Natural Resources
Conservation Service
Ecological site R030XA175CA
Sandy upper fan apron
5-8" p.z.
Last updated: 2/18/2025
Accessed: 08/20/2026
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Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Ecological site concept
This ecological site is located on alluvial fans and fan aprons. It is typically located near hills from which it receives more direct runoff than the lower end of the fan apron. This ecological site occurs on sandy and sandy-skeletal soils.
Please refer to group concept R030XA002CA to view the provisional STM.Table 1. Dominant plant species
Tree (1) Acacia greggii
Shrub (1) Ephedra californica
(2) Psorothamnus arborescensHerbaceous Not specified
Physiographic features
This ecological site is located on alluvial fans and fan aprons. It is typically located near hills from which it receives more direct runoff than the lower end of the fan apron.
Table 2. Representative physiographic features
Landforms (1) Fan apron
(2) Alluvial fan
(3) Drainageway
Flooding duration Very brief (4 to 48 hours) Flooding frequency None to rare Elevation 2460 – 3500 ft Slope 2 – 8 % Water table depth 72 – 0 in Aspect Aspect is not a significant factor Climatic features
The Mojave Deserts experiences clear, dry conditions for most of the year. Monthly minimum temperature averages range from 30 to 80 degrees F (-1 to 27 degrees C). Monthly maximum temperature averages range from 60 to 110 degrees F (16 to 43 degrees C). This ecological site receives 5 to 8 inches of rain in an average year. Rainfall distribution is bimodal.
">Influencing water features
Soil features
This ecological site occurs on sandy and sandy-skeletal soils.
Morongo--Mixed, thermic Typic Torripsamments
Arizo--Sandy-skeletal, mixed, thermic Typic Torriorthents
Table 3. Representative soil features
Surface texture (1) Sand
Family particle size (1) Sandy
Drainage class Somewhat excessively drained Permeability class Rapid to very rapid Soil depth 60 – 0 in Surface fragment cover <=3" 40 – 75 % Surface fragment cover >3" 0 – 10 % Available water capacity
(0-40in)1.6 – 3.2 in Calcium carbonate equivalent
(0-40in)0 – 1 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 4 Soil reaction (1:1 water)
(0-40in)6.2 – 7.8 Subsurface fragment volume <=3"
(Depth not specified)1 – 30 % Ecological dynamics
Please refer to group concept R030XA002CA to view the provisional STM.
Water is a major factor affecting this ecological site. The major species on this site have a greater water requirment than other Mojave Desert species. This site is typically found near hills from which it receives runon. Close to the hills, the water disturbance is more pronounced than on the lower fan apron. This allows several species tolerant of water disturbance to dominate.
The major species are catclaw (Acacia greggii), California jointfir (Ephedra californica), and Mojave indigobush (Psorothamnus arborescens). These species are found on alluvial soils as well as hilly, rocky areas from which water runs off quickly. The ability to adapt to these different growing substrates helps explain why this ecological site can be found on skeletal and non-skeletal soils.
This ecological site is located near urban areas that may affect the ecological site. Road and housing construction may alter flow of water down the alluvial fan and fan arpon. Disturbance-adapted, colonizing species such as burrobrush (Hymenoclea salsola) may become more abundant. Joints of cactus species such as golden cholla (Cylindropuntia echinocarpa) are easily broken off during a disturbance and readily distributed gravity and by attaching to distribution agents such as humans or animals.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
Catclaw-California jointfirCommunity 1.1
Catclaw-California jointfirThis ecological site is dominated by catclaw acacia (Acacia gregii) and California jointfir (Ephedra californica). Other species include burrobrush (Hymenoclea salsola) and Mojave indigobush (Psorothamnus arborescens). Big galleta (Pleuraphis rigida) may be present in small amounts.
Figure 1. Annual production by plant type (representative values) or group (midpoint values)
Table 4. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Shrub/Vine 100 500 800 Forb 25 250 500 Grass/Grasslike 25 100 200 Total 150 850 1500 Table 5. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 20-30% Grass/grasslike foliar cover 10-10% Forb foliar cover 10-30% Non-vascular plants 0% Biological crusts 0% Litter 10-20% Surface fragments >0.25" and <=3" 20-30% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 10-20% Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Shrub/Vine1 Shrubs 100–800 catclaw acacia ACGR Acacia greggii 150–300 – California jointfir EPCA2 Ephedra californica 100–300 – creosote bush LATR2 Larrea tridentata 0–100 – Mojave indigobush PSAR4 Psorothamnus arborescens 50–100 – burrobrush HYSA Hymenoclea salsola 25–75 – desert almond PRFA Prunus fasciculata 50–75 – Mojave yucca YUSC2 Yucca schidigera 25–75 – white ratany KRGR Krameria grayi 25–50 – Eastern Mojave buckwheat ERFA2 Eriogonum fasciculatum 25–50 – Mexican bladdersage SAME Salazaria mexicana 5–25 – Wiggins' cholla CYEC3 Cylindropuntia echinocarpa 5–15 – Grass/Grasslike2 Annual grasses 25–200 red brome BRRU2 Bromus rubens 25–200 – common Mediterranean grass SCBA Schismus barbatus 25–200 – Forb3 Annual forbs 25–500 pincushion flower CHFR Chaenactis fremontii 25–450 – redstem stork's bill ERCI6 Erodium cicutarium 25–200 – chuckwalla combseed PEHE Pectocarya heterocarpa 25–100 – small wirelettuce STEX Stephanomeria exigua 25–100 – Interpretations
Animal community
This area is suitable habitat for small mammals and reptiles.
Hydrological functions
This ecological site receives run-on from adjacent hills. Water availability and disturbance is an important factor affecting plant community composition.
Recreational uses
Urban development occurs in the vicinity of this ecological site.
Supporting information
Inventory data references
Cover data for this ecological site was described using 2 line-point intercept transects. The complete protocol for this sampling method is found in Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems, Volume 1: Quick Start. Production data for this ecological site was described using 2 modified double-sampling transects. The protocol was modified by California State Rangeland Ecologist Kendra Moseley to use fewer plots and less destructive sampling. The complete protocol for this sampling method is found in Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems, Volume 2: Design, supplementary methods and interpretation.
Contributors
Allison Tokunaga
Approval
Kendra Moseley, 2/18/2025
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 08/20/2026 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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