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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" p.z. Dry or intermittent washes of channels that benefit significantly from run-in moisture, but the water table is out of reach ot all but the deepest-rooted species.
Table 1. Dominant plant species
Tree (1) Salix gooddingii
(2) Populus fremontiiShrub (1) Salix exigua
(2) Baccharis sarothroidesHerbaceous (1) Phragmites australis
(2) Juncus balticusPhysiographic features
This ecological site occurs around perennial waters such as springs and along streams and rivers, especially in the backwaters. It occurs on all aspects and is characterized by obligate and faculative wetland species.
Table 2. Representative physiographic features
Landforms (1) Backswamp
(2) Shoreline
(3) Flood plain
Flooding duration Very brief (4 to 48 hours) to very long (more than 30 days) Flooding frequency Frequent Ponding duration Long (7 to 30 days) to very long (more than 30 days) Ponding frequency Occasional to frequent Elevation 1600 – 4600 ft Slope 0 – 6 % Water table depth 0 – 40 in 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 are generally moderately deep to very deep Fluvaquents, but can be shallow to a restrictive layer. They have been formed in alluvium of mixed sedimentary origin, and exhibit stratified layers with textures ranging from sand to silty clay.
Soils are non-sodic, non-saline to slightly saline with pH range of 7.9-8.4 (moderately alkaline).
Waterholding class is very low to low. Water table depth is shallow. Flow regime is perennial in a Riverine system; hydrologic group B. Run-on moisture influence is high.
Soil mapped on this site is:
SSA-701 Grand Canyon Area MU 41 Fluvaquents.Table 4. Representative soil features
Surface texture (1) Sand
(2) Sandy clay
Family particle size (1) Sandy
Drainage class Poorly drained Permeability class Slow Soil depth 10 – 60 in Surface fragment cover <=3" Not specified Available water capacity
(0-40in)0 – 2.5 in Calcium carbonate equivalent
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)Not specified 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
Custom diagramStandard diagram
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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 CommunityCommunity 1.1
Historic Climax Plant CommunityThis ecological site developed under historic Colorado Planteau climatic conditions, and reflects the natural influences of herbivores, climate fluctuations and occasional fire.
This plant community is dominated by obligate wetland species of grasses, grass-likes, and shrubs. Faculatitive wetland species, including some trees, are also common.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)Grass/Grasslike 1500 1920 2300 Shrub/Vine 1150 1435 1700 Tree 200 310 400 Forb 50 135 200 Total 2900 3800 4600 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Common Native Perennial Tall Grasses 760–1300 common reed PHAU7 Phragmites australis 380–760 – chairmaker's bulrush SCAM6 Schoenoplectus americanus 190–380 – broadleaf cattail TYLA Typha latifolia 190–380 – 2 Common Native Perennial Mid Grasses (Obligate) 380–760 water sedge CAAQ Carex aquatilis 190–380 – EQFE Equisetum ×ferrissii 190–380 – Grass, perennial 2GP Grass, perennial 40–190 – 3 Common Native Perennial Mid Grasses (Faculative) 190–380 deergrass MURI2 Muhlenbergia rigens 40–190 – Grass, perennial 2GP Grass, perennial 40–190 – bushy bluestem ANGL2 Andropogon glomeratus 40–190 – California satintail IMBR2 Imperata brevifolia 40–190 – 4 Occasional Native Perennial Mid Grasses 0–75 Grass, perennial 2GP Grass, perennial 0–35 – hairgrass DESCH Deschampsia 0–35 – 5 Occasional Native Perennial Short Grasses 0–40 saltgrass DISP Distichlis spicata 0–40 – Forb6 Occasional Native Perennial Forbs 0–75 Forb, perennial 2FP Forb, perennial 0–35 – scarlet monkeyflower MICA3 Mimulus cardinalis 0–35 – 7 Occasional Native Perennial Forbs 0–75 Forb, perennial 2FP Forb, perennial 0–40 – mint MENTH Mentha 0–40 – 8 Occasional Native Annual Forbs 0–115 Forb, annual 2FA Forb, annual 0–60 – cudweed GNAPH Gnaphalium 0–60 – Hooker's evening primrose OEEL Oenothera elata 0–60 – 9 Occasional Native Perennial Ferns and Allies 0–75 Fern or Fern Ally 2FERN Fern or Fern Ally 0–75 – maidenhair fern ADIAN Adiantum 0–75 – Shrub/Vine10 Common Native Shrubs 760–1400 mule-fat BASA4 Baccharis salicifolia 380–760 – narrowleaf willow SAEX Salix exigua 380–760 – 11 Occasional Native Shrubs 40–190 Emory's baccharis BAEM Baccharis emoryi 40–115 – honey mesquite PRGL2 Prosopis glandulosa 0–75 – New Mexico locust RONE Robinia neomexicana 0–75 – Shrub, other 2S Shrub, other 0–75 – catclaw acacia ACGR Acacia greggii 0–75 – Tree12 Common Native Trees 190–380 Goodding's willow SAGO Salix gooddingii 190–380 – 13 Occasional Native Trees 0–75 boxelder ACNE2 Acer negundo 0–40 – Fremont cottonwood POFR2 Populus fremontii 0–40 – Interpretations
Supporting information
Contributors
Art Meen
Larry D. EllicottRangeland 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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