Natural Resources
Conservation Service
Ecological site R035XB020NM
Loamy
6-10"
terrace
Last updated: 5/20/2025
Accessed: 05/12/2026
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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 stream terraces, and on former floodplains in systems were incision has lowered the high water table below the solum. Soils are very deep and well-drained. Soil textures are variable, and often stratified, but sandy textures are most common.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Atriplex canescens
Herbaceous (1) Achnatherum hymenoides
(2) Pleuraphis jamesiiPhysiographic features
This site occurs on low stream terraces, usually adjacent to washes and intermittent stream drainages. Historically, this site was primarily stream bottoms on floodplains, but through deep gully erosion, they no longer benefit from excess from run-in moisture. Slopes range from 0 to 2 percent. Elevations range from 5,500 to 6,000 feet.
Table 2. Representative physiographic features
Landforms (1) Stream terrace
Elevation 5500 – 6000 ft Slope 0 – 2 % 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
There are no water features on this site.
Soil features
The soils are very deep and well drained. They formed in alluvium derived from shale and sandstone. Surface textures include loamy fine sand. The subsoil has textures of loamy sand, fine sandy loam with thin strata of sandy clay loam, and stratified fine sandy loam to clay loam. Permeability is moderately slow. Available water holding capacity is moderate to high. Runoff is slow, and the hazard of water erosion is moderate. The hazard of soil blowing is severe. The soils are mildly to moderately alkaline (pH 7.4-8.4), slightly saline (EC 4-8), and slightly sodic (SAR 5-13).
Shiprock SSA:
190 – Jeddito loamy fine sand
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 Sodium adsorption ratio
(0-40in)5 – 13 Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Ecological dynamics
This site has a plant community made up primarily of grasses intermixed with shrubs. 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 cheatgrass, sixweeks grama, sixweeks dropseed, Russian thistle, mustard, black greasewood, and fourwing saltbush. 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 intermixed with shrubs. 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 cheatgrass, sixweeks grama, sixweeks dropseed, Russian thistle, mustard, black greasewood, and fourwing saltbush. 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.Figure 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 320 370 420 Shrub/Vine 80 110 150 Forb 5 20 30 Total 405 500 600 Figure 5. Plant community growth curve (percent production by month). NM0375 , R035XB020NM-Loamy Terrace 6-10 inch-HCPC. R035XB020NM-Loamy Terrace 6-10 inch-HCPC.
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 Community 1.2
Galleta - Blue Grama Grassland with Mixed ShrubsThis phase is dominated by galleta and blue grama. It also contains a mix of shrubs.
Community 1.3
Galleta Grassland/ShrublandThis phase is dominated by galleta and shrubs.
Pathway P1.1a
Community 1.1 to 1.2Season-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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Precipitation (decadal scale)
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Livestock grazing or browsing
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Climate
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Precipitation (annual scale)
Key ecosystem services affected
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Food and fiber: livestock forage
Pathway P1.2b
Community 1.2 to 1.1Prescribed grazing.
Conservation practices
Prescribed Grazing Key drivers
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Precipitation (decadal scale)
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Livestock grazing or browsing
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Climate
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Precipitation (annual scale)
Key ecosystem services affected
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Food and fiber: livestock forage
Pathway P1.2a
Community 1.2 to 1.3Season-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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Precipitation (decadal scale)
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Livestock grazing or browsing
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Climate
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Precipitation (annual scale)
Key ecosystem services affected
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Food and fiber: livestock forage
Pathway P1.3a
Community 1.3 to 1.2Prescribed grazing.
Conservation practices
Prescribed Grazing Key drivers
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Precipitation (decadal scale)
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Livestock grazing or browsing
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Climate
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Precipitation (annual scale)
Key ecosystem services affected
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Food and fiber: livestock forage
State 2
Native/Invasive Annuals StateThis state is dominated by a mix of native plants and non-native invasive annuals.
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. Drought can be a trigger event for this transition.
Key drivers
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Precipitation (decadal scale)
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Livestock grazing or browsing
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Seed dispersal by livestock
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Climate
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Precipitation (annual scale)
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Nonnative plant species presence and/or establishment
Key ecosystem services affected
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Erosion control
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Nutrient cycling
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Food and fiber: livestock forage
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Climate regulation: carbon cycling and storage
Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Indian ricegrass 20–30 Indian ricegrass ACHY Achnatherum hymenoides 80–180 – 2 galleta 60–120 James' galleta PLJA Pleuraphis jamesii 60–120 – 3 alkali sacaton 20–60 alkali sacaton SPAI Sporobolus airoides 20–60 – 4 sand dropseed 0–30 sand dropseed SPCR Sporobolus cryptandrus 0–30 – 5 squirreltail 5–30 squirreltail ELEL5 Elymus elymoides 4–30 – 6 blue grama 5–30 blue grama BOGR2 Bouteloua gracilis 4–30 – 7 Fendler's (red) threeawn 0–5 Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 0–12 – 8 other perennial grasses 0–20 Forb9 globemallow 0–10 globemallow SPHAE Sphaeralcea 0–12 – 10 other perennial forbs 0–10 11 annual forbs 0–5 Shrub/Vine12 fourwing saltbush 40–120 fourwing saltbush ATCA2 Atriplex canescens 40–120 – 13 broom snakeweed 0–10 broom snakeweed GUSA2 Gutierrezia sarothrae 0–12 – 14 Greene's rabbitbrush 0–20 Greene's rabbitbrush CHGR6 Chrysothamnus greenei 0–18 – 15 green rubber rabbitbrush 0–10 rubber rabbitbrush ERNAG Ericameria nauseosa ssp. nauseosa var. glabrata 0–12 – 16 other shrubs 0–10 Table 7. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 1.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Livestock -- This site is suitable for yearlong grazing by all classes of livestock and is easily traversed. It will respond quickly to a planned grazing system. This site is susceptible to erosion, particularly overgrazed areas, old roads, and concentration areas.
Wildlife – Mule deer may winter on this site. Competition between cattle and wildlife can be high.Hydrological functions
Runoff is slow, and the hazard of water erosion is moderate.
Recreational uses
Hunting, horseback riding, and wildlife observation are occasional recreational activities on this site. The general appearance of this site is grassland interspersed with shrubs. The landscape breaks the monotony of the surrounding rolling plains and is aesthetically pleasing.
Supporting information
Type locality
Location 1: San Juan County, NM Township/Range/Section T26N R18W S19 General legal description Sanostee East Quad – 5 miles NE of Sanostee, NM – 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 05/12/2026 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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