and renamed it the "Great Basin Shrub Steppe".[3][15] Although the EPA had refined the boundaries of the Central Basin and Range ecoregion by 2003,[14][b] when USGS geographer Christopher Soulard wrote his reports on the region, his maps used the 1999 boundary for the "Central Basin and Range",[1] which is essentially the same as the "Great Basin Shrub Steppe".[c] He states that the Great Basin Desert is "encompassed within" that area.[1]

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.

Climate

The climate of the Great Basin desert is characterized by extremes: hot, dry summers and cold, snowy winters; frigid alpine ridges and warm, windy valleys; days over 90 °F (32 °C) followed by nights near 40 °F (4 °C). This is the climate of the high desert.[18]

Orographic uplift resulting in a rain shadow as air descends and compresses, resulting in arid warming on the leeward side of a mountain.

The Great Basin desert climate begins with the Sierra Nevada in

saline lakes via streams, or disappears via evaporation or absorption into the soil.[6][7] The desert is the coldest of the deserts in North America.[6]

On any given day, the weather across the Great Basin desert is variable. The region is extremely mountainous, and the temperatures vary depending on the elevation. In general, temperature

decreases 3.6 degrees F for every 1000 feet gained in elevation. This translates to as much as a 30 °F (17 °C) difference between mountaintops and valley floors on the same day at the same time. In the heat of summer this difference can be even more pronounced. With some exceptions wind generally increases with elevation or altitude and thus strong winds are often encountered on mountain tops and ridges.[18]

This dry climate and rugged topography proves too harsh for many plant and animal species; however, genetic adaptations to these conditions have led to reasonably high species richness within the ecoregion.[7]

The Great Basin National Park, located in a central part of the Great Basin desert, provides perhaps the best example of a typical climate for the region.

Climate data for Great Basin National Park - Lehman Caves Visitor Center (elevation 6,840 feet (2,080 m))
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 67
(19)
66
(19)
74
(23)
81
(27)
91
(33)
97
(36)
100
(38)
96
(36)
93
(34)
83
(28)
77
(25)
67
(19)
100
(38)
Mean daily maximum °F (°C) 40.5
(4.7)
42.8
(6.0)
48.7
(9.3)
56.7
(13.7)
66.5
(19.2)
77.4
(25.2)
85.7
(29.8)
83.3
(28.5)
74.5
(23.6)
61.7
(16.5)
48.4
(9.1)
41.1
(5.1)
60.6
(15.9)
Mean daily minimum °F (°C) 18.9
(−7.3)
21.2
(−6.0)
25.5
(−3.6)
31.5
(−0.3)
40.0
(4.4)
49.0
(9.4)
57.4
(14.1)
55.8
(13.2)
47.0
(8.3)
37.1
(2.8)
25.9
(−3.4)
19.6
(−6.9)
35.7
(2.1)
Record low °F (°C) −20
(−29)
−15
(−26)
−2
(−19)
0
(−18)
6
(−14)
14
(−10)
32
(0)
32
(0)
10
(−12)
6
(−14)
−12
(−24)
−19
(−28)
−20
(−29)
Average precipitation inches (mm) 1.05
(27)
1.18
(30)
1.37
(35)
1.21
(31)
1.24
(31)
0.87
(22)
0.97
(25)
1.18
(30)
1.08
(27)
1.24
(31)
0.97
(25)
0.96
(24)
13.33
(339)
Average snowfall inches (cm) 12.8
(33)
13.8
(35)
13.2
(34)
7.1
(18)
2.1
(5.3)
0.2
(0.51)
0
(0)
0
(0)
0.2
(0.51)
3.7
(9.4)
8.7
(22)
10.7
(27)
72.6
(184)
[citation needed]

Forty Mile Desert, precipitation is rare, and summers are hot, though temperatures are more moderate than those in deserts like the Mojave and Sonoran
, due to the region's higher elevation and latitude. Winters in this section of the basin are still cold, however.

Climate data for Fallon, Nevada. (Elevation 3,960 feet (1,210 m))
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 71
(22)
78
(26)
84
(29)
90
(32)
102
(39)
106
(41)
108
(42)
105
(41)
100
(38)
92
(33)
81
(27)
72
(22)
108
(42)
Mean daily maximum °F (°C) 44.3
(6.8)
51.3
(10.7)
58.9
(14.9)
65.9
(18.8)
73.9
(23.3)
83.1
(28.4)
92.2
(33.4)
90.1
(32.3)
81.1
(27.3)
69.2
(20.7)
55.4
(13.0)
45.4
(7.4)
67.6
(19.8)
Mean daily minimum °F (°C) 18.1
(−7.7)
23.2
(−4.9)
27.8
(−2.3)
33.9
(1.1)
41.4
(5.2)
47.9
(8.8)
54.0
(12.2)
51.4
(10.8)
43.2
(6.2)
33.8
(1.0)
24.8
(−4.0)
18.9
(−7.3)
34.9
(1.6)
Record low °F (°C) −25
(−32)
−27
(−33)
1
(−17)
13
(−11)
20
(−7)
27
(−3)
35
(2)
33
(1)
21
(−6)
12
(−11)
0
(−18)
−21
(−29)
−27
(−33)
Average precipitation inches (mm) 0.54
(14)
0.54
(14)
0.46
(12)
0.51
(13)
0.60
(15)
0.43
(11)
0.16
(4.1)
0.22
(5.6)
0.28
(7.1)
0.41
(10)
0.38
(9.7)
0.48
(12)
4.98
(126)
Average snowfall inches (cm) 1.8
(4.6)
0.9
(2.3)
0.8
(2.0)
0.2
(0.51)
0.1
(0.25)
0
(0)
0
(0)
0
(0)
0
(0)
0.1
(0.25)
0.5
(1.3)
1.3
(3.3)
5.7
(14)
Source: The Western Regional Climate Center[19]

The

cold desert climate. Although still arid, it is worthy to note that this portion of the desert receives more precipitation than the similar playas and salt pans
on the western edge of the Great Basin desert.

Climate data for Knolls, Great Salt Lake Desert, Utah. (Elevation 4,250 feet (1,300 m))
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 63
(17)
63
(17)
79
(26)
87
(31)
98
(37)
104
(40)
106
(41)
103
(39)
99
(37)
89
(32)
71
(22)
66
(19)
106
(41)
Mean daily maximum °F (°C) 36.5
(2.5)
41.4
(5.2)
54.4
(12.4)
62.3
(16.8)
72.3
(22.4)
83.5
(28.6)
92.8
(33.8)
90.9
(32.7)
80.0
(26.7)
64.3
(17.9)
46.5
(8.1)
36.5
(2.5)
63.4
(17.4)
Mean daily minimum °F (°C) 16.9
(−8.4)
19.3
(−7.1)
29.1
(−1.6)
36.6
(2.6)
44.9
(7.2)
54.7
(12.6)
62.1
(16.7)
59.5
(15.3)
48.0
(8.9)
34.4
(1.3)
23.3
(−4.8)
14.5
(−9.7)
37.0
(2.8)
Record low °F (°C) −16
(−27)
−17
(−27)
−1
(−18)
14
(−10)
24
(−4)
35
(2)
43
(6)
39
(4)
25
(−4)
8
(−13)
−3
(−19)
−25
(−32)
−25
(−32)
Average precipitation inches (mm) 0.61
(15)
0.46
(12)
0.91
(23)
1.01
(26)
1.23
(31)
0.68
(17)
0.36
(9.1)
0.31
(7.9)
0.56
(14)
0.77
(20)
0.61
(15)
0.38
(9.7)
7.88
(200)
Average snowfall inches (cm) 0.3
(0.76)
0.1
(0.25)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.1
(0.25)
0.5
(1.3)
Source: The Western Regional Climate Center[20]

Biological communities

The pattern of 'basin and range' with adjacent basins and ranges in this region results in incredible biological diversity. Climate, elevation, soil type, and many anthropogenic variables greatly influence the diversity and distribution of shrubland, grassland, and woodland communities in the desert. 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".[21]

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

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.[21] The soil salinity and lack of moisture in this zone is not very conducive to most agriculture; however, livestock grazing and grain farming have historically contributed to a decline in the already scattered vegetation.[7][22]

Sagebrush zone

Sagebrush in the Virgin Mountains, Nevada

The drop in soil salinity and increase in moisture as elevation increases leads to a transition to sagebrush (

Mormon tea (ephedra).[21]

Pinyon-Juniper community

Pinyon-Juniper woodland in Elko County, Nevada

The

bitterbrush understory.[11] Other species of junipers also occur in this zone, including Juniperus communis and Juniperus occidentalis
.

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.[21] This zone of dense vegetation, made possible by thermal inversions and increased precipitation, is important to a wide variety of isolated animals that rely on this vegetation interface for survival (for example, Eutamias palmeri).[7][11]

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.[21]

Montane community

The taller ranges of the Great Basin desert 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 desert.[21]

Great Basin bristlecone pines

Isolated from one mountain range to the next, montane communities in the 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 effects of climate change and to genetic drift.[21]

Mountain mahogany often dominates drier, warmer south-facing slopes.[21] Pure stands of aspen are also common in this community.[11]

The bristlecone pine is an important species that is indicative of the Great Basin desert. 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.[21]

Alpine community

White Mountain
in California

Some mountain ranges in the Great Basin desert are high enough to have an

sedges, low perennial herbs, and wildflowers grow above treeline.[21]

Riparian community

Riparian habitat in the Trout Creek Mountains of southeastern Oregon

The

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.[21] These plants provide wood for beavers. In this community, silver buffaloberry often provides shelter for North American porcupines.[11]

Subregions

Map of ecoregions in Nevada. Some of the Level IV ecoregions are described in this article.

The U.S.

Environmental Protection Agency defines its Central Basin and Range ecoregion as Level III: it is at the third level of a tree of ecoregions that cover North America. It further defines sub-ecoregions at Level IV, which describe differences in the ecoregion at different locations.[10] The map shows the Level IV EPA ecoregions in Nevada. The low-elevation ecoregions lie in the Great Basin shrub steppe, while the high-elevation ones lie in the Great Basin montane forests (as defined by the WWF).[16]

Salt deserts

The Bonneville Salt Flats, Utah

The Salt desert ecoregion is composed of nearly level

inland saltgrass occur. Soils are not arable and there is very limited grazing potential. The salt deserts provide wildlife habitat and serve some recreational, military, and industrial uses.[25]

Shadscale-dominated saline basins

The Shadscale-dominated saline basins ecoregion is arid, internally drained and gently sloping to nearly flat. These basins are in, or are characteristic of, the

Lahontan and Tonopah playas

A playa in the Black Rock Desert

The nearly level and often barren Lahontan and Tonopah playas contain

sand dunes. This ecoregion has limited grazing potential. Windblown salt dust from exposed playas may affect upland soils and vegetation. The Lahontan and Tonopah playas are important as wildlife habitat, as well as for recreational and military uses.[25]

Lahontan salt shrub basin

The Lahontan salt shrub basin is an expansive dry plain that was once below Pleistocene Lake Lahontan. The

shadscale, other salt-tolerant shrubs, such as Shockley's desert-thorn and Bailey greasewood, cover the lower basin slopes. These shrubs distinguish the Lahontan salt shrub basin and the Tonopah Basin from other Nevada salt shrub ecoregions. Sand dunes may occur where windblown sand accumulates against a barrier; dune complexes support a specialized plant community and diverse small mammal populations. The Carson and Truckee Rivers, originating in the Sierra Nevada, provide water for irrigated farming. Riparian corridors along these rivers support the only trees found in this ecoregion.[25]

Lahontan sagebrush slopes

Lightning-sparked wildfires are common occurrences in the Great Basin desert.

Hills,

cheatgrass tends to replace the shrub community and provides fuel for recurrent fires.[25]

Lahontan uplands

The Lahontan uplands are restricted to the highest elevations of the mountains ranges within the Lahontan salt shrub basin. Slopes vary in elevation from 6,400 to 8,800 feet (2,000 to 2,700 m) and are covered in sagebrush, grasses, and scattered

Indian ricegrass, in the south.[25]

Upper Humboldt Plain

Sagebrush in the Upper Humboldt Plains (13m) ecoregion

The Upper Humboldt Plains ecoregion is an area of rolling plains punctuated by occasional

cheatgrass tends to replace the native grasses and shrubs. Grazing is the major land use, though there is some agriculture near the Humboldt River.[25]

Carbonate Sagebrush Valleys

The basins and semi-arid uplands of the Carbonate Sagebrush Valleys surround the carbonate ranges of eastern Nevada. These valleys are underlain by

blue grama (an indicator of summer rainfall) in the south.[25]

Central Nevada high valleys

The Central Nevada high valleys ecoregion contains sagebrush-covered rolling valleys that are generally over 5,000 feet (1,500 m) in elevation.

shadscale and fewer associated shrubs surround these playas than in other, lower more arid ecoregions in the west, including the Lahontan salt shrub ecoregion and the Tonopah Basin ecoregion. Valleys with permanent water support endemic fish populations, such as the Monitor Valley speckled dace.[25]

Central Nevada mid-slope woodland and brushland

The Central Nevada mid-slope woodland and brushland ecoregion at 6,500 to 8,000 feet (2,000 to 2,400 m) of elevation is analogous in altitudinal range to other woodland areas in Nevada. However, continuous woodland is not as prevalent on the mountains of central Nevada as in other woodland ecoregions, such as ecoregions 13d and 13q. Pinyon-

mountain big sagebrush and curlleaf mountain-mahogany, which straddles the transition between this mid-elevation brushland and the mountain brush zone of the higher Central Nevada Bald Mountains.[25]

Central Nevada Bald Mountains

The Toiyabe Range

The Central Nevada Bald Mountains are dry and mostly treeless. Although they rise only 100 miles (160 km) east of the

limber or bristlecone pines grow on ranges that exceed 10,000 feet (3,000 m). The Toiyabe Range (west of Big Smoky Valley) is high enough to have an alpine zone, but lacks a suitable substrate to retain snowmelt moisture. The isolation of these "sky islands" has led to the development of many rare and endemic plant species.[25]

Tonopah Basin

Big Smoky Valley is part of the Tonopah Basin

The Tonopah Basin lies in the transition between the Great Basin Desert and the more southerly

Railroad Valley tui chub, Pahranagat roundtail chub, Railroad Valley springfish, and the White River springfish are found in valleys with perennial water.[25]

Endangered species

The topography of the Great Basin desert ("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 desert is home to many threatened and endangered species:[21]

See also

Notes

  1. ^ The map on this website illustrates the boundaries of the "(Snake River) High Desert", which had been split off earlier from Ormernik's "Snake River Basin/High Desert".[14]
  2. ^ The Northern Basin and Range ecoregion was extended further east, contracting the eastern portion of the Central Basin and Range to the south, separating it from the Snake River Plain ecoregion.[17]
  3. ^ Both areas correspond to Omernik's Northern Basin and Range ecoregion.

References

  1. ^ a b c Soulard, Christopher E. (2012). "20. Central Basin and Range Ecoregion" (PDF). In Sleeter, Benjamin M.; Wilson, Tamara S.; Acevedo, William (eds.). Status and Trends of Land Change in the Western United States—1973 to 2000. U.S. Geological Survey. Professional Paper 1794–A.
  2. ^ a b c Hoekstra, J. M.; Molnar, J. L.; Jennings, M.; Revenga, C.; Spalding, M. D.; Boucher, T. M.; Robertson, J. C.; Heibel, T. J.; Ellison, K. (2010). Molnar, J. L. (ed.). The Atlas of Global Conservation: Changes, Challenges, and Opportunities to Make a Difference. .
  3. ^ a b c "Great Basin shrub steppe". Terrestrial Ecoregions. World Wildlife Fund.
  4. ^ a b "What is the Great Basin?". National Park Service. Retrieved 2015-07-14.
  5. ^ "Deserts - Great Basin National Park (U.S. National Park Service)".
  6. ^
    OCLC 668191550
    .
  7. ^ a b c d e f g h Public Domain This article incorporates public domain material from Christopher E. Soulard. Land-Cover Trends of the Central Basin and Range Ecoregion (PDF). United States Geological Survey.
  8. .
  9. .
  10. ^ a b Level III and IV Ecoregions of the Continental United States, EPA, archived from the original on 2016-01-23
  11. ^ a b c d e f g Brussard, P.F.; Charlet, D.A.; Dobkin, D.S.; Ball, L.C. (1998). "Great Basin-Mojave Desert Region" (PDF). In Mac, M.J.; Opler, P.A.; Puckett Haeker, C.E.; et al. (eds.). Status and trends of the nation's biological resources. Vol. 2. Reno, Nevada: U.S. Geological Survey. Archived from the original (PDF) on 2007-07-14.
  12. ^ a b Macey, J. Robert (May 28, 1986). The Biogeography of a Herpetofaunal Transition Between the Great Basin and Mojave Deserts (PDF) (Report). Retrieved 2011-11-22. Banta & Tanner (1964) felt that the Great Basin Desert [sic] deserved recognition…and defined it…as the interior drainage lying between the Sierra Nevada and the Wasatch Mountains of Utah. For the purpose of this study I am defining the Great Basin Desert as the high elevation desert that lacks Creosote Bush.
  13. ^ Omernik, James M. (1995). "Ecoregions: a framework for managing ecosystems" (PDF). The George Wright Forum. 12 (1): 35–51.
  14. ^ a b c "Ecoregional Boundaries; Omernik Ecoregions Level 3, Metadata". NV Geospatial Data Browser. EPA. 2003. Archived from the original on 2014-01-12.
  15. ^ .
  16. ^ a b "Great Basin montane forests". Terrestrial Ecoregions. World Wildlife Fund.
  17. ^ "Level III Ecoregions of the Continental United States (revised 2003)" (PDF).
  18. ^ a b c Public Domain This article incorporates public domain material from Climate: Past & Present (PDF). National Park Service. Retrieved 2015-07-20.
  19. ^ "Seasonal Temperature and Precipitation Information". Western Regional Climate Center. Retrieved April 1, 2013.
  20. ^ "Seasonal Temperature and Precipitation Information". Western Regional Climate Center. Retrieved August 28, 2013.
  21. ^ a b c d e f g h i j k l m Public Domain This article incorporates public domain material from Ecology of the Great Basin (PDF). National Park Service. Retrieved 2015-07-13.
  22. OCLC 43401391
    .
  23. .
  24. . Biological Report 28.
  25. ^ a b c d e f g h i j k l Public Domain This article incorporates public domain material from Level IV Ecoregions of Nevada--poster front side (PDF). United States Geological Survey. Retrieved 2015-07-18.
  26. ^ "White River Spinedace (Lepidomeda albivallis)". Nevada Fish & Wildlife Office. U.S. Fish & Wildlife Service.
  27. ^ "Utah prairie dog (Cynomys parvidens)". Nevada Fish & Wildlife Office. U.S. Fish & Wildlife Service. [permanent dead link]

Further reading

  • Trimble, Stephen (1999). The Sagebrush Ocean: A Natural History Of The Great Basin. Reno: University of Nevada Press. .

External links