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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
R035XE504AZ Schist Hills 6-10" p.z.
Schist Hills 6-10" pz Areas of intermixing of igneous formations such as Vishnu Schist.
R035XE516AZ Sedimentary Cliffs 6-10" p.z.
Sedimentary Cliffs 6-10" pz Areas characterized by cliff-forming formations or by significant residuum from other formations, on top of shales.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Encelia farinosa
(2) Ephedra torreyanaHerbaceous Not specified
Physiographic features
This site occurs as colluvial pockets and ledges, and alluvial fans on slope-forming shales and siltstones. Soils are very gravelly to extremely channery or bouldery, and surface textures range from loamy sand to silt loam. Soil depths are typically very shallow and shallow, but there are some deeper alluvial soils as well. Slopes are typically 10-30%, but can range from nearly level to as high as 60%. This site occurs on all aspects.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Ledge
(3) Pediment
Flooding frequency None Ponding frequency None Elevation 1600 – 4600 ft Slope 2 – 60 % 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
Typical surface soil textures are sandy loam and extremely channery or bouldery; however, the surface may range to silt loam or very gravelly. Soil depth is commonly 9-20 inches to bedrock. There can be short alluvial fans between the exposed rock outcrop that have deep soils in places. The soils on this site are normally slightly saline, depending on the influence of certain formations. The surface is strongly to violently effervescent.
Soil temperature regime is thermic; moisture class is typic; moisture regime is aridic. Water and wind erosion hazards are moderate. Soil restrictive layer is bedrock (lithic).
Surface pH range is 7.6-8.2. Surface effervescence is violent (15-30). Soils are non-sodic and very slightly saline.
Soil water holding class is very low. Water table depth is very deep. Run-in moisture has no influence.
Soil correlation:
AZ701-Grand Canyon Area, MU's 102 (Cellar family), 128 (Torriorthents) & (Lithic haplargds) and 105 (lithic torriorthents).Table 4. Representative soil features
Parent material (1) Alluvium – granite
Surface texture (1) Extremely channery loamy sand
(2) Extremely bouldery loamy very fine sand
(3) Very gravelly sandy loam
Family particle size (1) Sandy
Drainage class Well drained to excessively drained Permeability class Moderate to rapid Soil depth 9 – 60 in Surface fragment cover <=3" 0 – 30 % Surface fragment cover >3" 0 – 30 % Available water capacity
(0-40in)0 – 2.5 in Calcium carbonate equivalent
(0-40in)15 – 30 % Electrical conductivity
(0-40in)2 – 8 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.6 – 8.2 Subsurface fragment volume <=3"
(Depth not specified)0 – 35 % Subsurface fragment volume >3"
(Depth not specified)0 – 50 % Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The historical climax plant community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as grazing, fire, or drought.
Production data provided in this site description is standardized to air-dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity Index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity Index, compare the production (air-dry weight) 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 normal year production shown in the plant community description. If rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.
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 1
Historic Climax Plant CommuntyCommunity 1.1
Historic Climax Plant CommuntyThis plant community is predominantly shrubs and grasses.
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Additional community tables
Table 5. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Occasional Native Perennial Summer Mid Grasses 2–15 James' galleta PLJA Pleuraphis jamesii 2–15 – big galleta PLRI3 Pleuraphis rigida 2–15 – sand dropseed SPCR Sporobolus cryptandrus 0–5 – mesa dropseed SPFL2 Sporobolus flexuosus 0–5 – bush muhly MUPO2 Muhlenbergia porteri 0–5 – Grass, perennial 2GP Grass, perennial 0–2 – 2 Occasional Native Perennial Spring Mid Grasses 2–15 purple threeawn ARPU9 Aristida purpurea 2–10 – blue threeawn ARPUN Aristida purpurea var. nealleyi 2–10 – New Mexico feathergrass HENE5 Hesperostipa neomexicana 0–5 – slim tridens TRMU Tridens muticus 0–5 – desert needlegrass ACSP12 Achnatherum speciosum 0–5 – Grass, perennial 2GP Grass, perennial 0–2 – 3 Occasional Native Perennial Summer Short Grasses 0–10 low woollygrass DAPU7 Dasyochloa pulchella 0–10 – Rothrock's grama BORO2 Bouteloua rothrockii 0–5 – Grass, perennial 2GP Grass, perennial 0–2 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–2 – 4 Occasional Native Annual Grasses 0–10 Grass, annual 2GA Grass, annual 0–10 – sixweeks grama BOBA2 Bouteloua barbata 0–10 – sixweeks fescue VUOC Vulpia octoflora 0–10 – Forb5 Occasional Native Perennial Spring Short Forbs 2–10 Forb, perennial 2FP Forb, perennial 0–5 – desert trumpet ERIN4 Eriogonum inflatum 0–5 – globemallow SPHAE Sphaeralcea 0–5 – 6 Occasional Native Perennial Summer Short Forbs 0–5 Forb, perennial 2FP Forb, perennial 0–5 – brownfoot ACWR5 Acourtia wrightii 0–5 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–5 – white sagebrush ARLU Artemisia ludoviciana 0–2 – 7 Occasional Native Annual Short Forbs 0–5 Forb, annual 2FA Forb, annual 0–5 – fiddleneck AMSIN Amsinckia 0–5 – white easterbonnets ANLA7 Antheropeas lanosum 0–5 – milkvetch ASTRA Astragalus 0–5 – pincushion CHAEN Chaenactis 0–5 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–5 – fleabane ERIGE2 Erigeron 0–5 – Pringle's woolly sunflower ERPR4 Eriophyllum pringlei 0–5 – spurge EUPHO Euphorbia 0–5 – pepperweed LEPID Lepidium 0–5 – desertdandelion MALAC3 Malacothrix 0–5 – blazingstar MENTZ Mentzelia 0–5 – phlox PHLOX Phlox 0–5 – popcornflower PLAGI Plagiobothrys 0–5 – desert Indianwheat PLOV Plantago ovata 0–5 – Shrub/Vine8 Occasional Native Half Shrubs 0–2 broom snakeweed GUSA2 Gutierrezia sarothrae 0–10 – mountain phlox PHAU3 Phlox austromontana 0–5 – slender poreleaf POGR5 Porophyllum gracile 0–5 – Coues' cassia SECO10 Senna covesii 0–5 – pricklyleaf dogweed THAC Thymophylla acerosa 0–5 – turpentinebroom THMO Thamnosma montana 0–2 – Mojave woodyaster XYTO2 Xylorhiza tortifolia 0–2 – Shrub, other 2S Shrub, other 0–2 – brickellbush BRICK Brickellia 0–2 – starry bedstraw GAST Galium stellatum 0–2 – desert princesplume STPI Stanleya pinnata 0–2 – 9 Dominant Native Shrubs 15–75 brittlebush ENFA Encelia farinosa 15–75 – 10 Common Native Shrubs 15–45 shadscale saltbush ATCO Atriplex confertifolia 10–25 – Torrey's jointfir EPTO Ephedra torreyana 10–25 – mormon tea EPVI Ephedra viridis 10–25 – 11 Occasional Native Shrubs 0–15 catclaw acacia ACGR Acacia greggii 0–5 – Arizona desert-thorn LYEX Lycium exsertum 0–5 – Fremont's dalea PSFR Psorothamnus fremontii 0–5 – purple sage SADO4 Salvia dorrii 0–5 – button brittlebush ENFR Encelia frutescens 0–5 – Apache plume FAPA Fallugia paradoxa 0–2 – burrobrush HYSA Hymenoclea salsola 0–2 – Wright's beebrush ALWR Aloysia wrightii 0–2 – burrobush AMDU2 Ambrosia dumosa 0–2 – shortleaf baccharis BABR Baccharis brachyphylla 0–2 – sweetbush BEJU Bebbia juncea 0–2 – blackbrush CORA Coleogyne ramosissima 0–2 – Shrub, other 2S Shrub, other 0–2 – 12 Occasional Native Cacti 0–10 cottontop cactus ECPO2 Echinocactus polycephalus 0–3 – California barrel cactus FECY Ferocactus cylindraceus 0–3 – cactus apple OPEN3 Opuntia engelmannii 0–3 – beavertail pricklypear OPBA2 Opuntia basilaris 0–3 – dollarjoint pricklypear OPCH Opuntia chlorotica 0–2 – plains pricklypear OPPO Opuntia polyacantha 0–2 – grizzlybear pricklypear OPPOE Opuntia polyacantha var. erinacea 0–2 – Graham's nipple cactus MAGR9 Mammillaria grahamii 0–2 – Whipple cholla CYWH Cylindropuntia whipplei 0–2 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–2 – 13 Occasional Native Agave-Yucca-Like 0–2 Utah agave AGUT Agave utahensis 0–2 – Interpretations
Supporting information
Contributors
Art Meen
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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