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Appendix 2-1. Description of Natural Community Types Added for the California Gap Analysis Project

Twelve natural community types were mapped and described for the CA-GAP to supplement the types previously described by Holland (1986). These new descriptions are provided here to assist the reader in interpreting the results of the analysis. Often the descriptions are borrowed for other sources. The source (or author) of the description is listed at the end of each description.

In some cases, the types described by Holland were aggregated for CA-GAP to a higher classification level (e.g., all pinyon and/or juniper woodland types in the Great Basin were combined for CA-GAP into a Great Basin Woodlands type). These higher level types are described by a synthesis of Holland's descriptions of the individual types, and thus are not published here. Also, som ecommunity types were listed by Holland (1986) but not described. For these types (e.g. Limber Pine Forest), we relied on the descriptions in Sawyer and Keeler-Wolf (1995) or occasionally on Küchler (1977).

In addition to these twelve new types, CA-GAP mapped 27 non-vegetated or human-dominated land use types. These types were based on the classifications of Anderson et al. (1976), Cowardin et al. (1979), Mayer and Laudenslayer (1988), and Schultze (1994). A complete set of descriptions of all land cover and land use types mapped for CA-GAP is published at http://www.biogeog.ucsb.edu/projects/gap/data/cnddb/list.html.

A version of all the community descriptions is available for download here as a Windows help file.



Salvia dorri/Chamaebatiaria Scrub
Low Sagebrush Scrub
Silver Sagebrush Scrub
Black Sagebrush Scrub
Cercocarpus ledifolius Woodland
Desert Holly Scrub
Desert Native Grassland
Great Basin Wet Meadow
Southern Alluvial Fan Scrub
Pinyon-Oak Woodland
Modoc White Fir Forest
Red Fir-Western White Pine Forest


35110 Salvia dorri/Chamaebatiaria Scrub

Description: Moderate density of aromatic woody shrubs, mostly 1-2 m in height. Salvia dorrii and Chamaebatiaria millefolium are dominant, but many other Great Basin species may be present in shrub layer. Artemisia tridentata and Purshia tridentata are most important. Understory layer of scattered, diverse bunchgrasses and cheatgrass.

Site factors: Well drained substratum of basalt lava flow. Elevation of big sagebrush and juniper woodland. In ungrazed areas, a possible factor in promoting the abundance of the two dominant shrubs over sagebrush.

Characteristic species: Achnatherum lettermanii (Stipa), Achnatherum occidentalis (Stipa), Achnatherum speciosum (Stipa), Achnatherum thurberiana (Stipa), Artemisia tridentata, Bromus tectorum, Chamaebatiaria millefolium, Chrysothamnus viscidiflorus, Festuca idahoensis, Hesperostipa comata (Stipa), Poa secunda, Psuedoroegneria spicata (Agropyron spicatum), Purshia tridentata, Salvia dorrii.

Distribution: Occurs in Lava Beds National Monument, an area of relatively recent basalt lava flows. Elevations from about 1400-1600 m. Distribution elsewhere uncertain.

Source: Adapted from Erhard, D.H. 1979. Plant Communities and Habitat Types in the Lava Beds National Monument, California. Masters Thesis, Oregeon State University.


35211 Low Sagebrush Scrub

Description: Analogous to Subalpine Sagebrush scrub (35220), but at lower elevations. Scattered Artemisia arbuscula less than .5 m in height, with abundant bunchgrass. Shrub height and density decrease in low lying areas that are water logged longer during spring (scabland). Some taller Artemisia tridentata and Purshia tridentata may be mixed in.

Site factors: Areas of heavy clay soil that become saturated. Elsewhere where soil generally is of finer texture and more poorly drained than where Big Sagebrush occurs. Where low sage and big sage are intermixed on the Modoc Plateau, low sage generally occupies the poorer microsites. Low sage may, however, dominate rocky well drained sites that appear suited for big sage on the Modoc Plateau. Low sage may dominate south facing exposures in areas where north facing exposures are dominated by big sage.

Characteristic species: Achnatherum lettermanii (Stipa), Achnatherum occidentalis (Stipa), Achnatherum speciosum (Stipa), Achnatherum thurberiana (Stipa), Artemisia arbuscula, Artemisia tridentata, Bromus tectorum, Chrysothamnus nauseosus, Chrysothamnus viscidiflorus, Festuca idahoensis, Koeleria cristata, Psuedoroegneria spicata (Agropyron spicatum),Taeniantherum caput-medusae.

Distribution: Dominant vegetation over lower elevations (1300-1700 m) of the Modoc Plateau, Cascades, and northern Sierra Nevada. Also scattered at higher elevations.

Source: California Gap Analysis Project (Dennis Odion)


35212 Silver Sagebrush Scrub

Description: Similar to big sagebrush scrub, but dominated by Artemisia cana, and the relatively large bunchgrass Elymus cinereus. Other salt tolerant species (e.g. Sarcobatus vermiculatus) may be present, and increase in abundance toward bottom of basins which this type occurs in.

Site factors: More finely drained soils with higher salt content than where big sagebrush occurs. Pluvial lakebeds on the Modoc Plateau. Soil surface horizons are saturated by spring accumulations of snowmelt runoff, which forms a perched water table over slowly permeable lower horizons. Elevations slightly above Desert Greasewood Scrub.

Characteristic species: Artemisia Cana, Artemisa tridentata, Leymus cinereus (Elymus), Prunus andersonii, Sarcobatus vermiculatus, Sitanion histrix.

Distribution: Modoc Plateau, north, south and east of Honey Lake. Surprise Valley. Silver Sagebrush dominates, with different associated species, in most of bottomland area of Monanche and Templeton meadows, the largest "meadows" (potential meadow systems) in the Sierra Nevada.

Source: California Gap Analysis Project (Dennis Odion)


35213 Black Sagebrush Scrub

Description: Black sagebrush (Artemisia nova) is the sole or dominant shrub. Shrubs usually less than 0.5 meter in height.

Site Factors: Often found on limestone derived soils, on flats, slopes and ridges in mountains.

Characteristic species: Artemisia nova. Associated shrubs include green ephedra (Ephedra viridis), shadscale (Atriplex confertifolia), and/or winter fat (Krascheninnikovia lanata). Emergent Utah juniper (Juniperus osteosperma) and/or singleleaf pinyon (Pinus monophylla) may also be present.

Distribution: Found on ranges in east Mojave region, but mapped only on Cottonwood Mountains in Death Valley.

Source: California Gap Analysis Project (Kathryn Thomas)


35500 Cercocarpus ledifolius Woodland

Description: Scattered to nearly continuous, relatively large (2-4.5 m) Cercocarpus ledifolius with sagebrush and associated species occupying a lower stratum. Juniperus occidentalis and montane conifers occasionally present.

Site factors: Well drained rocky soils. Relatively moister sites within the sagebrush zones, but relatively drier and more exposed sites within the Ponderosa Pine and White Fir zones.

Characteristic species: Achnatherum lettermanii (Stipa), Achnatherum occidentalis (Stipa), Achnatherum speciosum (Stipa), Achnatherum thurberiana (Stipa), Artemisia arbuscula, Artemisia tridentata, Bromus tectorum, Cercocarpus ledifolius, Chrysothamnus nauseosus, Festuca idahoensis, Juniperus occidentalis, Pinus ponderosa, Psuedoroegneria spicata (Agropyron spicatum), Purshia tridentata, Taeniantherum caput-medusae.

Distribution: Eastern Sierra on exposed ridges from 2000-3000+ m in association with Pinyon Juniper woodland, Juniperus occidentalis, etc. Great Basin, scattered in Big Sagebrush zone, becoming most abundant in Juniper woodland zone, and at ecotone with other conifer vegetation.

Source: California Gap Analysis Project (Dennis Odion)


36150 Desert Holly Scrub

Description: Desert holly (Atriplex hymenelytra) is the sole or conspicuous shrub. Shrubs usually less than 1 meter in height.

Site factors: Found on alluvial fans, in washes, and on stoney outcrops and ridges.

Characteristic species: Atriplex hymenelytra. Associated species may include brittlebush (Encelia farinosa), creosote bush (Larrea tridentata), tidestromia (Tidestromia obongifolia) or bursage (Ambrosia dumosa).

Distribution: Very common in the Death Valley area.

Source: Adapted from Sawyer and Keeler-Wolf (1995).


42160 Desert Native Grassland

Description: Perennial bunchgrasses dominated solely or in combination by Indian Ricegrass (Oryzopsis hymenoides) and/or Desert Needlegrass (Achnatherum speciosum) and/or Big Galleta (Pleauraphis rigida). Grasses less one meter in height except for Indian Ricegrass which is less than 1.5 meters.

Site factors: Occurs on flat ridges, lower slopes, often in stabilized sandy areas. Stands are often small.

Characteristic species: Achnatherum speciosum, Oryzopsis hymenoides, Pleauraphis rigida. Emergent shrubs may be present where Big Galleta is dominant. Joshua Tree (Yucca brevifolia) also.

Distribution: This type includes at least three of the CNPS proposed alliances for the Mojave. Further study of the distribution of the type is recommended.

Source: California Gap Analysis Project (Kathryn Thomas)


45500 Great Basin Wet Meadow

Description. Analogous to Holland'ís Montane Meadow (45100). Dense growth of sedges, grasses and rushes. Generally somewhat taller (to 1.5m tall) than typical montane meadow vegetation. Very active and rapidly growing vegetation in summer due to rich soils and plentiful moisture in basins where appropriate habitat is found.

Site Factors. Fine-textured, permanently moist soils. Often heavily utilized by cattle. Many areas harvested as hay and manipulated to increase coverage by grasses as opposed to sedges and rushes. Hydrology often modified by network of irrigation ditches.

Characteristic species. Carex nebrascensis, Carex spp., Deschampsia caespitosa, Juncus spp., Phalaris arundinacea, many species listed under Montane Meadow in Holland.

Distribution. Scattered in basins throughout Modoc Plateau region. Extensive at Steele Swamp, Jess Valley, Ash Meadows, Fall River Mills, and along Pit River.

Source: California Gap Analysis Project (Dennis Odion)


63330 Southern Alluvial Fan Scrub

Description: This type is an open to moderately dense, broad-leaved phreatophyte evergreen scrub that attains a height of 1-1.5 m. It is dominated by Lepidospartum squamatum (Scalebroom), which is primarily restricted to floodplain habitats although it occurs rarely in other habitats such as in the Badlands of Riverside County.

Site factors: Southern Alluvial Fan Scrub is primarily restricted to floodplain habitats containing riverine cobbles, boulders, and sand. These areas apprarently flood only occasionally (every 5 to 10 years), therefore many upland species become established in the streamside habitat. The occasional flooding and sediment reworking, however, is the driving force that maintains this vegetation type.

Characteristic species: Common subdominant shrub species include Artemisia californica or A. tridentata ssp. parishii (mainly with desert affinities), plus Sambucus mexicana, and various coastal sage scrub and chaparral species. The open understory areas are typically dominated by ruderal herbaceous species (native and non-native) usually associated with grassland communities. Scattered riparian trees and shrubs are often found in association with Scalebroom and include Platanus racemosa, Baccharis salicifolia, and sometimes Populus fremontii. Southern Alluvial Fan Scrub is likely an early seral stage of Riversidian Alluvial Fan Sage Scrub (32720).

Distribution: Southern Alluvial Fan Scrub occurs in central and southern cismontane California from the Monterey Bay area to northern Baja California. Formerly extensive along floodplain habitats of southern and central California, it is now very much reduced by flood control, agriculture, and urban expansion.

Source: Adapted from Magney (1992).


71600 Oak-Piñon Woodland

Description: An unusual combination of Pinus monophylla with Quercus chrysolepis.

Site Factors: Dry sites in the transition between cismontance oak woodlands and transmontane piñon woodlands.

Characteristic Species: Arctostaphylos glauca, Cercocarpus betuloides, Pinus monophylla, Quercus berberidifolia, Q. chrysolepis, Q. wislizenii.

Distribution: Middle elevations of the southern Sierra Nevada near Walker Pass. In addition, there is one occurrence in Kings Canyon in Fresno County.

Source: California Gap Analysis Project (David Stoms)


84260 Modoc White Fir Forest

Description: Forest strongly dominated by Abies concolor. Many of associated forest trees found with white fir elsewhere in California are not present. Understory sparse. Size of forest trees smaller (25-40 m tall) in Modoc Plateau region compared to Sierra. Understory sparse except in openings. Described by Riegel, Thornburgh, and Sawyer (1990).

Site factors: Colder and more arid, continental climate than where white fir forest occurs elsewhere in the state. Preciptitation averages 454 mm at Jess Valley on the west side of the Warner Mountains (Pease 1965). Heavily impacted by cattle, particularly around the turn of the century (Pease 1965).

Characteristic species: Abies concolor, Arenaria jamesiana, Artemisia tridentata (openings), Hieracium albiflorum, Lupinus caudatus, Pinus ponderosa (lower elevs.), Pinus jeffreyi (higher elevs.), Pinus washoensis (higher elevs.), Osmorhiza chilensis, Pyrola picta, Ribes viscosissimum, Symphoricarpos vaccinoides.

Distribution: 1500-2500 m elevation in all mountain ranges of Modoc Plateau. Occurs on all aspects, except at lowest elevations, where mainly restricted to north-facing slopes and mesic canyon bottoms. White fir spans the elevation gradient occupied by both white (montane) and red (subalpine) fir in the Sierra Nevada. Especially important in the Warner Mountains.

Source: California Gap Analysis Project (Dennis Odion)


85120 Red Fir (or Lodgepole Pine)-Western White Pine Forest

Description: Scattered mixed stands of mainly Pinus monticola and Abies magnifica amidst the more dominant Red Fir and Lodgepole Pine types, sometimes in nearly pure small stands of P. monticola. Understory often underdeveloped or absent.

Site factors: Well-drained rocky soils, and other better drained and often drier and more exposed (e.g. south - southwest aspected) microsites in the Red Fir and Lodgepole Pine dominated zone.

Characteristic species: Pinus monticola, Abies magnifica, Pinus contorta ssp murrayana, Ribes spp., Symphoricarpos spp., Chrysolepis chrysophylla.

Distribution: Mainly in central and southern Sierra Nevada. In Yosemite Region typically between 8000-9500', small isolated patches at the bottoms of talus slopes or on exposed drier ridges.

Source: California Gap Analysis Project (Rich Walker)


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