Natural Resources
Conservation Service
Ecological site F041XA123AZ
Volcanic Hills
20-23" p.z.
(QUEM, JUDE2, QUAR)
Last updated: 4/09/2021
Accessed: 09/15/2026
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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
MLRA notes
Major Land Resource Area (MLRA): 041X–Madrean Archipelago
AZ 41.1 – Mexican Oak-Pine Forest and Oak Savannah
Elevations range from 4500 to 10,700 feet and precipitation ranges from 16 to 30 inches. Vegetation includes Emory oak, Mexican blue oak, Arizona white oak, one-seed juniper, alligator juniper, sacahuista, California bricklebush, skunkbush sumac, Arizona rosewood, wait-a-bit mimosa, sideoats grama, blue grama, purple grama, wooly bunchgrass, plains lovegrass, squirreltail, and pinyon ricegrass. The soil temperature regime ranges from thermic to mesic and the soil moisture regime ranges from aridic ustic to typic ustic. This unit occurs within the Basin and Range Physiographic Province and is characterized by numerous mountain ranges that rise abruptly from broad, plain-like valleys and basins. Igneous and metamorphic rock classes dominate the mountain ranges and sediments filling the basins represent combinations of fluvial, lacustrine, colluvial and alluvial deposits.Table 1. Dominant plant species
Tree (1) Quercus
(2) Juniperus deppeanaShrub Not specified
Herbaceous (1) Muhlenbergia
Physiographic features
This site occurs higher and adjacent to riverwash.
Table 2. Representative physiographic features
Landforms (1) Flood plain
Flooding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Flooding frequency Rare to occasional Elevation 4600 – 5600 ft Slope 0 – 5 % Aspect Aspect is not a significant factor Climatic features
Precipitation in this zone of the common resource area ranges from 16-20 inches per year with elevations from 4700-5500 feet. Approximately 40% of this moisture comes as gentle rain or snow during the winter-spring (Oct-Apr) season; originates in the north Pacific and Gulf of California and comes as frontal storms with long duration and low intensity. The remaining 60% falls in the summer season (May-Sep); originates in the Gulf of Mexico and are convective, usually brief, intense thunderstorms. Snow is common Dec-Mar, averaging 5-15 inches per year, but rarely lasts more than a week. May and June are the driest months. Humidity is low.
Temperatures are mild. Freezing temperatures are common at night from Oct-May, but daytime temperatures are almost always over 40 F. Below 0 F temperatures can occur Dec-Feb. Daytime summer highs rarely exceed 95 F.
Species like plains lovegrass, bottlebrush squirreltail, Arizona white oak and Emory oak begin growth in late March to April. Warm season grasses begin growth in July or August with receipt of the first summer rains.Table 3 Representative climatic features
Frost-free period (average) 200 days Freeze-free period (average) Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
These soils are deep with the surface textures of cobbly loam and subsurface textures of extremely cobbly sandy loam. They are not calcareous. Soil surfaces are well covered with gravels, cobbles, and stones. The soils are well drained, have moderate permeability, and low water holding capacities.
Soil series mapped on this unit include: SSA-666 Cochise county Northwest part MU 67 Rafter.Table 4. Representative soil features
Surface texture (1) Cobbly loam
Family particle size (1) Loamy
Drainage class Moderately well drained to well drained Permeability class Moderate Soil depth 10 – 20 in Surface fragment cover <=3" 0 – 5 % Surface fragment cover >3" 10 – 20 % Available water capacity
(0-40in)0 – 2.5 in Subsurface fragment volume <=3"
(Depth not specified)15 – 30 % Subsurface fragment volume >3"
(Depth not specified)30 – 55 % Ecological dynamics
The historic native state includes the native plant communities that occur on the site, including the historic climax plant community. This state includes other plant communities that naturally occupy the site following fire, drought, flooding, herbivores, and other natural disturbances. The historic climax plant community represents the natural climax community that eventually reoccupies the site with proper management.
State and transition model
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Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThis site haas a mixed plant community with an overstory of evergreen oaks, pinyon, juniper (20-30% canopy) and an understory of low shrubs, grasses and forbs. The oaks change their leaves in the spring. The acorns of the Emory oak are borne early in Jul-Sep, while those of Arizona white oak are borne later in Sep-Nov.
All the oak species present, along with the alligator juniper, are vigorous sprouters and quickly assume dominance after fire or cutting. With disturbance of the understory, shrubs like snakeweed can increase.
Forest understory. The production of understory plants can vary greatly, even within the same canopy class. Therefore, if the forage rating obtained by considering only the percentage of preferred plnats is very high or high, but the production is less than that expected for the existing canopy, reduce the final forage rating one class.
Additional community tables
Table 5. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site is not suited to summertime grazing by cattle. It is suitable to grazing by cattle int he winter-spring period when cool weather and free water permit more even use of the rugged terrain. It is suited to other species of livestock at any season, however; however, yearlong grazing should not be practiced on this site. Mountain lion predation on calves can be severe on this site. Cows should be removed from areas of this site when they calve in the spring.
Wildlife species of the Southern Arizona Mountains use this site extensively for food, water, and cover.Recreational uses
Landform is steep, rugged mountains and hillslopes. Landscape quality is high and includes evergreen cloaked hills with rock outcrop, dissected by mountain canyons and streams. Climate is moderate year-round; winter nights are cold. Activities include hunting, hiking, wildlife observation, horseback riding, and picnicking.
Wood products
Wood harvest is not recommended where slopes exceed 25%. Bedrock at shallow depths further limit safe harvest of wood products.
The woodland productivity site index for this site ranges from 40-80 (basal area when average stand diameter is 5 inches, measured at one foot above ground level). This represents a basal area of 75-135 sq. ft./ac at maturity. This site will produce an average yield of 20 cu. ft/ac/yr or 1/3 cords/ac/yr. The site index indicates a moderate productivity potential.Other products
Mining
Other information
T&E Species: Ocelot; Jaguar: Mexican lobo
Supporting information
Type locality
Location 1: Cochise County, AZ Township/Range/Section T22S R19E S8 General legal description Douglas FO - Ft. Huachuca Military Reservation - upper Blacktail Canyon - north slope NE 1/4 Contributors
Dan Robinett
Karlynn Huling
Larry D. EllicottApproval
Curtis Talbot, 4/09/2021
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 09/15/2026 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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