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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 35.3 – Colorado Plateau Sagebrush – Grasslands
Elevations range from 4500 to 6000 feet and precipitation averages 10 to 14 inches. Vegetation includes Wyoming big sagebrush, Utah juniper, Colorado pinyon - cliffrose, Mormon tea, fourwing saltbush, blackbrush Indian ricegrass, needle and thread, western wheatgrass Galleta, black grama, blue grama, and sand dropseed. The soil temperature regime is mesic and the soil moisture regime is ustic aridic. This unit occurs within the Colorado Plateau Physiographic Province and is characterized by a sequence of flat to gently dipping sedimentary rocks eroded into plateaus, valleys and deep canyons. Sedimentary rock classes dominate the plateau with volcanic fields occurring for the most part near its margin.Associated sites
R035XC302AZ Sedimentary Cliffs 10-14" p.z.
associated with rock outcrop
R035XC328AZ Cobbly Slopes 10-14" p.z.
Deep cobbly loam soils
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
Table 2. Representative physiographic features
Landforms (1) Structural bench
(2) Ledge
(3) Escarpment
Flooding duration Extremely brief (0.1 to 4 hours) Flooding frequency None to rare Ponding duration Very brief (4 to 48 hours) Ponding frequency None to rare Elevation 4500 – 6500 ft Slope 10 – 50 % Aspect Aspect is not a significant factor Climatic features
50-60% of moisture falls as rain Jul-Sep and is the most effective moisture for plant growth. The remaining moisture comes as snow during the winter.
Mean temperature for the hottest month (Jul) is 72 F; for the coldest month (Jan) is 32 F. Extreme temperatures of 105 F and -28F have been recorded. Long periods with little or no effective moisture are relatively common.
Cool season plants begin growth in early spring and mature early summer. Warm season plants take advantage of summer rains and are growing and nutritious Jul-Sep.
Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 190 days Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
Soils that are grouped together in this site have characteristics of being very shallow to moderately deep to bedrock or other plant root restricting layers. Surface soil texture has a minimum depth of 1-3 inches and can be extremely flaggy/channery sand, sand and loamy sand. Subsurface or substratum layers have a depth of 3 to 26 inches with textures ranging from sand to flaggy/channery sand with coarse fragments ranging from 10-30% by volume. The hazard of erosion by water is moderate and erosion by wind is slight to moderate. Soils are moderately alkaline to alkaline (pH 7.9-9). With good vegetative cover, infiltration rates are increased, stability against erosion is good and plant-soil moisture relationships are good.
Typical taxonomic units include:
SSA 707 Little Colorado Area MU 42 Reef & Progresso;
SSA-711 Navajo Mountain area MU 42 - Mathis
Table 4. Representative soil features
Parent material (1) Colluvium – sandstone
Surface texture (1) Sand
(2) Loamy sand
Family particle size (1) Sandy
Drainage class Moderately well drained to excessively drained Permeability class Moderately rapid to very rapid Soil depth 12 – 26 in Surface fragment cover <=3" 20 – 40 % Surface fragment cover >3" 15 – 25 % Available water capacity
(0-40in)0.8 – 1.1 in Calcium carbonate equivalent
(0-40in)0 – 2 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 4 Soil reaction (1:1 water)
(0-40in)7.9 – 9 Subsurface fragment volume <=3"
(Depth not specified)20 – 30 % Subsurface fragment volume >3"
(Depth not specified)5 – 15 % 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. The historic climax plant community was in dynamic equilibrium with its environment. It is the plant community that 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 these plant communities. The effects of these disturbances are part of the range of characteristics of the site that contribute to that dynamic equilibrium. Fluctuations in plant community 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 an ecological site. Some sites may have a small range of variation, while others have a large range.
The historic climax plant community of an ecological site is not a precise assemblage of species for which the proportions are the same from place to place or from year to year. In all plant communities, variability is apparent in productivity and occurrence of individual species. Spatial boundaries of the communities; however, can be recognized by characteristic patterns of species composition, association, and community structure. The HCPC for this ecological site has been estimated by sampling relict or relatively undisturbed sites and/or reviewing historic records.
Plant communities that are subjected to abnormal disturbances and physical site deterioration or that are protected from natural influences, such as fire and grazing, for long periods seldom typify the historic climax plant community. The physical site deterioration caused by the abnormal disturbance results 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 specie’s 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 2 submodel, plant communities
State 1
Reference StateCommunity 1.1
Reference State1.1 Reference plant community
Site is primarily a complex of shrubs and grasses with smaller amounts of trees and forbs. Common shrubs are CORA, ERCO14 and ARBI3. Grasses are a scattered mix of warm season bunch grasses with fewer cool season species. Production is low due to amount of rock outcrop and boulders per acre. Access is limited due to steep and uneven terrain, with vertical ledges and drop-offs.
1.2 Composite Shrubs, Succulents and Annual Forbs and Composite shrubs like GUSA2, CHYRS9, and succulents increase over more palatable shrubs. Perennial grasses decrease, annual forbs increase.
1.1a = Continuous herbivory and/or drought
1.2a = Prescribe grazing or rest with favorable climatic conditions
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 10 40 170 Shrub/Vine 50 75 155 Forb 5 25 50 Total 65 140 375 Table 6. Ground cover
Tree foliar cover 0-0% Shrub/vine/liana foliar cover 0-0% Grass/grasslike foliar cover 0-10% Forb foliar cover 0-0% Non-vascular plants 0-0% Biological crusts 0-0% Litter 0-10% Surface fragments >0.25" and <=3" 20-50% Surface fragments >3" 10-30% Bedrock 10-10% Water 0% Bare ground 10-10% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 0-2% 0-10% 0-20% 0-5% >0.5 <= 1 0-2% 0-10% 0-20% 0-5% >1 <= 2 0-2% 0-5% 0-5% 0-1% >2 <= 4.5 0-2% 0-1% 0% 0-1% >4.5 <= 13 0-1% 0% 0% 0% >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 4. Plant community growth curve (percent production by month). AZ3511 , 35.1 10-14" p.z. all sites. Growth begins in the spring and continues through the summer, most growth occurs during the summer rainy season. .
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 1 5 11 18 25 24 13 3 0 0 Figure 5. Plant community growth curve (percent production by month). AZ5102 , 35.1 10-14" p.z. blue grama. Growth occurs mostly in summer and early fall during the rainy season..
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 0 5 5 15 30 30 15 0 0 0 State 2
exotic annualsCommunity 2.1
exotic annuals2.1 Native Overstory with Mixed Native - Exotic Understory
Exotic annual grasses introduced into plant community. Vegetative composition is otherwise relatively unchanged from 1.1.
2.2 Exotic annual grasses dominate understory with a mix of native and exotic forbs. The site can degrade much further, with increased erosion and much greater presence of annuals.
2.1a = Continuous herbivory, increase of exotic annuals with favorable winter moisture
2.2a = Prescribed grazing, herbicide treatment, range planting, drought
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 grasses 20–165 James' galleta PLJA Pleuraphis jamesii 0–40 – Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 0–25 – sand dropseed SPCR Sporobolus cryptandrus 0–20 – black grama BOER4 Bouteloua eriopoda 0–20 – mesa dropseed SPFL2 Sporobolus flexuosus 0–15 – Indian ricegrass ACHY Achnatherum hymenoides 0–15 – sideoats grama BOCU Bouteloua curtipendula 0–10 – blue grama BOGR2 Bouteloua gracilis 0–10 – needle and thread HECO26 Hesperostipa comata 0–10 – Shrub/Vine2 Shrubs 20–155 blackbrush CORA Coleogyne ramosissima 0–40 – jointfir EPHED Ephedra 0–20 – crispleaf buckwheat ERCO14 Eriogonum corymbosum 0–20 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–20 – skunkbush sumac RHTR Rhus trilobata 0–20 – Bigelow sage ARBI3 Artemisia bigelovii 0–20 – Greene's rabbitbrush CHGR6 Chrysothamnus greenei 0–10 – fourwing saltbush ATCA2 Atriplex canescens 0–5 – Tree3 trees 10–270 oneseed juniper JUMO Juniperus monosperma 10–230 – twoneedle pinyon PIED Pinus edulis 0–20 – singleleaf ash FRAN2 Fraxinus anomala 0–20 – Forb4 Forbs 0–35 desert princesplume STPI Stanleya pinnata 0–20 – woolly paperflower PSTA Psilostrophe tagetina 0–4 – Colorado four o'clock MIMU Mirabilis multiflora 0–3 – trailing windmills ALIN Allionia incarnata 0–2 – Navajo tea THSU Thelesperma subnudum 0–2 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
On the less severe slopes this site is suitable for light grazing during any season by all types of livestock. Because soils are shallow and slopes are steep, grazing should be light in order to protect the native plant community and soils. When this range site is grazed yearlong or primarily in the spring, cool season mid grasses that are most readily damaged by grazing decline and less productive species dominate the plant community. Most vegetation is palatable to livestock but may not be available for grazing due to steep slopes.
The diversity of topography and vegetative form provides habitat for numerous wildlife species. Because of the rough broken nature of the site, it becomes important to adjacent sites for cover and protection from adverse weather.
Wildlife adapted to this site will benefit from practices that will restore or maintain the native plant community. Wildlife watering facilities are important to the site.
Recreational uses
Land form contains steep side slopes on hills and escarpments. Landscape quality includes an abundance of spring and summer flowering forbs. The aesthetic appeal is excellent due to the mixture of tree forms with shrub and grass understory. Winters are cold; however, relatively mild summers make this site attractive for wildlife observation, hunting, rock hounding and hiking.
Supporting information
Type locality
Location 1: Coconino County, AZ UTM zone N UTM northing 4076205 UTM easting 503610 General legal description Type location for MU 42 mathis soil Other references
Information and updates collected during 2009-2010 for this ESD was conducted as part of an Interagency Technical Assistance Agreement between the Bureau of Indian Affairs–Navajo Region and the NRCS-Arizona.
Contributors
Karlynn Huling
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) Dean Schlichting, Dan Carroll Contact for lead author Holbrook ESD Office Date 03/01/2010 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rill formation is slight and infrequent across the site. Most rills are found on exposed areas on the steeper slopes and in conjunction with slow permeability soils. Moderate permeability and abundance of surface rock fragments will help restrict rill formation. -
Presence of water flow patterns:
Water flow patterns are scattered on this site and plant distribution and exposed rock cover will depict where they will be present. -
Number and height of erosional pedestals or terracettes:
There will be some slight pedalstalling or terracettes in association with water flow patterns. Slight mounding will occur around the bases of long lived perennial plants and should not be considered pedestals. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
15 to 30% bare ground depending on rock and gravel cover. -
Number of gullies and erosion associated with gullies:
None expected on this site. -
Extent of wind scoured, blowouts and/or depositional areas:
No blowouts or wind scoured areas are expected on this site. There can be some mounding (depositional areas) at long lived perennial plants and around larger rocks and boulders. -
Amount of litter movement (describe size and distance expected to travel):
Most herbaceous and fine woody litter will be transported by wind and in water flow pathways, while a small percentage stays in place. Coarse woody litter and duff will accumulate under shrub canopies. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface resistance to erosion varies greatly depending on vegetative cover as well the distribution of rock, boulders and/or gravel. In areas of no vegetative cover or rock armoring, the surface erodes readily. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil surface to 3" is extremely flaggy sand and has a massive structure. Notice: the soil survey for the area and map unit that is being observed should be referenced for accurate information regarding the unique characteristics of that soil. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
This site is dominated by grass cover with up to 10% cover, and then by shrubs and trees with up to 2% cover for each category and with up to 1% cover in forbs and biological crust. The plant cover, rock cover and rapid permeability is beneficial for infiltration and runoff prevention. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None -
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:
ShrubsSub-dominant:
GrassesOther:
TreesAdditional:
Forbs -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
In an average year plant mortality is expected to be low (1 to 5%) in grasses and shrubs. During and after drought years there can be from 5 to 20% die off of shrubs, grasses and trees. Severe winter droughts affect shrubs, trees and cool season grasses the most. Severe summer droughts affect the warm season grasses the most.rasses the most. -
Average percent litter cover (%) and depth ( in):
Of the total litter amount, it would be expected that approximately 80-90% would be herbaceous litter and approximately 10-20% would be woody litter. Litter amounts increase during the first few years of drought, then decrease in later years. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
50-100 pounds per acre (dry weight) in drought years, 150-200 pounds per acre in median years, 300-350 pounds per acre in wet years. -
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:
Trees and Native shrubs such as Juniper (JUMO) and snakeweed (GUSA2) are on the site and can increase with time. -
Perennial plant reproductive capability:
The only natural limitations to reproductive capability are weather related and natural disease or herbivory that reduces reproductive capability. All plants native to this site are adapted to the climate and are capable of producing seeds, stolons and rhizomes except during the most severe droughts.
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