2012-10-18 P1010312 View south towards Big Bald Mountain from White Pine County Route 6 ascending Overland Pass from the east

Pinyon–juniper woodland, also spelled piñon–juniper woodland, is a

biome A biome () is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. In 1935, Tansley added the ...

found mid-elevations in arid regions of the

Western United States The Western United States (also called the American West, the Western States, the Far West, the Western territories, and the West) is List of regions of the United States, census regions United States Census Bureau. As American settlement i ...

, characterized by being an open

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

dominated by low, bushy, evergreen

junipers Junipers are coniferous trees and shrubs in the genus ''Juniperus'' ( ) of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely species distribution, distributed throughout the Northern Hem ...

pinyon pine The pinyon or piñon pine group grows in southwestern North America, especially in New Mexico, Colorado, Arizona, and Utah, with the single-leaf pinyon pine just reaching into southern Idaho. The trees yield edible Pine nut, nuts, which are a sta ...

s, and their associates. At lower elevations, junipers often predominate and trees are spaced widely, bordering on and mingling with

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominance (ecology), dominated by shrubs, often also including grasses, herbaceous plant, herbs, and geophytes. Shrubland may either occur naturally o ...

, but as elevation increases, pinyon pines become common and trees grow closer, forming denser canopies. Historically, pinyon-juniper woodland provided a vital source of fuel and food (particularly piñon nuts) for indigenous peoples of the American Southwest. The nuts continue to be a traditional indigenous food, and because nut-collecting was also adopted by the Spanish in the 1500s, the nuts are also traditionally harvested by some Hispanic communities. pinyon-juniper ecosystems have been under pressure from heavy

natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

extraction in southern Colorado and New Mexico. They have also been historically destroyed by land managers in the United States in favor of livestock pasture, due to a lack of perceived economic value. Pinyon-juniper woodlands also face threats from severe droughts caused or exacerbated by

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

, both through direct damage from heat and lack of moisture and through exacerbated insect attacks and wildfires. In some areas of New Mexico; more than 90% of piñon pines in a woodland have died due to long-term drought and insect attacks. However, in other areas the ecosystem is expanding, and while animals face threats from the woodlands becoming less diverse and productive, it is debated whether pinyon-juniper woodlands are gaining or losing territory overall.

Ecology

Both pinyon pine and juniper species reproduce exclusively through seed production, and produce most of their seeds during mast years, which occur about every three to five years. The seeds produced by the pinyon pines in mast cycles are the primary influence on population growth in the habitat; in lean years some animals move away in a nomadic fashion. Birds and small mammals in the ecosystem are the main distribution method for these seeds. An important example is the pinyon jays, a

keystone species A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in main ...

that is the primary distribution mechanism for pinyon pine seeds, having formed a mutualistic relationship with the trees. These birds are the only species capable of re-establishing pinyon pines after major disruptions like fires and beetle infestations, and according to

Audubon The National Audubon Society (Audubon; ) is an American non-profit environmental organization dedicated to conservation of birds and their habitats. Located in the United States and incorporated in 1905, Audubon is one of the oldest of such org ...

are critical to the ecosystem's survival. Pinyon-juniper woodlands support a number of native species including the

pinyon mouse The pinyon mouse (''Peromyscus truei'') is a species of rodent in the family Cricetidae. It is a species of the genus ''Peromyscus'', a closely related group of New World mice often called "deermice". It is native to the southwestern United Sta ...

and the

pinyon jay The pinyon jay (''Gymnorhinus cyanocephalus'') is a species of jay, and is the only member of the genus ''Gymnorhinus''. Native to Western North America, the species ranges from central Oregon to northern Baja California, and eastward as far a ...

. The woodlands also serve as refuges for desert and mountain animals attempting to escape heat or cold; few animals other than the

stay in the ecosystem year-round. However, it serves as important habitat for a number of endangered species, including Woodhouse's scrub jay and the

gray vireo The gray vireo (''Vireo vicinior'') is a small North American passerine bird. It breeds from the southwestern United States and northern Baja California to western Texas. It is a migrant, wintering in northwestern Mexico, in western Sonora state ...

Subtypes

Pinyon–juniper woodland has three major subtypes based on vegetation: pinyon-juniper savannah, pinyon-juniper wooded shrubland, and pinyon-juniper persistent woodland.

Pinyon-juniper savannah

Pinyon-juniper savannahs are dominated by grasses and

forb A forb or phorb is a herbaceous flowering plant that is not a graminoid (grass, sedge, or rush). The term is used in botany and in vegetation ecology especially in relation to grasslands and understory. Typically, these are eudicots without woo ...

s, with dense undergrowth and savannah-like sparser trees. Monsoon summer rains are common in pinyon-juniper savannahs, since they favor the growth of warm-season grasses. Common grass species are

blue grama ''Bouteloua gracilis'', the blue grama, is a long-lived, warm-season (C4 carbon fixation, C4) Perennial plant, perennial grass, native to North America. It is most commonly found from Alberta, Canada, east to Manitoba and south across the Rocky ...

, other species of grama grass, new mexico

muhly ''Muhlenbergia'' is a genus of plants in the grass family. The genus is named in honor of the German-American amateur botanist Gotthilf Heinrich Ernst Muhlenberg (1753-1815). Many of the species are known by the common name muhly. The greatest ...

, curlyleaf muhly, and needle and thread grass.

Pinyon-juniper persistent woodlands

Pinyon-juniper persistent woodlands are dominated by trees, with a variety of tree ages, often in areas with winter or bi-modal precipitation. Persistent woodland sites are usually unproductive, with thin soils and sparse ground or shrub cover, often occurring on rocky or rugged terrain.

Pinyon-juniper wooded shrublands

Pinyon-juniper wooded shrublands are transition zones where pinyon-juniper woodland is expanding or contracting, often bordering other vegetation types. In absence of fire, they shift from grass and forb-dominated, to shrub-dominated, to tree-dominated communities over time. Common shrub species are

big sagebrush '' Artemisia tridentata'', commonly called big sagebrush,MacKay, Pam (2013), ''Mojave Desert Wildflowers'', 2nd ed., , p. 264. Great Basin sagebrush or simply sagebrush (one of several related species of this name), is an aromatic shrub from the ...

, other species in that genus,

antelope bitterbrush ''Purshia tridentata'', with the common name bitterbrush, is a shrub in the genus ''Purshia'' of the family Rosaceae. It is native to mountainous areas of western North America. Common names include antelope bitterbrush, antelope bush, buckbrus ...

, rabbitbrush,

mountain mahogany ''Cercocarpus'', commonly known as mountain mahogany, is a small genus of at least nine species of nitrogen-fixing flowering plants in the rose family, Rosaceae. They are native to the western United States and northern Mexico, where they grow i ...

, and snakeweed.

Range and species composition

Today, pinyon–juniper woodland range spans from

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, to the eastern

Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

, the

Colorado Plateau The Colorado Plateau is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the Southwestern United States. This plateau covers an area of 336,700 km2 (130,000 mi2) within w ...

, the

Great Basin The Great Basin () is the largest area of contiguous endorheic watersheds, those with no outlets to the ocean, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja Californi ...

, and higher elevations of

Mountain ranges of the Mojave Desert A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

. The woodland's range includes the

Mogollon Rim The Mogollon Rim ( or or ) is a topography, topographical and geological feature cutting across Northern Arizona, the northern half of the U.S. state of Arizona. It extends approximately , starting in northern Yavapai County, Arizona, Yavapa ...

in the south, to its northern extent in the

Snake River Plain The Snake River cutting through the plain leaves many canyons and Canyon#List of gorges, gorges, such as this one near Twin Falls, Idaho The Snake River Plain is a geology, geologic feature located primarily within the U.S. state of Idaho. ...

. It typically occurs at between . Historically, however, the range and elevations of pinyon-juniper woodland have shifted based on differences in climate. On the order of 10,000 years ago during the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

, pinyon-juniper woodlands occurred in areas that today are the Chihuahuan, Mojave, and Sonoran desert lowlands, and since then pinyon-juniper altitude ranges have continued to change based on changing moisture and temperature ranges over time. In the last 200 years specifically, the area occupied by pinyon-juniper woodlands has increased by two to six times. This is attributed to a number of factors, but especially the direct and indirect effects of climate, overgrazing and altered fire regimes. Specifically, the wet period between the 1800s and 1900s boosted tree establishment, and livestock grazing both eliminated perennial grass cover that would hinder tree establishment, and removed fine fuels that could start large fires. Due to its temperature tolerance, pinyon generally does not naturally grow north of northern Utah, as well as some portions of southern Wyoming and Idaho. Pinyon-juniper woodlands prefer areas with cold winters and hot, dry summers. Usually, the habitat experiences freezing temperatures 150 or more days a year, with of annual precipitation, mostly falling as snow.

Arizona and New Mexico

The pinyon–juniper woodland is one of the most prevalent types of

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

ous

woodland A woodland () is, in the broad sense, land covered with woody plants (trees and shrubs), or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunli ...

in northern

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

and

. In Arizona the great basin woodland species are ''Juniperus arizonica, Juniperus californica'' in western Arizona, ''Juniperus deppeana, Juniperus monosperma, Juniperus osteosperma, Juniperus scopulorum'' at higher elevations, ''Pinus monophylla'' var. fallax below the Colorado plateau, and ''Pinus edulis'' on the Colorado plateau. In Arizona the great basin woodland includes many species of oaks: ''Quercus turbinella, Quercus gambelii'' at higher elevations, ''Quercus grisea, Quercus arizonica,'' and ''Quercus emoryi.'' In Southern Arizona, ''Pinus discolor, Juniperus deppeana,'' and ''Pinus leiophylla'' make up the conifer woodland with many oak species.

California

In California, pinyon-juniper woodland is mainly found in pockets on the eastern side of the

, and also somewhat in the

Transverse Ranges The Transverse Ranges are a group of mountain ranges of Southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Ba ...

and

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Pacific Coast Range ...

, as well as several isolated patches on desert mountaintops. In the eastern Sierra Nevada, the habitat forms in the transition zone between the wetter conifer forests to the west and the drier deserts to the east, in the gradient that forms due to the mountains'

rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from body of water, bodies of water (such as oceans and larg ...

. In the eastern Sierra Nevada, the elevation range is in the north, and feet in the southern reaches of the range. Pinyon–juniper woodland requires of annual precipitation, so is generally located above the

sagebrush scrub Sagebrush scrub is a vegetation type (biome) of mid-to-high elevation Western United States deserts characterized by low-growing drought-resistant shrubs including the sagebrush ('' Artemisia tridentata'') and its associates.Karen Wiese, Sierra Ne ...

vegetation type, which can survive on an average of per year. It is located below the

alpine zone Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation, with an associated alpine climate, harsh climate. As the latitude of a location approaches the poles, the threshold elevation for alp ...

. There is often an understory dominated by sagebrush (''

Artemisia tridentata '' Artemisia tridentata'', commonly called big sagebrush,MacKay, Pam (2013), ''Mojave Desert Wildflowers'', 2nd ed., , p. 264. Great Basin sagebrush or simply sagebrush (one of several related species of this name), is an aromatic shrub from the ...

'') and its associates. Co-dominants include Jeffrey Pine (''

Pinus jeffreyi ''Pinus jeffreyi'', also known as Jeffrey pine, Jeffrey's pine, yellow pine and black pine, is a North American pine tree. It is mainly found in California, but also in the westernmost part of Nevada, southwestern Oregon, and northern Baja Calif ...

'') and an understory of sagebrush scrub ('' Artemisia spp.'') or rabbitbrush scrub (''

Ericameria ''Ericameria'' is a genus of North American shrubs in the family Asteraceae. ''Ericameria'' is known by the common names goldenbush, rabbitbrush, turpentine bush, and rabbitbush. Most are shrubs, but one species ''(Ericameria parishii, E. paris ...

'' ''spp.'').

Utah and Canyonlands region

The pinyon–juniper plant community covers a large portion of

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

and the

Canyonlands Canyonlands National Park is a national park of the United States located in southeastern Utah near the town of Moab. The park preserves a colorful landscape eroded into numerous canyons, mesas, and buttes by the Colorado River, the Green Rive ...

region. Singleleaf ash (''

Fraxinus anomala ''Fraxinus anomala'' is a species of ash tree known by the common name single-leaf ash. It is native to the southwestern United States and northern Mexico, where it grows in a number of habitats including desert scrub and chaparral. It is unusu ...

''), and Utah serviceberry (''

Amelanchier utahensis ''Amelanchier utahensis'', the Utah serviceberry, is a species of serviceberry forming a shrub or small tree. It is native to western North America. Description ''Amelanchier utahensis'' is a spreading plant, reaching a maximum of in heigh ...

'') are codominants of pinyon pine and Utah juniper. In this region, the community occurs on rocky soils or jointed bedrock.

Mojave Desert

In the steppes adjoining the

Mojave Desert The Mojave Desert (; ; ) is a desert in the rain shadow of the southern Sierra Nevada mountains and Transverse Ranges in the Southwestern United States. Named for the Indigenous peoples of the Americas, indigenous Mohave people, it is located pr ...

, this vegetation type can be found in areas receiving inches of annual precipitation, and between . Associates include bitterbrush (''

Purshia glandulosa ''Purshia glandulosa'' is a species of flowering plant in the rose family known by the common names antelope bitterbrush, desert bitterbrush, Mojave antelope brush, and cliff-rose. Distribution The plant is endemic to the southwestern United Sta ...

''), Apache plume ('' Fallugia paradoxa''), desert sagebrush (''

''), green ephedra (''

Ephedra viridis ''Ephedra viridis'', known by the common names green Mormon tea, Brigham tea, green ephedra, and Indian tea, is a species of ''Ephedra (genus), Ephedra''. It is indigenous to the Western United States, where it is a member of varied scrub, woodlan ...

''), mountain mahoganies ('' Cercocarpus spp.''), and buckwheats ('' Eriogonum spp.''). In the Mojave, pinyon–juniper woodlands are generally above the

Joshua Tree woodland Joshua ( ), also known as Yehoshua ( ''Yəhōšuaʿ'', Tiberian: ''Yŏhōšuaʿ,'' lit. 'Yahweh is salvation'), Jehoshua, or Josue, functioned as Moses' assistant in the books of Exodus and Numbers, and later succeeded Moses as leader of the ...

s vegetation type, and requires more annual precipitation.

By Major Land Resource Area

Part, though not all, of the range of pinyon-juniper woodlands occurs interspersed with

sagebrush Sagebrush is the common name of several woody and herbaceous species of plants in the genus ''Artemisia (plant), Artemisia''. The best-known sagebrush is the shrub ''Artemisia tridentata''. Sagebrush is native to the western half of North Amer ...

throughout the D-region Major Land Resource Areas, including in D-35, D-36, D-38, and D-39, as well as in the two E-region areas E-49 and E-51.

D-35 (Colorado Plateau)

In the D-35 (Colorado Plateau) region, pinyon-juniper appears in a mosaic with sagebrush ecosystems extending across the region. Understories generally include galleta ('' Hilaria rigida''), blue grama (''

Bouteloua gracilis ''Bouteloua gracilis'', the blue grama, is a long-lived, warm-season ( C4) perennial grass, native to North America. It is most commonly found from Alberta, Canada, east to Manitoba and south across the Rocky Mountains, Great Plains, and U.S. M ...

''), black grama ('' Bouteloua eriopoda''), and western wheatgrass ('' Pascopyrum''). However, differences exist based on soil composition and elevation.

Alkaline In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...

regions at lower elevations include alkali sacaton (''

Sporobolus airoides ''Sporobolus airoides'' is a species of grass known by the common name alkali sacaton. It is native to western North America, including the Western United States west of the Mississippi River, British Columbia and Alberta in Canada, and northern ...

''), Indian ricegrass (''

Oryzopsis hymenoides ''Oryzopsis'' is a genus of Chinese and North American plants in the grass family. Species from this genus are commonly called ricegrass.Stipa ''Stipa'' is a genus of 141 species of large Perennial plant, perennial hermaphrodite, hermaphroditic grasses collectively known as feather grass, needle grass, and spear grass. They are placed in the subfamily Pooideae and the tribe Stipeae, w ...

spp.''), four-wing saltbush (''

Atriplex canescens ''Atriplex canescens'' (or chamiso, chamiza, four-wing saltbush) is a species of evergreen shrub in the family Amaranthaceae (subfamily Chenopodioideae) native to the western and midwestern United States. Description ''Atriplex canescens'' has ...

''), and winterfat (''

Krascheninnikovia lanata ''Krascheninnikovia lanata'' is a species of flowering plant currently placed in the family Amaranthaceae (previously, Chenopodiaceae), known by the common names winterfat, white sage, and wintersage. It is native to much of western North Americ ...

''). Regions with more saline soil include greasewood (''

Adenostoma fasciculatum ''Adenostoma fasciculatum'', commonly known as chamise or greasewood, is a flowering plant native to California and Baja California. This shrub is one of the most widespread plants of the California chaparral ecoregion. Chamise produces a specia ...

'') and shadescale (''

Atriplex confertifolia ''Atriplex confertifolia'', the shadscale or spiny saltbush, is a species of evergreen shrub in the family Amaranthaceae, which is native to the western United States and northern Mexico. Description The height of ''Atriplex confertifolia'' vari ...

'').

D-36 (Southwestern Plateaus, Mesas, and Foothills)

In the D-36 (Southwestern Plateaus, Mesas, and Foothills) region, pinyon-juniper woodland appears in a mosaic gradient with other ecosystems based on elevation. Gambel Oak (''

Quercus gambelii ''Quercus gambelii'', with the common name Gambel oak, is a deciduous small tree or large shrub that is widespread in the foothills and lower mountains of western North America. It is also regionally called scrub oak, oak brush, and white oak. T ...

''), mountain muhly ('' Muhlenbergia montana''), and snowberry (''

Symphoricarpos ''Symphoricarpos'' is a small genus of about 15 species of deciduous shrubs in the family Caprifoliaceae. With the exception of the Chinese coralberry, '' S. sinensis'', which is indigenous to western China, all species are native to North and C ...

spp.'') are interspersed throughout the lower-elevation pinyon-juniper woodlands.

D-38 (Mogollon Transition)

In the D-38 (Mogollon Transition) region, pinyon-juniper woodland is also distributed in an elevation gradient. The pinyon is predominantly Mexican pinyon pine (''

Pinus cembroides ''Pinus cembroides'', also known as pinyon pine, Mexican pinyon, Mexican nut pine, and Mexican stone pine, is a pine in the pinyon pine group. It is a small pine growing to about with a trunk diameter of up to . It is native to western North Am ...

''). Trees and shrubs associated with the ecosystem include Mexican blue oak ('' Quercus oblongifolia''), New Mexico locust ('' Robinia neomexicana''), buckbrush (''

Ceanothus cuneatus ''Ceanothus cuneatus'' is a species of flowering shrub known by the common names buckbrush and wedgeleaf ceanothus. Distribution This '' Ceanothus'' is native to Oregon, California, and northern Baja California, where it can be found in a number ...

''), and manzanita (''

Arctostaphylos ''Arctostaphylos'' (; from "bear" and "bunch of grapes") is a genus of plants comprising the manzanitas () and bearberries. There are about 60 species of ''Arctostaphylos'', ranging from ground-hugging arctic, coastal, and mountain shrub t ...

spp.''). Present in the understory are a diverse range of grass and forb species, including grama, needle-grasses and

jojoba Jojoba (; botanical name: ''Simmondsia chinensis'')also commonly called goat nut, deer nut, pignut, wild hazel, quinine nut, coffeeberry, and gray box bushis an evergreen, dioecious shrub native to the Southwestern United States and northern M ...

D-39 (Arizona and New Mexico Mountains)

In the D-39 (Arizona and New Mexico Mountains) region, pinyon-juniper woodland is distributed in an elevation gradient where pinyon-juniper woodlands are present at mid-elevations, over (in areas with deep soils) areas of grassland. The woodlands dominate north-facing slopes, but on north-facing slopes are intermixed with

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

species and an understory of fescues, blue-grasses, and brome species. Higher elevations are dominated by firs and spruces.

E regions

In the E-49 (Southern Rocky Mountain Foothills) region, pinyon-juniper woodlands are found exclusively in lower elevations in the south. They are mixed with

, mountain mahogany (''

Cercocarpus ''Cercocarpus'', commonly known as mountain mahogany, is a small genus of at least nine species of nitrogen-fixing flowering plants in the rose family, Rosaceae. They are native to the western United States and northern Mexico, where they grow i ...

spp.''), grama and needled grasses, and western wheatgrass. In the E-51 (High Intermountain Valleys) region, pinyon-juniper woodlands occur in a mosaic with shrub-grasslands extending across the region. Patches of pinyon-juniper systems are present in E-47 (Wasatch and Uinta Mountains) and E-48A (Southern Rocky Mountains).

References

Sources

* * {{DEFAULTSORT:Pinyon-juniper woodland Deserts and xeric shrublands in the United States Montane forests Plant communities of the Western United States Plant communities of California Forests of Nevada Natural history of the Mojave Desert