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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): 035X–Colorado Plateau
AZ CRA 35.5 – Grand Canyon Corridor
Elevations range from 1600 to 4500 feet and precipitation averages 6 to 10 inches per year. Extreme elevation and aspect changes make this area unique. Vegetation includes Mormon tea, catclaw, white brittlebush, blackbrush, prickly pear, cholla species, big galleta, and blue threeawn. The soil temperature regime ranges from thermic to mesic and the soil moisture regime is typic aridic. This unit occurs within the Colorado Plateau Physiographic Province and is characterized by extreme vertical escarpments and strong aspect differences over short distances. Sedimentary rock classes dominate the Grand Canyon and exposures consist of a thick sequence of relatively undeformed formations.Associated sites
R035XE511AZ Sandy Wash 6-10" p.z.
Sandy Wash 6-10" pz Often found as the current drainage channel through the older terraces.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site occurs on older stream terraces and outwash areas that no longer benefit from the water table, or that receive frequent run-on floodwater. The site benefits moderately from run-on sheet flow. Soil textures are sandy loam to loam with high amounts of gravels, stones and boulder. The site occurs on all aspets. Slopes are usually 1-6%, but can be higher.
Table 2. Representative physiographic features
Landforms (1) Stream terrace
(2) Terrace
(3) Outwash fan
Flooding duration Extremely brief (0.1 to 4 hours) Flooding frequency None to very rare Elevation 1600 – 4600 ft Slope 1 – 15 % Aspect Aspect is not a significant factor Climatic features
The climate of the land resource unit is arid to semiarid with warm summers and cool winters. The mean annual precipitation ranges from 6 – 10 inches, but it is very erratic, often varying substantially from year to year. The majority of the precipitation falls during the between October through May. This precipitation comes as gentile rain or occasionally snow from frontal storms coming out to the Pacific Ocean. Snow is infrequent and rarely last more than 1-2 days. The remaining precipitation comes from July through September as spotty, unreliable and sometimes violent thunderstorms. The moisture for this precipitation originates in the Gulf of Mexico (and the Pacific Ocean in the fall) and flows into the area on the north end of the Mexican monsoon. Late May through late June is generally a dry period. The mean annual air temperature ranges from 55 to 69 degrees Fahrenheit (F). The frost-free period (air temperature > 32 degrees F) ranges from 180 to 220 days (@ 50 percent probability).
Table 3 Representative climatic features
Frost-free period (average) 200 days Freeze-free period (average) 220 days Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soils that characterize this site have a sandy loam to loam surface texture and are very to extremely stony or cobbly. They are deep to very deep and are moderately effervescent at soil surface. Common inclusions are: soils that are shallow to bedrock, soils with a petrocalcic horizon,and soils that are occasionally flooded.
Typical taxonomic units on this site include:
SSA-699 Hualapai-Havasupai Area MU 2 Lostman;
SSA-701 Grand Canyon Area MU's 25 Cliffdown family and 137 typic calciargids & typic haplocalcids.Table 4. Representative soil features
Surface texture (1) Very cobbly sandy loam
(2) Very stony loam
(3) Extremely stony very fine sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate to moderately rapid Soil depth 40 – 60 in Surface fragment cover <=3" 15 – 40 % Surface fragment cover >3" 20 – 50 % Available water capacity
(0-40in)5 – 7 in Calcium carbonate equivalent
(0-40in)5 – 15 % Electrical conductivity
(0-40in)0 – 4 mmhos/cm Soil reaction (1:1 water)
(0-40in)7.8 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)20 % Subsurface fragment volume >3"
(Depth not specified)50 % Ecological dynamics
The historic climax plant community (HCPC) for a site in North America is the plant community that existed at the time of European immigration and settlement. It is the plant community that was best adapted to the unique combination of environmental factors associated with the site at that time. The HCPC was in dynamic equilibrium with its environment and was able to avoid displacement by the suite of disturbances and disturbance patterns (magnitude and frequency) that naturally occurred within the area occupied by the site. Natural disturbances, such as drought, fire, grazing of native fauna, and insects, were inherent in the development and maintenance of the plant community. The effects of these disturbances are part of the range of characteristics of the site that contribute to the dynamic equilibrium. Fluctuations in the plant community’s structure and function caused by the effects of these natural disturbances establish the boundaries of dynamic equilibrium. They are accounted for as part of the range of characteristics for the ecological site. The HCPC is not a precise assemblage of species for which the proportions are the same from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species.
The HCPC for this ecological site has been estimated by sampling relict or relatively undisturbed sites and/or reviewing historic records.
A plant community that is subjected to abnormal disturbances and physical site deterioration or that is protected from natural influences, such as fire and grazing, for long periods seldom typifies the HCPC. Any physical site deterioration caused by the abnormal disturbance may result in the crossing of a threshold or irreversible boundary to another state, or equilibrium, for the ecological site. There may be multiple thresholds and states possible for an ecological site, determined by the type and or severity of abnormal disturbance. The known states and transition pathways for this ecological site are described in the accompanying state and transition model.
The “Plant Community Plant Species Composition” table provides a list of species and each species or group of species’ annual production in pounds per acre (air-dry weight) expected in a normal rainfall year. Low and high production yields represent the modal range of variability for that species or group of species across the extent of the ecological site.
The “Annual Production by Plant Type” table provides the median air-dry production and the fluctuations to be expected during favorable, normal, and unfavorable years.
The present plant community on an ecological site can be compared to the various common vegetation states that can exist on the site. The degree of similarity is expressed through a similarity index. To determine the similarity index, compare the production of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum shown for the group. Divide the resulting total by the total representative value shown in the “Annual Production by Plant Type” table for the reference plant community. Variations in production due to above or below normal rainfall, incomplete growing season or utilization must be corrected before comparing it to the site description. The “Worksheet for Determining Similarity Index” is useful in making these corrections. The accompanying growth curve can be used as a guide for estimating percent of growth completed.
State and transition model
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
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
Historic Climax Plant Community1Community 1.1
Historic Climax Plant Community1This site has an abundance of mid-shrubs mixed with occasional taller shrubs and cacti. Warm season perennial grasses are common and cool season perennial grasses are slightly less so. Production on this site is often higher than on other sites because of run-on sheet flow from surrounding areas.
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)Shrub/Vine 215 – 310 Grass/Grasslike 145 – 215 Forb 2 – 70 Total 362 – 595 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 70–120 sand dropseed SPCR Sporobolus cryptandrus 25–50 – black grama BOER4 Bouteloua eriopoda 25–50 – spike dropseed SPCO4 Sporobolus contractus 5–25 – mesa dropseed SPFL2 Sporobolus flexuosus 5–25 – 2 0–15 Grass, perennial 2GP Grass, perennial 0–5 – cane bluestem BOBA3 Bothriochloa barbinodis 0–5 – sideoats grama BOCU Bouteloua curtipendula 0–5 – bush muhly MUPO2 Muhlenbergia porteri 0–5 – James' galleta PLJA Pleuraphis jamesii 0–5 – 3 0–10 Grass, perennial 2GP Grass, perennial 0–4 – low woollygrass DAPU7 Dasyochloa pulchella 0–4 – saltgrass DISP Distichlis spicata 0–4 – 4 25–50 Indian ricegrass ACHY Achnatherum hymenoides 5–25 – desert needlegrass ACSP12 Achnatherum speciosum 5–25 – blue threeawn ARPUN Aristida purpurea var. nealleyi 5–25 – 5 0–25 Grass, annual 2GA Grass, annual 0–10 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–10 – sixweeks fescue VUOC Vulpia octoflora 0–10 – Forb6 5–25 Forb, perennial 2FP Forb, perennial 0–15 – Forb, perennial 2FP Forb, perennial 0–15 – desert trumpet ERIN4 Eriogonum inflatum 0–10 – globemallow SPHAE Sphaeralcea 0–10 – desert trumpet ERIN4 Eriogonum inflatum 0–10 – globemallow SPHAE Sphaeralcea 0–10 – 7 0–20 Forb, perennial 2FP Forb, perennial 0–15 – fragrant white sand verbena ABEL Abronia elliptica 0–10 – brownfoot ACWR5 Acourtia wrightii 0–10 – trailing windmills ALIN Allionia incarnata 0–10 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–10 – 8 0–20 Forb, annual 2FA Forb, annual 0–10 – white easterbonnets ANLA7 Antheropeas lanosum 0–10 – milkvetch ASTRA Astragalus 0–10 – cryptantha CRYPT Cryptantha 0–10 – pepperweed LEPID Lepidium 0–10 – desertdandelion MALAC3 Malacothrix 0–10 – desert Indianwheat PLOV Plantago ovata 0–10 – Shrub/Vine9 10–35 white sagebrush ARLU Artemisia ludoviciana 0–15 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–15 – pricklyleaf dogweed THAC Thymophylla acerosa 0–15 – Mojave woodyaster XYTO2 Xylorhiza tortifolia 0–10 – alkali goldenbush ISAC2 Isocoma acradenia 0–10 – mountain phlox PHAU3 Phlox austromontana 0–10 – Shrub, other 2S Shrub, other 0–10 – 10 145–190 Apache plume FAPA Fallugia paradoxa 50–70 – catclaw acacia ACGR Acacia greggii 25–50 – fourwing saltbush ATCA2 Atriplex canescens 25–50 – mormon tea EPVI Ephedra viridis 25–50 – 11 0–10 Emory's baccharis BAEM Baccharis emoryi 0–5 – honey mesquite PRGL2 Prosopis glandulosa 0–5 – Sonoran scrub oak QUTU2 Quercus turbinella 0–5 – skunkbush sumac RHTR Rhus trilobata 0–5 – 12 5–25 Shrub, other 2S Shrub, other 0–10 – shortleaf baccharis BABR Baccharis brachyphylla 0–10 – brittlebush ENFA Encelia farinosa 0–10 – rubber rabbitbrush ERNA10 Ericameria nauseosa 0–10 – water jacket LYAN Lycium andersonii 0–10 – Fremont's dalea PSFR Psorothamnus fremontii 0–10 – 13 5–50 beavertail pricklypear OPBA2 Opuntia basilaris 5–25 – dollarjoint pricklypear OPCH Opuntia chlorotica 5–25 – plains pricklypear OPPO Opuntia polyacantha 5–25 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–10 – 14 0–15 Utah agave AGUT Agave utahensis 0–10 – banana yucca YUBA Yucca baccata 0–10 – Interpretations
Supporting information
Contributors
Larry D. Ellicott
Steve BarkerRangeland 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 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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PrintThe Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
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