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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.
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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): 077B–Southern High Plains, Northwestern Part
MLRA 77B is characterized by nearly level to gently sloping plains with a minimal
number of playa depressions and moderately sloping breaks along drainageways.
Loamy and sandy soils are generally deep and occur in a mesic soil temperature
regime and ustic soil moisture regime bordering on aridic. Current land use is
dominantly rangeland with minor cropland.Classification relationships
This ecological site is correlated to soil components at the Major Land Resource Area (MLRA) level which is further described in USDA Ag Handbook 296.
Characteristic Soils Are:
Amarillo, Bascom, Clovis, Friona, Larimer
Mansker, Olton, Portales, Potter, Pullman,
SlaughterEcological site concept
The Gravelly Loam ecosite occurs over moderately deep and deep, well drained soils on uplands and alluvial fans. These soils may be loamy to sandy. The reference vegetation consists of midgrasses and shortgrasses with scattered forbs and shrubs. Abusive grazing practices can lead to a decline in the more palatable species and a shift in the plant community. Without fire or alternative brush management activities, woody species canopy may increase across the site. This site may have up to 35 percent surface gravel present.
Associated sites
R077BY016TX Limy Upland 12-17" PZ
Adjacent and slightly downslope from the Gravelly Loam site. The soils are loam to clay loam in surface texture. Shortgrasses dominate but a good mixture of midgrasses are found on this site. Production is higher than on the Gravelly Loam site.
R077BY021TX Sandy Loam 12-17" PZ
Adjacent and slightly downslope from the Gravelly Loam site. The soils are sandy loam in surface texture. Midgrasses dominate but some tallgrasses can be found on this site. Production is less than on the Gravelly Loam site.
R077BY658TX Sandy 12-17" PZ
Adjacent and slightly downslope from the Gravelly Loam site. The soils are loamy sand in surface texture. Tallgrasses dominate but some midgrasses can be found on this site. Production is less than on the Gravelly Loam site.
Similar sites
R077BY009NM Gravelly
Similar to the Gravelly Loam site is the Gravelly site. The soils are loamy to sandy in surface texture. Midgrasses dominate but there is a good mixture of shorgrasses on this site. Production is higher than the Gravelly Loam site.
R077EY053TX Gravelly 16-24" PZ
Similar to the Gravelly Loam site is the Gravelly site in MLRA 77E. Slopes are greater, up to 25%. Mean annual temperature is greater (59 to 63 degrees F). Mean annual precipitation is greater (16 to 24 inches). Production is higher than the Gravelly site in MLRA 77B.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Yucca madrensis
Herbaceous (1) Bouteloua gracilis
(2) Bouteloua dactyloidesPhysiographic features
This site is on nearly level to undulating plains. Elevation ranges from approximately 3,800 to 5,000 feet above sea level. Slopes range from 0 to 9 percent.
Table 2. Representative physiographic features
Landforms (1) Plateau > Plain
(2) Plateau > Alluvial fan
Runoff class Very low to low Flooding frequency None Ponding frequency None Elevation 3800 – 5000 ft Slope 0 – 9 % Water table depth 80 in Aspect W, NW, N, NE, E, SE, S, SW Climatic features
The climate of this area can be classified as “semi-arid continental”.
Annual average precipitation ranges from 15 to 19 inches. Seventy percent of the moisture usually falls during the six-month period May through October. Most of this summer precipitation falls in the form of brief and heavy afternoon and evening thunderstorms. Hail may accompany the more severe summer storms. Spring precipitation (March, April, May) accounts for approximately 25 percent of the annual precipitation. Most of this comes as light rain showers. Winter moisture may occur as either rain or snow and usually averages less than ½ inch per month.
Temperatures are characterized by distinct seasonal change and large annual and diurnal temperature ranges. Summers are moderately warm; maximum temperatures average above 90 degrees F in July and August. Temperatures usually fall rapidly after sundown and range in the low 60’s on most summer nights. Winters are mild, sunny and dry. Daytime shade temperatures in mid-winter usually rise to the 50’s. However, freezing temperatures normally occur at night from mid-November to mid-March.
The frost-free season ranges from 181 to 199 days. Dates of the last freeze vary from April 10th to April 23rd and the first freeze varies from October 18th to October 26th.
Wind velocities in this area are high and average about 5.3 miles per hour on an annual basis. The spring months are characterized by frequent windstorms with velocities in excess of 45 miles per hour, which cause excessive erosion on soils not protected by a good ground cover of vegetation. Humidity is low and evaporation is high.
Both temperature and rainfall distribution favor production of warm-season, perennial plants in this area. However, sufficient late winter and early spring moisture allows cool-season species to occupy an important component within most plant communities.
Climate data was obtained from the WCCR web site using 50 % probabilities for freeze-free and frost-free season using 28.5 degrees F and 32.5 degrees F respectively.Table 3 Representative climatic features
Frost-free period (characteristic range) 140-150 days Freeze-free period (characteristic range) 170-170 days Precipitation total (characteristic range) 20-20 in Frost-free period (actual range) 140-150 days Freeze-free period (actual range) 170-170 days Precipitation total (actual range) 20-20 in Frost-free period (average) 140 days Freeze-free period (average) 170 days Precipitation total (average) 20 in Characteristic rangeActual rangeBarLineFigure 2. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 3. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 4. Monthly maximum temperature range
BarLineFigure 5. Monthly average minimum and maximum temperature
Figure 6. Annual precipitation pattern
Figure 7 Annual average temperature pattern
Climate stations used
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(1) ROSEBUD 7NW [USC00297585], Mosquero, NM
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(2) MCCARTY RCH [USC00295516], Nara Visa, NM
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(3) UTE DAM [USC00299284], Logan, NM
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(4) AMISTAD 5 SSW [USC00290377], Amistad, NM
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(5) DALHART 6 SW [USC00412235], Hartley, TX
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(6) CLAYTON 1 N [USC00291883], Clayton, NM
">Influencing water features
Water features are not an influencing factor in this site.
Wetland description
None.
Soil features
These are moderately deep and deep, well drained soils on uplands and alluvial fans. The surface layers are silt loam, loam or clay loam. The subsoil and substratum ranges in texture from sandy loam through clay loam. The surface runoff is medium. The permeability is slow to moderately rapid. Infiltration rate is medium to moderately slow. Available water-holding capacity is high. Effective rooting depth is 20 to 60 inches or more.
Soils correlated to this site: Bascom fine sandy loamTable 4. Representative soil features
Parent material (1) Alluvium – igneous, metamorphic and sedimentary rock
(2) Eolian deposits – igneous, metamorphic and sedimentary rock
Surface texture (1) Gravelly loam
(2) Gravelly fine sandy loam
(3) Gravelly sandy clay loam
Family particle size (1) Fine-loamy
(2) Loamy-skeletal
Drainage class Well drained Permeability class Moderate to moderately rapid Soil depth 10 – 80 in Surface fragment cover <=3" 15 – 35 % Surface fragment cover >3" Not specified Available water capacity
(0-40in)3 – 6 in Calcium carbonate equivalent
(0-40in)5 – 55 % Electrical conductivity
(0-40in)0 – 8 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)6.6 – 9 Subsurface fragment volume <=3"
(0-40in)35 – 60 % Subsurface fragment volume >3"
(0-40in)15 – 35 % Ecological dynamics
Warm-season short grasses, principally blue grama and buffalograss dominate this site. Mid-grasses and forbs are
in smaller amounts. Cool-season grasses make up a minor component of the plant community. Few woody species
are found in the plant community. Western wheatgrass and switchgrass usually grow in the small depressions in
which water collects.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 StateThe reference vegetation consists of midgrasses and shortgrasses with scattered forbs and shrubs.
Dominant plant species
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blue grama (Bouteloua gracilis), grass
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buffalograss (Bouteloua dactyloides), grass
Community 1.1
Reference community phaseWarm-season short grasses, principally blue grama and buffalograss dominate this site. Mid-grasses and forbs are in smaller amounts. Cool-season grasses make up a minor component of the plant community. Few woody species are found in the plant community. Western wheatgrass and switchgrass usually grow in the small depressions in which water collects.
Figure 8. 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 560 800 1280 Forb 105 150 240 Shrub/Vine 35 50 80 Total 700 1000 1600 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0% Grass/grasslike foliar cover 40% Forb foliar cover 0-10% Non-vascular plants 0% Biological crusts 0% Litter 20% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Figure 9. Plant community growth curve (percent production by month). NM4726 , R077BY026NM Gravelly Loam Reference State. R077BY026NM Gravelly Loam Reference State.
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 3 3 5 5 25 30 15 10 2 0 Additional community tables
Table 7. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Blue Grama 300–350 blue grama BOGR2 Bouteloua gracilis 300–350 – 2 Galleta Tobosa 100–120 James' galleta PLJA Pleuraphis jamesii 100–120 – tobosagrass PLMU3 Pleuraphis mutica 100–120 – 3 Buffalograss 80–100 4 Sideoats grama 80–100 sideoats grama BOCU Bouteloua curtipendula 80–100 – 5 sand dropseed 50–70 sand dropseed SPCR Sporobolus cryptandrus 50–70 – 6 western wheatgrass switchgrass 50–70 western wheatgrass PASM Pascopyrum smithii 50–70 – switchgrass PAVI2 Panicum virgatum 50–70 – 7 ring muhly wolftail 30–50 common wolfstail LYPH Lycurus phleoides 30–50 – ring muhly MUTO2 Muhlenbergia torreyi 30–50 – 8 Threeawn Spp. 30–50 threeawn ARIST Aristida 30–50 – 9 vine-mesquite 30–50 vine mesquite PAOB Panicum obtusum 30–50 – 10 cane and silver bluestem 30–50 cane bluestem BOBA3 Bothriochloa barbinodis 30–50 – silver bluestem BOSA Bothriochloa saccharoides 30–50 – 11 Bottlebrush squirreltail 30–50 squirreltail ELEL5 Elymus elymoides 30–50 – 12 Little bluestem 30–50 little bluestem SCSC Schizachyrium scoparium 30–50 – 13 needleand thread black grama plains bristlegrass s 30–50 Graminoid (grass or grass-like) 2GRAM Graminoid (grass or grass-like) 30–50 – black grama BOER4 Bouteloua eriopoda 30–50 – needle and thread HECO26 Hesperostipa comata 30–50 – Hall's panicgrass PAHA Panicum hallii 30–50 – plains bristlegrass SEVU2 Setaria vulpiseta 30–50 – slim tridens TRMU Tridens muticus 30–50 – Forb14 globemallow 10–30 globemallow SPHAE Sphaeralcea 10–30 – 15 annual sunflower 10–30 common sunflower HEAN3 Helianthus annuus 10–30 – 16 astragulas spp. 10–30 milkvetch ASTRA Astragalus 10–30 – 17 annual forbs 30–50 Forb, annual 2FA Forb, annual 30–50 – 18 perennial forbs 30–50 Forb, perennial 2FP Forb, perennial 30–50 – Shrub/Vine19 yucca spp. 10–30 yucca YUCCA Yucca 10–30 – 20 winterfat groundsel spp. 10–30 winterfat KRLA2 Krascheninnikovia lanata 10–30 – ragwort SENEC Senecio 10–30 – 21 pricklypear cholla cactus 0–10 plains pricklypear OPPO Opuntia polyacantha 0–10 – pricklypear OPUNT Opuntia 0–10 – Interpretations
Hydrological functions
The runoff curve numbers are determined by field investigations using hydrologic cover conditions and hydrologic soil groups.
Soil Series----Hydrologic Group
Amarillo-------B
Bascom---------B
Clovis---------B
Friona---------C
Larimer--------B
Mansker--------B
Olton----------C
Portales-------B
Potter---------D, B
Pullman--------C
Slaughter-------CRecreational uses
Recreation potential is limited largely by the lack of water and firewood. Suitability for camping, hiking and picnicking is fair. The terrain typical of the “wide open spaces” of the area enhances aesthetic appeal. Hunting is fair for small game and upland game birds and hunting is good for antelope.
Wood products
This site produces no wood products.
Other products
Grazing:
This site can be grazed any season of the year by all classes and ages of livestock. The site provides good winter grazing but offers little natural protection against storms. It is better suited to cow-calf or yearlings due to the large percentage of grass in the potential plant community. Continuous yearlong grazing or grazing continually during the period from March through October by cattle will result in a decrease of species such as sideoats grama, vine-mesquite, little bluestem, western wheatgrass, bottlebrush squirreltail and winterfat. Species such as blue grama, galleta or tobosa, buffalograss, ring muhly, threeawn spp. and broom snakeweed will increase. Cholla cactus will increase on this site under continuous heavy grazing pressure where there is an available seed source. Blue grama will form a low dense turf under continuous grazing pressure. A system of deferred grazing by domestic livestock, which varies the season of grazing and rest during successive years, will result in healthy, high forage producing plant community. Fall and winter rest will benefit species such as winterfat. Spring rest (April-June) will allow species such as western wheatgrass and bottlebrush squirreltail to grow and reproduce. Summer rest will benefit warm-season species such as blue grama, sideoats grama and vine-mesquite to gain vigor and produce. Ninety-five percent of the annual production is from species that provide forage for grazing animals. Where the plant community has deteriorated to low turflike blue grama, buffalograss and ring muhly, grazing management alone may not achieve the desired range improvement. Mechanical range treatment and interseeding may be needed also.Other information
Guide to Suggested Initial Stocking Rate Acres per Animal Unit Month
Similarity Index-----Ac/AUM
100 - 76-------------2.3 – 4.9
75 – 51--------------2.8 – 5.9
50 – 26--------------4.0 – 9.0
25 – 0---------------9.0+Supporting information
Type locality
Location 1: Curry County, NM Location 2: Harding County, NM Location 3: Quay County, NM Other references
Data collection for this site was done in conjunction with the progressive soil surveys within the Southern High Plains 77 Major Land Resource Area of New Mexico. This site has been mapped and correlated with soils in the following soil surveys: Curry, Harding & Quay
Contributors
Christine Bishop
Don Sylvester
Elizabeth Wright
John Tunberg
Todd CarrApproval
Bryan Christensen, 9/11/2023
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 08/18/2026 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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