CA_back_v18_Final to SPN_Feb2016.ai 02/18/2016

The Pluvial Lake Basins ecoregion of northwestern Nevada, northeastern California, 

and south-central Oregon was last filled with water during the Pleistocene Epoch. 

Presently, some basin floor playas seasonally collect and evaporate water. Ecoregion 80d has 

cooler mean annual temperatures than the Lahontan Salt Shrub Basin ecoregion (13j) in Nevada. 

Greasewood, inland saltgrass, and seepweed grow in more alkaline soil, and Wyoming big 

sagebrush, basin big sagebrush, and associated grasses dominate better drained, less alkaline 

soils. The dry lakebeds near the Cascade Mountains have a significant ash layer. The land is 

used for rangeland, and alfalfa is grown on a limited basis in irrigated areas. The California part 

includes Surprise Valley in the north and the Madeline Plains and Grasshopper Valley to the 

south, with elevations mostly ranging from 4,500 to 5,500 feet.

The High Lava Plains ecoregion of southeastern Oregon, northeastern California, and 

northwestern Nevada is part of a vast sagebrush steppe that extends northward to the Blue

Mountains of Oregon. It contains scattered volcanic cones and buttes, and is internally drained. As a

result of this internal drainage, the fish assemblage of Ecoregion 80g lacks an anadromous 

component. Bluebunch wheatgrass generally is associated with Wyoming big sagebrush, except 

where bunchgrasses have been depleted by grazing and replaced by cheatgrass. Scattered 

intermittent lakes and ephemeral pools are characteristic of Ecoregion 80g; they harbor unique 

flora and fauna as do those in the Sierra Nevada-Influenced Ranges ecoregion (13x) to the south.

The Semiarid Uplands ecoregion covers disjunct areas across southeastern Oregon, 

northern Nevada, and northeastern California. It includes hills, low mountains, volcanic 

cones, buttes, and the mid-elevation zones of mountain ranges that rise out of the drier 

Dissected High Lava Plateau (80a) and High Lava Plains (80g) ecoregions. Western juniper, 

mountain sagebrush, and grasses such as Idaho fescue grow on rocky substrates. Elevational 

banding is much less apparent on the mountains of Ecoregion 80j than in Ecoregion 13 to the 

south. The density and extent of juniper woodland varies with long-term climate fluctuations, 

grazing pressure, and fire frequency. Juniper woodland is absent in some of the mountains, but 

mountain brush and scattered aspen groves occupy the woodland zone. In California, the 

ecoregion includes the Skedaddle Mountains and Shaffer Mountain northeast of Honey Lake, 

and the Cottonwood Mountains farther north, with elevations generally ranging from 5,000 to 

7,600 feet. These mountains have some pinyon, juniper, mountain-mahogany, and aspen.

The Imperial/Lower Coachella Valleys ecoregion occurs in the basin of Pleistocene 

Lake Cahuilla. In the Quaternary period, the Colorado River meandered across its delta, 

sometimes flowing north and creating huge inland lakes in the Salton Basin. The deposited silt 

and sediments created rich agricultural soils and, with imported Colorado River water and an 

extensive canal system, cropland dominates the ecoregion’s land cover. The ecoregion mostly is 

below sea level. The Salton Sea is a terminal lake occupying the lowest parts of the Salton 

Trough. The elevation of the ecoregion ranges from about 50 feet above sea level to more than 

225 feet below sea level at the surface of the Salton Sea. With annual precipitation of less than 3 

inches, water levels of the Salton Sea are sustained mostly by agricultural runoff, with some 

municipal effluent and storm water that flows into the sea through rivers and creeks in the 

Imperial, Coachella, and Mexicali Valleys. The Salton Sea area is a complex ecosystem of both 

exotic and endemic species. It has great ecological importance to wintering, migratory, and 

breeding waterbirds in the Pacific Flyway; however, serious problems exist with effects of 

increasing salinity, contaminants, disease outbreaks, and large die-offs of birds.

The Lower Colorado/Gila River Valleys ecoregion includes the low elevation corridors 

along the Colorado and lower Gila Rivers. It is mostly an area of riverine alluvium and 

river- and fan-terraces, and large parts of the ecoregion are in agriculture. Elevations range from 

about 70 feet in the south where the Colorado River leaves Arizona and enters Mexico, to about 

1,000 feet on slopes in the north. The riparian and wetland habitats of the ecoregion have been 

extensively altered. Exotic plants such as tamarisk now cover river banks that once were shaded 

by cottonwoods, willows, and mesquite. Only a few oxbows remain with some freshwater 

marshes and remnants of original riparian vegetation. Creosotebush and white bursage occupy 

most upland areas. Soil temperature regimes are hyperthermic and soil moisture regimes are 

aridic. The climate is almost frost-free and crops include wheat, barley, hay and alfalfa, cotton, 

lettuce, citrus, broccoli, and melons.

The Sonoran Playas ecoregion in California includes the Danby, Ford, and Palen dry 

lake areas in the low elevation basins of Ecoregion 81j. Danby Dry Lake is part of a 

large, northwest-trending structural trough that also includes Bristol and Cadiz Dry Lakes to the 

northwest in Ecoregion 14f. The elevation of Ecoregion 81h is about 600–620 feet. Danby Dry 

Lake is the sump of a large drainage basin that includes Ward Valley and adjacent upland areas. 

Playa lake sediments consist of silt and sand, tend to be orange or light yellowish-brown in color, 

and contain saline layers. The mostly barren cover has some sparse saltbush on the margins. Where 

moisture is sufficient, velvet ash and mesquite occur. Playas are dynamic environments with 

surface channels, playa margins, alluvial materials, and biota changing with each flooding event.

Similar to Ecoregion 81a, the Central Sonoran/Colorado Desert Mountains ecoregion 

is the erosional highlands of exposed bedrock that rise above the more gently sloping 

sediment-filled basins (Ecoregion 81j). Unlike the Western Sonoran Mountains ecoregion (81a), 

these ranges receive more summer precipitation. The rugged terrain is dissected by dry washes 

that can flood during the infrequent rainfall events. The climate is hot, arid, and continental. Soil 

temperature regimes are hyperthermic with a typic aridic soil moisture regime. Soil moisture is 

driest from May to June and intermittently moist during the July–September and 

December–February periods. The vegetation of this mostly rocky terrain typically is Sonoran 

creosotebush scrub transitioning into succulent scrub with ocotillo and numerous cacti. Species 

include creosotebush, white bursage, brittlebush, ocotillo, teddy bear and staghorn cholla, range 

ratany, barrel cactus, and beavertail cactus, with some littleleaf paloverde in the Arizona part.

The Central Sonoran/Colorado Desert Basins ecoregion includes the broad alluvial 

plains, fans, and bajadas that occur between the higher relief mountain ranges of Ecoregion

81i. Large areas of the region are dominated by creosotebush and white bursage. On alluvial 

fans and coarse soils, ocotillo, brittlebush, and cholla occur. Shrub density is low to moderate, 

with shrub spacing from several feet to tens of feet. The Colorado Desert is more sparsely 

vegetated than eastern Sonoran ecoregions (81k, 81l) in Arizona, with a less diverse avifauna. 

Desert saltbush scrub occurs, often on finer textured, poorly drained soils with high alkalinity and

salinity. Allscale is the dominant shrub along with some fourwing saltbush, mesquite, and bush 

seepweed. In the washes and ephemeral streams, mesquite and exotic tamarisk are mixed with 

creosotebush. Microphyll woodland habitat is found along some dry-wash channels, with blue 

paloverde, ironwood, smoke tree, or desert willow, and these plants support a diversity of wildlife.

The Arizona Upland/Eastern Sonoran Mountains ecoregion includes highland areas 

that have more rainfall (7–20 inches annually) than Sonoran Desert mountains farther 

west (Ecoregions 81a, 81i) and have more rain in summer. Most of the ecoregion is in Arizona, 

and it is one of the highest and coldest parts of the Sonoran Desert. Vegetation includes saguaro, 

foothill paloverde, creosotebush, triangle bursage, pricklypear, cholla, nettlespurge, wolfberry, 

bush muhly, threeawns, ocotillo, and globe mallow. The soil temperature regime is thermic and 

soil moisture regime is typic aridic. In California, only the eastern part of the Whipple 

Mountains is in this ecoregion, with about 6–8 inches of annual rainfall. With cliffs, spires, 

natural bridges, and deep canyons, the Whipple Mountains are diverse in elevation and geology 

and contain plant species representative of both the Mojave and Sonoran Deserts. Ecoregion 81k 

is one of the few areas of California that has naturally occurring saguaro cactus.

The Western Transverse Range Lower Montane Shrub and Woodland ecoregion 

provides a transition from the Coast Ranges to the west to the rest of the Transverse 

Range. The ecoregion has similarities to Ecoregion 8e, although the geology here primarily is 

Tertiary and Cretaceous marine sedimentary rock. The climate has more marine influence than 

Southern California Mountain regions farther inland. Elevations range from about 1,000 to more

than 6,000 feet. Some coastal sage scrub occurs at low elevations. Scattered patches of coast live 

oak, canyon oak, Coulter pine, California bay, or bigcone Douglas-fir occur in a mostly 

chaparral-dominated landscape of chamise, ceanothus, manzanita, and scrub oaks, with smaller 

populations of other species such as cherry and birchleaf mountain-mahogany. The region provides 

habitat to the California condor and many other rare or endangered plant and animal species.

The Western Transverse Range Montane Forest ecoregion has two separate areas of 

high-elevation montane forest, with elevations ranging from 5,000 to more than 7,500 

feet. The steep slopes are underlain mostly by Eocene and Cretaceous-age sandstone. Soil 

temperature regimes are mesic and soil moisture regimes are xeric. Annual precipitation is about 

24–28 inches, with less snow in the winter than in Ecoregion 8f to the east. Along with some of 

the conifers at lower elevations, this high-elevation ecoregion contains a more continuous mixed

coniferous forest with Jeffrey pine, sugar pine, white fir, incense cedar, hardwoods such as canyon

live oak, and areas of montane chaparral. There is less ponderosa pine in this ecoregion than 

Ecoregion 8f to the east. In addition to the California condor, the ecoregion supports bird species 

such as the mountain chickadee, white-headed woodpecker, Cooper’s hawk, and golden eagle.

The Arid Montane Slopes ecoregion is diverse, has Mojave Desert influences, and has 

vegetation communities ranging from desert scrub to semi-desert montane chaparral to 

singleleaf pinyon-California juniper woodlands. It stretches along the northern side of the San Gabriel

and San Bernardino Mountains, with elevations about 3,000 to 7,000 feet. The geology is mostly 

granitic and gneissic rocks. There also are areas of carbonate geology (limestone and dolomite) in

the San Bernardino Mountains that provide unique habitat for several endangered endemic plants.

The Southern California Subalpine/Alpine ecoregion includes the highest elevation 

areas, generally 8,500 to greater than 11,000 feet, including peaks such as Mounts San 

Antonio (Baldy), San Gorgonio, and San Jacinto. Mount San Gorgonio in the San Bernardino 

Mountains at 11,502 feet is the southernmost point in California with evidence of glaciation. 

The large distances between these “islands” of high elevation habitat contribute to distinctive 

floras on each major peak. A few endemic alpine plant species occur. Scattered krummholz trees 

grow in some areas. The subalpine areas contain lodgepole pine, limber pine, and white fir. Some 

Sierra juniper occurs along with montane chaparral scrub. Gneiss, schist, and granitic rocks are 

dominant. Annual precipitation ranges from about 36 to 44 inches, and winter snowfall is typical. 

The Southern California Lower Montane Shrub and Woodland ecoregion occurs on 

the igneous-dominated mountains of the eastern Transverse Range and the Peninsular 

Ranges at elevations ranging from about 3,000 to 5,000 feet. The chaparral-dominated landscape

also contains patches of mixed evergreen woodland consisting mostly of bigcone Douglas-fir 

and canyon live oak. These fragmented, compact groves typically occur in deep canyons and on 

steep north-facing slopes. Some minor areas of coastal sage scrub occur near the lower margins, 

although most of that scrub occurs at lower elevations in Ecoregions 85c and 85f. The mosaic of 

land cover and vegetation communities is complex in the Peninsular Ranges. Certain chaparral 

shrubs in the Peninsular Ranges, such as mission manzanita and red shank, have limited ranges in 

southern California and Baja California. Other shrubs, such as California buckwheat, are ubiquitous.

The Southern California Montane Conifer Forest ecoregion occurs on the 

igneous-dominated mountains of the eastern Transverse Range and the Peninsular 

Ranges, at elevations generally ranging from 5,000 to 8,500 feet. These high elevations contain 

a mixed coniferous forest with ponderosa pine, Jeffrey pine, sugar pine, white fir, incense cedar, 

hardwoods such as canyon live oak and black oak, and areas of montane chaparral. Ponderosa 

pine tends to be limited to moist areas with deeper soils, with extensive stands occurring in the 

western San Bernardino Mountains and on the western slope of San Jacinto Mountain. Fires are 

common in these forests, and in San Diego County in 2003, nearly all conifers in the Cuyamaca 

area were burned. Recovery of conifers in these southern areas remains uncertain.

The Northern Transverse Range is a dry, montane ecoregion on the northern side of the 

Transverse Range with elevations ranging from about 3,000 to nearly 7,000 feet. It has 

some similarities to Ecoregion 8c to the east, although here there is more Mediterranean rather 

than Mojavean influence. Transitional areas are influenced more by Ecoregions 6 and 7 to the 

west and north, or by the Tehachapi Mountains ecoregion (5o) to the northeast. Diverse 

vegetation communities occur, including desert scrub, annual grasslands, semi-desert montane 

chaparral, Tucker oak shrubland, blue oak woodlands, and pinyon-juniper woodlands. The geology

includes areas of sandstone and conglomerate, with some granitic and gneissic rocks to the east.

The Cascade Subalpine/Alpine ecoregion contains the prominent volcanic peaks of the high

Cascades. Pleistocene glaciation reshaped the mountains, leaving moraines, glacial lakes,

and U-shaped glacial canyons. Glaciers and permanent snowfields still occur on the highest peaks. 

The vegetation is adapted to high elevations, cold temperatures, short growing season, harsh winds,

and deep winter snow pack. Herbaceous subalpine meadow vegetation and scattered patches of 

mountain hemlock and whitebark pine occur near timberline. In Oregon and Washington, some 

subalpine fir also occurs. Elevations of the ecoregion in California typically are above 7,600 feet.

The High Southern Cascades Montane Forest ecoregion is an undulating, volcanic 

plateau containing isolated buttes, cones, and peaks. Some parts of the region are 

glaciated. The terrain often is less dissected than that of Ecoregion 4f. Elevations of Ecoregion 4e

are generally intermediate to elevations in the Low Southern Cascades Mixed Conifer Forest (4f)

and the Cascade Subalpine/Alpine (4d) ecoregions. In California, elevations of the ecoregion are 

mostly 5,500–8,500 feet, but are lower in Oregon at 4,000–8,200 feet. Cryic soils support mixed 

coniferous forests dominated by mountain hemlock, lodgepole pine, and, in Oregon, some Pacific

silver fir; the soils are colder than the mesic and frigid soils of the Low Southern Cascades 

Mixed Conifer Forest ecoregion (4f). White fir and Shasta red fir also occur in the ecoregion, with 

some grand fir in Oregon. This region has a longer summer drought and more intermittent streams

than the Cascade Crest Montane Forest ecoregion (4c) to the north in Oregon and Washington.

The Low Southern Cascades Mixed Conifer Forest ecoregion generally is lower in 

elevation and less rugged than the more highly dissected Western Cascades Montane 

Highlands (4b) to the north in Oregon. Although still mostly a mesic mixed conifer region, the

climate is drier than in the western Cascades of Oregon (Ecoregions 4a and 4b), and the 

vegetation reflects this. Western hemlock and western redcedar, indicator species of Ecoregions 

4a and 4b, decrease in abundance southward in this ecoregion in Oregon and are replaced by 

Sierra Nevada species, such as incense cedar, white fir, Shasta red fir, and Jeffrey pine that tolerate 

prolonged summer drought. In California, shrubs such as manzanita and ceanothus are common. 

Curl-leaf mountain-mahogany, big sagebrush, and antelope bitterbrush occur as well, with their 

dispersion centers in the Great Basin regions farther east. River and stream discharge is significantly

less than in systems to the north. Soil temperarure regimes are mesic and frigid, and the soil moisture

regime is xeric. Elevations in the California part of this ecoregion are about 3,000 to 7,600 feet.

The California Cascades Eastside Conifer Forest ecoregion is drier than the other 

California Cascades regions. It is dominated by ponderosa pine and, in some areas, 

Jeffrey pine where conditions are harsher. In lower, drier areas, the region blends into the 

western juniper and sagebrush fields more typical of adjacent Ecoregion 9. The region wraps around

to the western side (that is, the Mount Shasta foothills), as similar dry conditions exist from the 

rain shadow cast by the Klamath Mountains to the west. Elevations range from 3,000 to 7,100 feet.

The Southern Cascades Foothills ecoregion of volcanic hills and plateaus is mostly in 

the 2,000–4,000 foot elevation range, stretching from the town of Paradise in the south to 

the Pit River in the north. It contains dry-mesic mixed conifer forest and lower montane black 

oak-conifer forest and woodland. Ponderosa pine is abundant along with some Douglas-fir, and, at 

higher elevations, white fir. Hardwoods typically are black oak and canyon live oak. Soil 

temperature regimes are mostly mesic with some frigid, and soil moisture regimes are xeric.

The Sierran Alpine ecoregion is above tree line and includes the highest elevations of the 

Sierra Nevada. Tree line generally occurs at about 10,500 feet in the southern and central 

areas and at about 9,600 feet in the north. On the eastern side, elevations of the alpine zone may start 

as high as 12,000 feet. Numerous peaks are higher than 14,000 feet. In the harsh climate of this 

region, growing seasons are short and cool, and winters are long, cold, and snowy. Vegetation is 

limited or non-existent on the exposed bedrock, boulder fields, and talus slopes. Cushion plants, 

tufted grasses, alpine willows, sedges, and various shrubs and herbaceous plants occur, as well 

as krummholz forms of high-elevation conifers in the lower alpine zone, such as mountain 

hemlock and whitebark pine. Only a few animals are adapted to this area, such as the American pika,

Belding’s ground squirrel, and yellow-bellied marmot. Soil temperature regimes are mostly cryic.

Above the upper montane forests of Ecoregion 5c, the Northern Sierra Subalpine 

Forests ecoregion is typified by lodgepole pine, whitebark pine, western white pine, and 

mountain hemlock. It mostly lacks the foxtail pine that is found in the Southern Sierra Subalpine 

Forests ecoregion (5k). Elevations generally range from 8,000 to 10,000 feet, although in some 

eastern areas, elevations can start and range higher. With heavy snowfall, high winds, cold 

climates, and shallow soils, trees at high elevations have slow growth rates and are not very large.

The Northern Sierra Upper Montane Forests ecoregion ranges in elevation mostly 

from 6,000 to 8,000 feet, and its forests have a mix of conifers, including red fir, white 

fir, Jeffrey pine, sugar pine, incense cedar, and some lodgepole pine. Intermixed are areas of 

quaking aspen groves. Some montane chaparral also occurs in areas of harsh exposure, repeated 

fires, and clear cuts. Geology types are mostly Mesozoic granitic rocks and Tertiary volcanics, 

although in the north these occur along with some areas of slate, sandstone, metavolcanics, and 

metasedimentary rocks. Soil temperature regimes are mostly frigid, with some cryic. Soil 

moisture regimes are mostly xeric, but are udic in areas where snow persists through spring.

In contrast to the volcanic and granitic rocks of similarly zoned Ecoregion 5g to the 

south, in the Northern Sierra Mid-Montane Forests ecoregion, metamorphic rocks are 

abundant, with Paleozoic metasedimentary argillite, phyllite, and quartzite, and some 

metavolcanics, as well as Mesozoic peridotite and serpentine. Elevations range mostly from 

3,000 to 6,000 feet, with some lower west-end canyon elevations. This higher elevation mixed 

conifer forest has more white fir and Douglas-fir and less ponderosa pine than in the lower 

elevation Ecoregion 5h to the south. Jeffrey pine occurs on ultramafic rocks and some drier 

areas to the east. Black oak and tanoaks are common hardwoods, along with canyon live oak. 

Soil temperature regimes are mostly mesic and soil moisture regimes are mostly xeric.

Generally lower in elevation than adjacent Ecoregion 5d, the Northern Sierra Lower 

Montane Forests ecoregion has a mix of montane hardwood, montane 

hardwood-conifer, and mixed conifer forests. Elevations range mostly from 2,000 to 4,000 feet, 

with a few higher areas. Ecoregion 5e has less ponderosa pine than Ecoregions 5h and 5n to the 

south. Douglas-fir is a more widespread conifer, and hardwoods include canyon live oak, 

interior live oak, black oak, and tanoak. Annual precipitation is somewhat higher than in Ecoregion

5h immediately to the south. Geology is a complex mix of Mesozoic granitic rocks, Jurassic to 

Triassic metavolcanics, and some Mesozoic to Paleozoic metasedimentary and ultramafic rocks.

The Northeastern Sierra Mixed Conifer-Pine Forests ecoregion includes many of the 

drier eastside forests of the northern Sierra Nevada that occur north of Bridgeport, in the 

Lake Tahoe area, and to the northern extent of the Sierra near Susanville. These are mid-elevation 

dry forests, typically between 5,000 and 8,000 feet, with a diverse mix of conifers, such as Jeffrey, 

ponderosa, and sugar pines; incense cedar; and California white fir. The understory can include 

sagebrush, antelope bitterbrush, and a fire-maintained chaparral component of snowbrush and 

manzanita. Soil temperature regimes are frigid and soil moisture regimes are mostly xeric.

The Central Sierra Mid-Montane Forests ecoregion, generally 4,000 to 6,000 feet in 

elevation, has a higher elevation, cooler climate, and a somewhat denser and different 

forest mix than Ecoregion 5h to the west. Although it is aspect-dependent, in general, a more mesic

mixed conifer forest occurs in this region consisting of Douglas-fir; ponderosa pine; and canyon,

live, and black oaks, compared to the abundance of pines, oaks, and chaparral more typical of 

Ecoregion 5h. Bedrock is volcanic (Tertiary andesite and ryholite) and granitic (Cretaceous 

granodiorite and quartz monzonite) in contrast to Ecoregion 5d to the north that has more 

metamorphic rock. Gently sloping Neogene-age lahars and lava flows cap some of the older 

plateau surfaces. Soil temperatures are mesic and some frigid and soil moisture regimes are xeric.

Similar to the higher Ecoregion 5d, the Central Sierra Lower Montane Forests

ecoregion has abundant metamorphic rocks, mostly Paleozoic metasedimentary argillite 

and quartzite, as well as some Jurassic slate and graywacke, and minor areas of Mesozoic 

peridotite and serpentine. Elevations here are mostly lower than Ecoregions 5d and 5g, 

generally 2,000–4,000 feet with a few higher elevation areas. Soil temperature regimes are 

mostly mesic and soil moisture regimes are xeric. Ponderosa pine and gray pine occur, with 

more mixed conifer forest at high elevations. Montane hardwood forests may include canyon 

live oak, interior live oak, black oak, or areas of shrubby tanoak. Lower montane mixed 

chaparral occurs in many areas, with manzanita, chamise, ceanothus, and other shrubs.

The Eastern Sierra Great Basin Slopes ecoregion comprises the very steep eastern 

slope of the Sierra Nevada. It tends to have more conifers and sagebrush, in contrast to 

the sparser Mojave Desert scrub typical of Ecoregion 5j to the south. Singleleaf pinyon pine and 

sagebrush are common, with some areas of bitterbrush and Utah juniper. Some Jeffrey and 

lodgepole pines occur at high elevations. Soil temperature regimes are mostly mesic and frigid. 

Soil moisture regimes are mostly xeric in the north to aridic in the south.

The Eastern Sierra Mojavean Slopes ecoregion on the eastern low slopes of the Sierra 

Nevada is a transitional area to the Mojave Basin and Range ecoregion (14). Elevations 

range mostly from 4,000 to 6,000 feet. Many of the steep slopes are bare or have some desert 

scrub and can include blackbrush and some Joshua trees as well. There is less sagebrush and 

juniper than in the Eastern Sierra Great Basin Slopes ecoregion (5i) to the north. Soil temperatures 

are mesic, with thermic at lowest elevations, and soil moisture regimes are mostly xeric.

Located above the upper montane forests of Ecoregion 5l, and below the alpine zone of 

Ecoregion 5a, the Southern Sierra Subalpine Forests ecoregion is typified by 

lodgepole pine, whitebark pine, western white pine, mountain hemlock, foxtail pine, and, on the 

eastern side, limber pine. Elevations generally range from 9,000 to 11,000 feet, although in 

some eastern areas, elevations can range from about 10,000 to as high as 12,000 feet.

The Southern Sierra Upper Montane Forests ecoregion is typically found in the 

7,000–9,000 foot elevation range on the western slope of the southern Sierra Nevada. 

Vegetation, from low to high elevations in this range, primarily is mixed conifer, white fir, and red 

fir forests. In some harsher or drier areas, especially to the east, Jeffrey pine and lodgepole pine 

occur. Some montane chaparral is found throughout the region. Soil temperature regimes are 

mostly frigid, but some high peaks may be cryic. Soil moisture regimes are mostly xeric. Soils 

have udic moisture regimes where snow persists through spring. Most of the runoff flows to the 

Tuolumne, Merced, San Joaquin, Kings, Kaweah, Tule, or Kern Rivers. 

The Southern Sierra Mid-Montane Forests ecoregion comprises the mid-elevations of 

the western slope of the southern Sierra Nevada. Elevations typically are in the 5,000–7,500

foot range, and slightly higher to the south. Soil temperature regimes are mostly mesic. Soil 

moisture regimes are xeric. Common vegetation includes ponderosa pine forests at low elevations 

and mixed conifer forest at high elevations. Some Jeffrey pine occurs in the eastern part of the 

region. Ecoregion 5m also contains most of the giant sequoia groves in the Sierra Nevada. 

Sequoias are not drought-tolerant and are limited to mesic sites with sufficient moisture. 

The Southern Sierra Lower Montane Forest and Woodland ecoregion is lower in 

elevation, warmer, and drier than adjacent Ecoregion 5m. The oak woodlands and 

chaparral-covered hills of the low elevations transition to forest and woodlands dominated by 

ponderosa pine. Elevations typically are between 3,000 to 5,000 feet, but can range from near 2,500

to almost 6,000 feet. Geology is almost all Mesozoic granite, granodiorite, and quartz monzonite. 

Soil temperature regimes are mesic to some thermic and soil moisture regimes are xeric.

The Tehachapi Mountains form a connecting highland link from the core of the Sierra 

Nevada ecoregion (5) to the Transverse and Coast Ranges of Ecoregions 8 and 6. Although

rugged topography and geology of the Tehachapi Mountains ecoregion have similarities to the 

southern Sierra Nevada, the diverse vegetation of this region reflects its biogeographic crossroads 

position and the influences from the Sierra, desert, oak woodlands, and grasslands that surround 

it. The vegetation includes large areas of oak savanna (with blue oak, gray pine, and some valley 

oak) that are intermixed with junipers, yuccas, and other species from adjacent ecoregions. Steep 

canyons and slopes contain canyon live oak and interior live oak, as well as chamise, ceanothus, 

and singleleaf pinyon. Some minor areas of ponderosa or Jeffrey pine also occur. Soil temperature 

regimes are thermic and mesic and soil moisture regimes are xeric and aridic.

The Western Sonoran Mountains ecoregion includes the erosional highlands of exposed

bedrock that rise above the more gently sloping sediment-filled basins (Ecoregion 81c). 

The terrain is dissected by dry washes that can flash flood during the infrequent rainfall events. 

The mountains in this western ecoregion receive less summer precipitation than the ranges in 

Ecoregions 81i and 81k to the east. The vegetation of this mostly rocky terrain typically is Sonoran

creosotebush scrub transitioning into succulent scrub with numerous ocotillo and cacti. There is 

some Mojavean as well as Peninsular Range influence compared to Sonoran mountain ranges to 

the east. Ocotillo, white bursage, teddy bear cholla, range ratany, barrel cactus, brittlebush, 

staghorn cholla, beavertail cactus, yucca, jojoba, Mormon tea, and a few juniper are present. 

Spring annual forbs include fiddleneck, popcorn flower, desertbells, and desert mariposa lily.

The Western Sonoran Mountain Woodland and Shrubland ecoregion, at the western 

edge of the Sonoran Desert, is a montane transition region that occurs generally above 

3,000 feet in elevation, as one ascends into the Peninsular Range toward Ecoregion 8. It includes 

parts of the Santa Rosa Mountains in the north, several mountainous parts of the Anza-Borrego 

area, and parts of the In-Ko-Pah and Jacumba Mountains in the south. Among the granitic 

boulders, desert chaparral as well as singleleaf pinyon and California juniper occur. A few canyon

live oaks occur near the western margin. In some steep canyons, native fan palm oases are 

found. These mountainous slopes provide habitat for a population of Peninsular bighorn sheep.

The Western Sonoran Basins ecoregion includes the alluvial plains, fans, and bajadas 

that occur between the higher relief mountain ranges of Ecoregions 81a and 81b. The 

region of rolling terrain and some badlands of the Anza Borrego and Yuha Desert areas slopes to 

the east toward the Salton Sea and Imperial Valley. These basins have some similarities to 

Ecoregion 81j to the east, although this western ecoregion receives less summer precipitation. 

Much of this area is underlain by Late Miocene to Latest Pleistocene marine and non-marine 

sandstones and mudstones of the Palm Springs Formation. Alluvium, colluvium, and lacustrine 

deposits are thicker in the eastern, gently sloping part of the ecoregion and thinner in the western 

part where tectonic forces have uplifted Palm Springs Formation deposits to the surface where 

they form incised badland topography. Soils typically are sandy to gravelly loam in texture and 

highly permeable, with high potential for wind erosion. Sonoran creosotebush scrub covers large 

areas of the ecoregion. On alluvial fans and coarse soils, ocotillo, brittlebush, and cholla occur. 

Shrub density varies from low to moderate, with shrub spacing from several feet to tens of feet. 

Some desert saltbush scrub occurs on fine-textured, poorly drained soils with high alkalinity and 

salinity. In the washes and ephemeral streams, mesquite and nonnative tamarisk are mixed with 

creosotebush. Microphyll woodland habitat is found along some dry-wash channels. In these 

washes, blue paloverde, ironwood, smoke tree, or desert willow occur, and these additional 

vegetation species support a diversity of wildlife. Fauna of the ecoregion include reptiles such as 

the desert flat-tailed horned lizard, side-blotched lizard, desert iguana, zebra-tailed lizard, and 

Colorado Desert sidewinder, and mammals such as the black-tailed jackrabbit, desert cottontail, 

California ground squirrel, coyote, and desert kit fox.

The Sand Hills/Sand Dunes ecoregion occurs in California, Arizona, and Baja California,

and is one of the largest dune complexes in North America. In California, it includes 

lower elevation sandy areas of East Mesa as well as the higher elevation Algodones Dunes to the 

east. East Mesa has more stabilized aeolian deposits, possibly because of groundwater rises 

from human modifications of the hydrology. The wind-blown sand originated from the former 

beach deposits and lakebed of Pleistocene Lake Cahuilla to the west. This is one of the driest 

and hottest areas of the United States, with annual precipitation of only about 3 inches. The 

well-drained aridic soils are mostly Typic Torripsamments with hyperthermic temperature 

regimes. Although vegetation appears sparse on the dunes and sand hills, the ecoregion contains 

the largest number of dune-endemic plants in North America, as well as several specialized 

animal species. Psammophytic (“sand loving”) scrub occurs in the interior part of the sand dune 

system, both in the active sand dunes and partially stabilized areas. Some microphyll woodland, 

Sonoran desert scrub, and canal-influenced vegetation also occurs. Peirson’s milk-vetch, a 

federally listed threatened plant, is found here, along with Wiggins’ croton and the Algodones 

Dunes sunflower. The flat-tailed horned lizard, desert tortoise, and Colorado Desert fringe-toed 

lizard occur in the ecoregion, and the dunes provide habitat for the Andrews’ dune scarab beetle. 

The ecoregion includes areas managed for wilderness as well as for off-road vehicle recreation. 

The Upper Coachella Valley and Hills ecoregion is surrounded by mountains, except 

to the south where it descends toward the agricultural lands and Salton Sea of Ecoregion 

81f. Alluvial deposits cover most of the ecoregion, mantled by sand deposits in some areas. On 

the northeastern side of the San Andreas Fault, some sandstone and conglomerate underlie the 

low, rolling Indio Hills and Mecca Hills. Elevations range from sea level in the southeast to 

about 1,800 feet in the Mecca Hills. Soil temperatures are hyperthermic and soil moisture 

regimes are aridic. In some of the canyons of the Indio Hills, native California fan palms occur. 

In sandy areas, the Coachella Valley fringe-toed lizard is one of several animal and plant species 

threatened or endangered because of habitat loss. The southwestern part of the ecoregion is 

mostly urbanized in the Palm Springs/Palm Desert area. It is a transitional desert region with 

some affinities to the Mojave Basin and Range ecoregion (14) to the north.

sea level to more than 2,500 feet. It has more relief and coniferous forest than the Marin Hills 

ecoregion (6o). Various types of coniferous and hardwood forests occur, composed mostly of 

Douglas-fir, redwoods, tanoak, madrone, California bay, and coastal live oak. Mount Tamalpais 

and Bolinas Ridge force moisture out of the air as it cools and ascends the steep western 

mountain faces. These western parts are heavily forested with redwoods and Douglas-fir. A few 

areas of drier exposures or shallow soils contain grasslands, coastal scrub, or chaparral.

The Fort Bragg/Fort Ross Terraces ecoregion forms an elevated coastal plain that has 

less relief (200–800 feet) than the adjacent mountains of Ecoregion 1k. Quaternary and 

Tertiary sandstones and mudstones form the terraces, and some areas are deeply dissected, 

forming ravines that expose Cretaceous sedimentary rocks. Elevations range from sea level to 

about 1,300 feet. Soil moisture regimes are udic and some aquic, and soil temperatures are 

isomesic. Monthly and annual temperature variations are minimal and summer fog is common. 

Vegetation includes coastal grasslands and shrubs, stunted beach pine, Bishop pine, or pygmy 

cypress, along with areas of some grand fir and western hemlock. Terrace soils typically are 

unsuitable for redwoods, although they do occur in ravines and on some bluffs.

The Point Reyes/Farallon Islands ecoregion includes the Point Reyes Peninsula, 

Bodega Head and the sand spit at the north end of Bodega Bay, and the offshore 

Farallon Islands. The maritime climate is temperate and humid, with frequent fog. There are 

granitic rocks along with Pliocene and Miocene sandstone and mudstone, and Quaternary sands. 

Soil temperature regimes are mostly isomesic, with some mesic. Soil moisture regimes are 

mostly ustic. Common vegetation includes Douglas-fir, tanoak, Bishop pine, coast live oak, 

Pacific reedgrass, and coyote brush. A few redwoods occur. Most of the streams are small, and 

dry by the end of the summer. The Farallon Islands, about 20 miles southwest of Point Reyes, 

are a group of small granitic islands providing important habitat for seabirds, seals, and sea lions.

The Santa Cruz Mountains ecoregion covers the western and southwestern parts of the 

range where vegetation includes redwood, Douglas-fir, tanoak, coast live oak, and 

California bay, along with some chaparral and coastal scrub species. The shrub layer under 

forest canopy generally is sparse. Species of limited range in this area include the Santa Cruz 

cypress and Shreve oak. Forests of this region are ecologically and genetically distinct from 

those of the redwood ecoregions (1i, 1k) farther north. Clear-cut logging was typical from the 

late 1800s to about the 1960s. Most logging now uses smaller selective cuts. Climate varies 

from the west to the east, as the high mountain ridges reduce the penetration of maritime air. 

Winters are cool and wet. On the western side, summers are cool, and fog or low overcast is 

typical. Soil temperature regimes are mostly mesic and isomesic, with some thermic. Soil 

moisture regimes are mostly ustic and xeric. Streams on the northeastern side of the mountains 

generally are dry during the summer, but streams on the seaward side generally are perennial. 

The San Mateo Coastal Hills ecoregion has lower relief and elevations than Ecoregion 

1n, with more coastal scrub vegetation and a few small areas of cropland rather than the 

denser forest and woodland of the Santa Cruz Mountains ecoregion (1n). Marine terraces, 

coastal benches, and small valleys are the primary landforms. Elevations range from sea level to 

about 1,000 feet. Pliocene sandstone and siltstone are the main rock types compared to the mix 

of geology in Ecoregion 1n that includes older sedimentary and some igneous rocks. Mollisols 

are typical, with mostly thermic to isomesic temperature regimes. Soil moisture regimes are 

mostly xeric and ustic. Summer fog is common and winters are cool and moist.

The Coastal Lowlands ecoregion contains beaches, dunes, and marine terraces below 

400 feet in elevation. Wet forests, lakes, estuarine marshes, and tea-colored (tannic) 

streams are characteristic features of the landscape. Wetlands have been widely drained with 

many converted to dairy pastures. Residential, commercial, and recreational developments are 

expanding in the coastal corridor. In California, the region includes the Crescent City Plain, and 

Humboldt Bay Flats and Terraces. Soil moisture regimes are udic and aquic and soil 

temperatures are isomesic. Dune communities, grassland, coastal scrub, beach pine, bishop pine,

and Sitka spruce are more typical than the redwoods in adjacent Ecoregion 1i. Riparian areas 

contain red alder, conifers, bigleaf maple, salmonberry, rhododendron, and willows.

The low mountains of the Northern Franciscan Redwood Forest ecoregion lie entirely in

the coastal fog zone and are characteristically covered by fog-dependent coast redwoods 

and Douglas-fir. Historically, unbroken redwood forests occurred and moderated local climate 

by trapping coastal fog and producing shade. The combination of shade, root competition, 

young soils with a deep organic debris layer on the soil surface, occasional fire, and silting by 

floods limits the number of plant species. The region extends north only about 10 miles into 

Oregon near Brookings. In some factors, this region has more similarities to the temperate rain 

forests of the Oregon and Washington Coast Ranges than to redwood forest regions to the south. 

Dominated by conifers, the region also includes western hemlock, western redcedar, Port Orford 

cedar, grand fir, and some Sitka spruce near the coast. Hardwoods such as red alder and tanoak 

occur. Fine and fine-loamy, isomesic, Ultisols and Alfisols are typical.

In contrast to the redwood forests to the north and south, the vegetation of the King 

Range/Mattole Basin ecoregion includes a mixed evergreen forest of Douglas-fir, 

tanoak, and madrone, as well as areas of grassland. Prairies and coastal scrub cover many of the 

headlands. Although this is one of the wettest spots in California, the King Range rises above the

coastal fog. In summer, warm, dry, offshore winds also help keep the fog away, making the King 

Range too dry to support the redwood forests that surround it on three sides. The King Range 

thrusts 4,000 feet above the Pacific, making this area one of the more spectacular and remote 

stretches of coastline in the continental United States. In the northern part of the region, the Bear 

and Mattole Rivers drain a hilly-to-steep landscape of mixed evergreen forest, with a land cover 

that includes a relatively greater amount of annual grasslands than in Ecoregions 1i to the north 

or 1k to the south. Timber production, livestock grazing, and recreation are primary land uses.

The main part of the Coastal Franciscan Redwood Forest ecoregion extends through 

Mendocino County from just south of the King Range to just south of the Russian River 

in Sonoma County. Unlike the conifer-dominated forests of Ecoregion 1i to the north, these 

central redwood forests typically are more a mixture of conifers and hardwoods. Vegetation 

includes a multi-story canopy of redwood, Douglas-fir, tanoak, bigleaf maple, evergreen shrubs, 

and various grasses. In the southern parts of the region, there are more coast live oaks and 

grassland savannas that are intermixed with denser areas of forest. The near-coastal part of the 

region that is influenced more by fog has more redwoods and similarities to Ecoregion 1i to the 

north. Soil temperature regimes are mostly isomesic and mesic. Soil moisture regimes are 

predominantly udic, ustic, and xeric. Runoff is rapid and many of the smaller streams are dry by 

the end of the summer. Natural lakes are absent. A small outlier of the region occurs in the south in 

Marin County that includes the coniferous and hardwood forests of Mount Tamalpais and Bolinas 

Ridge. This small area of redwoods and other forest types ranges in elevation from

The Tuscan Flows ecoregion is a gently southwest-sloping plateau with some steep 

canyons and a few steep volcanic cones. Although the region is geologically related to the 

southwestern end of the Cascades ecoregion (4), it has ecosystem similarities to the Sierra Nevada 

foothills part of Ecoregion 6. Blue oak woodlands, annual grasslands, and foothill pine occur.

The Northern Sierran Foothills consist of moderately steep to steep mountains and hills 

at the western foot of the northern and central Sierra Nevada. The Melones Fault Zone is 

in this unit. Geology is a complex mix of mafic volcanics, granodiorite, slate and graywacke, 

argillite and quartzite, and some ultramafic bands of peridotite and serpentinite. The soil 

temperature regime is thermic and soil moisture regime is xeric. Common vegetation includes 

needlegrass and annual grasslands, chamise, manzanita, interior live oak, ceanothus, blue oak, and 

foothill pine. Runoff is rapid; streams drain to the Feather, Sacramento, and San Joaquin Rivers.

The moderately steep hills and low mountains of the Southern Sierran Foothills

ecoregion represent a transition from the Central California Valley (7) to the Sierra Nevada

(5). Ecoregion 6c is somewhat warmer and drier than Ecoregion 6b to the north, but not as arid as 

Ecoregion 6ae to the south. The soil temperature regime is thermic and soil moisture regime is 

xeric. Vegetation includes blue oak, needlegrass and annual grasslands, chamise, ceanothus, mixed

oaks, and foothill pine. Woodlands increase in the high elevation and eastern parts of the region.

The Camanche Terraces are on gently sloping to moderately steep hills and dissected 

terraces along the eastern edge of the Central California Valley (7) downslope from the 

central Sierra Nevada foothills. Sandstone, andesitic conglomerate, rhyolitic tuff, and some clay 

underlie the major terraces, in contrast to the metamorphic and igneous bedrock of Ecoregion 6b 

to the east and the younger alluvium of Ecoregion 7a to the west. The soil temperature regime is 

thermic and soil moisture regimes are xeric and aquic. Needlegrass and annual grasslands are 

common, along with some blue oak, vernal pool habitats, and cottonwood and willow near streams.

The Tehama Terraces ecoregion forms a dissected plain between the coastal hills to the 

west and the western margin of the Sacramento Valley. Quaternary alluvial and colluvial 

materials overlie slightly consolidated Pliocene sandstone and conglomerate. The soil 

temperature regime is thermic and soil moisture regime is xeric. Common vegetation includes 

blue oak; needlegrass dominates on some fine-textured soils, and vernal pools are common.

The Foothill Ridges and Valleys ecoregion includes ridges, steep hills, and narrow 

valleys in the interior northern California Coast Ranges. It extends from the Vaca 

Mountains and Blue Ridge in the south, to the Bald Hills in the north near the Klamath Mountains 

(78). Ecoregion 6f is at a higher elevation and more hilly than Ecoregions 6e and 6h to the east, but

lower elevation and drier than ecoregions to the west. Soil temperature regime is thermic and soil 

moisture regime is xeric. Vegetation includes purple needlegrass, blue oak, chamise, and foothill pine. 

The North Coast Range Eastern Slopes ecoregion is located along the steep, 

north-trending eastern edge of the Northern Coast Range mountains with sedimentary and 

ultramafic rocks. It has more relief and higher elevations than Ecoregion 6f to the east, with mostly

chaparral vegetation compared to the grassland and blue oak to the east. It has few conifers 

compared to the higher elevation Ecoregion 78r to the west. The disjunct southern unit of the 

region between Clear Lake and Lake Berryessa has a complex pattern of Mesozoic sedimentary, 

metasedimentary, metavolcanic, and ultramafic rocks. Elevations range from about 450 feet near 

Lake Berryessa to the high point 3,196-foot Brushy Skyhigh, and relief is mostly 500–1,200 feet. 

Vegetation includes leather oak on serpentine soils, chamise on other shallow soils, and mixed 

conifer on deeper, mesic soils. Some hills contain McNab or Sargent cypress or some foothill and 

knobcone pine. Areas of blue oak woodland occur in low elevation, flatter areas. All but the larger 

streams are dry through most of the summer. Soil temperature regimes are mostly thermic, but are 

mesic on some north-facing slopes and at high elevations. Soil moisture regimes are xeric. 

The Western Valley Foothills/Dunnigan Hills ecoregion consists of the Dunnigan Hills, 

English Hills, Capay Valley, and other low hills or terraces adjacent to the western margin 

of the Central California Valley ecoregion (7). Elevations range from 150 feet in the south to nearly

1,000 feet in the northwest, and relief is mostly 200–300 feet. Soil temperature regimes are thermic

and soil moisture regimes are xeric. Common vegetation series include needlegrass grasslands 

and some areas of blue oak. All but the larger streams are dry through most of the summer. 

The Clear Lake Hills and Valleys ecoregion is a relatively low elevation area of the 

northern Coast Ranges, surrounded by ecoregions with higher elevation hills and mountains

and greater relief. Elevations are 1,300–2,400 feet. Clear Lake, a large, shallow eutrophic lake, 

occupies a large part of the region. Much of the terrestrial part of the region, especially to the west, 

occurs on nearly level to gently sloping Quaternary sediments on terraces, alluvial fans, and basin 

fill. Some cropland, orchards, and vineyards occur in this ecoregion. Soil temperature regimes are 

mostly thermic. Soil moisture regimes are mostly xeric, with some aquic moisture regimes in 

alluvium around Clear Lake. Vegetation includes blue oak and needlegrass, with chamise and 

chaparral on hills to the east. The lake’s hydrology and nutrient balance have been greatly altered, and

sediment volumes and mercury concentrations are high due to mining activities in the watershed.

The Mayacmas Mountains ecoregion is an interior coastal range that contrasts with the 

Ukiah/Russian River Valleys (6l) to the west and Clear Lake Hills and Valleys (6i) to the 

east. The mountains rise to more than 3,900 feet in elevation. The geology is a continuation of the 

Cretaceous and Jurassic Franciscan Complex sedimentary and metasedimentary rocks found in 

Ecoregion 78m to the north, along with some Mesozoic metavolcanics. Soil temperature regimes 

are thermic and soil moisture regimes are xeric. Annual grasslands and montane hardwoods are at 

low elevations, with mixed chaparral higher on the hills. Some blue oak woodland occurs, as well 

as patches of Sargent or McNab cypress. Scattered Douglas-fir grows in more mesic areas.

The Napa-Sonoma-Lake Volcanic Highlands ecoregion has two separate units. In the 

north, in Lake County, the region includes the volcanic terrain around Mount Konocti and 

the mostly volcanic terrain that extends to the southeast. Its Quaternary volcanic geology of 

rhyolite, andesite, and dacite differs from the Franciscan Complex geology of Ecoregion 6j to the 

west and from the abundance of ultramafic rocks of adjacent Ecoregion 6g. The unit in the south 

in Napa and Sonoma Counties has mostly Tertiary volcanic geology. Elevations in the ecoregion 

range from about 500 feet in the south to the high points of 4,286-foot Mount Konocti, 4,343-foot 

Mount St. Helena, and 4,722-foot Cobb Mountain. Soil temperature regimes are mostly thermic, 

but are mesic on some north-facing slopes and at high elevations. Soil moisture regimes are xeric. 

The vegetation mosaic includes mixed chaparral, mixed hardwoods (including coast live oak, 

madrone, and California bay), and some areas of Douglas-fir or pines and cypress.

The Napa-Sonoma-Russian River Valleys ecoregion is lower, flatter, more populated, 

and has more cropland, vineyards, and orchards than the surrounding more mountainous 

ecoregions (6j, 6k, and 6m). The Ukiah/Russian River valley in the north has less marine influence

and fog than the valleys to the south. Quaternary alluvium covers large parts of the region, along 

with some other areas of older, loosely consolidated sedimentary material. The southern valleys of

the North Coast Range include the Napa, Sonoma, Petaluma, and Cotati Valleys, and the Santa 

Rosa Plain. Elevations range from about 20 feet near the river deltas and bay flats of Ecoregion 6p

to more than 500 feet in the northern hilly margins. Grape vineyards are extensive, as well as some 

areas of orchards or specialty crops. The southern low elevation parts of the valleys have more marine 

influence and fog than the high elevation northern parts, affecting grape varietals and production.

Located inland from the wetter, denser redwood and coniferous forests of Ecoregion 1k, 

the Sonoma-Mendocino Mixed Forest ecoregion is characterized primarily by a mixed 

hardwood forest. It includes tanoak, black oak, madrone, Oregon white oak, Douglas-fir, and only a 

few small areas of redwoods. Annual grasslands and chaparral also occur in the mosaic. The geology

includes Tertiary sandstone and shale, as well as some Cretaceous and Jurassic Franciscan 

Complex metasedimentary rocks. Most streams in Ecoregion 6m drain east to the Russian River.

The Bodega Coastal Hills ecoregion has less relief than Ecoregion 6o to the south, with 

Pliocene sandstone and mudstone compared to the Cretaceous and early Tertiary 

sedimentary material to the north and south, or to the younger Quaternary alluvium in Ecoregion 

6l to the east. It is mostly all grassland and coastal scrub, compared to the hilly woodland of the 

Marin Hills ecoregion (6o) to the south or to the forest of Ecoregion 1k to the north.

The Marin Hills ecoregion consists of mountains and hills between San Francisco Bay 

and the San Andreas Fault. Soil temperature regimes are mostly mesic and thermic, with 

some isomesic. Soil moisture regimes are mostly xeric. Vegetation is mostly coast live oak, annual 

grasslands, coastal scrub, and some tanoak and Douglas-fir. Ecoregion 6o has less relief and 

coniferous forest than Ecoregion 1k. Most of the smaller streams are dry by the end of the summer. 

The Bay Flats ecoregion includes the near-water flats around San Pablo Bay in the north 

and those at the southern end of San Francisco Bay. Elevations are sea level to about 10 feet

on Quaternary bay fill of silt and clay. High tides inundate most of the area. Soil temperature 

regimes are isomesic and soil moisture regimes are aquic. Common vegetation includes 

pickleweed and saltgrass. The southern part of the ecoregion is warmer and drier than the northern 

part, and has less summer fog. The southern part receives 14–16 inches of annual precipitation, 

whereas the northern part receives 20–28 inches. Several salt evaporation ponds are found in the 

southern Bay Flats, where saltwater is impounded within levees in the former tidelands. As the water 

evaporates, microorganisms of several kinds change the color of the water. Restoration efforts are 

underway to return some salt ponds to a mix of tidal marsh, mudflat, and other wetland habitats.

The low-elevation Suisun Terraces and Low Hills ecoregion occurs on mostly 

Quaternary alluvium, surrounding Suisun Bay, upland from the lower part of the Delta 

(7j). A few low hills occur, such as the Portrero Hills and Montezuma Hills. Ecoregion 6q is 

mostly an urban or urbanizing region, and includes the cities of Fairfield, Concord, Pittsburg, and 

Antioch. The Montezuma Hills are mostly non-native grasslands, used for grazing and wind farms.

The East Bay Hills/Western Diablo Range ecoregion consists of the East Bay Hills to 

the east of the Berkeley-Oakland-Hayward urban area, Mount Diablo and the Black Hills 

area farther east, as well as the hills of the western Diablo Range. Soil temperature regimes are 

thermic, with some mesic on northern slopes. Soil moisture regimes are xeric. Common 

vegetation series include coast live oak, blue oak, valley oak, and chamise. All but the larger 

streams are dry through the summer. In the urban/suburban areas, eucalyptus and other flammable 

exotic vegetation present fire-management concerns.

The San Francisco Peninsula ecoregion occurs at the northern end of the peninsula, with 

a climate affected greatly by the marine influence. It is cooler than much of adjacent 

Ecoregion 6t, and fog is common. Soil temperature regimes are mostly isomesic, with some 

thermic on the bay side. Some metamorphosed sedimentary and volcanic rocks occur, but large 

areas are covered by Quaternary marine and sand dune deposits, with recent alluvium and large 

areas of fill on the bay side. There are some small serpentine outcrops and bluffs. Natural 

vegetation consisted of California oatgrass, purple needlegrass, coast live oak, California bay, 

dune communities, and some saltmarsh species. Some rare and endangered plant species persist. 

Like Ecoregion 6t, the San Francisco Peninsula ecoregion is nearly all urbanized.

The Paso Robles Hills and Valleys ecoregion is a dissected plain with low, rolling to 

moderately steep hills. It is lower, drier, and has less relief than the adjacent Ecoregions 6ai

and 6al. The rolling hills are underlain by Plio-Pleistocene nonmarine sediments, with areas of 

Quaternary alluvium on the flatter plains. Some small areas of Miocene and Pliocene marine 

sediments occur. The soil temperature regime is thermic and soil moisture regime is xeric. 

Common vegetation includes blue oak savannas and annual grasslands. Some valley oak occurs 

on deep soils and a few small areas of chamise chaparral are found on shallow or dry soils. 

Ranching and livestock grazing is a dominant land use, with some pasture, hay, and cropland in 

the valleys. Grape vineyards have become more extensive in the ecoregion. 

In contrast to the igneous and metamorphic rocks of the Gabilan Range ecoregion (6y) to 

the northwest, the Salinas-Cholame Hills ecoregion occurs on Pliocene and Miocene 

marine and nonmarine sediments, as well as Plio-Pleistocene unconsolidated sedimentary 

materials. These hills are less steep than Ecoregion 6y, the soils tend to be more calcareous, and 

there is more grassland and blue oak woodland and fewer coastal oaks. The soil temperature regime

is thermic and soil moisture regime is xeric. Elevations range mostly from 600 to 2,600 feet.

Occupying an alluvial-filled synclinal basin, the Cuyama Valley ecoregion consists of 

alluvial fans, pediments, and terraces along the Cuyama River. The semi-arid climate has hot

summers and cool winters, with only about 5 inches of annual precipitation. Land cover is mostly 

grassland, hay and pastureland, and some cropland. Some oil field activities occurred in the past. 

On the transitional slopes leading to Ecoregion 8, juniper, chaparral, and blue oak woodland occur.

Elevations range from about 1,600 feet in the northwest to 3,400 feet on the southern boundary.

The Carrizo Plain ecoregion is a nearly level to very gently sloping alluvial plain with low

hills on the margins. Although the ecoregion is in the Coastal Ranges, the climate is arid 

with long dry summers, similar to a desert basin. Average annual precipitation is only 7–9 inches 

per year. Runoff from the surrounding coastal mountains and hills flows in ephemeral drainage 

channels to Soda Lake, a terminal alkali lake. The inflow is lost to evaporation, leaving behind 

concentrated salts and minerals. The soil temperature regime is thermic and soil moisture regimes 

are aridic and xeric. Vegetation includes annual grassland, needlegrass, saltgrass, and emergent 

aquatics. Ecoregion 6an is one of the largest areas of native grassland remaining in the State. It is 

home to several endangered wildlife species, including the San Joaquin kit fox, San Joaquin 

antelope squirrel, and the blunt-nosed leopard lizard. Tule elk and pronghorn antelope have been 

reintroduced to the area. Some livestock grazing occurs, but remains a controversial issue.

The narrow, south-facing Santa Barbara Coastal Plain and Terraces ecoregion consists 

of beaches, terraces, and alluvial slopes that occur at the foot of the Santa Ynez Mountains 

of Ecoregion 8a. Elevations range from sea level to 1,000 feet. Many of the Tertiary and 

Quaternary terraces are uplifted, folded, and faulted, and the numerous active or potentially active 

faults pose an earthquake hazard. Large areas are in urban and residential land cover. The steep 

slopes and landslide deposits along the foothills of the Santa Ynez Mountains, along with 

chaparral and introduced vegetation, present wildfire and development issues. Ecoregion 85a has 

less cropland than Ecoregion 85b to the east, but a few small areas of citrus, avocados, or specialty 

crops occur. There are onshore and offshore oil and gas production activities.

The Oxnard Plain and Valleys ecoregion occurs on nearly level floodplains and gently 

sloping alluvial fans and terraces in the valleys of the Santa Clara River and Calleguas 

Creek. Its landforms, alluvial geology, and land use contrast with the mountains of Ecoregion 8 to 

the north and the Venturan-Angeleno Coastal Hills ecoregion (85c) to the south and east. The hot, 

subhumid climate is modified greatly to moderately by marine air; early summer fog is common. 

The soil temperature regime is thermic and soil moisture regime is xeric. Vegetation historically 

included coastal sage scrub, coast live oak, and brome and needlegrass grasslands. Most of the 

natural vegetation has been replaced by cropland, citrus orchards, and urban and residential uses. 

The Santa Clara River drains much of the ecoregion and is perennial; Calleguas Creek is ephemeral.

The Venturan-Angeleno Coastal Hills ecoregion includes the Santa Monica Mountains, Simi

Hills, Oak Ridge, Verdugo Mountains, San Rafael Hills, Chino Hills, Puente Hills, San Jose

Hills, and the hills of the Palos Verdes Peninsula. These shrub-covered hills and mountains, with 

elevations ranging from sea level to more than 3,000 feet, contrast with the adjacent heavily urbanized

flat plains and valleys. Mesozoic and Tertiary sedimentary rocks and some Miocene volcanics occur. 

In the Santa Monica Mountains, climate is modified greatly on the southern side by marine air, 

whereas climate on the northern side and on inland hills is affected more moderately by marine air. 

Annual precipitation ranges from 14 to 26 inches. Soil temperature regimes are thermic and soil 

moisture regimes are xeric. Vegetation includes annual grassland, California sagebrush, California 

buckwheat, mixed sage, chamise chaparral, mixed chaparral, and coast live oak. There are some 

differences in coastal sage communities and species compared to those found to the north in 

Ecoregion 6, as well as to those in the southern parts of Ecoregion 85 in San Diego and Baja California.

The Los Angeles Plain ecoregion is on nearly level floodplains and terraces and very 

gently to gently sloping alluvial fans that include the San Fernando and San Gabriel 

valleys. Marine air influence is great on the Los Angeles Plain and moderate in the San Fernando 

Valley. Annual precipitation ranges from 10 to 17 inches. The soil temperature regime is thermic and

soil moisture regime is xeric. Typical vegetation historically included California sagebrush, California 

buckwheat, coast live oak, chamise chaparral, and annual grasslands, although most all of the region

has been converted to urban and residential land cover. Hydrology has been greatly modified and 

channelized. The Los Angeles River drains the San Fernando Valley and San Gabriel Mountains. 

The Diegan Coastal Terraces ecoregion inlcudes nearly level to gently sloping dissected 

marine terraces, and a narrow strip of beach and dune sand along the coast from Newport 

Beach south into Mexico’s Baja California. The ecoregion is modified greatly by oceanic influence. 

Soil temperatures are thermic and soil moisture regime is xeric. Vegetation is mostly coastal sage 

scrub, with maritime succulent, Diegan coastal sage scrub, and chaparral communities. California 

sagebrush, California buckwheat, black sage, ceanothus, coast live oak, and annual grasslands occur. 

A few vernal pools remain, as well as a small coastal stand of rare Torrey pines. Runoff is rapid

except from undissected terraces with vernal pools. Urban and suburban land cover is widespread.

The Diegan Coastal Hills and Valleys ecoregion consists of coastal terraces and some 

moderately steep to steep foothills along the western side of the Peninsular Ranges from 

the Santa Ana River southeast to the Mexican border. It is cut by numerous canyons and a few 

wide valleys. It has more elevation and relief than Ecoregion 85e to the west, and less elevation 

and relief than Ecoregion 85g to the east. Tertiary and some Cretaceous sedimentary rocks occur, 

along with Mesozoic granitic rocks to the south and east. The climate is modified greatly by 

oceanic influence. The soil temperature regime is thermic and soil moisture regime is xeric. 

Vegetation includes coastal scrub and chaparral, annual and perennial grasslands, and some small 

pockets of coastal oak woodlands. Although not as urbanized as Ecoregions 85d and 85e to the west, 

some parts of the ecoregion have experienced rapid urban and suburban growth in recent decades. 

The Rogue/Illinois/Scott Valleys ecoregion supports Oregon white oak and California 

black oak woodland, ponderosa pine, and grassland. As in most developed valleys, 

vegetation is greatly altered, with only a few remnants of oak savanna, prairie vegetation, or seasonal

ponds remaining. Land cover includes pastureland, cropland, orchards, grassland, and developed,

with patches of woodland mostly near the margins. In California, the Scott Valley is a nearly level

alluvial basin along the Scott River, with mesic soil temperatures and aridic soil moisture regimes.

The Serpentine Siskiyous ecoregion is lithologically distinct from the rest of Ecoregion 78.

Many plants have difficulty growing in its serpentine soils because of a shortage of calcium

and high amounts of magnesium, nickel, and chromium. As a result, vegetation often is sparse and

composed of specialist species. The dissected mountainous region covers diverse areas and plant 

communities. Jeffrey pine and endemic oak, ceanothus species, and many forbs have evolved to 

grow in the potentially toxic and nutrient-poor serpentine soils. Douglas-fir and western white pine

also occur, especially coastward. Historical mining continues to cause some water-quality issues.

The forested Inland Siskiyous ecoregion occurs in Oregon with only two small areas 

extending across the California border. It is higher and more mountainous than 

neighboring foothill and valley ecoregions (78a, 78b, and 78c). Ecoregion 78e has a higher fire 

frequency, less annual precipitation, and longer summer droughts than the Coastal Siskiyous 

ecoregion (78f) to the west. Forest cover in Ecoregion 78e is a diverse and multi-layered mix of 

conifers, broadleaf evergreens, and deciduous trees and shrubs in contrast to the predominantly 

coniferous forests in the Coast Range (1) or Cascades (4) ecoregions.

The Klamath River Ridges ecoregion has a dry, continental climate and receives about 

25–35 inches of precipitation annually. Higher altitudes and north-facing slopes have 

Douglas-fir and white fir; lower elevations and south-facing slopes are mostly ponderosa pine 

and western juniper, species that are more drought-resistant than other vegetation types found in 

Ecoregion 78. Some Oregon white oak occurs, and canyon live oak can grow on steep rocky 

slopes. Ecoregion 78g has less precipitation, more sunny days, and a greater number of cold, clear

nights than the Inland Siskiyous ecoregion (78e) to the northwest in Oregon or the western Klamath

Mountains in California. Mesic soil temperatures and xeric soil moisture regimes predominate.

The Border High-Siskiyous ecoregion consists of relatively high elevation mountains along

the border area of Oregon and California. Elevations range from about 5,000 to greater 

than 7,000 feet, with a high point of 7,533 feet at Mount Ashland, Oregon. Soil temperature regimes

are predominantly frigid, with some cryic at high elevations and soil moisture regimes are xeric. 

White fir and red fir forests occur, with some Jeffrey pine on ultramafic rocks, and a few areas of 

subalpine habitats. With a large western to eastern extent, conditions are slightly drier to the east.

The Western Klamath Low Elevation Forests ecoregion is at elevations generally less 

than 3,500 feet. Douglas-fir and Port Orford cedar occur on lower slopes, grading into 

Douglas-fir and tanoak, or higher areas with canyon live oak. Red and white alder are typical

along streams. Mixed oak stands occur on drier sites. The ecoregion generally is wetter and has 

a somewhat denser forest landscape than the drier Ecoregion 78k to the east.

The Western Klamath Montane Forests ecoregion generally is higher than Ecoregion 

78i, with elevations typically ranging from 3,500 to 6,900 feet. Annual temperatures are 

cooler than in Ecoregion 78i, and precipitation is greater. Soil temperature regimes are mostly 

frigid, with some mesic at low elevations and soil moisture regimes are xeric. The vegetation 

consists mostly of Douglas-fir and white fir forests, with some red fir forests at high elevations. 

Ecoregion 78j lacks the serpentine geology of nearby Ecoregion 78d, and is composed mostly of 

Mesozoic quartz diorite, with areas of Jurassic slate, graywacke, shale, and sandstone.

The Eastern Klamath Low Elevation Forests ecoregion is geologically and botanically

diverse, and has some drier forests than the Western Klamath Low Elevation Forests (78i)

to the west. Elevations generally are less than 3,500 feet. Forest and woodland types can include 

areas of Douglas-fir, ponderosa pine, canyon live oak, and knobcone pine, along with chaparral 

of chamise, deer brush, and manzanita. Along streams, cottonwoods, white alder, and willows 

occur. Soil temperatures are mesic to near thermic and soil moisture regimes are mostly xeric. 

Typically at elevations greater than 4,000 feet, the Eastern Klamath Montane Forests

ecoregion includes a mosaic of forest and chaparral types. It often has more open tree 

canopies and understories than western Klamath regions. White fir, incense cedar, Douglas-fir, 

ponderosa pine, and sugar pine are dominant, with mountain dogwood in the understory. Some 

minor areas of Shasta fir or red fir occur at high elevations. Black and canyon live oaks mix with 

scattered conifers on drier sites, with understories of huckleberry oak and other chaparral species.

The Marble/Salmon Mountains-Trinity Alps ecoregion includes the Salmon Mountains,

Marble Mountains, and Trinity Alps in the montane elevations mostly from 3,500 or 4,000 

feet to about 7,000 feet. The rugged region has steep slopes and numerous canyons and narrow 

mountain valleys. Granitic, metavolcanic, and metasedimentary rocks occur, including some 

areas of serpentinized peridotite. Soil temperature regimes are predominantly frigid and soil 

moisture regimes are xeric. The climate is colder than surrounding lower elevation ecoregions 

78g, 78i, and 78k. Forests include Douglas-fir, white fir, and at high elevations, red fir. 

The Scott Mountains ecoregion is dominated by ultramafic rocks with Mesozoic mafic 

intrusions, along with some granitic rocks near the Trinity Alps and at Castle Crags. 

Elevations generally range from 3,000 to 7,000 feet. Soil temperature regimes are mostly frigid, with

some mesic at low elevations and soil moisture regimes are xeric. Ecoregion 78n has more ultramafic

rocks and less precipitation than Ecoregion 78m to the west. Vegetation includes Jeffrey pine, mixed

conifer, and white fir. The ecoregion drains to the Trinity, Sacramento, Scott, and Shasta Rivers. 

The Klamath Subalpine ecoregion is higher, wetter, and colder than surrounding areas, 

with elevations generally greater than 6,800 feet. Most of the region was glaciated, shown 

by the numerous cirques, moraines, and other glacial features. Shasta red fir, mountain hemlock, 

and some western white pine occur, as well as subalpine meadows with various mixes of shrubs, 

herbs, and grasses. Some foxtail pine occurs as well as small areas of Pacific silver fir to the north. 

Soils tend to be thin and rocky, across various bedrock types including granitics, gabbro, and 

ultramafic rocks. Soils deepen downslope and have cryic with some frigid soil temperature regimes.

The Duzel Rock ecoregion is slightly lower in elevation with less relief than Klamath 

Mountain ecoregions immediately north or south, and it has more juniper and big sagebrush,

along with scattered woodland. Ponderosa pine, Oregon white oak, and areas of Jeffrey pine occur.

Some Douglas-fir is found at higher elevations and on northern slopes. Curl-leaf mountain-mahogany

is common in the western and southern parts. The geology is mostly Cambrian through Devonian 

metasedimentary and minor metavolcanic rocks including metamorphosed conglomerate, 

sandstone, shale, chert, limestone, and basalt. Soil temperature regimes are mesic with some frigid 

at high elevations and soil moisture is xeric. The region drains to the Scott and Shasta Rivers. 

Just inland from the redwood forests of Ecoregion 1, the Outer North Coast Ranges

ecoregion occurs in the central part of the northern California Coast Ranges. It is 

characterized by high rainfall and mixed evergreen and mixed hardwood forests including 

Douglas-fir, tanoak, Oregon white oak, and some needlegrass grasslands. Some redwood occurs 

in areas closest to the coast. Mountain peaks are lower in elevation than those in the High North 

Coast Ranges ecoregion (78r) to the east. Soil temperature regimes are predominantly mesic, with 

some thermic in the southern part of the region and soil moisture regimes are xeric. Landslides occur

frequently in this region, and high sediment loads occur in streams and rivers. All but the larger 

streams are dry by the end of the summer. Natural lakes are absent, but there are a few reservoirs.

The High North Coast Ranges ecoregion includes the high elevation part of the northern 

California Coast Ranges that are far enough inland that the Pacific Ocean has little influence

on climate. The ecoregion has more winter snow and more montane and subalpine coniferous forest

than Ecoregion 78q to the west. Cretaceous sandstone, mudstone, blueschist, and metasedimentary

rocks are typical. Elevations range mostly from 3,000 to 7,000 feet, with a high point of 8,092 feet 

at Mount Linn. Common vegetation includes mixed conifer and Douglas-fir forests, along with 

tanoak. White fir forest and some red fir occur at high elevations. Soil temperature regimes are 

predominantly mesic, with some frigid and minor areas of cryic and soil moisture regimes are 

almost exclusively xeric. All but the larger streams are dry through much of the summer. 

higher elevations, ponderosa pine, Jeffrey pine, Washoe pine, aspen, and white fir are common. 

Streams on the western side of this fault-block mountain drain to Goose Lake or the Pit River, 

and streams on the eastern side, which are much shorter, drain to Surprise Valley in Ecoregion 80.

The High Elevation Warner Mountains ecoregion is a subalpine/alpine area that ranges

in elevation from about 7,800 to 9,892 feet at Eagle Peak. This high-elevation zone 

contains aspen and lodgepole pine, with whitebark pine as the primary subalpine and timberline 

tree above about 8,500 feet. Drought-tolerant alpine cushion plants also occur. Soil temperature 

regimes are cryic. Annual precipitation is about 28–32 inches with deep winter snow.

The small Likely Tableland ecoregion is a gently sloping footslope west of the Warner 

Mountains (9m). Relief is only about 100–300 feet. Elevations range from 4,500 to 5,500

feet. The sagebrush and grassland of Ecoregion 9o contrast with the adjacent higher relief hills and

mountains of Ecoregion 9p that have abundant pinyon-juniper woodland and some pine. Annual 

precipitation is only 12–15 inches. The Quaternary andesite and basalt are younger than the Tertiary

volcanics of Ecoregion 9p. Some perennial streams cross the region from the Warner Mountains 

to the Pit River. Soil temperature regimes are mesic and moisture regimes are aridic and xeric. 

The Modoc/Lassen Juniper-Shrub Hills and Mountains ecoregion is a faulted and 

eroded volcanic plateau with many volcanic hills and mountains. Soil temperature 

regimes are mesic and frigid. Soil moisture regimes are mostly xeric and aridic. Vegetation is 

mainly western juniper, big sagebrush, and perennial bunchgrasses. On the higher-elevation 

mountains, however, some small areas of Jeffrey pine, ponderosa pine, and white fir occur. There

are few streams and most of those are dry during summer. Streams that flow from the ecoregion

drain to either the Pit River, the Madeline Plains, or in the south, to the Honey Lake Valley.

The Adin/Horsehead Mountains Forest and Woodland ecoregion consists of 

mountains to the north, east, and south of Big Valley. Elevations range from about 5,000 

to 7,036 feet. Ecoregion 9q has more pine and mixed conifer forest than the drier Ecoregion 9p to

the east or the adjacent lower Ecoregion 9r. Soil temperature regimes are frigid and mesic and soil

moisture regimes are mostly xeric. Vegetation is a mix of Jeffrey pine, ponderosa pine, and some 

white fir, and at low elevations, western juniper, big sagebrush, birchleaf mountain-mahogany, 

and other deciduous shrubs. There are a few streams and springs, but almost no lakes.

The Adin/Dixie Low Hills ecoregion consists of hills and lava plateaus to the west of 

Ecoregion 9q that are lower in elevation (4,000–6,000 feet) with less relief. The 

vegetation is mostly big sagebrush, low sagebrush, and scattered junipers, and generally lacks 

the pine of the nearby mountain ecoregions (9q, 4g). Soil temperature regimes are mesic and soil 

moisture regimes are xeric. Some streams cross the ecoregion to the Pit River, and several small 

shallow reservoirs occur here. Ranching and livestock grazing are predominant land uses.

The Modoc Lava Flows and Buttes ecoregion is a volcanic plateau surrounding the 

Medicine Lake Highlands of the Cascades ecoregion (4). It is lower and drier than those

highlands, with more juniper and pine. Soil temperature regimes are mesic and soil moisture 

regimes are aridic and xeric. Vegetation includes western juniper, big sagebrush, and native 

perennial grassland. Water drains down through joints in the basalt rock to the groundwater 

reservoir, limiting overland flow of water and development of stream channels on the plateau.

The Old Cascades ecoregion is composed of foothills and low mountains of middle 

Tertiary volcanic rocks north of Mount Shasta and extending up the Klamath River in 

Oregon. Soil temperature regimes are mesic and soil moisture regimes are xeric. Big sagebrush 

and other shrublands are widespread, with some Oregon white oak north of the Klamath River 

and on north-facing slopes. Some ponderosa pine and mixed conifers occur on north-facing 

slopes at high elevations. Wedgeleaf ceanothus and native grassland communities are common 

on south-facing slopes at low elevations. Water drains to the Klamath River.

The Klamath/Goose Lake Basins ecoregion covers river floodplains, terraces, and lake 

basins. Various wildrye, bluegrass, hairgrass, sedge, and rush species once covered the 

basins, but most of the wet meadows and wetlands have been drained for agriculture. Sagebrush 

and bunchgrass occur on most of the upland areas. Several marshland wildlife refuges here are 

critical to preserving the regional biodiversity, particularly for at-risk bird and fish species. In 

California, Butte Valley also is included in the ecoregion. Although the Butte Valley area differs 

somewhat from the Lower Klamath and Tule Lake Basins, it also has pasture and cropland.

The Fremont Pine/Fir Forest ecoregion occurs mostly in Oregon, with a small area west 

of Goose Lake in California. It contains mid-elevation mountains and high plateaus that 

rarely exceed timberline. Closed-canopy forests contrast with the savanna of the Klamath Juniper 

Woodland/Devils Garden ecoregion (9j). Ponderosa pine is widespread, but white fir, sugar pine, 

lodgepole pine, and incense cedar also grow at elevations greater than 6,500 feet and on northern 

slopes. Residual soils are common in contrast to ecoregions farther north in Oregon where residual

soils have been buried by pumice and ash. Ecoregion 9h has a high density of lakes and reservoirs.

Only a small arm of the Southern Cascades Slope ecoregion occurs in California, with 

most of it extending to the Upper Klamath Lake in Oregon. It is a transitional zone between

the Cascades (4) and the drier Eastern Cascade Slopes and Foothills (9). Ecoregion 9i is lower in 

elevation and moister than Ecoregion 9h, and it has a greater mix of forest types. Ponderosa pine 

woodland becomes mixed with white fir, incense cedar, Shasta red fir, and Douglas-fir at high elevations.

The Klamath Juniper Woodland/Devils Garden ecoregion is composed of undulating 

hills, benches, and escarpments covered with a mosaic of rangeland and woodland. 

Western juniper grows on shallow, rocky soils with an understory of low sagebrush, mountain big 

sagebrush, bitterbrush, and bunchgrasses. Other shrubland/grasslands include shrub species 

uncommon in eastern Oregon, such as woolly mule-ears, Klamath plum, and birchleaf 

mountain-mahogany. The diverse shrublands provide important wildlife habitat. Reservoirs dot 

the landscape and are important to lowland irrigation. Soil temperature regimes in the California 

part of Ecoregion 9j are mesic, whereas soil temperatures in the Oregon part are mesic and frigid. 

The Devils Garden place name appears on topographic maps in both States, 60 miles apart.

The semi-arid Shasta Valley ecoregion is located in the rain shadow of the Klamath 

Mountains (78) to the west and the Cascades (4) to the east. Quaternary alluvium occurs 

along with small hills of Tertiary volcanic rocks protruding through the alluvium. Quaternary 

debris avalanche flow deposits and Quaternary basalt flows also occur. Nearly level to moderately 

sloping floodplains, terraces, and alluvial fans are found here along with undulating lava flows and

many small, moderately sloping to steep hills on the alluvial plain. Elevations range from about 

2,500 to 3,700 feet. Soil temperature regimes are mesic and soil moisture regimes are aridic, xeric, 

and aquic. Big sagebrush, western juniper, annual grasslands, and sedge meadow communities are 

the main vegetation types. Most streams and rivers originate in adjacent mountain ecoregions. Lake

Shastina is a large reservoir, and other small ponds occur in the region. Agriculture is affected by 

local springtime flooding and a short growing season, restricting crops to pasture, alfalfa, small 

grains, and some limited field crops. Cattle production is a prominent land use of the region.

The Pit River Valleys ecoregion consists of low areas along the Pit River with large areas 

of Quaternary alluvium. It includes Big, Round, and Fall River Valleys, and the smaller 

Ash Valley. Land cover is mostly pasture, hay, and cropland. Soil temperature regimes are mesic and 

soil moisture regimes are aridic, xeric, and aquic. Typical vegetation includes big sagebrush and 

sedge meadow communities. The Pit River is a tributary of the Sacramento River.

The Warner Mountains ecoregion comprises the low to mid-elevations of the Warner 

Mountains. In contrast to the mesic soils of the surrounding lower ecoregions, soil 

temperature regimes here are frigid. Soil moisture regimes are xeric. Vegetation includes big 

sagebrush, low sagebrush, perennial bunchgrasses, and western juniper at low elevations. At

The Diegan Western Granitic Foothills ecoregion consists of inland low hills at the 

intermediate elevations of central San Diego County, in the Escondido, Ramona, and 

Alpine areas. Part of the lower Peninsular Ranges, the mountains and hills are moderately steep to 

steep with narrow to rounded summits. A few narrow to broad valleys occur. Although there is 

some mild influence by marine air, it is much less than in Ecoregions 85e and 85f to the west. The 

soil temperature regime is thermic and soil moisture regime is xeric. Typical vegetation includes 

foothill needlegrass, coast live oak, chamise, mixed chaparral, and California sagebrush. 

The Morena/Boundary Mountain Chaparral ecoregion is a transitional area between 

Ecoregions 85 and 8, on the border with Mexico. Elevations and relief are less than in 

Ecoregion 8e to the north, and Ecoregion 85h lacks much of the hardwood and conifer woodland of 

Ecoregion 8. It is slightly higher than Ecoregion 85g to the west, except for that ecoregion’s high 

hills near the international border. Vegetation is predominantly mixed chaparral and some chamise.

The Northern Channel Islands ecoregion consists of four east-west trending islands off 

of the Southern California coast: San Miguel, Santa Rosa, Santa Cruz, and Anacapa 

Islands. These islands are a seaward extension of the Santa Monica Mountains of Ecoregion 85c. 

The islands are mostly steep mountains and hills with some gently sloping plateaus and dissected 

marine terraces. Peak elevations are greater than 2,450 feet on Santa Cruz Island. The maritime 

climate is mostly frost-free, except at high elevations. Soil temperature regimes are isothermic 

and thermic, and soil moisture regimes are ustic and xeric. These northern islands have some 

climatic, soil, and vegetational differences from the Southern Channel Islands ecoregion (85m). 

Annual grassland, coastal sage scrub, and chaparral are typical, with some scattered mixed 

broadleaf woodland, island oak and coastal live oak woodlands, and a few Bishop or Torrey pine 

stands on sheltered slopes and canyons, or on ridges exposed to frequent fogs. Many unique plants 

and animals are endemic to the islands, as well as rich and globally significant marine ecosystems. 

These islands, plus Santa Barbara Island to the south, form Channel Islands National Park.

The Southern Channel Islands ecoregion consists of the San Nicolas, Santa Barbara, Santa

Catalina, and San Clemente Islands. These northwest-trending islands have some similarities

to the Northern Channel Islands ecoregion (85i), although there are some warmer ocean currents, 

higher average air temperatures, slightly less precipitation, less woodland, and more open xeric 

scrub vegetation. Ecoregion 85j has larger distances between islands and a more diverse flora than 

Ecoregion 85i, with more xeric components. Steep mountains and hills and dissected marine 

terraces occur, with a high elevation of 2,123 feet on Santa Catalina Island. The maritime climate is 

frost-free, soil temperature regimes are mostly thermic, and soil moisture regimes are ustic and xeric. 

The Inland Valleys ecoregion has less marine influence on climate compared to other valley

regions to the west such as Ecoregions 85b and 85d. It consists of alluvial fans and basin 

floors immediately south of the San Gabriel and San Bernardino Mountains of Ecoregion 8, and 

includes the San Jacinto and Perris Valleys toward the south. Ecoregion 85k includes some floodplains

along the Santa Ana River. The soil temperature regime is thermic and soil moisture regime is xeric.

Vegetation historically included Riversidean coastal sage scrub, valley grasslands, and some riparian

woodlands. The ecoregion now is heavily urbanized. A few areas of pasture or cropland persist. 

The moderately steep to steep Inland Hills ecoregion is in a hotter and drier environment 

than the coastal hills of Ecoregion 85c to the west. Elevations generally are between 1,000 

and 3,000 feet. Mesozoic granitic rocks are common along with some gabbro, diorite, and Jurassic 

argillite and graywacke. Diverse habitat mosaics occur with various types of sage scrub mixing 

with areas of grassland and chaparral. This contrasts with the mostly urbanized surrounding 

lowland of Ecoregion 85k. Interior or Riversidian sage scrub is more widespread than coastal sage 

scrub communities typical of ecoregions to the west. Annual precipitation is mostly 10–14 inches.

The Santa Ana Mountains ecoregion is steep to very steep with narrow to rounded 

summits and narrow canyons. Elevations range from about 700 to 5,687 feet at Santiago 

Peak. Ecoregion 85m is modified moderately by marine air, and generally is hotter and drier on the

inland side. Annual precipitation of 14–24 inches is greater than in the adjacent lower-elevation 

ecoregions. Soil temperature regimes are thermic and mesic and the soil moisture regime is xeric. 

Vegetation includes mixed and chamise chaparral, coastal sage scrub, coast live oak, and areas of 

annual grassland. Some canyon live oak occurs, bigcone Douglas-fir is found at the heads of some 

canyons, and sparse stands of Coulter pine are at high elevations. In the southeast, the Santa Rosa 

Plateau supports areas of vernal pools, native grasslands, and some Engelmann oak woodlands. 

The nearly level and often barren Lahontan and Tonopah Playas ecoregion contains mud

flats, alkali flats, and intermittent saline lakes, such as the Black Rock Desert, Carson 

Sink, and Sarcobatus Flat in Nevada, and the Honey Lake Basin in California. Marshes, remnant 

lakes, and playas are all that remain of Pleistocene Lake Lahontan, which was once the size of 

Lake Erie. Playas occur at the lowest elevations in the Lahontan Basin and are the terminus or “sink” 

of rivers flowing east from the Sierra Nevada. They fill with seasonal runoff from surrounding 

mountain ranges during winter, providing habitat for migratory birds. Black greasewood or 

four-winged saltbush grows around the perimeter in the transition to the salt shrub community, 

often stabilizing areas of low sand dunes. Ecoregion 13h has very 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 and for some recreational and military uses.

The Tonopah Basin ecoregion lies in the transition between the Great Basin and the more 

southerly Mojave Desert. The Tonopah Basin shows varying degrees of Great Basin and 

Mojave Desert characteristics. The western side of the Tonopah Basin is a continuation of the 

Lahontan Basin, whereas the lower and hotter Pahranagat Valley on the eastern side is more like 

the Mojave Desert. Similar to basins farther north, shadscale and associated arid land shrubs cover 

broad rolling valleys, hills, and alluvial fans. However, unlike the Lahontan Salt Shrub Basin (13j) 

and Upper Lahontan Basin (13z) ecoregions, the shrubs often co-dominate in highly diverse 

mosaics. The shrub understory includes warm season grasses, such as Indian rice grass and galleta 

grass. Valleys with perennial water contain endemic fish species, including the Railroad Valley tui 

chub, Pahranagut roundtail chub, Railroad Valley springfish, and White River springfish.

The Tonopah Sagebrush Foothills ecoregion includes the low mountains and hills rising 

from the floor of the flatter Tonopah Basin ecoregion (13u). The substrate is rocky and 

lacks the fine sediments found at lower elevations in Ecoregion 13u. Great Basin species are 

common in this ecoregion as they are farther north in the Lahontan Sagebrush Slopes ecoregion 

(13k). However, because Ecoregion 13v is in the rain shadow of the Sierra Nevada and is adjacent 

to the Mojave Desert, it is more arid than Ecoregion 13k. As a result, black sagebrush is more 

prevalent in the shrub overstory of Ecoregion 13v, and the more mesic understory species that are 

farther north and east are largely absent. Mojave Desert species, such as blackbrush, Joshua tree, 

and cholla cactus, become more common in the east and south, where summer moisture is more 

prevalent. Streams are ephemeral and flow during and immediately after storms. Storm events can 

be of sufficient magnitude to move large quantities of sediment in streambeds. Because of the 

droughty conditions, Ecoregion 13v has a low carrying capacity for cattle.

The Sierra Nevada-Influenced Ranges ecoregion includes the wooded Great Basin 

mountains that have climatic and biotic affinities to the Sierra Nevada. Ecoregion 13x 

receives greater precipitation than the mountain ranges of central Nevada; however, precipitation 

amounts vary from range to range in relation to the local strength of the Sierra Nevada rain 

shadow. Because of minimal summer rainfall, Ecoregion 13x contains pinyon–juniper woodland, 

but lacks oak and ceanothus species. The White, Sweetwater, Pine Nut, Wassuk, and Virginia 

Ranges of Nevada support varying amounts of Sierra Nevada flora, including small stands of 

ponderosa, lodgepole, Jeffrey, and western white pine. Scattered ephemeral pools perched over 

areas of flat, impermeable volcanic bedrock, similar to those in the High Lava Plains ecoregion 

(80g), support unique assemblages of flora and fauna. High ranges near the Sierra Nevada are more

likely to have perennial streams. Bighorn sheep, deer, and black bear inhabit these mountains.

The Sierra Nevada-Influenced High Elevation Mountains occupy the elevational zone 

above the woodland-covered Sierra Nevada-Influenced Ranges (13x), and are affected in 

varying degrees by Sierra Nevada climate. Elevations range from 9,000 to greater than 14,000 feet.

White Mountain Peak at 14,252 feet is the third highest peak in California. Ecoregion 13y is 

covered by shrubs (for example, mountain big sagebrush, low sagebrush, and mountain-mahogany), 

small aspen groves (on moist sites), scattered stands of high elevation conifers, and Sierra Nevada 

subalpine and alpine forbs. The alpine flora of the White Mountains shares more than 70 percent of

its species with the Sierra Nevada. In the White Mountains, the bristlecone pines prefer the 

northern slopes and often are associated with the white, rocky soil derived from dolomite. In these 

nutrient-poor soils, few other plants grow, and the white rock color tends to reflect sunlight, 

possibly making a cooler and moister soil than on the areas of granite or quartzite. At high 

elevations, reproduction of limber pine is greater than bristlecone pine. Moisture amounts captured

by the highest ranges in Ecoregion 13y result in substantial perennial streamflow in some areas.

The Sierra Nevada-Influenced Semiarid Hills and Basins ecoregion includes the basins 

and lower mountain slopes immediately east of the Sierra Nevada that are affected by its 

climate or that have its characteristic granitic substrate. Ecoregion 13aa differs from the Lahontan 

Sagebrush Slopes ecoregion (13k) to the east in Nevada in that plants with slightly higher moisture 

requirements, such as antelope bitterbrush and desert peach, may be associated with the semiarid 

shrub community, especially near the Sierra Nevada front. Three large river systems, the Truckee, 

Carson, and Walker Rivers, flow eastward through this region from the Sierra Nevada, providing 

water for agriculture and urban development. Their floodplains support some of the best remaining 

riparian cottonwood forest in Nevada, which has been degraded in many areas by grazing, 

agriculture, and invasive weeds. The Truckee and Walker Rivers and their tributaries also provide 

habitat for the threatened Lahontan cutthroat trout. In California, the Susan River flows through 

Ecoregion 13aa to Honey Lake, and to the south, the upper Owens River flows to Lake Crowley. 

An intermontane valley with elevations ranging from 4,800 to 5,200 feet, the Sierra Valley

ecoregion is surrounded by mountains with elevations mostly 6,000 to 8,000 feet. The 

valley is a down-faulted basin, and formerly was a Pleistocene lakebed. It now is filled with 

sediment up to 2,000 feet thick. The valley also has some thermal activity, such as Marble Hot 

Springs located in the western part. Annual precipitation averages 14–20 inches, falling mostly as 

snow. Soil temperatures are mesic with xeric, aquic, and aridic soil moisture regimes. The valley 

floor has a grassland and sagebrush ecosystem and contains extensive freshwater marshes filled 

with cattails, bulrushes, and alkaline flats that drain into the Middle Fork Feather River. Many 

species of wildlife use the valley, including migratory birds, wintering waterfowl, and raptors. More

than 260 bird species have been observed in the valley, and 160 are known to breed here. Sandhill 

cranes nest in the valley. Pasture for cattle is extensive along with some hay and alfalfa fields. 

The Upper Owens Valley ecoregion is a large north-to-south valley area with several 

segments, including Queen, Benton, Hammil, Chalfant, and Upper Owens Valleys on the 

western side of the White Mountains, and Round Valley near the Sierra Nevada. Gently to 

moderately sloping alluvial fans and mostly level basin floors, terraces, and floodplains are the 

primary landforms. The region also includes the distinct Alabama Hills in the far south. Elevations 

range from about 3,800 feet along the Owens River in the south to more than 6,000 feet where the 

higher fans descend from adjacent mountain ecoregions. Quaternary alluvium covers the region, and

the Upper Owens Valley has some small areas of lava flows. Soil temperature regimes are mesic 

to thermic and soil moisture regimes are aridic with some xeric. Shrub-covered rangeland is the 

dominant land cover, with minor areas of hay and pastureland. Several small towns serve the local 

ranching and farming sector, as well as cater to mountain-related tourism. Vegetation includes big 

sagebrush, rabbitbrush, spiny hopsage, antelope bitterbrush, saltbush, ephedra, and several perennial

grasses including desert needlegrass. Along the Owens River, some restoration of cottonwoods, 

willows, and wetlands has occurred, although water continues to be exported to Los Angeles.

The Mono/Adobe Valleys ecoregion includes the nearly level to gently sloping lake plain 

around Mono Lake at the base of the Sierra Nevada ecoregion (5), as well as the Adobe Valley

to the southeast. Pleistocene and recent lacustrine deposits predominate. Ash layers occur from 

eruptions of the numerous volcanic domes that are mostly in adjacent Ecoregion 13x. Elevations 

range from 6,400 to 7,200 feet, with relief of 200–400 feet. Soil temperature regimes are mesic 

and soil moisture regimes are aridic. Big sagebrush, bitterbrush, and some singleleaf pinyon occur. 

Greasewood occurs in seep areas. Water from Sierra Nevada streams that flows to Mono Lake 

historically has been diverted for municipal use in Los Angeles, affecting lake levels and chemistry.

The Bishop Volcanic Tableland ecoregion occurs just north of the town of Bishop and 

Upper Owens Valley in Inyo and Mono Counties. The gently to moderately sloping 

tableland of volcanic rhyolite and tuff ranges in elevation from about 4,200 to 6,600 feet, with 

relief mostly 200–800 feet. The landscape was formed more than 700,000 years ago when 

volcanic materials spewed from the Long Valley Caldera to the northwest. The welded Bishop 

Tuff has a depth of more than 140 feet, and the nutrient-poor soils are very shallow and 

well-drained, with rocky and loamy soil textures. Soil temperature regimes are mostly thermic and 

soil moisture regimes are aridic. Vegetation is mostly shadscale and blackbrush, with some Indian 

ricegrass and desert needlegrass, and a variety of desert forbs. Annual precipitation is 6–7 inches. 

A few intermittent streams trend southwest across the region, with runoff draining to the Owens 

River. The Owens River Gorge traverses the southwestern part of the tableland. Recreation has 

become an important land use on the BLM public lands, including bouldering and rock-climbing.

The Bay Terraces/Lower Santa Clara Valley ecoregion is an urbanized area on alluvial 

plains that wrap around San Francisco Bay between the East Bay Hills ecoregion (6r) on the

east and the Leeward Hills ecoregion (6x) to the west. Ecoregion 6t also includes the urbanized area

around San Jose and the lower Santa Clara Valley. Soil temperature regimes are mostly thermic, with

some isomesic. Soil moisture regimes are xeric with some aquic. Common vegetation historically 

included coast live oak, California oatgrass, and needlegrass grasslands, although land use now is 

nearly all urban and residential. All but the larger streams are dry through most of the summer. 

The Livermore Hills and Valleys ecoregion consists of the Livermore, Amador, and San 

Ramon Valleys and the low hills that surround them. Large areas are relatively flat, now 

mostly urbanized, and occur on Quaternary alluvium. Ecoregion 6u includes the cities of 

Livermore, Pleasanton, Dublin, San Ramon, and part of Danville. The low hills occur on loosely 

consolidated Plio-Pleistocene deposits and are mostly grassland, with some scattered blue oak or 

coastal live oak. Elevations range mostly from 300 to 1,100 feet. Soil temperature regimes are 

thermic and soil moisture regimes are xeric. Streams are dry through most of the summer.

The Upper Santa Clara Valley ecoregion is a low-relief alluvial plain in the upper Santa 

Clara Valley, including the San Benito Valley. It retains more agricultural land and is not 

as urbanized as the Bay Terraces/Lower Santa Clara Valley ecoregion (6t). Late Quaternary 

alluvium is predominant. Soil temperature regimes are thermic and soil moisture regimes are 

xeric. Common vegetation series include valley oak, coast live oak, California oatgrass, and 

needlegrass grasslands, but most of the region is in cropland or urban and residential land. Runoff 

is slow across the alluvial plain. All but the larger streams are dry through most of the summer.

The coastal Monterey Bay Plains and Terraces ecoregion occurs on alluvial plains and 

terraces that wrap around Monterey Bay. The marine-influenced climate of Ecoregion 6w 

makes it cooler than the Salinas Valley ecoregion (6af) that stretches inland to the southeast, and 

Ecoregion 6w has higher annual precipitation. Elevations range from sea level to about 400 feet. 

Quaternary marine and non-marine deposits and terraces occur. There are recent dunes along the 

western side of Monterey Bay, and stabilized dune sand is extensive on the southeastern side of 

the bay. Soil temperature regimes are isomesic near the ocean and thermic inland. Soil moisture 

regimes are mostly xeric but some are aquic on floodplains. Soluble salts accumulate in some 

soils near the ocean. Coast live oak and California oatgrass occur on the plains. Dunes support 

some herbaceous communities with coastal scrub and sage on stabilized dunes in the southeast. 

Pickleweed occurs in estuaries. Summer fog is common. There is a long frost-free period that 

helps support cropland agriculture including artichokes, strawberries, and lettuce.

The Leeward Hills ecoregion includes mountains and hills with rounded ridges, steep 

and moderately steep sides, and narrow canyons. It occurs inland from the wetter Santa 

Cruz Mountains ecoregion (1n). Elevations range from about 200 feet to peaks greater than 3,700 

feet. Metasedimentary and metavolcanics of the Franciscan Complex occur along with other 

Cretaceous sedimentary rocks, and minor areas of ultramafics and Plio-Pleistocene non-marine 

sediments. Soil temperature regimes are thermic and soil moisture regimes are xeric. Common 

vegetation includes annual grassland, coast live oak, California bay, and a few areas of chaparral.

The Gabilan Range contains steep mountains between the San Andreas Fault on the 

northeast and the Salinas Valley on the southwest. These mountains are steeeper (with 

granitic, metamorphic, and volcanic rocks) and have more coastal oaks than the 

sedimentary-dominated hills of Ecoregion 6al to the southeast. Although Mesozoic granitic rocks 

are found in most of the region, Miocene rhyolite and pyroclastic rocks are exposed in the hills of 

Pinnacles National Park. Coast live oak is common on north-facing slopes in the northwestern 

part, with more blue oak to the south and east. Some black oak and mixed conifers occur on 

north-facing slopes at high elevations. Chamise is common on shallow soils.

The Diablo Range ecoregion includes mountains with rounded ridges and steep to 

moderately steep sides, along with narrow canyons and valleys. It is higher and wetter 

than Ecoregion 6aa to the east, and it has a different geology and vegetation mosaic compared to 

Ecoregions 6y and 6al to the west. The elevation ranges from about 600 feet near San Luis 

Reservoir to about 4,000–5,000 feet on the high elevation mountains, with a peak of 5,248 feet on 

San Benito Mountain. Ecoregion 6z is dominated by Cretaceous-Jurassic Franciscan sedimentary, 

minor volcanic, and metamorphic rocks that are intensely folded and faulted. Ultramafic rocks are 

widely scattered throughout the region. The hills along the San Andreas Fault also include some 

Paleocene marine, Miocene marine, Plio-Pleistocene nonmarine, and Quaternary stream terrace 

deposits. Soil temperature regimes are mostly thermic, but are mesic on north-facing slopes at 

high elevations. Soil moisture regimes are xeric. The natural plant communities include blue oak 

woodlands and savannas and, on shallow soils, chamise. Leather oak occurs on serpentine soils, 

as well as mixed chaparral shrublands. Sargent cypress occurs, but is sparse on serpentine soils. 

Some black oak and mixed conifers are on north-facing slopes at high elevations, and Jeffrey pine 

occurs on serpentine soils on San Benito Mountain. All but the larger streams are dry through 

most of the summer. Natural lakes are absent, but there are a few reservoirs in the area.

The Eastern Hills ecoregion includes the low, steep mountains and foothills on the eastern 

side of the Diablo Range, including the Panoche, Ciervo, and Kettleman Hills, and 

Avenal Ridge at the southern end. Elevations range from about 100 feet in the north to 

2,000–3,000 feet on the highest hills. Ecoregion 6aa is drier, lower, and mostly grassland 

compared to Ecoregion 6z to the west. It is more hilly and lacks cropland compared to Ecoregions 

7o and 7q to the east. The rocks are predominantly Cretaceous sandstone and shale, intensely 

folded and faulted. Eocene, Miocene, and Pliocene marine sediments, Plio-Pleistocene nonmarine 

sediments, and Quaternary alluvium also occur. The soils are well-drained; many are calcareous 

in their subsoils. Soil temperature regimes are thermic and soil moisture regimes are mostly xeric, 

with some aridic in the southeastern part of the region. The predominant vegetation is needlegrass 

and annual grasslands. There is some blue oak on north-facing slopes in wetter areas and some 

chamise on shallow soils. Valley oak occurs in valleys along the San Andreas Fault zone.

The Pleasant Valley/Kettleman Plain ecoregion contains disjunct small valleys and 

relatively flat plains of Quaternary alluvium that contrast with the steeper, adjacent hills 

of Ecoregions 6z and 6aa. Elevations in the southern areas are 600 to 1,000 feet. Ecoregion 6ab 

also includes the Panoche Valley in the north, with elevations mostly 1,000–1,800 feet. Some of 

the soils are similar to soils in the southern Central California Valley ecoregion (7), and cropland 

occurs here (typically dryland grain, such as barley and winter wheat). Other parts of the region are

used as rangeland, especially following seasonal rains. Native grass and shrub communities have 

been replaced by cropland or species such as redstem filaree, soft chess, red brome, foxtail barley, 

and burclover. Soil temperature regimes are thermic and soil moisture regimes are xeric to aridic. 

The Temblor Range/Elk Hills ecoregion contains steep mountains and moderately steep 

hills around the Temblor Range and the lower, gentler Elk Hills. Elevations range from 

400 to greater than 4,300 feet. The soil temperature regime is thermic and soil moisture regimes 

are xeric and aridic. Soils generally are more saline than those in the Caliente Range ecoregion 

(6ao) farther west, and annual precipitation is only about 6–10 inches. Common vegetation series 

are purple needlegrass, annual grassland, blue oak, chamise, and California juniper. 

The Grapevine Transition ecoregion is an intermediate region between the Southern 

California Mountains (8) and Central California Valley (7). It consists of moderately steep 

to steep hills, dissected terraces, and some areas of sloping alluvial fans toward the valley, with 

elevations ranging from 600 to greater than 4,000 feet. The hills are mostly Miocene and Pliocene 

sandstone and conglomerate. Soil temperature regimes are thermic and soil moisture regimes are 

aridic and xeric. Vegetation includes allscale and needlegrass, with a few blue oaks or valley oaks.

The Tehachapi Foothills ecoregion consists of moderately steep to steep mountains and 

hills on mostly granitic terrain. The ecoregion covers the lower slopes around the 

southern end of the Greenhorn Mountains and on the western sides of Breckenridge Mountain and 

the Tehachapi Mountains. As with Ecoregion 6c to the north, vegetation series include blue oak, 

needlegrass and annual grasslands, chamise, ceanothus, mixed oaks, and foothill pine, although this

region tends to be more semi-arid than subhumid, and the mosaic of soil characteristics is 

different. The soil temperature regime is thermic and soil moisture regimes are xeric and aridic. 

The Salinas Valley ecoregion includes gently sloping alluvial plains, stream terraces, and 

nearly level floodplains of the Salinas Valley, inland from Salinas and Ecoregion 6w. 

Pleistocene and some Plio-Pleistocene nonmarine deposits and recent alluvium predominate. 

Soils are mostly well drained, with some poorly drained on floodplains. Soil temperature regimes 

are thermic and soil moisture regimes are xeric, with some aquic on floodplains. The climate in the

lower, northwestern part has more coastal influence with cooler summer temperatures and milder 

winter temperatures compared to the greater climate extremes in the upper valley to the southeast. 

Valley oak and needlegrass grasslands occur, but cropland is the dominant land cover. Lettuce, 

broccoli, spinach, tomatoes, celery, peppers, flowers, and grapes are grown in the ecoregion.

The Northern Santa Lucia Range ecoregion on the northern and coastal side of the 

Santa Lucia Range contains mountains with rounded ridges, steep sides, and narrow 

canyons. It has predominantly Mesozoic granitic and pre-Cretaceous metamorphic rocks, as well 

as Miocene marine sedimentary rocks. Soil temperature regimes are thermic and mesic at high 

elevations, and soil moisture regimes are xeric and ustic. Coast live oak occurs widely, especially 

on north-facing slopes, and California sagebrush-black sage is on south-facing slopes near the 

northwestern end of the Santa Lucia Range and inland. Canyon live oak is on steep canyon 

sideslopes, and chamise and live oak shrublands are on shallow soils inland and at higher 

elevations. There are less Douglas-fir, tanoak, and redwood compared to coastal Ecoregion 6ah.

The Santa Lucia Coastal Forest and Woodland ecoregion is a near-coastal zone that 

stretches from Carmel Bay in the north to near Salmon Creek in the south. It has more 

Douglas-fir, tanoak, redwoods, rain, and fog than the more interior parts of the Santa Lucia Range, 

and has a dense shrub understory. With steep relief (elevations range from sea level to about 4,000 

feet), landslides are frequent, especially during heavy winter rains. Some of the high-gradient 

streams support anadromous fish such as steelhead trout. Coastal tourism is economically important.

The Interior Santa Lucia Range ecoregion is a steep, mountainous part of the Santa Lucia

Range that is inland enough to diminish marine effects on climate compared to Ecoregions

6ag and 6aj to the west. It stretches southeast from near Greenfield in the Salinas Valley ecoregion 

(6af), to near the Sisquoc River, east of the Santa Maria Valley ecoregion (6aq). The geology is 

mostly Cretaceous sedimentary rocks and Miocene marine sediments. The Miocene-age 

Monterey Formation contains calcareous shales, sandstone, and mudstone. Vegetation is blue oak 

and coast live oak woodlands, chamise or mixed chaparral shrublands, and annual grasslands.

The Southern Santa Lucia Range includes northwest-trending mountains and hills with 

rounded ridges, steep sides, and narrow canyons. Along the coast are narrow benches on 

marine terraces, and small areas of sand dunes. Mesozoic-age metamorphic rocks of the 

Franciscan Complex occur, with Miocene sandstone in the south. Elevations range from sea level 

to 3,408 feet on Pine Mountain. The soil temperature regime is thermic and soil moisture regime is 

xeric. Vegetation includes coast live oak woodlands, chaparral shrublands, and annual grasslands. 

The Caliente Range, composed mostly of Miocene and Pliocene sandstone, siltstone, and 

conglomerate, is characterized by steep mountains with narrow canyons. It contrasts with the 

lower elevations and relief and the Quaternary alluvium of Ecoregion 6am to the south, and with 

the drier Carrizo Plain (6an) to the north. Soil temperatures are thermic and mesic and soil moisture

regimes are xeric and aridic. Shrub and herbaceous cover dominates the ecoregion, with annual 

and perennial grasslands and forbs, mixed chaparral, blue oak woodland, and some coast live oak.

The moderately steep to steep hills of the Solomon-Purisima-Santa Ynez Hills

ecoregion have a mosaic of coastal sage scrub, chaparral, and oak woodland, interspersed 

with some grasslands used for cattle ranching. There are some transitional vegetation zones with a 

few species having either northern or southern range limits here. The hilly relief and marine 

sediments of Miocene and Pliocene sandstone and mudstone contrast with the flatter, more 

populated valleys of Quaternary alluvium in adjacent Ecoregion 6aq. Some oil and gas production 

occurs in the ecoregion, and wine grape production has expanded in the valleys and low hills.

The Santa Maria/Santa Ynez Valleys ecoregion occurs on alluvial plains along the Santa 

Maria and Santa Ynez Rivers. With prevailing west-northwest winds, these east-west 

valleys have cool coastal temperatures and become progressively warmer inland. Coastal summer 

fogs occur. Soil temperature regimes are thermic, with some nearly mesic. Soil moisture regimes 

are mostly xeric. Runoff is slow across the alluvial plains. Natural vegetation historically was 

mostly valley oak, coast live oak, grasslands, and riparian willows and other shrubs. Some central 

maritime or sandhill chaparral occurs, with endemic plants such as sand mesa manzanita, 

Purisima manzanita, and coast ceanothus, although much of this habitat has been converted or 

fragmented. Some dunes and sand hills occur along the coast. Most of the valleys now are in 

agricultural, urban, residential, and military land uses. Wine grape production has expanded in many

of these valleys and adjacent low hills. Flowers and vegetables are produced in the Lompoc area.

The Upper Sacramento River Alluvium ecoregion includes the floodplains and terraces of

the Sacramento River and lower Cottonwood Creek in the area between Redding and Red 

Bluff. It is flatter and has more cropland and irrigated hay and pastureland than the adjacent 

Tehama Terraces ecoregion (6e) that is mostly rolling and dissected woodlands and grasslands used

for grazing. Although it has similarities to the northern parts of Ecoregions 7e and 7b in the 

Central California Valley, this narrow ecoregion is influenced by the surrounding oak woodlands. 

Natural vegetation consisted of riparian woodlands of Fremont cottonwood, California sycamore, 

willow, box-elder, and valley oak, and at higher elevations, some blue oak woodland and savanna.

The Northern Terraces ecoregion occurs on gently sloping to sloping terraces and 

alluvial fans at the northern end and eastern side of the Sacramento Valley. It is mostly 

rolling grassland and has less agriculture than in the alluvium of adjacent Ecoregion 7b or in the 

floodplain soils of Ecoregion 7e. It also generally lacks the oaks that are upslope in Ecoregion 6. 

Soil temperature regimes are thermic and soil moisture regimes are xeric. Common soil series 

include Tuscan and Anita on the east and Corning, Redding, Hillgate, and Newville on the west. 

Although the terraces of the Tuscan Formation on the east have geological and soil differences 

from the Tehama Formation terraces on the west, the landforms, climate, vegetation, and land 

cover generally are similar. The vegetation of annual grasses and forbs is used mostly for dryland 

range and pasture. A few areas of blue oak woodlands occur, primarily at high elevations near the 

boundary with Ecoregion 6. Vernal pools are in some areas. Streams drain mostly to the Sacramento 

River, with a few in the south draining to the lower San Joaquin River.

The North Valley Alluvium ecoregion covers the recent alluvial plain, very gently 

sloping recent alluvial fans, and some minor floodplains in the northern part of the 

Sacramento Valley. Elevations range from 100 to 300 feet. The soil temperature regime is thermic 

and soil moisture regime is xeric, with Tehama, Hillgate, and Arbuckle as common soil series. A mix

of cropland, orchards, and pasture occurs here. Typical vegetation is annual grasslands, scattered 

blue oaks, and valley oaks on stream terraces and alluvial plains. Vernal pools are common. 

The Butte Sink/Sutter and Colusa Basins ecoregion occurs on nearly level to very gently

sloping alluvial fans, floodplains, and basin floors that are split by the alluvium of the 

Sacramento River (Ecoregion 7e). Elevations range from about 20 to 150 feet. The Holocene 

basin deposits of silt and clay are covered by mostly fine-textured soils of low permeability, such 

as Vertisols. Winter and spring rains historically flooded wide areas, but these areas now are 

confined by artificial levees. There are no lakes in the ecoregion, but winter ponding occurs. 

Historical flood regimes likely contributed to seasonal wetlands and flat marshes. There is 

extensive agriculture of rice, and some orchards and pasture; however, the region also offers 

wildlife habitat for waterfowl and pheasant, and drainage canals support a warm-water fishery. 

Many of the rice fields are flooded and leased as private waterfowl hunting clubs in winter. In the 

western part of Ecoregion 7c, the Colusa Basin Drain is the single largest source of agricultural 

return flows to the Sacramento River. The natural vegetation historically consisted of perennial 

grasslands, but now is mostly annual grasslands, with some willows and cottonwoods along streams.

The Southern Hardpan Terraces ecoregion is on very gently sloping terraces, 

floodplains, and alluvial fans along the eastern edge of the San Joaquin Valley. Elevations 

range from 150 to 500 feet. Ecoregion 7d is warmer and drier than the Northern Terraces ecoregion

(7a) to the north. Soil temperature regimes are thermic and soil moisture regimes are xeric, nearing

aridic in the south. Common vegetation includes annual grasslands, ceanothus shrublands, blue 

oak savannas, and scattered foothill pines in the draws and protected slopes. Vernal pools are 

common. Streams drain to the San Joaquin River or the San Joaquin Valley closed basins. 

The Sacramento/Feather Riverine Alluvium ecoregion consists of nearly level 

floodplains and levees associated with the Sacramento, Feather, and lower Yuba and Bear 

Rivers. Much of the unweathered gravel, sand, and silt deposits are in contact with present-day 

river systems and have constantly changing morphology. Flows of the major rivers are artificially 

controlled, and confined by built levees. Entisols, Mollisols, and Alfisols are more common 

compared to the Vertisols typical of the adjacent basins of Ecoregion 7c. The xeric soils are 

moderately well to somewhat poorly drained and support pasture, wheat, fruit and nut orchards, 

and woody wetlands. Cottonwoods and mixed willows are present, along with some grasslands. 

Affected in places by historical mining practices in the Sierra Nevada, the riverine region includes 

areas of gold field tailings on the Yuba and Feather Rivers.

The Sutter Buttes ecoregion is a small but distinctive circular area of volcanic hills that 

rise above the surrounding Sacramento Valley to an elevation of 2,117 feet. The region is 

only about 10 miles across, and the cluster of peaks, locally, is called “the world's smallest 

mountain range.” In contrast to the surrounding regions that are mostly flat with cropland and 

orchards, this area is hilly grassland, with some areas of scattered blue oak woodland and 

chaparral, similar to some foothill areas of Ecoregion 6. The Sutter Buttes are the remains of an 

extinct volcano that erupted between 1.6 and 1.3 million years ago. Rhyolite and andesite are the 

most common bedrock types. Soil temperatures are thermic and the soil moisture regime is xeric.

The Yolo Alluvial Fans ecoregion contains Pleistocene and recent alluvial fan material 

from the Coast Ranges and from hills on the lower western side of the Sacramento Valley. 

The soil temperature regime is thermic and soil moisture regime is xeric. Common vegetation 

includes grasslands and valley oak, with cottonwoods and willows along streams. Most of the 

region is in cropland, with some areas of pastureland. Alfalfa, winter wheat, sunflowers, corn, 

tomatoes, strawberries, and stonefruit, walnut, and almond orchards are typical crops.

The Yolo/American Basin ecoregion includes nearly level to very gently sloping stream 

channels, levees, overflow basins, and alluvial fans of the main alluvial plain adjacent to 

the lower Sacramento River. The American Basin, just east of the river, is the northern unit, and 

the Yolo Basin, just west of the river, is the southern unit. Elevations range from about 10 to 40 

feet. Some flooding and high water tables occur during wet winters, although much of the region 

is protected by artificial levees, dams, and diversions. The Yolo Bypass goes through the region, 

carrying Sacramento River water at overflow toward the Delta ecoregion (7j). Cropland, hay and 

pasture land, and herbaceous wetlands cover most of the region, with rice being the most 

extensive crop. The soil temperature regime is thermic and soil moisture regimes are aquic and 

xeric. Common vegetation includes annual grasslands and in riparian areas some cottonwood, 

willow, and sycamore. Emergent vegetation in the permanent wetlands includes cattails, tules, and 

sedges. The seasonal and permanent wetlands provide resting and feeding habitat for ducks, geese, 

rails, and songbirds; and foraging habitat for wading birds such as herons, egrets, pelicans and ibis.

The Delta ecoregion is a low elevation area, near sea level, at the confluence of major 

rivers. It is characterized by numerous sloughs and channels formed where the 

Sacramento, San Joaquin, Cosumnes, Mokelumne, and Calaveras Rivers enter the ecoregion. Water

from these rivers commingles in the Delta and is influenced by tidal action, streamflow, and water 

diversion as it flows toward San Francisco Bay. Brackish tidal water enters the area when river 

flow is low during the summer and autumn. In the main part of the region, former wetland islands 

have been reclaimed for intensive agriculture with a network of levees. Corn, alfalfa, hay, and 

wheat are the most extensive crops on these organic soils, although various crops were grown 

historically. Soil temperature regimes are thermic and soil moisture regimes are mostly aquic, 

with some xeric on levees. Land subsidence and salinity intrusion are two of many important 

resource issues here. The western part of the ecoregion includes areas of brackish and seasonally 

freshwater marshes and wetlands that surround Grizzly Bay and Suisun Bay. The native vegetation

historically consisted of aquatic plants such as tules, cattails, and rushes. Saltgrass was dominant 

in many areas. Many of the diked wetlands are managed for waterfowl hunting. The Delta plays a 

central role in the distribution of water from the State's wetter northern regions to its southern, 

arid, and populous cities and agricultural areas. These water diversions can have adverse effects 

on species such as delta smelt, Chinook salmon, Central Valley steelhead, and green sturgeon.

The small Lodi Alluvium ecoregion is on nearly level to very gently sloping floodplains 

and alluvial fans of the Mokelumne and Calaveras Rivers and smaller streams between the

Delta (7j) and the Northern Terraces (7a) along the eastern edge of the Central California Valley. 

Elevations range from about 20 to 100 feet. Nearly the entire ecoregion is in cropland, with some 

urban land around Lodi. Grapes are dominant in the northern part, whereas walnuts are typical in 

the south. The soil temperature regime is thermic and soil moisture regimes are xeric and aquic. 

The natural vegetation historically included perennial and annual grasslands, valley oak savannas, 

cottonwoods, and willows. Streams drain to the west to the Delta area or to the Stockton Basin (7l). 

The Stockton Basin ecoregion is a nearly level basin floor on the eastern edge of the 

Delta (7j). Nearly one-half of the ecoregion is urban and residential land of Stockton that 

covers most of the western part. To the east is cropland of corn, wheat, alfalfa, grapes, and walnuts.

The soil temperature regime is thermic and soil moisture regimes are aquic and xeric. Vertisols are 

more common than in adjacent Ecoregion 7k. Winter ponding occurs. Natural vegetation historically

included perennial and annual grasslands, valley oak savannas, cottonwoods, and willows. 

The San Joaquin Basin ecoregion, including the downstream Caswell Basin, is on nearly 

level floodplains and basin floors in the middle of the San Joaquin Valley. It is upstream 

of the Delta ecoregion (7j) and between alluvial fans from the Coast Ranges on the west and 

alluvial fans from the Sierra Nevada on the east. Elevations range from near sea level in the north to

130 feet in the south. The predominant soils are poorly drained, and much of the region is flooded 

periodically. The soil temperature regime is thermic and soil moisture regimes are aquic and xeric. 

Although cropland and hay/pasture land cover most of the region, large areas, particularly in the 

central part, are herbaceous wetlands. Alfalfa and corn are typical crops in the north, whereas 

cotton, alfalfa, corn, and tomatoes are grown in the south. Common vegetation includes emergent 

aquatics, cottonwood, willow, valley oak, saltgrass, alkali sacaton, creeping wildrye, and allscale.

The Manteca/Merced Alluvium ecoregion is on very gently to gently sloping floodplains

and alluvial fans that slope from the higher terraces and foothills in regions to the east 

toward the San Joaquin River to the west. The soil temperature regime is thermic and soil moisture 

regimes are xeric and aquic. Natural vegetation historically included perennial and annual grasslands,

valley oak savannas, cottonwoods, and willow. Cropland, pasture, and urban uses now dominate.

The Westside Alluvial Fans and Terraces ecoregion is on very gently to gently sloping 

terraces and alluvial fans along the western edge of the San Joaquin Valley, adjacent to the 

Coast Ranges. Elevations range mostly from 5 to 300 feet, reaching 900 feet in the west. The soil 

temperature regime is thermic; soil moisture regimes are xeric, but aridic in the south. Vegetation 

includes perennial and annual grasslands and bladderpod and ephedra shrublands. Vernal pools 

and winter ponding occur. Agricultural land use is dominant, with grassland at the western margin.

The Granitic Alluvial Fans and Terraces ecoregion is on nearly level to very gently 

sloping alluvial fans and basins that are below older fans or terraces on the eastern side of the

San Joaquin Valley. Elevations range from 100 to 500 feet. The soil temperature regime is thermic 

and soil moisture regimes are xeric and aquic. Natural vegetation included grasslands and valley 

oak on the fans, cottonwood and willow along streams, and emergent wetland species in basins. 

Almost the entire region now is in cropland, hay and pastureland, and some urban and suburban uses.

The Panoche and Cantua Fans and Basins ecoregion is on nearly level to gently sloping 

alluvial fans of streams that drain from the Coast Ranges toward the San Joaquin Valley 

and partly on basin floors in the west-central part of the valley. Elevations range from 140 to 800 

feet. The soil temperature regime is thermic and soil moisture regime is aridic. Annual 

precipitation is only 6–8 inches and streams often are dry. The grassland and shrubland vegetation 

has been replaced by cropland and orchards. Soil salinity is a concern in several areas.

The Tulare Basin/Fresno Slough ecoregion contained historical Tulare Lake, which was 

once the largest freshwater lake west of the Mississippi River. The Tulare Basin was 

formed by the merging of alluvial fans from the Kings River to the east and Los Gatos Creek from 

the Coast Ranges to the west, generally blocking the basin’s outlet. When the seasonal lakes 

(Tulare, Buena Vista, Kern, and Goose Lakes) filled beyond capacity from winter and spring 

runoff, the overflow was sent down the Fresno Slough. In the dry season, subsurface flow from 

the Tulare Basin still helped to sustain flows in the San Joaquin River. Both areas once supported 

extensive freshwater marshes and interconnecting natural sloughs. Although the hydrology now is 

greatly modified by drainage canals, dams, and agricultural land uses, during major flood events, 

some water still collects in the lake basins and sloughs. Soils are mostly fine-textured and poorly 

drained, with a thermic temperature regime and aquic soil moisture regime. Ponding occurs.

The Kern Terraces ecoregion consists of gently sloping terraces, dissected alluvial fans, 

and mostly small floodplains at the southeastern edge of the San Joaquin Valley. 

Elevations range from a low of 400 feet in the west to 2,100 feet near the eastern margin. 

Ecoregion 7s is warmer and more arid than the terraces of Ecoregion 7d to the north, with slightly 

more relief, and fewer hardpan soils or vernal pools. The soil temperature regime is thermic and 

soil moisture regime is aridic. Common vegetation includes perennial and annual grasslands, with 

scattered areas of allscale scrublands, and a few small areas of blue oak savanna, especially near 

the transition to the Tehachapi Foothills ecoregion (6ae). Beavertail cactus is one indicator of the 

desert influences here. Streams drain westward to the canals and closed basins of the southern San 

Joaquin Valley. Streams are low gradient and intermittent, although the dam-controlled Kern 

River also cuts across the region. Some cropland occurs on the western margins, which are flatter 

and lower in elevation. Oil production occurs, especially near Bakersfield.

The South Valley Alluvium ecoregion occurs on a level basin and on nearly level to 

gently sloping alluvial fans in the southern San Joaquin Valley. The soil temperature 

regime is thermic and soil moisture is aridic. Vegetation includes perennial bunchgrasses and 

annual grasslands, allscale scrub, mesquite dunelands, and some iodinebush. Basin ponding occurs. 

Cropland, pasture and grassland, and urban are dominant land uses. Numerous oil fields occur.

The dry, hot Antelope Plain ecoregion occurs on nearly level to gently sloping alluvial fans 

along the southwestern edge of the San Joaquin Valley. Elevations range from 250 to 

1,200 feet. Relief is slightly greater than in the flat Ecoregion 7v to the east. The soil temperature 

regime is thermic and soil moisture regime is aridic. Precipitation averages 6 inches annually. 

Allscale scrub, bush seepweed scrub, and annual and alkali sacaton grasslands are typical cover. 

About one-half of the ecoregion now is in cropland, and the western margin is mostly grazed. 

Some oil fields occur.

The Southern Clayey Basins ecoregion consists of the low basin areas around the Buena 

Vista, Kern, and Goose Lake beds, and the area of fine-textured soils that extends into the 

Tulare Basin ecoregion (7r) to the north. The flat basins have elevations of about 200–300 feet. 

Cropland is the dominant land use, with some grassland and herbaceous wetlands in the north 

around the Kern National Wildlife Refuge and numerous private wetlands operated as hunting 

clubs. This area provides wintering habitat for migrating birds, shorebirds, and waterfowl in the 

southern San Joaquin Valley. The endangered Buena Vista Lake shrew, San Joaquin kit fox, and 

blunt-nosed leopard lizard also find remnant habitat here. Wetlands are maintained by a complex 

of canals, pipelines, deep wells, pump stations, and water control structures.

The creosotebush-dominated Eastern Mojave Basins ecoregion includes the valleys 

lying between the scattered mountain ranges of the Mojave Desert at elevations ranging 

from 1,800 to 4,500 feet. Elevations are lower, soils are warmer, and evapotranspiration is higher 

than in the Central Basin and Range ecoregion (13) to the north. Limestone- and 

gypsum-influenced soils occur, but overall, precipitation amount has a greater ecological 

significance than geology. Toward the south and east, as summer rainfall increases, the Sonoran 

influence grows, and woody leguminous species, such as mesquite, acacia, and smoke tree, 

become more common. Creosotebush, white bursage, and galleta grass are typical in Ecoregion 

14a. Pocket mice, kangaroo rats, and desert tortoise are faunal indicators of the desert 

environment. Desert willow, coyote willow, and mesquite grow in riparian areas, although the 

alien invasive tamarisk is rapidly replacing native desert riparian vegetation.

The Eastern Mojave Low Ranges and Arid Footslopes ecoregion is composed of 

alluvial fans, basalt flows, hills, and low mountains that rise above the basin floors of the 

Mojave Desert to upper elevations of about 5,000–6,000 feet. Areas of sparsely vegetated soils, 

depending on slope, soil type, and grazing history, can be susceptible to erosion during storm 

events. In areas transitional to the Great Basin in the north, blackbrush dominates slopes just 

above the upper elevational limit for creosotebush. Elsewhere, a mixture of typical Mojave Desert 

forbs, shrubs, and succulent species occurs, including Joshua tree, other yucca species, and cacti 

on rocky, well-drained sites. Ecoregion 14b has a diverse array of reptiles including iguanas, 

chuckwallas, and desert tortoises, as well as leopard, collared, horned, and spiny lizards. Desert 

bighorn sheep also may be present on some remote rocky outcrops.

The Eastern Mojave Mountain Woodland and Shrubland ecoregion occurs in 

California, Nevada, Utah, and Arizona, at elevations from about 5,000 to greater than 7,000

feet, where mean annual precipitation increases to between 10 and 16 inches per year. Vegetation 

includes pinyon, juniper, curl-leaf mountain-mahogany, and cliffrose. In many areas, a denser and 

more diverse mixture of large interior chaparral shrubs occurs, including oaks, ceanothus, 

silktassel, and Apache plume. A sagebrush zone is largely absent, but some Wyoming big 

sagebrush may be found in the understory of the woodland along with blackbrush. Higher riparian 

zones along the few perennial streams have willow, mountain brush, and cottonwood, whereas 

other canyons have canyon live oak, or singleleaf pinyon and desert scrub oak. In California, the 

Kingston Range and New York and Providence Mountains are areas of unique plant communities. 

The Arid Valleys and Canyonlands ecoregion includes steep canyons and benchlands 

less than 2,000 feet in elevation near the Colorado River. This is a hot, dry ecoregion, 

receiving about 5 inches of rain per year in the California part. Rocky colluvial soils cover eroded 

slopes and deeper soils occur on benches. Vegetation is a sparse but diverse shrub cover that 

includes creosotebush, white brittlebush, white bursage, and occasional Sonoran desert elements, 

such as ocotillo. Along the rivers, exotic tamarisk is replacing native riparian vegetation such as 

Fremont cottonwood and willow. The presence of the Colorado River, Lake Mead, and Lake 

Mohave greatly influences the management and ecology of this ecoregion.

The Mojave Playas generally are smaller than the Lahontan and Tonopah Playas (13h) 

and are not part of the broad Pleistocene pluvial basins found in the Central Basin and 

Range ecoregion (13) to the north in Nevada. The high salt and clay content of playa surface mud, 

and the hot, dry conditions inhibit plant growth. Ecoregion 14f is largely barren and only sparse 

saltbush vegetation typically is found on the margins. Where moisture is sufficient, cold-intolerant 

trees and woody legumes such as velvet ash and mesquite occur, particularly in the southern 

Mojave. Playas are dynamic environments with surface channels, playa margins, alluvial 

materials, and biota changing with each flooding event. Physical and biological crusts on soil 

surfaces are important, stabilizing soil and reducing erosion from wind and water.

The Amargosa Desert ecoregion is an arid, internally drained basin. It has greater 

temperature extremes and less Sonoran influence than the Eastern Mojave Basins (14a). 

This is due in part to the Spring Mountains that border Ecoregion 14g on the east and block summer

rainfall. In the Amargosa Desert, rainfall occurs mostly between October and April, with annual 

amounts of about 4–6 inches in California. Creosotebush and white bursage predominate in this 

ecoregion as they do in Ecoregion 14a, but there is less diversity of shrub species in Ecoregion 14g. 

The Amargosa Valley is a discharge point for an underground water system. Where the Amargosa 

River surfaces, it creates important wetland oases in the Mojave. A larger, but isolated, system of 

seeps and springs at Ash Meadows in Nevada is a wetland area of international importance, providing 

habitats for a large number of endemic plants and animals. In California, the ecoregion includes part of 

the Amargosa Valley, as well as the Stewart, Chicago, Pahrump, California, and Mesquite Valleys.

The Death Valley/Mojave Central Trough ecoregion includes the alluvial plain of parts 

of Death Valley, the Silurian Valley, and the great depressions that contain Soda, Bristol, 

and Cadiz dry lakes of Ecoregion 14f. The line of basins in this trough is lower in elevation and 

warmer than adjacent basins to the east or west, with soil temperatures mostly hyperthermic rather 

than thermic. The far northern part of the ecoregion, where elevations are greater than 4,000 feet 

near the Nevada border, is slightly cooler than the lower-elevation central and southern parts. 

Some areas in the central part are at or below sea level. Creosotebush, white bursage, and mixed 

saltbush communities occur. Drainage is internal. Although some consider this trough as a 

convenient divide between the eastern and western Mojave, summer rainfall and certain plant 

species characteristic of the east occur slightly farther to the west of Ecoregion 14h.

The Mesquite Flats/Badwater Basin ecoregion encompasses one of the most extreme 

environments on the continent—the low elevations of Death Valley. With stark contrasts 

to nearby mountains, it is one of the driest and hottest ecoregions and contains the lowest 

elevation in North America at 282 feet below sea level. High elevations are near sea level. It is a 

mostly level lake plain and basin floor, internally drained, and with little relief. The Mesquite 

Flats part in the north surrounds some of the sand dunes and sand sheets of Ecoregion 14o. To the 

center and south, Badwater Basin contains one of the largest protected salt flats in the world, along 

with other playa deposits and the fluvial floodplain of the Amargosa River. Large parts of the 

region are barren or sparsely vegetated. A few areas have iodinebush, seepweed, saltbush, 

arrowweed, allscale, or saltgrass and, at the higher margins, some creosotebush and desert holly. 

Soil temperature regimes are hyperthermic and soil moisture regimes are aridic. Annual 

precipitation is 2–3 inches, although in some years no rain is recorded. Lake Manly was the 

pluvial lake that filled this ecoregion in the Pleistocene and into the Holocene. Recently, a large lake 

reappeared briefly in 2005 after a wet winter and a previous flood event in summer 2004.

The Western Mojave Basins ecoregion includes the alluvial plains, fans, and bajadas of 

the major valleys lying between the scattered mountain ranges of Ecoregion 14k. There is 

some variation in climate and vegetation from north to south, but the basins typically are dominated

by creosotebush and white bursage, with areas of shadscale, fourwing saltbush, and on some upper

bajadas and fans, scattered Joshua trees. The Western Mojave Basins ecoregion has little summer 

rainfall compared to the Eastern Mojave Basins (14a), and typically lacks species such as Mojave 

yucca and big galleta found more to the east. Some annual plant species associated more with 

Mediterranean climates occur here, but not in the Eastern Mojave Basins. Soil temperature regimes

are thermic and soil moisture regimes are aridic. Drainage is internal to closed basins in the Mojave.

The Western Mojave Low Ranges and Arid Footslopes ecoregion consists of erosional 

highlands of exposed bedrock that rise above the alluvium of the basin floors. Granitic 

rocks are more typical in this western ecoregion compared to a mix of geology in the eastern 

Mojave ranges of Ecoregion 14b. Many of these western granitic outcrops have relatively low 

elevations and relief. Creosotebush shrubland occurs on hills along with areas of Joshua tree 

woodland on some footslopes. This ecoregion receives little summer rainfall compared to 

Ecoregion 14b, and lacks some of the shrubs, yuccas, and grasses in the eastern Mojave. The 

ranges in the north have some Great Basin desert scrub influence. Blackbrush shrubland and 

sagebrush occur more in the north in the transition to Ecoregion 13. The large highland area of 

Ecoregion 14k east of Owens Lake has a few small valleys or flats in it that are more similar to 

Ecoregion 14j, particularly between the Coso Range and Cottonwood Mountains.

The Western Mojave Mountain Woodland and Shrubland ecoregion occurs at 

elevations greater than about 6,000 feet on mountains in the northwestern part of 

Ecoregion 14. It includes parts of the Panamint, Argus, Coso, and Nelson Ranges. In contrast to 

the mostly creosotebush shrubland of the lower elevations in Ecoregion 14k, the vegetation of this 

higher, cooler, and wetter zone includes singleleaf pinyon, juniper, and sagebrush. It is somewhat 

drier and less diverse than Ecoregion 14c in the eastern Mojave. Soil temperature regimes are 

mesic and frigid and soil moisture regimes are aridic and xeric aridic.

The Western Mojave High Elevation Mountains ecoregion covers the highest elevations

of the Panamint Range, from about 8,000 to over 11,000 feet on Telescope Peak. It differs 

from the high elevation Ecoregion 14d in the eastern Mojave because it receives less monsoonal 

precipitation in the summer, and lacks ponderosa pine, Rocky Mountain white fir, and other species

found on the Spring Mountains of Nevada. Limber pine, mountain-mahogany, and big sagebrush 

occur, and at high elevations, bristlecone pines, some more than 3,000 years old. A distinctive bird 

fauna is found here in the breeding season, including the hairy woodpecker, mountain chickadee, 

red-shafted northern flicker, western bluebird, Audubon’s warbler, and Oregon junco.

The Mojave Lava Fields ecoregion includes the most recent volcanic features in the 

Mojave, and in many places these have changed little since the lava last erupted. The 

ecoregion includes Pliocene to Holocene rhyolitic and basaltic lava domes and flows. Seven 

different units of lava fields in California are mapped here, including the Coso volcanic field near 

the Sierra Nevada, the Lavic Lake volcanic fields east of Barstow, the Cinder Cone Lava Beds east 

of Baker, and Amboy Crater near Bristol Lake. These are the larger units of volcanic lava fields, 

and smaller areas of lava occur as part of the mosaic in other Mojave ecoregions. The lava flows 

have both ropy (pahoehoe) and blocky (aa) surfaces, and some areas have lava tubes and caves. 

Few if any plant communities have become established on these younger cinder cones and lava 

flows, except in a few pockets where shallow soils have developed. 

The Mojave Sand Dunes ecoregion includes migrating dunes, vegetation-stabilized 

dunes, and sand sheets. Although areas of eolian sand occur in many of the basins of the 

Mojave, only the largest areas have been mapped here. These include the Kelso dunes, Mesquite 

Flat dunes in Death Valley, Saline Valley dunes, Panamint dunes, Dumont dunes, Olancha dunes 

near Owens Lake, and Cadiz dunes. Plants and animals have adapted to the shifting sands and dry 

surfaces, and several of the dunes areas have endemic species. The Kelso Dune Field, about 30 

miles southeast of Baker, is the largest field of eolian sand deposits in the Mojave Desert. The 

tallest dunes rise 650 feet above the surrounding terrain. The Kelso dunes have several endemic 

insect species, as well as several other rare native bees, wasps, and beetles. These dunes also 

provide habitat for the Mojave fringe-toed lizard. 

80d

80g

80j

81a

81b

81c

81d

81e

81g

81i

81f

4d

4e

4f

4g

4h

5a

5b

5c

5j

5k

1a

1i

1j

1k

1n

1o

1m

6a

6b

6c

6d

6e

6f

6g

6ak

6al

6am

6an

5d

5e

85a

85b

85c

85d

85e

85f

78a

78d

78e

78g

78h

78i

9g

9h

9i

9j

9k

9o

9t

9n

9l

9m

1l

5f

5g

5h

5i

5l

5m

5n

5o

85g

85h

85i

85j

85k

85l

8e

8g

8a

8b

8c

8f

9q

9p

9s

9r

78j

78k

78l

78m

78n

78o

78p

78q

78r

13h

13u

13v

13x

13y

13aa

13ab

13ac

13ad

13ae

6k

6l

6i

6j

6h

6m

6n

6o

6p

6t

6u

6v

6w

6x

6ab

6ac

6z

6aa

6y

6ad

6ae

6af

6ao

6ap

6aq

6ar

7a

7b

7c

7d

7e

7f

7g

7j

7h

7n

7o

7p

7q

7r

7s

7t

7l

7v

7k

7u

6q

6r

6ag

6ah

7m

14a

14b

14c

14e

14f

14g

14h

14j

14k

14l

14m

14n

14o

14i

81h

6s

6ai

6aj

81j

81k

85m

8d

4. Cascades

5. Sierra Nevada

6. Central California Foothills and Coastal Mountains

7. Central California Valley

8. Southern California Mountains

81. Sonoran Basin and Range

80. Northern Basin and Range

1. Coast Range 6. Central California Foothills and Coastal Mountains (continued)

85. Southern California/Northern Baja Coast

78. Klamath Mountains/California High North Coast Range

9. Eastern Cascades Slopes and Foothills

13. Central Basin and Range

14. Mojave Basin and Range

SUGGESTED CITATION: Griffith, G.E., Omernik, J.M., Smith, D.W., Cook, T.D., Tallyn, E., Moseley, K., and Johnson, C.B., 2016, Ecoregions of 

California (poster): U.S. Geological Survey Open-File Report 2016–1021, with map, scale 1:1,100,000, http://dx.doi.org/10.3133/ofr20161021.

Descriptions of the Level IV Ecoregions of California

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2016-1021 Sheet 2 of 2