Ecological site R030XB204AZ

General information

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.

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Figure 1. Mapped extent

Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.

MLRA notes

Major Land Resource Area (MLRA): 030X–Mojave Basin and Range

AZ CRA 30.2 – Middle Mohave Desert

Elevations range from 1500 to 3200 feet and precipitation averages 6 to 9 inches per year. Vegetation includes creosotebush, white bursage, yucca, prickly pear and cholla species, Mormon tea, flattop buckwheat, ratany, winterfat, bush muhly, threeawns, and big galleta. The soil temperature regime is thermic and the soil moisture regime is typic aridic. This unit occurs within the Basin and Range Province and is characterized by broad basins, valleys, and old lakebeds. Widely spaced mountains trending north to south occur throughout the area. Isolated, short mountain ranges are separated by an aggraded desert plain. The mountains are fault blocks that have been tilted up. Long alluvial fans coalesce with dry lakebeds between some of the ranges.

LRU notes

AZ LRU 30-2 – Middle Mohave Desert

Elevations range from 1500 to 3200 feet and precipitation averages 6 to 9 inches per year. Vegetation includes creosotebush, white bursage, yucca, prickly pear and cholla species, Mormon tea, flattop buckwheat, ratany, winterfat, bush muhly, threeawns, and big galleta. The soil temperature regime is thermic and the soil moisture regime is typic aridic.

Ecological site concept

This ecological site is located on steeply sloping uplands (slopes 15%-65%). Soils vary greatly in depth over fractured sandstone. They are very cobbly and gravelly, effervescent, sandy loams throughout.

Associated sites

R030XB214AZ	Limy Upland 6-9" p.z. Limy Upland, 6 to 10

R030XB214AZ

Limy Upland 6-9" p.z.

Limy Upland, 6 to 10

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Ambrosia dumosa
Herbaceous	Not specified

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Physiographic features

This ecological site occurs in an upland position on escarpments. It is found on all aspects.

Table 2. Representative physiographic features

Landforms	(1) Escarpment
Flooding frequency	None
Ponding frequency	None
Elevation	488 – 1,036 m
Slope	15 – 70%
Aspect	Aspect is not a significant factor

Climatic features

The climate is arid and warm. Annual precipitation ranges from 6 to 9 inches. About 65 percent of the rainfall comes from October through May as gentle rain from Pacific storms which may last for a couple of days. The rest of the rainfall comes during the summer monsoon season from July through September as spotty, brief, intense thunderstorms. Snow rarely falls, and only remains on the ground a few hours at most. Annual air temperature ranges from 59 to 70 degrees F. The average frost-free period ranges from 156 to 259 days.

Table 3. Representative climatic features

Frost-free period (average)	259 days
Freeze-free period (average)	290 days
Precipitation total (average)	229 mm

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Figure 2. Monthly precipitation range

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Figure 3. Monthly average minimum and maximum temperature

Soil features

Soil depth of the ecological site varies between shallow to very deep. Soil parent materials are alluvium and colluvium from sedimentary formations. The available water capacity of the soil is very low to low. The soil's erosion hazard by water is very severe; by wind is slight. The soil moisture regime is typic aridic and the temperature regime is thermic. Varying amounts of lime are found in the surface and subsoil.

A typical soil profile is:
A-0 to 2 inches; very channery fine sandy loam; strongly effervescent
C-2 to 6 inches very channery fine sandy loam; strongly effervescent
R-6 inches; fractured sandstone

This ecological site has been correlated to map unit 701071, Lithic Torriorthents in the Grand Canyon Area, AZ, Parts of Coconino and Mohave County SSA.

Table 4. Representative soil features

Surface texture	(1) Very cobbly sandy loam (2) Gravelly clay loam
Family particle size	(1) Loamy
Drainage class	Well drained
Permeability class	Rapid to moderately rapid
Soil depth	25 – 127 cm
Surface fragment cover <=3"	45 – 65%
Subsurface fragment volume <=3" (Depth not specified)	45 – 65%

Ecological dynamics

Breaks, 6"-9" p.z., is a dispersed desert shrub dominated ecological site. Perennial grasses and forbs are widely scattered. Annual forbs and grasses flourish following rainfall. Natural disturbances are rare. After introduction of non-native annuals (forbs and/or grasses), seasonal herbaceous production may increase following periods of rain. Dominant shrubs are creosote and white bursage. Assorted half-shrubs are widely scattered.

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 text

State 1
Historic Climax Plant Community

Community 1.1
Historic Climax Plant Community

The dominant aspect of this ecological site is desert shrub. The major shrubs are white bursage, creosotebush and Nevada Morman tea. Large animal access is severely limited due to steep slopes. The site's total biomas production by weight (air-dried)is comprised of: grasses and grasslike plants - 5 to 15 percent, forbs 1 to 5 percent, shrubs 80 to 90 percent and trees 1 to 3 percent.

Figure 4. Annual production by plant type (representative values) or group (midpoint values)

Table 5. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Shrub/Vine	105	241	319
Grass/Grasslike	6	28	45
Forb	1	6	17
Tree	–	6	11
Total	112	281	392

Table 6. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	0%
Grass/grasslike foliar cover	0%
Forb foliar cover	0%
Non-vascular plants	0%
Biological crusts	0%
Litter	0%
Surface fragments >0.25" and <=3"	0%
Surface fragments >3"	0%
Bedrock	0%
Water	0%
Bare ground	0%

Table 7. Canopy structure (% cover)

Height Above Ground (m)	Tree	Shrub/Vine	Grass/ Grasslike	Forb
<0.15	–	–	–	–
>0.15 <= 0.3	–	–	–	–
>0.3 <= 0.6	–	–	–	–
>0.6 <= 1.4	–	4-6%	–	–
>1.4 <= 4	–	–	–	–
>4 <= 12	–	–	–	–
>12 <= 24	–	–	–	–
>24 <= 37	–	–	–	–
>37	–	–	–	–

Figure 5. Plant community growth curve (percent production by month). AZ3022, 30.2 6-9" p.z. upland sites. Growth begins in the late winter, most growth occurs in the spring..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	2	19	33	18	7	7	11	3	0	0	0

State 2
Historic Native Plant Community plus Introduced Annuals

Community 2.1
Non-native Annuals

This plant community resembles the historic native plant community, but exotic annuals have been introduced. Non-native species include Asian mustard (Brassica tournefortii), red brome, Mediterranean grass (Schismus spp.), and filaree. The flourish of non-native annuals that occurs following rainfalls may preclude native annuals.

Transition T1A
State 1 to 2

Introduction of non-native annual forb and grass seed.

Restoration pathway R2A
State 2 to 1

None known.

Additional community tables

Table 8. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (kg/hectare)	Foliar cover (%)
Grass/Grasslike
1				8–21
	big galleta	PLRI3	Pleuraphis rigida	8–21	–
2				2–8
3				0–6
	sand dropseed	SPCR	Sporobolus cryptandrus	0–6	–
4				0–6
	mesa dropseed	SPFL2	Sporobolus flexuosus	0–6	–
5				0–6
	threeawn	ARIST	Aristida	0–6	–
6				0–13
	Grass, perennial	2GP	Grass, perennial	0–13	–
7				0–8
	Grass, annual	2GA	Grass, annual	0–8	–
Forb
8				0–8
	desert globemallow	SPAM2	Sphaeralcea ambigua	0–8	–
9				2–8
	Forb, perennial	2FP	Forb, perennial	2–8	–
10				0–8
	Forb, annual	2FA	Forb, annual	0–8	–
Shrub/Vine
11				133–160
	burrobush	AMDU2	Ambrosia dumosa	56–67	–
12				13–40
	Nevada jointfir	EPNE	Ephedra nevadensis	13–40	–
13				13–40
	creosote bush	LATR2	Larrea tridentata	13–40	–
14				2–8
	broom snakeweed	GUSA2	Gutierrezia sarothrae	2–8	–
15				13–40
	Shrub, other	2S	Shrub, other	1–6	–
	blackbrush	CORA	Coleogyne ramosissima	1–6	–
	button brittlebush	ENFR	Encelia frutescens	1–6	–
	burrobrush	HYSA	Hymenoclea salsola	1–6	–
	white ratany	KRGR	Krameria grayi	1–6	–
	winterfat	KRLA2	Krascheninnikovia lanata	1–6	–
	desert almond	PRFA	Prunus fasciculata	1–6	–
	Fremont's dalea	PSFR	Psorothamnus fremontii	1–6	–
	Mojave sage	SAMO3	Salvia mohavensis	1–6	–
	banana yucca	YUBA	Yucca baccata	1–6	–
Tree
16				2–8
	Joshua tree	YUBR	Yucca brevifolia	2–8	–

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	11/21/2024
Approved by	Kendra Moseley
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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:
Perennial plant reproductive capability:

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Natural ResourcesConservation Service

Ecological site R030XB204AZ

Breaks 6-9" p.z.

Last updated: 10/21/2024 Accessed: 11/21/2024

General information

Figure 1. Mapped extent

MLRA notes

LRU notes

Ecological site concept

Associated sites

Table 1. Dominant plant species

Ecosystem states

State 1 submodel, plant communities

State 2 submodel, plant communities

Natural Resources
Conservation Service

Last updated: 10/21/2024
Accessed: 11/21/2024