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Conservation Service
Ecological site R038XC317AZ
Volcanic Hills
20-24"
Last updated: 5/07/2020
Accessed: 09/19/2026
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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.
MLRA notes
Major Land Resource Area (MLRA): 038X–Mogollon Transition South
AZ 38.3 – Upper Mogollon Transition
Elevations range from 5100-7000 feet and precipitation averages 20 to 27 inches per year. Vegetation includes Gambel oak, Arizona white oak, Emory oak, pinyon, alligator juniper, one seed juniper, Arizona cypress, ponderosa pine, shrubby buckwheat, sacahuista, skunkbush sumac, Wright silktassle, blue grama, sideoats grama, muttongrass, western wheatgrass, and bottlebrush squirreltail. The soil temperature regime is mesic and the soil moisture regime is typic ustic. This unit occurs within the Transition Zone Physiographic Province and is characterized by canyons and structural troughs or valleys. Igneous, metamorphic and sedimentary rock classes occur on rough mountainous terrain in association with less extensive sediment filled valleys exhibiting little integrated drainage.Associated sites
R038XB205AZ Limestone Hills 16-20" p.z.
The Limestone Hills ecological site in LRU 38-2 is at the elevations below this site. Turbinella oak will increase in abundance and alligator juniper will decrease in abundance on the Limestone Hills site in 38-2.
R038XC303AZ Clay Loam Upland 20-24" p.z.
The Clayloam Upland ecological site is on soils with less than 15% slope and in LRU 38-3 is likely a slightly more mesic site and tends to be less prone to invasion by oaks and other shrubs. The Clayloam Upland ecological site tends to have minimal to no oaks on the site.
R038XC316AZ Clayey Slopes 20-24"
The Clayey Slopes ecological site in LRU 38-3 has deep cobbly soil, has slightly more herbaceous production, and less amounts of shrub and tree production than the Volcanic Hills site.
Table 1. Dominant plant species
Tree (1) Juniperus deppeana
(2) Quercus griseaShrub (1) Cercocarpus montanus
Herbaceous (1) Bouteloua curtipendula
(2) Elymus elymoidesPhysiographic features
Thimble soils generally occur on summits and backslopes of mountains with Ruidoso soils generally occuring on lower back slopes and along drainageways.
Table 2. Representative physiographic features
Landforms (1) Mountain
(2) Mountain slope
Flooding frequency None Ponding frequency None Elevation 5000 – 7200 ft Slope 15 – 70 % Aspect N, E, S Climatic features
Precipitation in this common resource area averages approximately 20 to 24 inches annually. Precipitation is lower and temperatures are cooler in the eastern part of the MLRA. The winter-summer rainfall ratio ranges from about 60/40% in the western part of the area to 45/55% in the eastern part. Summer rains fall July through September; and are from high-intensity convective thunderstorms. This moisture originates primarily from the Gulf of Mexico, but can come from the remnants of Pacific hurricanes in September. Winter moisture is frontal, originates in the north Pacific, and falls as rain or snow in widespread storms of low intensity and long duration. Snowfall ranges from 10 to 18 inches per year and can occur from November through April. May and June are the driest months of the year. Humidity is generally low all year.
Average annual air temperatures range from 50 to 57 degrees F (mesic temperature regime). Daytime temps in the summer are commonly in the mid 80's in the eastern portion of the MLRA and the low to mid 90's in the western portion. Freezing temperatures are common from October through April. The actual precipitation, available moisture and temperature varies, depending on, region, elevation, rain shadow effect and aspect.Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 190 days Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
Thimble soils generally occurs on summits and back slopes with parent material of clayey alluvium and/or colluvium derived from basalt and/or volcanic breccia.
Ruidoso family soils generally occurs on lower back slopes and along drainageways with the parent material of colluvium and/or slope alluvium over residuum weathered from
volcanic breccia
Soils mapped on this site include: from SSA-675 San Carlos IR Area - MU's Thimble-82 & 73, Ruidoso family-73.Table 4. Representative soil features
Parent material (1) Residuum – andesite
(2) Residuum – basalt
(3) Colluvium – basic volcanic breccia
Surface texture (1) Extremely cobbly loam
(2) Very cobbly loam
(3) Very cobbly loam
Family particle size (1) Clayey
Drainage class Moderately well drained Permeability class Moderately slow to slow Soil depth 8 – 20 in Surface fragment cover <=3" 20 – 50 % Surface fragment cover >3" 30 – 40 % Available water capacity
(0-40in)0.6 – 4.3 in Calcium carbonate equivalent
(0-40in)0 – 5 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)6.6 – 7.8 Subsurface fragment volume <=3"
(Depth not specified)25 – 90 % Subsurface fragment volume >3"
(Depth not specified)35 – 55 % Ecological dynamics
The historic native plant community is a savanna with equal amounts of trees and shrubs on south slopes and lesser amounts of succulents and forbs. Shrubs are less prevalent on north slopes. Alligator juniper is the primary juniper species. The plant community includes a flora of native annual grasses and forbs of both the winter and summer seasons. Periodic wildfires occurred at moderate intervals (10 to 15 years) and helped maintain a balance between herbaceous plants and trees and shrubs. In the absence of fire for longer periods, shrubby species and trees can become dominant. The interactions of drought, fire and continuous livestock grazing can, over time, result in the loss of palatable perennial grasses and half shrubs.
Warm aspects can be dominated by oneseed or redberry juniper instead of alligator juniper. In some areas, young (< 8-10" DRC) alligator juniper trees have experienced mortality at the lower elevations and/or warmer aspects of the site. These trees likely established in a wetter period at the lower elevational range of the species and have died in the recent drought.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 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Reference StateGrass, shrubs, and trees are all represented in the Reference State.
Community 1.1
Mixed life form community
Midgrasses are the dominant herbaceous species. Mature grey oak and alligator juniper trees > 18-24" Diameter at Root Collar (DRC) are present at 10-20 per acre. Mature Emory oak > 18" DRC are present at 2-5/ac and pinyon pine > 12" DBH are present at 2-5/acre. Mountain mahogany is the dominant shrub and has approximately 10-15% canopy on warm exposures and 1-2% on cool exposures. Fires likely burned at 7-10 year intervals as the adjacent ponderosa pine forest communities.
Plains lovegrass, bullgrass, and cane beargrass are more prevalent on warmer aspects in the western part of the LRU.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)Grass/Grasslike 725 1125 1425 Tree 610 710 810 Shrub/Vine 300 335 385 Forb 50 190 290 Total 1685 2360 2910 Table 6. Soil surface cover
Tree basal cover 0-0% Shrub/vine/liana basal cover 0-0% Grass/grasslike basal cover 10-10% Forb basal cover 0-0% Non-vascular plants 0% Biological crusts 0% Litter 50-60% Surface fragments >0.25" and <=3" 10-10% Surface fragments >3" 30-40% Bedrock 0% Water 0% Bare ground 0% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – 2-5% 2-5% >0.5 <= 1 – – 5-10% 5-10% >1 <= 2 – – 20-30% 2-5% >2 <= 4.5 – 5-10% 15-25% – >4.5 <= 13 0-1% – – – >13 <= 40 5-10% – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 4. Plant community growth curve (percent production by month). AZ3813 , 38.3 20-24"p.z. all sites. Growth begins in the spring and continues into the summer and fall..
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 0 5 15 10 15 15 20 10 5 5 0 State 2
Short grass StateMidgrasses have been replaced by short grasses.
Community 2.1
Blue grama herbaceous community
The vigor of sideoats grama has been reduced from continuous heavy herbivory by cattle, elk, or horses. It has been replaced by blue grama or hairy grama. Blue grama is the dominant herbaceous plant in the plant community on cooler aspects and hairy grama on warmer aspects. Trees and shrubs are represented as in the Reference Plant Community.
State 3
Woodland StateTree regeneration has grown to maturity in the absence of fire for very long periods and dominates the site.
Community 3.1
High cover juniper/oak woodland community
As found in the Reference Plant Community, mature grey oak and alligator juniper trees > 18-24" Diameter at Root Collar (DRC) are present at 10-20 per acre. Mature Emory oak > 18" DRC are present at 2-5/ac and pinyon pine > 12" DBH are present at 2-5/acre. In addition, juniper and oak regeneration in the interspaces of parent trees have increased in size to 10-15 feet in height and < 12” DRC in the absence of fire and now dominate the interspaces of parent trees. In some areas grasses still occupy the interspaces at 100-200 lbs/ac.
Warm aspects can be dominated by one seed or redberry juniper instead of alligator juniper. In some areas, young (< 8-10" DRC) alligator juniper trees have experienced mortality at the lower elevations and/or warmer aspects of the site. These trees likely established in a wetter period at the lower elevational range of the species and have died in the recent drought.Transition 1a
State 1 to 2High intensity continuous herbivory by livestock or wildlife reduces the vigor and abundance of sideoats grama and increases the abundance of short grasses like blue grama on cool aspects or hairy grama on warm aspects. Horses being more apt to use steeper slopes can have equally detrimental effects.
Transition 1b
State 1 to 3Absence of fires for very long periods allows tree regeneration to grow to maturity, increase in size, and dominate the site.
Transition 2a
State 2 to 3Absence of fires for very long periods allows tree regeneration to grow to maturity, increase in size, and dominate the site.
Restoration pathway 3a
State 3 to 1This restoration pathway is an assumption and needs additional investigation. Areas with 80-90% tree canopy have been observed with mid grass densities of 5-10 plants per square yard. Extreme wildfire is the only practical way to reduce tree abundance. Brush management applied to similar wooded environments with similar grass plant densities in LRU 38-3 has demonstrated favorable responses in grass production where range planting was unnecessary. This restoration is only practical where there is remnant mid grasses in tree interspaces and they are not destroyed by fire. Aerial range planting is the only practical seeding method and may be required in the event of high grass mortality.
Restoration pathway 3b
State 3 to 2This restoration pathway is an assumption and needs additional investigation. Areas with 80-90% tree canopy have been observed with short grass densities of 5-10 plants per square yard. Extreme wildfire is the only practical way to reduce tree abundance. Brush management applied to similar wooded environments with similar grass plant densities in LRU 38-3 has demonstrated favorable responses in grass production where range planting was unnecessary. This restoration is only practical where there is remnant short grasses in tree interspaces and they are not destroyed by fire. Aerial range planting is the only practical seeding method and may be required in the event of high grass mortality.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Midgrasses 600–850 sideoats grama BOCU Bouteloua curtipendula 600–800 – plains lovegrass ERIN Eragrostis intermedia 5–100 – longtongue muhly MULO Muhlenbergia longiligula 20–60 – Texas bluestem SCCI2 Schizachyrium cirratum 5–10 – green sprangletop LEDU Leptochloa dubia 5–10 – 2 Short grasses 20–100 blue grama BOGR2 Bouteloua gracilis 20–100 – hairy grama BOHI2 Bouteloua hirsuta 20–100 – 3 Cool season grasses 175–375 squirreltail ELEL5 Elymus elymoides 100–225 – prairie Junegrass KOMA Koeleria macrantha 50–100 – muttongrass POFE Poa fendleriana 25–50 – 4 Miscellaneous grasses 0–50 cane bluestem BOBA3 Bothriochloa barbinodis 0–25 – bullgrass MUEM Muhlenbergia emersleyi 0–25 – Hall's panicgrass PAHA Panicum hallii 0–5 – Fendler threeawn ARPUL Aristida purpurea var. longiseta 0–5 – spidergrass ARTE3 Aristida ternipes 0–5 – 5 Annual grasses 10–50 Eastwood fescue VUMIC Vulpia microstachys var. ciliata 1–25 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 1–25 – witchgrass PACA6 Panicum capillare 1–5 – Mexican panicgrass PAHI5 Panicum hirticaule 1–5 – sixweeks threeawn ARAD Aristida adscensionis 1–5 – prairie threeawn AROL Aristida oligantha 1–5 – Arizona brome BRAR4 Bromus arizonicus 0–1 – tufted lovegrass ERPE Eragrostis pectinacea 0–1 – Forb6 Perennial forbs 50–125 white sagebrush ARLU Artemisia ludoviciana 50–75 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 5–25 – Cooley's bundleflower DECO2 Desmanthus cooleyi 1–5 – Lewis flax LILE3 Linum lewisii 1–2 – New Mexico groundsel PANE7 Packera neomexicana 0–1 – Oak Creek ragwort PAQU8 Packera quercetorum 0–1 – Flagstaff ragwort SEAC2 Senecio actinella 0–1 – catnip noseburn TRNE Tragia nepetifolia 0–1 – branched noseburn TRRA5 Tragia ramosa 0–1 – tarragon ARDR4 Artemisia dracunculus 0–1 – bluedicks DICA14 Dichelostemma capitatum 0–1 – fleabane ERIGE2 Erigeron 0–1 – southwestern mock vervain GLGO Glandularia gooddingii 0–1 – sego lily CANU3 Calochortus nuttallii 0–1 – Indian paintbrush CASTI2 Castilleja 0–1 – bastard toadflax COUM Comandra umbellata 0–1 – pale agoseris AGGL Agoseris glauca 0–1 – 7 Annual forbs 5–50 longleaf false goldeneye HELO6 Heliomeris longifolia 5–30 – Wright's bird's beak COWR2 Cordylanthus wrightii 0–15 – desert Indianwheat PLOV Plantago ovata 0–10 – American wild carrot DAPU3 Daucus pusillus 0–2 – Virginia pepperweed LEVI3 Lepidium virginicum 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – cryptantha CRYPT Cryptantha 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – Shrub/Vine8 Evergreen shrubs 40–250 alderleaf mountain mahogany CEMO2 Cercocarpus montanus 20–170 – pointleaf manzanita ARPU5 Arctostaphylos pungens 20–60 – hollyleaf redberry RHIL Rhamnus ilicifolia 0–25 – Sonoran scrub oak QUTU2 Quercus turbinella 0–5 – 9 Miscellaneous shrubs 1–10 catclaw mimosa MIACB Mimosa aculeaticarpa var. biuncifera 0–10 – skunkbush sumac RHTR Rhus trilobata 1–3 – 10 Sub shrubs 1–15 prairie acacia ACAN Acacia angustissima 0–10 – bastardsage ERWR Eriogonum wrightii 1–10 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–4 – 11 Succulents 15–60 goldenflower century plant AGCH2 Agave chrysantha 5–25 – sacahuista NOMI Nolina microcarpa 5–15 – Parry's agave AGPA4 Agave parryi 5–10 – cactus apple OPEN3 Opuntia engelmannii 0–5 – walkingstick cactus CYSP8 Cylindropuntia spinosior 0–1 – pinkflower hedgehog cactus ECFE Echinocereus fendleri 0–1 – Tree12 Trees 310–710 gray oak QUGR3 Quercus grisea 180–360 – Emory oak QUEM Quercus emoryi 40–150 – redberry juniper JUCO11 Juniperus coahuilensis 0–100 – alligator juniper JUDE2 Juniperus deppeana 50–100 – oneseed juniper JUMO Juniperus monosperma 0–100 – twoneedle pinyon PIED Pinus edulis 40–100 – singleleaf pinyon PIMO Pinus monophylla 40–100 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site is a significant habitat for whitetail deer. Elk and mule deer utilize this site to a fair degree given the diversity of forage.
This site has limited use by livestock in summer unless water is less than 1/2 mile away. There are limited areas of very cobbly surfaces that receive little livestock use. This site has some susceptibility to erosion in areas with very high livestock or wildlife utilization like bed grounds, trails, and areas adjacent to water. High gravel and rock cover protect the site to a fair degree. Horses make significant use of this site and can severely deteriorate areas if left unmanaged.Hydrological functions
The Reference Plant Community is not conducive to rill formation. There is a high cover of grass, trees, and shrubs with woody species being scattered and herbaceous species being abundant to the perimeter of woody species. Grass plants are less than 1 foot apart in the interspaces of woody species and provide a highly sinuous flow path for overland flow. Gravel and cobble covers are high on this site and add to the protection and sinuous water flow path of the site.
Where grass cover is lost soil erosion can become a problem however it is hard to detect since gravels and cobbles remain in place.
When trees increase they can become relatively effective at capturing high amounts of rainfall in their canopies. This high interception is suggested by Hydrologic Model TR-55 for high juniper cover. However substantial soil loss has likely occurred where nearly all herbaceous plants have been lost, this being difficult to detect where gravels and cobbles have been left on site.Recreational uses
Hunting, horseback riding, backpacking, rock hounding, photography.
Wood products
Limited harvest of fuel-wood, fence posts and stays from juniper, pinyon, and oak species. These activities are restricted to the tops of slopes where access roads have been installed on ridges or where roads have been installed across gentler sloping areas that have low cobble cover.
Other products
Western Apache use approximately 700 species of plants in the region. This site provides an
important source of plants and animals for traditional uses in the reference state. As the site degrades to woodland the number of species of plants and animals used for traditional purposes declines significantly.Supporting information
Type locality
Location 1: Gila County, AZ General legal description Slopes southeast of and above Seneca Lake Contributors
Dave Womack
Larry D. EllicottApproval
Scott Woodall, 5/07/2020
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) Dave Womack, Scott Stratton, Dan Robinett, Emilio Carrillo Contact for lead author USDA NRCS Tucson Area Office. Date 05/15/2011 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
The reference site is not conducive to rill formation. There is high cover of grass, trees, and shrubs with woody species being scattered and herbaceous species abundant to the perimeter of woody species. Grass plants are less than 1 foot apart in the interspaces of woody species and in addition to high gravel and rock cover provide a highly sinuous flow path for overland flow. -
Presence of water flow patterns:
Water flow paths are very hard to observe on the site due to high herbaceous litter, high density of herbaceous plants, and high gravel and rock cover. Perennial grass plants are less than 1 foot apart in the interspaces of woody species and in addition to high gravel and rock cover provide a highly sinuous flow path for overland flow. -
Number and height of erosional pedestals or terracettes:
None present on the site. Herbaceous production is dominated by very dense bunchgrasses that are not conducive to pedestalling or terracette formation. There are approximately 10-15 perennial bunch grass plants per square yard in the interspaces between woody species. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
0-1%. -
Number of gullies and erosion associated with gullies:
None present on the site. -
Extent of wind scoured, blowouts and/or depositional areas:
None present on the site. Plant community is shrub and tree dotted savanna with very dense perennial bunch grass plants and 35-45% gravel and rock cover in the interspaces that is not conducive to wind erosion. -
Amount of litter movement (describe size and distance expected to travel):
Herbaceous litter is transported less than 2 feet before being intercepted by high density perennial bunch grass plants. Woody litter stays in place near parent plants. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Stability values range from 5-6 across most of the site. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak to moderate fine to medium granular structure 1-2 inches thick. Color is 5YR 4/2 to 7.5YR 3/2 dry and 5YR 2.5/2 to 7.5YR 23/2 moist. Organic matter is 1-3%. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Perennial bunch grass plants are the most extensive in terms of canopy cover on the site and at 10-15 plants per square yard in interspaces of trees are highly effective at promoting infiltration and reducing the energy of water that leaves the site. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None present on the site. Argillic horizon at 1-2 inches deep may be mistaken for a compaction layer. High gravel and cobble in subsurface are usually easily detected. -
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:
perennial bunch grass > trees > cool season grass > evergreen shrubs > perennial forbs = short grassesSub-dominant:
succulents = miscellaneous grass = annual grass = annual forbsOther:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
5-10% canopy mortality of trees and shrubs. -
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):
1685 lbs/ac in below average year, 2360 lbs/ac in average year, 2910 lbs/ac in above average year. -
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:
Alligator juniper is the most common species on cooler aspects, one seed or redberry juniper on warmer aspects. Oaks are second most common species. Annual goldeneye can become problematic where trees and shrubs have not increased and continuous herbivory from livestock or wildlife have reduced vigor of short grasses. -
Perennial plant reproductive capability:
Not affected despite several years of prolonged drought in region.
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