What's New
Research & Projects Publications

| Home | Contact | UCSB | Bren | ICESS |

Appendix ESN. The East Of Sierra Nevada Region


Contributing Author: David Stoms

Regional Character
Land Stewardship
Plant Community Types

Regional Character

The East of the Sierra Nevada (ESN) Region of the Great Basin Province encompasses 13,128 km², consisting principally of three basins: the Owens Valley, the Mono Basin-Long Valley Caldera, and the Walker River drainage in Mono and northern Inyo counties (Figure ESN-1). The primary ranges area the Sweetwater Mountains and the White-Inyo Mountains, plus the lower escarpment of the eastern flank of the Sierra Nevada. The upper elevational limit of the western edge of the region occurs at the transition between pinyon-juniper of the ESN with the Jeffrey pine of the Sierra Nevada. At its southern extremity, the boundary with the Mojave Desert is the transition from sagebrush to creosote bush scrub. The region is artificially truncated by the California-Nevada border on the eastern side.


Figure ESN-1. Shaded relief image of the East of the Sierra Nevada Region.

The climate is cooler than the Mojave Desert to the south, causing most of the precipitation to be winter snow (Schoenherr 1992). The Sierra Nevada range creates a rain-shadow effect, however, so the region is extremely dry. Bishop, in the Owens Valley, receives an annual average of just 14 cm of precipitation. The crest of the Sierra Nevada and White Mountain Peak both exceed 4,000 m, while the intervening Owens Valley is only ~1,500 m. Thus the high relief of the region produces a wide diversity of habitats. Alpine dwarf scrub and subalpine conifer forests of Bristlecone and Limber pines occur at the highest elevations. Below this is a band of pinyon-juniper woodland, consisting of Singleleaf pinyon and either Western juniper on the eastern face of the Sierra Nevada or Utah juniper elsewhere. There is also extensions of Jeffrey pine and other conifer forests in the Sweetwater Mountains and south of Mono Lake. Blackbush scrub is found in the Owens Valley below the pinyon-juniper zone, and below that is the hallmark of the Great Basin­sagebrush scrub, often in conjunction with Antelope Brush (Purshia tridentata). Shadscale (Atriplex confertifolia) replaces sagebrush on more alkaline soils closer to intermittent lakes. In the wettest locations in these alkaline basins, alkali sink scrub communities with succulent leaves form. Some communities characteristic of the Mojave Desert occur at the margins of the region, such as creosote scrub and Joshua tree woodland. Wetland and riparian communities are extremely critical in this arid environment, including montane meadows, alkali meadow, freshwater and alkali marshes, aspen, black cottonwood, and riparian scrub.

Despite the harshness of the environment, the region has nevertheless experienced significant human impacts on its biodiversity. Water is a primary resource conflict, with competition between urban consumers, recreationists, and wildlife. A large proportion of water in the Owens River system has been diverted since 1913 by the City of Los Angeles Department of Water and Power aqueduct. This diversion has resulted not only in a significant drop in the water level in Mono Lake, but has also changed the volume and timing of flows in streams, which in turn has affected riparian habitats. Since the 1970s, groundwater has also been exported to supplement surface water diversions into the Los Angeles Aqueduct. Groundwater pumping has adversely affected or eliminated phreatophytic shrubs and grasses that depend on groundwater in favor of species with lower water requirements, including many weedy species (Groeneveld 1992).

Recreation is the lifeblood of the regional economy. Fishing is extremely popular, adding to the demands for water resources. The ESN region is also the gateway to the recreational resources of the Sierra Nevada, from skiing at Mammoth Mountain and June Mountain to the eastern entrance to Yosemite National Park. Many tourists come to enjoy the scenery and natural history of such unusual attractions as Mono Lake and the ancient Bristlecone pine forests in the White Mountains. Livestock grazing was once extremely intensive, especially sheep which were moved as vast herds. Overgrazing in sagebrush communities leads to a decline in Purshia tridentata which was preferred by native browsers. Fire suppression may also favor sagebrush over P. tridentata and perennial grasses. Mining was once an important economic activity but its main legacy is in historical ghost towns like Bodie. Logging in Jeffrey pine forests does occur on USFS lands but is not nearly as important economically as it is on the Modoc Plateau portion of the Great Basin province.

Land Stewardship

The wilderness designations and expansions to National Parks made by the California Desert Protection Act of 1994 were incorporated from a preliminary digital map of the Bureau of Land Management (BLM) state office. The Bishop Resource Area office of BLM provided digital coverages of the Areas of Critical Environmental Concern under its jurisdiction.

East of Sierra Region Managed Areas

Figure ESN-2. Management status of lands in the East of Sierra Nevada Region. See text for definitions of management levels.

Public agencies manage almost the entire ESN region (94.5%), distributed among USFS (43.1% of the region), BLM (31.1%), NPS (6.8%), Indian reservations (0.1%), California Fish & Game and other state agencies (1.0%), and local governments (11.1%, largely managed by the City of Los Angeles Department of Water and Power in the Owens Valley). The remainder is privately owned (5.5%) or water bodies (1.2%). Private land occurs mostly in the Antelope and Bridgeport valleys at the northern end of the region.

Table ESN-1. Area and percentage of land surface by management status level of the East of the Sierra Nevada Region.

Status Area (km²) %
1 2,112 16.3
2 640 4.9
3 9,435 72.8
4 781 6.0
Total 12,968 100.0

Management profiles by elevation zone are somewhat atypical in the ESN region compared to other regions where higher elevations tend to be better represented than lower elevations. In the ESN (Figure ESN-3), all zones except between 2000-2500 m are represented proportional to their area. This pattern of less status 1 and 2 management at middle elevations reflects the allocation of biodiversity management at the lower elevations in Death Valley National Park and the wilderness areas and botanical areas in the White-Inyo Mountains.

Elevation Bias in ESN Region

Figure ESN-3. Proportion of management status of lands in the East of the Sierra Nevada Region by elevation zones.

Plant Community Types

Landscapes on the eastern flank of the Sierra Nevada range south of Mono Lake were generalized from the 1980 Vegetation Resource Inventory (U. S. Forest Service, unpublished maps). The White-Inyo Mountains were mapped from the Landsat TM-based Inyo National Forest vegetation map. The floor of the Owens Valley was derived from the 1:24,000 scale BLM-SCS soil-vegetation mapping. The remaining areas were delineated subjectively by photointerpretation of patterns in the satellite imagery in conjunction with the CALVEG map (Parker and Matyas 1981), another BLM soil-vegetation map published in the Bodie/Coleville Grazing EIS for the Bodie and Antelope Valley areas, and the VTM maps. Final delineation of a landscape unit was an iterative process based on evidence from the satellite imagery, existing vegetation maps, and field reconnaissance.

Floristic information was derived mainly from the Inyo Vegetation Resource Inventory, the BLM soil-vegetation maps, unpublished maps produced by the VTM survey and from our own field survey. These sources all contained dominant species data. For the White Mountain area, the Forest Service map was classified by CALVEG type (Parker and Matyas 1981). We ascribed dominant species to each of the vegetation types because we felt the types were relatively simple and consistent. The BLM-SCS data for the Owens Valley represented plots which they extrapolated to landscapes of the same community type. Researchers at UCSB then summarized the three dominant species associated with each community type. Of the 1,371 landscapes in the region, 175 were visited in the field during 1995, covering 44% of the region. These landscapes tend to be larger than average because of the absence of detailed existing maps.

Because source information ranged widely in date and reliability, the current database is uneven in both level of detail and accuracy. We did not have the resources to assess the statistical accuracy of the vegetation map and associated database. However, we have appraised the product using less formal methods that have guided our use of it. Classes are probably more accurate than species data in the White Mountains where species were inferred from CALVEG classes. Forest Service maps depict Pinyon-juniper types which may contain patches dominated by either species alone or co-dominated by both. In the absence of field data to the contrary, both species were coded in the database and assigned to the more general Great Basin Woodlands type. Subalpine Sagebrush Scrub, which is well-developed in the White-Inyo Mountains (Holland 1986), was not identified in existing map sources; therefore this type does not appear in the gap analysis database. Portions of the region without existing vegetation maps such as east of the White Mountains have the least spatial detail and were assigned species attributes from sparse field reconnaissance. These areas will tend to be the most generalized and least accurate.

We classified 12,191 km² (92.8%) of the ESN region as vegetated other than agricultural or horticultural land cover. In other words, 7.2% has been converted to urban or agricultural uses or contains open water or bare ground. The vegetation layer was delineated into 1,371 landscape units with an average size of 967 ha. Distributional information is provided on 72 dominant plant species, 38 community types and 9 land use/land cover types.

Based on our system for converting dominant species assemblages into natural community types, we mapped 38 community types within the ESN region. Twenty-four of the 38 types were mapped with an area greater than 25 km². Great Basin Woodlands, Great Basin Mixed Scrub, and Shadscale Scrub are the most extensive types, covering 2,429 km², 2,223 km², and 1,053 km², respectively. Eight community types contribute 76% of the region's total vegetated area. Two new community types were described by the Gap Analysis project to supplement the Holland (1986) classification for this region­Low Sagebrush Scrub and Cercocarpus ledifolius Woodland.

Table ESN-2. Percent area of each CNDDB community type at each management status level in the East of Sierra Nevada Region. * indicates an addition to the standard CNDDB classification (Holland 1986).

CNDDB Code CNDDB Community Name (Holland 1986) CNDDB Rank Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
34100 Mojave Creosote Bush Scrub S4 85.0 0.0 14.8 0.2 644.6 85.0
34210 Mojave Mixed Woody Scrub S3.2 7.0 2.3 88.1 2.5 718.3 9.3
34300 Blackbush Scrub S3.2 3.7 1.0 91.7 3.6 284.5 4.7
35100 Great Basin Mixed Scrub S4 11.6 6.4 75.2 6.9 2,223.0 18.0
35210 Big Sagebrush Scrub S4 17.6 0.5 75.5 6.4 949.0 18.1
35211 Low Sagebrush Scrub * -- 1.9 8.1 77.8 12.2 196.6 10.0
35400 Rabbitbrush Scrub S5 30.0 0.0 67.9 2.1 8.2 30.0
35500 Cercocarpus ledifolius Woodland * -- 10.3 3.6 82.6 3.5 408.3 13.9
36110 Desert Saltbrush Scrub S3.2 13.2 13.0 70.4 3.3 602.9 26.2
36120 Desert Sink Scrub S3.1 43.8 2.0 51.0 3.1 399.6 45.8
36130 Desert Greasewood Scrub S3.2 0.6 12.8 72.0 14.5 342.6 13.4
36140 Shadscale Scrub S3.2 7.3 5.0 85.3 2.4 1,053.1 12.3
42200 Non-Native Grassland S4 0.0 80.6 19.3 0.1 2.9 80.6
43000 Great Basin Grassland S1.1 0.0 1.2 98.2 0.6 17.5 1.2
45100 Montane Meadow S3.2 0.4 3.2 64.7 31.7 33.3 3.6
45200 Subalpine or Alpine Meadow S3.2 5.9 0.0 86.7 7.3 13.5 5.9
45310 Alkali Meadow S2.1 0.0 10.9 82.1 4.0 429.0 10.9
52320 Transmontane Alkali Marsh S2.1 2.2 20.6 54.0 23.2 13.4 22.8
52420 Transmontane Freshwater Marsh S2.2 0.0 0.0 30.6 69.4 98.9 0.0
61520 Aspen Riparian Forest S3.2 0.9 6.5 76.4 16.2 59.3 7.4
61530 Montane Black Cottonwood Riparian Forest S3.2 0.0 7.4 26.3 66.3 20.2 7.4
61610 Modoc-Great Basin Cottonwood-Willow Riparian Forest S2.1 0.0 0.0 99.9 0.1 14.9 0.0
63500 Montane Riparian Scrub S4 0.0 0.0 100.0 0.0 1.4 0.0
63600 Modoc-Great Basin Riparian Scrub S2.1 0.0 18.9 63.5 17.6 60.3 18.9
71150 Interior Live Oak Woodland S3.2 100.0 0.0 0.0 0.0 0.2 100.0
72100 Great Basin Woodlands S3.2/4 16.1 3.8 74.9 5.2 2,428.5 19.9
72200 Mojavean Pinyon and Juniper Woodlands S3.2/4 71.8 0.0 28.2 0.0 10.8 71.8
73000 Joshua Tree Woodland S3.2 88.3 0.0 11.0 0.8 50.0 88.3
81320 Canyon Live Oak Forest S4 64.3 0.0 35.7 0.0 0.9 64.3
81B00 Aspen Forest S3.2 0.4 0.7 96.2 2.7 59.2 1.1
85100 Jeffrey Pine Forest S4 1.4 5.8 89.3 3.5 617.3 7.2
85210 Jeffrey Pine-Fir Forest S4 0.3 59.0 39.1 1.6 12.2 59.3
86100 Lodgepole Pine Forest S4 2.6 0.7 89.3 7.4 53.3 3.3
86220 Whitebark Pine-Lodgepole Pine Forest S4 8.5 0.0 89.9 1.6 43.4 8.5
86400 Bristlecone Pine Forest S2.3 32.9 17.6 49.5 0.0 95.3 50.5
86600 Whitebark Pine Forest S4 10.1 0.0 87.6 2.3 7.3 10.1
86700 Limber Pine Forest S2.3 0.0 0.0 100.0 0.0 0.4 0.0
94000 Alpine Dwarf Scrub S4 11.5 2.5 85.9 0.0 217.1 14.0

Regional Total-Natural Communities


Regional Total (incl nonvegetated)
16.3 4.9 72.8 6.0 13,128 21.2

1. Plant community types mainly on status 4 (primarily private) lands. Because most of the region is publicly owned, few of the 38 types have the majority of their distributions on private land. The two exceptions are Transmontane Freshwater Marsh and Montane Black Cottonwood Riparian Forest, although the latter covers slightly less than 25 km².

2. Scrub and herbaceous types mainly located in unprotected areas. Three of the 21 scrub and herbaceous types were mapped with areas greater than 25 km² and with less than 10% of their distribution in Status 1 and 2 managed areas, which are designated for conservation of native biodiversity. These include Blackbush Scrub, Low Sagebrush Scrub, and Montane Meadow. Blackbush (Coleogyne ramosissima) is a paleoendemic or a relict species whose range was formerly much wider (Stebbins and Major 1965). Mojave Mixed Woody Scrub also meets these criteria but is considered to be a marginal type in this region. Alkali Meadow has 10.9% of its mapped area in managed areas but is also of concern because of the potential adverse impact of groundwater pumping. Lowering the water table can reduce cover or eliminate entirely the native grasses and Atriplex lentiformis ssp. torreyi (Groeneveld 1992). Other wetland and riparian types also appear poorly represented on Status 1 and 2 lands but have mapped distributions below the criterion. Therefore, we have less confidence in the accuracy of their management profiles. Slight errors in mapping could make significant differences in whether or not they appear protected.

3. Forest and woodland types mainly located in unprotected areas. Three of the 16 forest and woodland types were mapped with areas greater than 25 km² and with less than 10% of their distribution in Status 1 and 2 areas. These include Aspen Riparian Forest, Aspen Forest and Jeffrey Pine Forest. These types are almost exclusively on public lands, and are of management concern primarily because of grazing, which is widespread. Lodgepole Pine Forest and Whitebark Pine-Lodgepole Pine Forest also meet these criteria but are more characteristic of the Sierra Nevada and tend to be outliers in the ESN region.

4. Community types that appear well-protected. Five types were mapped with areas greater than 25 km² and with more than 25% of their distribution in Status 1 and 2 areas. These include Mojave Creosote Bush Scrub, Desert Saltbush Scrub, Desert Sink Scrub, Joshua Tree Woodland, and Bristlecone Pine Forest. These types represent the lower elevation sites in Death Valley National Park and the higher elevations in the White-Inyo Mountains. These types are of relatively low priority for additional land acquisition or allocation to Status 1 and 2. Other types common in the Great Basin such as sagebrush and the piñon-juniper woodlands are also relatively well-represented but not to the same level as the types listed above.

The ESN Region is the southernmost portion of the Great Basin Province in California (Hickman 1993). The management status of community types in the ESN region may not be representative of the province as a whole. Therefore, our findings should be considered tentative and apply only to the California portion of the ecoregion. However, most Great Basin types are not well-represented in managed areas in other states within the ecoregion either (Caicco et al. 1995. Edwards et al. 1995).

CA-GAP Home | Overview | Report | Download GIS | CD-ROM | Site Index | National GAP

Top of Page

Send your comments to: stoms@geog.ucsb.edu

UCSB Biogeography Lab Home

Email stoms@bren.ucsb.edu