Natural Resources
Conservation Service
Ecological site R035XB034NM
Sandy Terrace
6-10"
sodic
Last updated: 5/20/2025
Accessed: 04/24/2026
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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.
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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.
Ecological site concept
This site occurs on low stream terraces on valley floors. Slopes range from 0 to 3 percent.
The soils are very deep and well drained. They formed in alluvium derived from sandstone and shale. Surface textures include loamy fine sand. The soils are slightly sodic (SAR 5-13), slightly saline (EC 4-8), and moderately to strongly alkaline (pH 7.9-9.0).Table 1. Dominant plant species
Tree Not specified
Shrub (1) Atriplex obovata
Herbaceous (1) Sporobolus airoides
(2) Achnatherum hymenoidesPhysiographic features
This site occurs on low stream terraces on valley floors. It does not benefit from run-in water from adjacent areas, nor does it suffer from excessive run-off. Slopes range from 0 to 3 percent. Elevations range from 4,700 to 6,000 feet.
Table 2. Representative physiographic features
Landforms (1) Stream terrace
Elevation 4700 – 6000 ft Slope 0 – 3 % Aspect Aspect is not a significant factor Climatic features
Mean annual precipitation varies from 5 to 8 inches with about 60% of it coming as rain from April through October. May and June are the driest months. Most of the precipitation from November through March comes as snow. High-velocity winds are common in late winter and early spring.
Mean temperatures for the hottest month, July, are about 83 degrees F. The coldest month is January, when the mean temperature is about 27 degrees F. Extreme temperatures of 104 and -17 degrees F have been recorded. The frost-free period ranges from 140 to 160 days.
The cool-season plants start growth in March and end with plant maturity and seed dissemination about mid-June. Warm-season plants grow from June through September, taking advantage of the moisture and warmth from tropical air out of the Gulf of Mexico. About 40 percent of the total precipitation is received during these summer months. The other 60 percent, received from fall through spring, influences cool-season plants.
The tabular climate summary for this ESD was generated by the Climate Summarizer
(http://www.nm.nrcs.usda.gov/technical/handbooks/nrph/Climate_Summarizer.xls) using data
from the following climate stations (results are unweighted averages):
296098 Newcomb, NM (Period of record = 1948 to 1971)
298284 Shiprock, NM (Period of record = 1926 to 2006)Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 190 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
This is an upland site, and is not associated with water features or wetlands. During heavy rain events, this site may receive run-on moisture from landforms above and contribute runoff to landforms below.
Soil features
The soils are very deep and well drained. They formed in alluvium derived from sandstone and shale. Surface textures include loamy fine sand. The subsoil has textures of loamy fine sand, loamy very fine sand, clay loam, fine sandy loam, and silty clay loam. Permeability is moderately slow. Available water holding capacity is high. Runoff is slow, and the hazard of water erosion is slight. The hazard of soil blowing is severe. The soils are slightly sodic (SAR 5-13), slightly saline (EC 4-8), and moderately to strongly alkaline (pH 7.9-9.0).
Shiprock SSA:
165 – Jeddito-Escavada Association (Jeddito part)
Additional information may be found in Section II of the Field Office Technical Guide.Table 4. Representative soil features
Surface texture (1) Loamy fine sand
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately slow Soil depth 60 in Electrical conductivity
(0-40in)4 – 8 mmhos/cm Soil reaction (1:1 water)
(0-40in)7.9 – 9 Ecological dynamics
This site has a plant community made up primarily of grasses, shrubs, and a minor amount of forbs. The reference plant community contains a mixture of cool-season and warm-season grasses.
Plant species most likely to invade or increase on this site when it deteriorates are black greasewood, Torrey seepweed (Mojave seablite), annual grama, Russian thistle, and other annual forbs. Continuous livestock grazing during winter and spring decreases the cool-season grasses and increases lower forage value grasses and shrubs.
The reference plant community has been determined by study of relict areas or areas protected from excessive grazing. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been used.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 StateThis state represents the most ecologically stable conditions in terms of resistance to erosion. Moreover, this state has the highest potential for productivity and plant diversity.
Community 1.1
Reference Plant CommunityThis site has a plant community made up primarily of grasses, shrubs, and a minor amount of forbs. The reference plant community contains a mixture of cool-season and warm-season grasses.
Plant species most likely to invade or increase on this site when it deteriorates are black greasewood, Torrey seepweed (Mojave seablite), annual grama, Russian thistle, and other annual forbs. Continuous livestock grazing during winter and spring decreases the cool-season grasses and increases lower forage value grasses and shrubs.
The reference plant community has been determined by study of relict areas or areas protected from excessive grazing. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been usedFigure 4. 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 200 330 450 Shrub/Vine 50 100 160 Forb 5 20 30 Total 255 450 640 Figure 5. Plant community growth curve (percent production by month). NM0382 , R035XB034NM-Sandy Terrace 6 to 10 inch sodic-Reference State. R035XB034NM-Sandy Terrace 6 to 10 inch sodic-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 6 6 7 6 6 5 11 14 12 12 8 7 State 2
Degraded StatePlant species most likely to invade or increase on this site when it deteriorates are black greasewood, Torrey seepweed (Mojave seablite), annual grama, Russian thistle, and other annual forbs. Continuous livestock grazing during winter and spring decreases the cool-season grasses and increases lower forage value grasses and shrubs.
Dominant plant species
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greasewood (Sarcobatus vermiculatus), shrub
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prickly Russian thistle (Salsola tragus), other herbaceous
Transition T1A
State 1 to 2Season-long grazing providing little rest and recovery for preferred grazed plants during critical growing periods, coupled with high utilization.
Key drivers
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Wildlife grazing or browsing
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Livestock grazing or browsing
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Nonnative plant species presence and/or establishment
Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 alkali sacaton 110–190 alkali sacaton SPAI Sporobolus airoides 113–195 – 2 Indian ricegrass 70–130 Indian ricegrass ACHY Achnatherum hymenoides 68–130 – 3 galleta 20–60 James' galleta PLJA Pleuraphis jamesii 23–65 – 4 sand dropseed 0–20 sand dropseed SPCR Sporobolus cryptandrus 0–20 – 5 squirreltail 0–30 squirreltail ELEL5 Elymus elymoides 0–33 – 6 other perennial grasses 0–10 Forb7 perennial forbs 5–20 8 annual forbs 0–10 Shrub/Vine9 mound saltbush 40–100 mound saltbush ATOB Atriplex obovata 45–98 – 10 fourwing saltbush 0–5 fourwing saltbush ATCA2 Atriplex canescens 0–7 – 11 shadscale saltbush 0–5 shadscale saltbush ATCO Atriplex confertifolia 0–7 – valley saltbush ATCU Atriplex cuneata 0–7 – 12 black greasewood 5–30 greasewood SAVE4 Sarcobatus vermiculatus 5–33 – 13 other shrubs 0–10 Interpretations
Animal community
Livestock -- This site is suitable for grazing by all classes of livestock most seasons of the year and is well suited to planned grazing systems. Soils on this site have a high wind erosion hazard, and with site deterioration, erosion occurs on overgrazed area, roads, livestock trails, and concentration areas.
Wildlife – Mule deer winter on this site. Competition exists between wildlife and livestock during fall and winter.Hydrological functions
Permeability is moderately slow. Available water holding capacity is high. Runoff is slow, and the hazard of water erosion is slight.
Recreational uses
This site is suited to hunting, horseback riding, and wildlife observation. The general appearance of this site in excellent or good condition is grassland interspersed with shrubs. In poorer conditions, black greasewood often dominates, making an interesting contrast to surrounding sites.
Supporting information
Type locality
Location 1: San Juan County, NM Township/Range/Section T26N R17W S32 General legal description Little Water Quad – 1 mile N of Little Water, NM – SW ¼ of Sec. 32, T26N, R17W - Navajo Reservation, NM. Contributors
John Tunberg
Michael Carpinelli
UnknownApproval
Kendra Moseley, 5/20/2025
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 04/24/2026 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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