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.
MLRA notes
Major Land Resource Area (MLRA): 026X–Carson Basin and Mountains
The area lies within western Nevada and eastern California, with about 69 percent being within Nevada, and 31 percent being within California. Almost all this area is in the Great Basin Section of the Basin and Range Province of the Intermontane Plateaus. Isolated north-south trending mountain ranges are separated by aggraded desert plains. The mountains are uplifted fault blocks with steep side slopes. Most of the valleys are drained by three major rivers flowing east across this MLRA. A narrow strip along the western border of the area is in the Sierra Nevada Section of the Cascade-Sierra Mountains Province of the Pacific Mountain System. The Sierra Nevada Mountains are primarily a large fault block that has been uplifted with a dominant tilt to the west. This structure leaves an impressive wall of mountains directly west of this area. This helps create a rain shadow affect to MLRA 26. Parts of this eastern face, but mostly just the foothills, mark the western boundary of this area. Elevations range from about 3,806 feet (1,160 meters) on the west shore of Pyramid Lake to 11,653 feet (3,552 meters) on the summit of Mount Patterson in the Sweetwater Mountains.
Valley areas are dominantly composed of Quaternary alluvial deposits with Quaternary playa or alluvial flat deposits often occupying the lowest valley bottoms in the internally drained valleys, and river deposited alluvium being dominant in externally drained valleys. Hills and mountains are dominantly Tertiary andesitic flows, breccias, ash flow tuffs, rhyolite tuffs or granodioritic rocks. Quaternary basalt flows are present in lesser amounts, and Jurassic and Triassic limestone and shale, and Precambrian limestone and dolomite are also present in very limited amounts. Also of limited extent are glacial till deposits along the east flank of the Sierra Nevada Mountains, the result of alpine glaciation.
The average annual precipitation in this area is 5 to 36 inches (125 to 915 millimeters), increasing with elevation. Most of the rainfall occurs as high-intensity, convective storms in spring and autumn. Precipitation is mostly snow in winter. Summers are dry. The average annual temperature is 37 to 54 degrees F (3 to 12 degrees C). The freeze-free period averages 115 days and ranges from 40 to 195 days, decreasing in length with elevation.
The dominant soil orders in this MLRA are Aridisols and Mollisols. The soils in the area dominantly have a mesic soil temperature regime, an aridic or xeric soil moisture regime, and mixed or smectitic mineralogy. They generally are well drained, are clayey or loamy and commonly skeletal, and are very shallow to moderately deep.
This area supports shrub-grass vegetation characterized by big sagebrush. Low sagebrush and Lahontan sagebrush occur on some soils. Antelope bitterbrush, squirreltail, desert needlegrass, Thurber needlegrass, and Indian ricegrass are important associated plants. Green ephedra, Sandberg bluegrass, Anderson peachbrush, and several forb species also are common. Juniper-pinyon woodland is typical on mountain slopes. Jeffrey pine, lodgepole pine, white fir, and manzanita grow on the highest mountain slopes. Shadscale is the typical plant in the drier parts of the area. Sedges, rushes, and moisture-loving grasses grow on the wettest parts of the wet flood plains and terraces. Basin wildrye, alkali sacaton, saltgrass, buffaloberry, black greasewood, and rubber rabbitbrush grow on the drier sites that have a high concentration of salts.
Some of the major wildlife species in this area are mule deer, coyote, beaver, muskrat, jackrabbit, cottontail, raptors, pheasant, chukar, blue grouse, mountain quail, and mourning dove. The species of fish in the area include trout and catfish. The Lahontan cutthroat trout in the Truckee River is a threatened and endangered species.
LRU notes
The Sierra Influenced Ranges LRU is characterized by wooded great basin mountains with climatic and biotic affinities to the Sierra Nevada mountain range. The Sierra Influences Ranges LRU receives greater precipitation that the mountain ranges of central NV. Amount of precipitation varies in relation to the local strength of the Sierra NV rain shadow, characterized by pinyon and juniper trees. The White, Sweetwater, Pine Nut, Wassuk, and Virginia ranges of Nevada support varying amounts of Sierra Nevada flora, such as ponderosa pine. Elevations range from 1610 to 2420 meters and slopes range from 5 to 49 percent, with a median value of 22 percent. Frost free days (FFD) ranges from 92 to 163.
Ecological site concept
This site occurs on summits and sideslopes of fan remnants and hills. Slopes range from 2 to 75 percent. Slopes occur most typically between 15 and 30 percent. Elevations are 4300 to 6500 feet. The soils are typically shallow and formed in residuum and colluvium from extrusive igneous rocks. The soil surface is medium in texture over fine-textured subsoil. The dominant plants are little sagebrush (Artemisia arbuscula ssp. longicaulis) and desert needlegrass (Achnatherum speciosum).
This site occurs on summits and sideslopes of fan remnants and hills. Slopes range from 2 to 75 percent. Slopes occur most typically between 15 and 30 percent. Elevations are 4300 to 6500 feet.
Table 2. Representative physiographic features
Landforms
(1) Hill (2) Fan remnant
Elevation
1,311–1,981 m
Slope
15–30%
Aspect
Aspect is not a significant factor
Climatic features
The climate associated with this site is semiarid, characterized by cool, moist winters and warm, dry summers. Average annual precipitation is 8 to about 10 inches. Mean annual air temperature is 45 to 51 degrees F. The average growing season is about 90 to 130 days.
Nevada’s climate is predominantly arid, with large daily ranges of temperature, infrequent severe storms, heavy snowfall in the higher mountains, and great location variations with elevation. Three basic geographical factors largely influence Nevada’s climate: continentality, latitude, and elevation. Continentality is the most important factor. The strong continental effect is expressed in the form of both dryness and large temperature variations. Nevada lies on the eastern, lee side of the Sierra Nevada Range, a massive mountain barrier that markedly influences the climate of the State. The prevailing winds are from the west, and as the warm moist air from the Pacific Ocean ascend the western slopes of the Sierra Range, the air cools, condensation occurs and most of the moisture falls as precipitation. As the air descends the eastern slope, it is warmed by compression, and very little precipitation occurs. The effects of this mountain barrier are felt not only in the West but throughout the state, with the result that the lowlands of Nevada are largely desert or steppes. The temperature regime is also affected by the blocking of the inland-moving maritime air. Nevada sheltered from maritime winds, has a continental climate with well-developed seasons and the terrain responds quickly to changes in solar heating.
Nevada lies within the mid-latitude belt of prevailing westerly winds which occur most of the year. These winds bring frequent changes in weather during the late fall, winter and spring months, when most of the precipitation occurs. To the south of the mid-latitude westerlies, lies a zone of high pressure in subtropical latitudes, with a center over the Pacific Ocean. In the summer, this high-pressure belt shifts northward over the latitudes of Nevada, blocking storms from the ocean. The resulting weather is mostly clear and dry during the summer and early fall, with scattered thundershowers. The eastern portion of the state receives significant summer thunderstorms generated from monsoonal moisture pushed up from the Gulf of California, known as the North American monsoon. The monsoon system peaks in August and by October the monsoon high over the Western U.S. begins to weaken and the precipitation retreats southward towards the tropics (NOAA 2004).
Table 3. Representative climatic features
Frost-free period (characteristic range)
Freeze-free period (characteristic range)
Precipitation total (characteristic range)
203-254 mm
Frost-free period (average)
110 days
Freeze-free period (average)
Precipitation total (average)
229 mm
Bar
Line
Figure 1. Monthly precipitation range
Bar
Line
Figure 2. Monthly average minimum and maximum temperature
Figure 3. Annual precipitation pattern
Figure 4. Annual average temperature pattern
Influencing water features
There are no influencing water features associated with this site.
Soil features
The soils associated with this site are typically shallow and formed in residuum and colluvium from extrusive igneous rocks. The soil surface is medium in texture over fine-textured subsoil. Permeability is slow and the soils are well drained. Available water capacity is low. Infiltration is restricted as once these soils are wetted they are subject to water loss by runoff. The soils commonly have over 60 percent gravels, cobbles and stones on the surface which provide a stabilizing affect on surface erosion conditions. Soil series associated with this site include Fulstone, Jaybee, Ceejay, Doorkiss, Loomer, and Soar.
Table 4. Representative soil features
Parent material
(1) Alluvium–igneous rock
Surface texture
(1) Cobbly loam
(2) Extremely cobbly loam
Family particle size
(1) Clayey
Drainage class
Well drained
Permeability class
Slow to moderately slow
Soil depth
36–51 cm
Surface fragment cover <=3"
10–30%
Surface fragment cover >3"
10–33%
Available water capacity (0-101.6cm)
4.06–6.86 cm
Calcium carbonate equivalent (0-101.6cm)
0–1%
Electrical conductivity (0-101.6cm)
0 mmhos/cm
Sodium adsorption ratio (0-101.6cm)
0
Soil reaction (1:1 water) (0-101.6cm)
6.1–7.8
Subsurface fragment volume <=3" (Depth not specified)
2–42%
Subsurface fragment volume >3" (Depth not specified)
10–28%
Ecological dynamics
As ecological condition declines, Lahonton sagebrush, rabbitbrush, bottlebrush squirreltail, and Sandberg's bluegrass increase as desert needlegrass decreases. Shadscale occurs only at the lower elevations within the range of this site. Cheatgrass is the species most likely to invade this site. Juniper will increase on this site.
Fire Ecology:
The mean fire return intervals for lahontan sagebrush communities have been estimated to be from 35 to over 100 years. Fire most often occurs during wet years with high forage production. Lahontan sagebrush is very susceptible to fire damage. Lahontan sagebrush is usually killed by fire and does not re-sprout. The recovery in burned areas is usually via small, light, wind-dispersed seed for all low sagebrush subspecies. Partially injured lahontan sagebrush may re-grow from living branches, but sprouting does not occur.
Desert needlegrass has persistent dead leaf bases, which make it susceptible to burning. Fire removes the accumulation; a rapid, cool fire will not burn deep into the root crown.
Disturbance Response Group (DRG) 1 consists of eight ecological sites, R026XY050NV, R026XY025NV, R026XY041NV, R026XY047NV, R026XY088NV, R026XY090NV, R026XY033NV, and R026XF066CA.
State and Transition Model Narrative for Group 1
This is a text description of the states, phases, transitions, and community pathways possible in the State and Transition model for the MLRA 26 Disturbance Response Group 1.
Reference State 1.0: The Reference State 1.0 is a representative of the natural range of variability under pristine conditions. The reference state has three general community phases: a shrub-grass dominant phase, a perennial grass dominant phase and a shrub dominant phase. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.
Community Phase 1.1: This community is dominated by Lahontan sagebrush, Thurber’s needlegrass and Sandberg bluegrass. Forbs and other grasses make up smaller components. Pinyon and/or juniper may be present.
Community Phase Pathway 1.1a, from Phase 1.1 to 1.2: Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires will typically be low severity resulting in a mosaic pattern due to low fuel loads. A fire following an unusually wet spring may be more severe and reduce sagebrush cover to trace amounts.
Community Phase Pathway 1.1b, from Phase 1.1 to 1.3: Time and lack of disturbance such as fire allows for sagebrush to increase and become decadent. Long-term drought, herbivory, or combinations of these will cause a decline in perennial bunchgrasses and fine fuels leading to a reduced fire frequency and allowing sagebrush to dominate the site.
Community Phase 1.2: This community phase is characteristic of a post-disturbance, early/mid-seral community. Thurber’s needlegrass, squirreltail, and other perennial bunchgrasses dominate. Depending on fire severity patches of intact sagebrush may remain. Rabbitbrush and other sprouting shrubs may be sprouting. Perennial forbs may be a significant component for a number of years following fire.
Community Phase Pathway 1.2a, from Phase 1.2 to 1.1: Time and lack of disturbance will allow sagebrush to increase.
Community Phase 1.3: Sagebrush increases in the absence of disturbance. Decadent sagebrush dominates the overstory and the deep-rooted perennial bunchgrasses in the understory are reduced either from competition with shrubs and/or from herbivory.
Community Phase Pathway 1.3a, from Phase 1.3 to 1.1: A low severity fire, herbivory or combinations will reduce the sagebrush overstory and create a sagebrush/grass mosaic.
Community Phase Pathway 1.3b, from Phase 1.3 to 1.2: Fire will decrease or eliminate the overstory of sagebrush and allow for the perennial bunchgrasses to dominate the site. Fires may be high severity in this community phase due to the dominance of sagebrush resulting in removal of overstory shrub community.
T1A: Transition from the Reference State 1.0 to Current Potential State 2.0
Trigger: This transition is caused by the introduction of non-native annual plants, such as cheatgrass, mustards, redstem stork’s bill (Erodium cicutarium), or bur buttercup (Ceratocephala testiculata).
Slow variables: Over time the annual non-native species will increase within the community.
Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Annual non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.
Current Potential State 2.0: This state is similar to the Reference State 1.0. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. This state has four general community phases. These non-native species can be highly flammable, and promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal.
Community Phase 2.1:This community phase is similar to the Reference State Community Phase 1.1, with the presence of non-native species in trace amounts. Sagebrush, Thurber’s needlegrass and Sandberg bluegrass dominate the site. Forbs and other shrubs and grasses make up smaller components of this site.
Community Phase Pathway 2.1a, from Phase 2.1 to 2.2: Fire reduces the shrub overstory and allows for perennial bunchgrasses to dominate the site. Fires are typically low severity resulting in a mosaic pattern due to low fuel loads. A fire following an unusually wet spring or a change in management favoring an increase in fine fuels may be more severe and reduce sagebrush cover to trace amounts. Annual non-native species are likely to increase after fire.
Community Phase Pathway 2.1b, from Phase 2.1 to 2.3: Time and lack of disturbance allows for sagebrush to increase and become decadent. Long-term drought reduces fine fuels and leads to a reduced fire frequency, allowing sagebrush to dominate the site. Inappropriate grazing management reduces the perennial bunchgrass understory; conversely Sandberg bluegrass may increase in the understory depending on grazing management.
Community Phase 2.2:This community phase is characteristic of a post-disturbance, early to mid-seral community where annual non-native species are present. Sagebrush is present in trace amounts; perennial bunchgrasses dominate the site. Depending on fire severity patches of intact sagebrush may remain. Rabbitbrush maybe sprouting or dominant in the community. Perennial forbs may be a significant component for a number of years following fire. Annual non-native species are stable or increasing within the community.
Community Phase Pathway 2.2a, from Phase 2.2 to 2.1: Time and lack of disturbance and/or grazing management that favors the establishment and growth of sagebrush allows the shrub component to recover. The establishment of low sagebrush can take many years.
Community Phase Pathway 2.2b, from Phase 2.2 to 2.4: Higher than normal spring precipitation favors annual non-native species such as cheatgrass. Non-native annual species will increase in production and density throughout the site. Perennial bunchgrasses may also increase in production.
Community Phase 2.3 (At Risk):This community is at risk of crossing a threshold to another state. Sagebrush dominates the overstory and perennial bunchgrasses in the understory are reduced, either from competition with shrubs or from inappropriate grazing, or from both. Rabbitbrush may be a significant component. Squirreltail or Sandberg bluegrass may increase and become dominant. Annual non-native species may be stable or increasing due to lack of competition with perennial bunchgrasses. This site is susceptible to further degradation from grazing, drought, and fire.
Community Phase Pathway 2.3a, from Phase 2.3 to 2.1: A change in grazing management that reduces shrubs will allow for the perennial bunchgrasses in the understory to increase. Heavy late-fall or winter grazing may cause mechanical damage and subsequent death to sagebrush, facilitating an increase in the herbaceous understory. Low and Lahontan sagebrush are palatable shrub species and can decrease with increased grazing pressure. Brush treatments with minimal soil disturbance will also decrease sagebrush and release the perennial understory. A low severity fire would decrease the overstory of sagebrush and allow for the understory perennial grasses to increase. Due to low fuel loads in this state, fires will likely be small creating a mosaic pattern. Annual non-native species are present and may increase in the community.
Community Phase Pathway 2.3b, from Phase 2.3 to 2.2:Fire eliminates/reduces the overstory of sagebrush and allows for the understory perennial grasses to increase. Fires may be high severity in this community phase due to the dominance of sagebrush resulting in removal of overstory shrub community. Annual non-native species respond well to fire and may increase post burn.
Community Phase Pathway 2.3c, from Phase 2.3 to 2.4:Fall, winter, and spring precipitation and temperatures mediate the ability for annual grasses and perennial grasses to germinate and/or survive. Higher than normal spring precipitation creates high annual production of annual grasses (Bradley et al. 2016). Higher than normal spring precipitation favors annual non-native species such as cheatgrass. Non-native annual species increase in production and density throughout the site. Perennial bunchgrasses may also increase in production.
Community Phase 2.4 (At Risk): This community is at risk of crossing into an annual state. Native bunchgrasses dominate; however, annual non-native species such as cheatgrass may be sub or co-dominant in the understory. Annual production and abundance of these annuals may increase drastically in years with heavy spring precipitation. Seeded species may be present. Sagebrush is a minor component. This site is susceptible to further degradation from grazing, drought, and fire.
Community Phase Pathway 2.4a, from Phase 2.4 to 2.2: Fall, winter, and spring precipitation and temperatures mediate the ability for annual grasses and perennial grasses to germinate and/or survive. Depending on temperatures and precipitation in winter and spring, annual grass production may be reduced in favor of perennial bunchgrasses.
Community Phase Pathway 2.4b, from Phase 2.4 to 2.3: Rainfall patterns favoring perennial bunchgrasses. Less than normal spring precipitation followed by higher than normal summer precipitation will increase perennial bunchgrass production.
T2A: Transition from Current Potential State 2.0 to Shrub State 3.0:
Trigger: To Community Phase 3.1: Inappropriate grazing will decrease or eliminate deep rooted perennial bunchgrasses and increase bare ground and shallow-rooted grazing-tolerant grasses. Shrub growth and establishment is favored under these conditions. To Community Phase 3.2: Severe fire in Community Phase 2.3 will remove sagebrush overstory, decrease perennial bunchgrasses and enhance annual and perennial forb growth. Squirreltail and/or Sandberg bluegrass may increase. Annual non-native species are present.
Slow variables: Long term decrease in deep-rooted perennial grass density.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
T2B: Transition from Current Potential State 2.0 to Annual State 4.0:
Trigger: Fire or soil disturbing treatment would transition to Community Phase 4.1.
Slow variables: Increased production and cover of non-native annual species.
Threshold: Loss of deep-rooted perennial bunchgrasses and shrubs changes temporal and spatial nutrient capture and cycling within the community. Increased, continuous fine fuels modify the fire regime by increasing frequency, size and spatial variability of fires.
Shrub State 3.0: This state is a product of many years of heavy grazing during time periods harmful to perennial bunchgrasses. Squirreltail and/or Sandberg bluegrass increase with a reduction in deep rooted perennial bunchgrass competition and become the dominant grasses. Bare ground increases significantly. Annual forbs may be a significant or dominant component of the understory, resulting in bare ground after they senesce in the summer. Sagebrush dominates the overstory and rabbitbrush may be a significant component. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. The shrub overstory and bluegrass understory dominate site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed.
Community Phase 3.1 (At Risk): Decadent sagebrush dominates the overstory. Rabbitbrush may be a significant component. Deep-rooted perennial bunchgrasses are present in trace amounts and may be absent from the community. Squirreltail, bluegrass species, and/or annual forbs dominate the understory. Bare ground may be significant. Pinyon and/or juniper may be encroaching but are not yet affecting understory vegetation.
Community Phase Pathway 3.1a, from Phase 3.1 to 3.2: Fire, heavy fall grazing causing mechanical damage to shrubs, and/or brush treatments with minimal soil disturbance, will greatly reduce the overstory shrubs to trace amounts and allow for Sandberg bluegrass to dominate the site.
Community Phase 3.2: Annual and perennial forbs dominate the site (i.e. redstem stork’s bill (Erodium cicutarium), Hooker’s balsamroot (Balsamorhiza hookeri) and tapertip hawksbeard (Crepis acuminata)). Squirreltail and/or Sandberg bluegrass may increase and be co-dominant with forbs. Deep-rooted perennial bunchgrasses are a minor component or missing. Annual non-native species may be present but are not dominant. Trace amounts of sagebrush or rabbitbrush may be present.
Community Phase Pathway 3.2a, from Phase 3.2 to 3.1: Time and lack of disturbance and/or grazing management that favors the establishment and growth of sagebrush allows the shrub component to recover. The establishment of low and/or Lahontan sagebrush can take many years.
T3A: Transition from Shrub State 3.0 to Annual State 4.0:Trigger: Fire and/or treatments that disturb the soil and existing plant community.
Slow variables: Increased seed production (following a wet spring) and cover of annual non-native species.
Threshold: Increased, continuous fine fuels modify the fire regime by changing frequency, intensity, size and spatial variability of fires. Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture and impact the temporal and spatial aspects of nutrient cycling and distribution.
T3B: Transition from Shrub State 3.0 to Tree State 5.0:Trigger: Absence of disturbance over time allows Utah juniper and/or singleleaf pinyon dominance. Feedbacks and ecological processes: Trees increasingly dominate use of soil water, contributing to reductions in soil water availability to grasses and shrubs. Overtime, grasses and shrubs are outcompeted. Reduced herbaceous and shrub production slows soil organic matter inputs and increases soil erodibility through loss of cover and root structure.
Slow variables: Long-term increase in pinyon pine and/or Utah juniper density.
Threshold: Trees overtop sagebrush and out-compete shrubs for water and sunlight. Shrub skeletons exceed live shrubs in number. There is minimal recruitment of new shrub cohorts.
Annual State 4.0: An abiotic threshold has been crossed and state dynamics are driven by fire and time. The herbaceous understory is dominated by annual non-native species such as cheatgrass and mustards. Resiliency has declined and further degradation from fire facilitates a cheatgrass and sprouting shrub plant community. Fire return interval has shortened due to the dominance of cheatgrass in the understory and is a driver in site dynamics.
Community Phase 4.1: Annuals nonnative species dominate. Sagebrush and perennial bunchgrasses may still be present in trace amounts. Surface erosion may increase with summer convection storms and would be verified through increased pedestalling of plants, rill formation or extensive water flow paths.
Community Phase Pathway 4.1a, from Phase 4.1 to 4.2: Time and lack of disturbance allows rabbitbrush and/or other sprouting shrubs to recover after fire. Probability of sagebrush establishment is extremely low.
Community Phase 4.2: Rabbitbrush is typically the dominant overstory shrub. Sagebrush is a minor component or missing. Annual non-native species dominate the understory.
Community Phase Pathway 4.2a, from Phase 4.2 to 4.1: Fire reduces/eliminates overstory brush component and allows for annual non-native species to dominate the site.
Tree State 5.0: This state is characterized by a dominance of Utah juniper and/or singleleaf pinyon in the overstory. Big sagebrush and perennial bunchgrasses may still be present, but they are no longer controlling site resources. Soil moisture, soil nutrients and soil organic matter distribution and cycling have been spatially and temporally altered.
Community Phase 5.1: Utah juniper and/or singleleaf pinyon dominates the overstory and site resources. Trees are actively growing with noticeable leader growth. Trace amounts of bunchgrasses may be found under tree canopies with trace amounts of Sandberg bluegrass and forbs in the interspaces. Sagebrush is stressed and dying. Annual non-native species are present under tree canopies. Bare ground interspaces are large and connected.
Community Phase Pathway 5.1a, from Phase 5.1 to 5.2: Time and lack of disturbance or management action allows Utah juniper and/or singleleaf pinyon to further mature and dominate site resources.
Community Phase 5.2: Utah juniper and/or singleleaf pinyon dominates the site and tree leader growth is minimal; annual non-native species may be the dominant understory species and will typically be found under the tree canopies. Trace amounts of sagebrush may be present, however, dead skeletons will be more numerous than living sagebrush. Bunchgrass may or may not be present. Sandberg bluegrass or mat forming forbs may be present in trace amounts. Bare ground interspaces are large and connected. Soil redistribution is evident.
T5A: Transition from Tree State 5.0 to Annual State 4.0: Trigger: Catastrophic fire causing a stand replacement event will transition Annual State 4.0. Inappropriate tree removal practices with soil disturbance will cause a transition to the Annual State 4.
Slow variables: Increased production and cover of non-native annual species under tree canopies.
Threshold: Closed tree canopy with non-native annual species dominant in the understory changes the intensity, size and spatial variability of fires. Changes in plant community composition and spatial variability of vegetation due to the loss of perennial bunchgrasses and sagebrush truncate energy capture and impact nutrient cycling and distribution.
The reference plant community is dominated by Lahontan sagebrush and desert needlegrass. Spiny hopsage and fourwing saltbush are other important species associated with this site.
Potential vegetative composition is about 40% grasses, 5% forbs and 55% shrubs and trees.
Figure 5. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type
Low (kg/hectare)
Representative value (kg/hectare)
High (kg/hectare)
Shrub/Vine
119
208
297
Grass/Grasslike
90
157
224
Forb
11
20
28
Tree
4
7
11
Total
224
392
560
Additional community tables
Table 6. Community 1.1 plant community composition
Livestock Interpretations:
This site has limited use for livestock grazing due to steep slopes low forage production. Grazing management should be keyed to desert needlegrass. Desert needlegrass produces considerable basal foliage and is good forage while young. Young desert needlegrass is palatable to all classes of livestock. Mature herbage is moderately grazed by horses and cattle but rarely grazed by sheep. Domestic sheep and to a much lesser degree cattle consume Lahontan sagebrush, particularly during the spring, fall and winter.
Stocking rates vary over time depending upon season of use, climate variations, site, and previous and current management goals. A safe starting stocking rate is an estimated stocking rate that is fine tuned by the client by adaptive management through the year and from year to year.
Wildlife Interpretations:
Lahontan sagebrush is considered a valuable browse plant for wild ungulates during the spring, fall and winter months. In some areas it is of little value in winter due to heavy snow. Lahontan sagebrush is an important food source for sage grouse throughout the year, especially between October and April. Mule deer utilize and sometimes prefer low sagebrush, particularly in winter and early spring. Sagebrush-grassland communities provide critical sage-grouse breeding and nesting habitats. Open Wyoming sagebrush communities are preferred nesting habitat. Meadows surrounded by sagebrush may be used as feeding and strutting grounds. Sagebrush is a crucial component of their diet year-round, and sage-grouse select sagebrush almost exclusively for cover. Leks are often located on sagebrush sites, grassy openings, dry meadows, ridgetops, and disturbed sites. Desert needlegrass is also an important forage species for several wildlife species.
Hydrological functions
Runoff is very high. Permeability is slow. Rills and water flow patterns are rare. A few can be expected on steeper slopes in areas subjected to summer convection storms or rapid spring snowmelt. Pedestals are rare with occurrence typically limited to area within water flow patterns. Frost heaving of shallow rooted plants should not be considered as normal condition. Gullies are rare in areas of this site that occur on stable landforms. Where this site occurs on inset fans gullies and head cuts associated with ephemeral channel entrenchment are common. Gullies and head cuts should be healing or stable. Perennial herbaceous plants (especially deep-rooted bunchgrasses [i.e., desert needlegrass] slow runoff and increase infiltration. Shrub canopy and associated litter break raindrop impact and provide opportunity for snow catch and accumulation on site. Coarse textured surface soils allow medium to rapid infiltration.
Recreational uses
Aesthetic value is derived from the diverse floral and faunal composition and the colorful flowering of wild flowers and shrubs during the spring and early summer. This site is used for camping and hiking and has potential for upland and big game hunting.
Other information
Desert needlegrass seeds are easily germinated and have potential for commercial use. Desert needlegrass may be used for groundcover in areas of light disturbance, but it is susceptible to excessive trampling.
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)
GK BRACKLEY
Contact for lead author
State Rangeland management Specialist
Date
02/21/2007
Approved by
Kendra Moseley
Approval date
Composition (Indicators 10 and 12) based on
Annual Production
Indicators
Number and extent of rills:
Rills are rare. A few can be expected on steeper slopes in areas subjected to summer convection storms or rapid spring snowmelt.
Presence of water flow patterns:
Water flow patterns are rare but can be expected in areas subjected to summer convection storms or rapid snowmelt.
Number and height of erosional pedestals or terracettes:
Pedestals are rare with occurrence typically limited to area within water flow patterns. Frost heaving of shallow rooted plants should not be considered as normal condition.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are
not bare ground):
Bare Ground ±20%; surface rock fragments to 60%; shrub canopy to >20%; basal area for perennial herbaceous plants ±5%.
Number of gullies and erosion associated with gullies:
Gullies are rare in areas of this site that occur on stable landforms. Where this site occurs on inset fans gullies and head cuts associated with ephemeral channel entrenchment are common. Gullies and head cuts should be healing or stable.
Extent of wind scoured, blowouts and/or depositional areas:
None to slight
Amount of litter movement (describe size and distance expected to travel):
Fine litter (foliage from grasses and annual & perennial forbs) is expected to move the distance of slope length during intense summer convection storms or rapid snowmelt events. Persistent litter (large woody material) will remain in place except during catastrophic events.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range
of values):
Soil stability values should be 3 to 6 on most soil textures found on this site. Areas of this site occurring on soils that have a physical crust will probably have stability values less than 3. (To be field tested.)
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Surface structure is typically thin to thick platy, subangular blocky, or massive. Soil surface colors are light. Organic carbon of the surface 2 to 3 inches is typically 1 to 1.5 percent dropping off quickly below. Organic matter content can be more or less depending on micro-topography.
Effect of community phase composition (relative proportion of different functional groups) and spatial
distribution on infiltration and runoff:
Perennial herbaceous plants (especially deep-rooted bunchgrasses [i.e., desert needlegrass] slow runoff and increase infiltration. Shrub canopy and associated litter break raindrop impact and provide opportunity for snow catch and accumulation on site. Coarse textured surface soils allow medium to rapid infiltration.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be
mistaken for compaction on this site):
Compacted layers are not typical. Platy or massive sub-surface horizons, subsoil argillic horizons or hardpans shallow to the surface are not to be interpreted as compacted.
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):
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or
decadence):
Dead branches within individual are shrubs common and standing dead shrub canopy material may be as much as 25% of total woody canopy; some of the mature bunchgrasses (<20%) have dead centers.
Average percent litter cover (%) and depth ( in):
Between plant interspaces (± 10%) and depth (± ¼-in.)
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
For normal or average growing season, ± 350 lbs/ac; Spring moisture significantly affects total production.
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:
Douglas'' rabbitbrush increases on this site. Cheatgrass; filaree, snakeweed, horsebrush, Russian thistle, and annual mustards are invaders on this site.
Perennial plant reproductive capability:
All functional groups should reproduce in average (or normal) and above average growing season years.
The 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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