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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
Classification relationships
Holland, R.F. 1986. Preliminary descriptions of the terrestrial natural communities of California. Unpublished report. State of California, The Resources Agency, Department of Fish and Game, Natural Heritage Division, Sacramento, CA. (Updated September 2003). Element Code: Curlleaf Mountain Mahogany- Big Sagebrush 76.200.01.
Sawyer, J.O. and T. Keeler-Wolf. 1995. A Manual of California Vegetation. California Native Plant Society, Sacramento, CA. Curlleaf Mountain-mahogany Series.
Associated sites
R021XE206CA Mountain Shoulders 30+ P.Z.
R021XE210CA Mahogany Savanna
R021XE221CA Claypan 30+ P.Z.
R021XE222CA Loamy Slope 30+ P.Z.
Similar sites
R021XE210CA Mahogany Savanna
Less productive site, more open canopy with a diverse understory of shrubs and perennial grasses and forbs.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Cercocarpus ledifolius
Herbaceous (1) Achnatherum
(2) Bromus marginatusPhysiographic features
This site occurs on mountain sideslopes, often associated with rock outcrops. Slopes range from 15 to 50 percent. Elevations range from 6000 to 8300 feet.
Table 2. Representative physiographic features
Landforms (1) Mountain slope
Elevation 6000 – 8300 ft Slope 15 – 50 % Aspect Aspect is not a significant factor Climatic features
The climate of this site is subhumid, characterized by warm, dry summers and cold, moist winters. The area's precipitation comes mostly from winter Pacific cyclonic storms, with a very slight summer monsoonal season that is erratic but can be locally significant. Average annual precipitation is 30 to 50 inches with most occurring during the winter months. Approximately half the precipitation falls as snow; half as rain. The mean annual air temperature is 38 to 44 degrees F. The average growing season is about 50 to 80 days.
Table 3 Representative climatic features
Frost-free period (average) 80 days Freeze-free period (average) 0 days Precipitation total (average) 50 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
There are no influencing water features associated with this site.
Soil features
The soils associated with this site are very shallow and shallow to weathered, fractured andesite. They are well drained and formed in volcanic ash and colluvium over residuum derived from andesite or tuff. These soils have high amounts of vitric volcanic ash and glass throughout the profile which enhances the waterholding capacity of the soil. The profile is modified with 60 to 80 percent rock fragments, mainly gravels. A mollic epipedon occurs from the mineral soil surface to 13 inches. An argillic horizon occurs from 4 to 13 inches. Soil series associated with this site include Dawgbuffer.
Table 4. Representative soil features
Parent material (1) Colluvium – andesite
Surface texture (1) Very gravelly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid Soil depth 7 – 14 in Surface fragment cover <=3" 35 – 40 % Surface fragment cover >3" 0 – 5 % Available water capacity
(0-40in)1 – 2 in Calcium carbonate equivalent
(0-40in)Not specified Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)6.3 – 6.5 Subsurface fragment volume <=3"
(Depth not specified)40 – 70 % Subsurface fragment volume >3"
(Depth not specified)0 – 5 % Ecological dynamics
The successional role of curlleaf mountain mahogany varies with community type. Mountain brush communities in which curlleaf mountain mahogany is either dominant or codominant are generally stable. Changes in relative abundance of codominant species may occur; however, succession rates are extremely slow because vegetation changes depend on soil development which is also slow. As ecological condition declines, understory grasses and forbs are reduced. Heavy browsing by livestock or big game animals can adversely affect the productivity and reproduction of curlleaf mountain mahogany.
Fire Ecology:
The presettlement fire regime of curlleaf mountain mahogany communities probably varied with community type and structure. Curlleaf mountain mahogany may depend on fire to reduce conifer competition and produce favorable soil conditions for seedling establishment. Individual curlleaf mountain-mahogany are severely damaged by fire. Because many dead branches persist in the crown and leaves are slightly resinous, curlleaf mountain-mahogany is probably very flammable. Curlleaf mountain mahogany is a weak sprouter after a fire. In many instances, patterns of burning are indicated by old, large trees in rocky, fire-resistant sites adjacent to young stands in less rocky sites more vulnerable to fire.
Little specific information is available on adaptations of Letterman's needlegrass to fire. It is morphologically similar to Columbia needlegrass, which is only slightly to moderately damaged by fire. Season of burn affects the plant's ability to survive a fire. Needlegrasses tends to be more susceptible to fire when burned during mid-summer. Post fire regeneration is through seeding and tillering.State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Reference StateCommunity 1.1
Reference Plant CommunityThe reference plant community is dominated by a very dense stand of curlleaf mountain mahogany, usually averaging less than 25-feet high. Mountain big sagebrush, needlegrass and bluegrass are important species in the relatively sparse understory. Overstory canopy cover of mountain mahogany exceeds 50 percent. Potential vegetative composition is about 15% grasses, 5% forbs and 80% shrubs.
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Shrub/Vine 3200 4000 5200 Grass/Grasslike 600 750 975 Forb 200 250 325 Total 4000 5000 6500 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Primary Perennial Grasses 480–800 Letterman's needlegrass ACLE9 Achnatherum lettermanii 175–250 – western needlegrass ACOCO Achnatherum occidentale ssp. occidentale 175–250 – mountain brome BRMA4 Bromus marginatus 100–250 – bluegrass POA Poa 30–50 – 2 Secondary Perennial Grasses 100–400 big squirreltail ELMU3 Elymus multisetus 25–100 – slender wheatgrass ELTRT Elymus trachycaulus ssp. trachycaulus 25–100 – Idaho fescue FEID Festuca idahoensis 25–100 – bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 25–100 – Forb3 Perennial Forbs 225–450 common yarrow ACMI2 Achillea millefolium 25–50 – sagebrush mariposa lily CAMAM9 Calochortus macrocarpus var. macrocarpus 25–50 – castilla CASTI Castilla 25–50 – tapertip hawksbeard CRAC2 Crepis acuminata 25–50 – naked buckwheat ERNU3 Eriogonum nudum 25–50 – lupine LUPIN Lupinus 25–50 – Brown's peony PABR Paeonia brownii 25–50 – cold-desert phlox PHST11 Phlox stansburyi 25–50 – woolly mule-ears WYMO Wyethia mollis 25–50 – 4 Annual Forbs 50–100 Shrub/Vine5 Primary Shrubs 3000–4250 curl-leaf mountain mahogany CELE3 Cercocarpus ledifolius 3000–4250 – 6 Secondary Shrubs 250–1000 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 50–200 – gooseberry currant RIMO2 Ribes montigenum 50–200 – American black elderberry SANIC4 Sambucus nigra ssp. canadensis 50–200 – roundleaf snowberry SYRO Symphoricarpos rotundifolius 50–200 – Interpretations
Animal community
Livestock Interpretations:
This site has limited value for livestock grazing due to steep slopes and limited access. Grazing management should be keyed to palatable shrub and perennial grass production. Needlegrass species begin growth early in the year and remain green throughout a relatively long growing season. This pattern of development enables animals to use needlegrass when many other grasses are unavailable. Cattle prefer needlegrass in early spring before fruits have developed as it becomes less palatable when mature. Needlegrasses are usually grazed in the fall only if the fruits are softened by rain.
Stocking rates vary over time depending upon season of use, climate variations, site, and previous and current management goals. A safe starting stocking rate is an estimated stocking rate that is fine tuned by the client by adaptive management through the year and from year to year.
Wildlife Interpretations:
The evergreen nature of mountain mahogany and mountain big sagebrush make stands of these species important year-round habitat for mule deer. Mountain mahogany provides valuable browse, and hiding and thermal cover in both summer and winter. Mountain mahogany is one of the few browse species that meets or exceeds the protein requirements for wintering big game animals.
Hydrological functions
Runoff is medium to high.
Wood products
Mountain mahogany is used for barbecue fuel.
Other information
Mountain mahogany may be planted to help stabilize soil in disturbed areas such as roadcuts and mine spoils. Because of its tolerance to heat and drought, mountain mahogany can be used for water-efficient landscaping.
Letterman’s needlegrass has been used successfully in revegetating mine spoils, and erosion control.Supporting information
Type locality
Location 1: Modoc County, CA Township/Range/Section T39N R16E S35 Latitude 41° 12′ 38″ Longitude 120° 6′ 58″ General legal description Near mouth of Snowslide Canyon, on the Modoc National Forest in the Warner Mountains, Modoc County, CA. Other references
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).
Contributors
P.NOVAK-ECHENIQUE
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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