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.
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 010X–Central Rocky and Blue Mountain Foothills
This MLRA is characterized by gently rolling to steep hills, plateaus, and low mountains at the foothills of the Blue Mountains in Oregon and the Central Rocky Mountains in Idaho. The geology of this area is highly varied and ranges from Holocene volcanics to Cretaceous sedimentary rocks. Mollisols are the dominant soil order and the soil climate is typified by mesic or frigid soil temperature regimes, and xeric or aridic soil moisture regimes. Elevation ranges from 1,300 to 6,600 feet (395 to 2,010 meters), increasing from west to east. The climate is characterized by dry summers and snow dominated winters with precipitation averaging 8 to 16 inches (205 to 405 millimeters) and increasing from west to east. These factors support plant communities with shrub-grass associations with considerable acreage of sagebrush grassland. Big sagebrush, bluebunch wheatgrass, and Idaho fescue are the dominant species. Stiff sagebrush, low sagebrush, and Sandberg bluegrass are often dominant on sites with shallow restrictive layers. Western juniper is one of the few common tree species and since European settlement has greatly expanded its extent in Oregon. Nearly half of the MLRA is federally owned and managed by the Bureau of Land Management. Most of the area is used for livestock grazing with areas accessible by irrigation often used for irrigated agriculture.
Ecological site concept
This ecological site occurs on exposed lava flows and lava blisters or small knolls dispersed across nearly level basalt lava plains, overlain by eolian pumice sands. Elevations range from 2,500 to 4,000 feet (750 to 1,200 meters) and slopes range from 0 to 10 percent but is typically less 3 percent. The soils associated with this site are shallow to very shallow to bedrock, and commonly interspersed with rock outcrop. The soil climate is mesic (soil temperature regime) and aridic (soil moisture regime). The reference plant community is characterized by an overstory of old growth western juniper, which are over 150 years old and express old growth morphological and structural characteristics. Spacing of trees is variable based on the amount of soil and rock. The understory is sparse. It is dominated by mountain big sagebrush, antelope bitterbrush, and bluebunch wheatgrass, with widely varying amounts of other grasses such as Sandberg bluegrass, Thurber’s needlegrass and Idaho fescue. Idaho fescue commonly dominates under the trees and within influence of the tree crowns. Pockets of deeper soils with coarser surface textures also provide a niche for needlegrasses and Indian ricegrass.
This site occurs on exposed lava flows and lava blisters or small knolls dispersed across lava plains. Slopes range from 0 to 10 percent. Elevations range from 2,500 to 4,000 feet.
Table 2. Representative physiographic features
Landforms
(1) Lava plain > Lava plateau
Flooding frequency
None
Ponding frequency
None
Elevation
2,500–4,000 ft
Slope
10%
Aspect
Aspect is not a significant factor
Climatic features
The annual precipitation ranges from 10 to 12 inches which occurs mainly between the months of October and June, mostly in the form of rain and snow. The average annual air temperature is 48 degrees F. with extreme temperatures ranging from -27 to 105 degrees F. The frost free period is 40 to 90 days. The optimum period for plant growth is from late March through June.
Table 3. Representative climatic features
Frost-free period (characteristic range)
52 days
Freeze-free period (characteristic range)
102 days
Precipitation total (characteristic range)
10-12 in
Frost-free period (actual range)
52 days
Freeze-free period (actual range)
102 days
Precipitation total (actual range)
10-12 in
Frost-free period (average)
52 days
Freeze-free period (average)
102 days
Precipitation total (average)
11 in
Characteristic range
Actual range
Bar
Line
Figure 2. Monthly precipitation range
Characteristic range
Actual range
Bar
Line
Figure 3. Monthly minimum temperature range
Characteristic range
Actual range
Bar
Line
Figure 4. Monthly maximum temperature range
Bar
Line
Figure 5. Monthly average minimum and maximum temperature
Figure 6. Annual precipitation pattern
Figure 7. Annual average temperature pattern
Climate stations used
(1) BEND 7 NE [USC00350699], Bend, OR
Influencing water features
This site is not associated with riparian or wetland features.
Soil features
The soils of this site are shallow or very shallow to basalt bedrock and are commonly associated with rock outcrops. They are formed from eolian deposited pumice ash, primarily derived from Mt. Mazama. They are typically well drained and have an ashy sandy loam texture throughout the profile. They are generally found on lava flows which have created a very uneven land surface. Volcanic ash soil fills rock fractures and pockets on the lava in which plants take root. Herbaceous vegetation primarily occupies the areas with soil. Juniper trees and some shrubs are able to penetrate cracks in the bedrock, allowing trees to also occupy the associated rock outcrops. Permeability is moderately rapid to rapid and the available water holding capacity is 1.5 to 3 inches for the profile. The potential for wind erosion is high. Soil temperature regime is mesic. Soil moisture regime is aridic.
Table 4. Representative soil features
Parent material
(1) Volcanic ash (2) Residuum–basalt
Surface texture
(1) Stony, ashy sandy loam
(2) Ashy sandy loam
(3) Cobbly, ashy loamy sand
Family particle size
(1) Loamy
(2) Ashy
Drainage class
Well drained to somewhat excessively drained
Permeability class
Moderately rapid to rapid
Soil depth
10–20 in
Surface fragment cover <=3"
15%
Surface fragment cover >3"
5–45%
Available water capacity (0-20in)
1.5–3 in
Calcium carbonate equivalent (Depth not specified)
Not specified
Electrical conductivity (0-20in)
2 mmhos/cm
Sodium adsorption ratio (0-20in)
Not specified
Soil reaction (1:1 water) (0-20in)
6.6–7.8
Subsurface fragment volume <=3" (0-20in)
10%
Subsurface fragment volume >3" (0-20in)
20%
Ecological dynamics
This site occurs on exposed lava flows and lava blisters or small knolls dispersed across nearly level basalt lava plains, overlain by eolian pumice sands and supports a juniper woodland plant community. These woodlands are characterized by old growth western juniper, which are over 150 years old and express old growth morphological and structural characteristics. The understory is sparse. It is dominated by mountain big sagebrush, antelope bitterbrush, and bluebunch wheatgrass, with widely varying amounts of other grasses such as Sandberg bluegrass, Thurber’s needlegrass and Idaho fescue. Idaho fescue commonly dominates under the trees and within influence of the tree crowns. Pockets of deeper soils with coarser surface textures also provide a niche for needlegrasses and Indian ricegrass.
Woodland ecological sites existing on these eolian-volcanic sands collectively represent the most extensive old growth western juniper woodlands within the range of the species (Waichler et al. 2001). Trees in this region have been aged at over 1,600 years old and standing snags have been dated back to 100 BC. When compared to younger trees, old growth trees have a more rounded canopy shape with limited leader growth, deep vertical furrows in their bark, rot pockets, cavities, abundant arboreal lichen cover, and changing branch structure, including large basal branches. These woodlands have evolved over centuries and are relatively stable, resulting in the accumulation of dead wood in the form of snags, dead branches in live trees, logs, and weathered stumps (RMRS-GTR-403, pg 57). It also predominately stays aloft throughout the decay process, deteriorating more through abiotic weathering than biotic decomposition; greatly limiting contributions to soil organic matter and nitrogen pools (Waichler et al. 2001).
Western juniper is highly susceptible to fire, so old growth juniper woodlands are often isolated in fire resistant locations such as “rock outcrops, knolls, ridges, and/or soils that are shallow, coarse, rocky, and often high in clay or sand” (RMRS-GTR-403, pg 57). This site occurs on pressure ridges of basalt lava flows overlain with shallow to very shallow pumice ash, primarily derived from Mt. Mazama. Soils on this site are commonly intermixed with rock outcrops. The juniper can penetrate the fractures in the lava bedrock allowing it to occupy both these shallow soils and the associated rock outcrops. The soils on this site are geologically young; less than 7,000 years old, and primarily course pumice sands with limited pedogenic development. The amount of rock exposure and low productivity in the understory makes this site very fire resistant, so any fire events are typically contained to one or several trees. Stand replacement fires and mixed-severity fires were historically rare (return intervals measured in centuries) (Tech Bulletin 152, 2005, pg 21 and RMRS-GTR-403, pg 112); meaning climatic conditions, such as severe drought, are the primary influence on tree mortality and establishment and understory dynamics.
While soils are shallow and soil textures are coarse, the soil particles themselves are porous and can hold water in addition to the capillary water of the profile. Some of this water is plant available, greatly increasing the available water capacity (AWC) of the soil compared to non-pumice soils with similar textures. (Ecological Provinces, SR 990, pg 89). These pumice soils also have high albedo. The light color on the surface absorbs less sunlight and thus keeps the soil cooler than soils with darker A horizons. The porous nature of these soils also makes them very insulating, moderating subsurface temperatures, and keeping them cooler longer into the growing season. These unique characteristics result in a diverse species composition in the understory community that is typically more common on cooler, wetter, higher production sites. Spatial distribution of these understory species is further influenced by the size of the pumice sands. Redistribution of the pumice ash by wind resulted in varying surface textures across the site. The courser sands favor the needlegrasses, while the finer sands favor other species like bluebunch wheatgrass and Idaho fescue.
Paleobotany and Climate:
Western juniper first arrived in its current geographical range in Central Oregon between 4,800 to 6,600 years ago, during the mid Holocene era. Cool and moist conditions 4,000 to 3,000 years ago favored tree growth, cone production and seedling establishment, resulting in rapid expansion; Western juniper reached its prehistoric maximum across most of its present-day range during this period. A subsequent warm period 2,500 to 3,000 years ago caused severe droughts, major fires, and regional declines in western juniper stands. With the onset of the Little Ice Age conditions again became cooler and wetter and pollen records indicate juniper again began to gradually increase to its current range. (RMRS-GTR-403, pg 102, 103). Under a natural disturbance regime, climate is the primary driver of juniper distribution and persistence, particularly in juniper woodlands. It directly influences seed production, seedling establishment, and plant mortality while also influencing other disturbances such as fire, competition, insects, and disease. (RMRS-GTR-403, pg 123)
Cool, moist conditions favor juniper expansion, while severe or extended drought and warmer conditions cause tree stress and mortality (RMRS-GTR-403, pg 102). Some mortality is the direct result of drought stress, while some trees succumb to secondary disturbances due to reduced vigor. Old trees are susceptible to heart-rots, which target the heartwood of the trunk and large limbs. Heart-rots rarely kill the tree but can structurally weaken them. Stressed trees are also more susceptible to mistletoe infestations and insects. In spite of vulnerabilities, western juniper is very resistant to many pressures. Overall, tree mortality in old growth juniper woodlands is typically low (RMRS-GTR-403, pg 42 to 48); estimated at less than one percent per century (RMRS-GTR-403, pg 111).
Western Juniper Woodland Infill:
While old growth juniper woodlands are relatively stable, they are not static. They have historically experienced cycles of infill and mortality in response to climatic conditions. With the end of the Little Ice Age in the 1850s, evidence suggests these woodlands were slowly expanding and infilling. Rate of infill throughout the Great Basin greatly accelerated in the late 1800s, peaking in the early 1900s. Infill rates slowed with the onset of widespread severe droughts starting in the 1920s. This acceleration coincides with a significant rise in settlement throughout the Intermountain West and is attributed to a combination of factors including climate, grazing, altered fire regimes, and increased CO2 levels (RMRS-GTR-403, pg 83, 104).
Woodland infill, precipitated by the end of the Little Ice Age, coincided with a time of rapid settlement and introduction of livestock grazing in the Great Basin, altering understory dynamics and fire behavior. Wetter periods, as were experienced during this timeframe, typically result in the accumulation of fine fuels (RMRS-GTR-403, pg 83). In addition to effects increased understory vegetation has on fire cycles, paleobotany literature suggests competition with herbaceous vegetation may limit tree seedling establishment and/or result in thinning. This indicates a robust understory can provide some competition to juniper establishment, limiting infill (RMRS-GTR-403, pg 112). Large numbers of domestic livestock grazing during this period prevented fine fuel accumulation and areas of heavy grazing would have resulted in understory plant stress. Without fire or competition, young juniper trees were able to rapidly establish.
Carbon dioxide (CO2) levels have also increased since the end of the Little Ice Age. Increased CO2 can increase water use efficiency in conifers relative to herbaceous species, resulting in faster tree growth and denser canopies (RMRS-GTR-403, pg 119). As climate conditions became warmer and drier in the early 1900s, expansion and infill slowed but still exceeded historic rates under similar conditions. This suggests CO2 concentrations and reduced competition from perennial grasses could be playing a significant role in current woodland expansion (RMRS-GTR-403, pg 121 and 123). These factors have resulted in altered stand structure in many persistent woodlands.
Infill trees compete with understory vegetation for water and other resources. Shrubs decline as trees increase in dominance, with sagebrush being highly sensitive to tree competition. Bitterbrush and Idaho fescue will persist longer as infill progresses, in part due to their superior shade tolerance relative to other species but will also eventually be removed from the site. (RMRS-GTR-403, pg 52; Miller et al., 2000). Herbaceous species are more resistant to tree competition, but also decline with increased tree dominance. Microclimate conditions under old growth trees shelter Idaho fescue, so interspace species are the first to decline. Understory decline is accelerated when plants are stressed by other disturbances such as drought, heavy grazing, or recreational use (RMRS-GTR-403, pg 48 to 55).
Rate of infill on this site is slower than adjacent sites with deeper soils due to limited site resources, and density of infill trees is highly variable based on resource availability associated with soil depth and number of rock outcrops. However, with time, trees have the potential to dominate site resources and deplete understory species.
Non-Native Species:
If the native plant understory experiences stress and mortality, there is greater opportunity for establishment of non-native species and native increasers. This site is susceptible to cheatgrass, an invasive annual grass, and introduced annual forbs like pale madwort (Alyssum alyssoides). Medusahead and Ventenata dubia are not a concern on this site, as they typically do not establish in these coarse textured pumaceous soils. With repeated disturbance, sprouting shrubs (e.g. rabbitbrush species) and forbs (e.g. granite prickly phlox, Linanthus pungens and tansymustard Descurainia sp.) also increase and fill open spaces in the understory.
Over time, this can create fuel continuity that is atypical of old growth woodlands, making this site more prone to fire. Fires become more frequent and widespread. Higher tree densities from juniper infill also creates ladder fuels, making old trees more susceptible to fire, leading to more stand-replacing fires. (RMRS-GTR-403, pg 115). Recurring fires favor re-establishment of annual and sprouting species over native perennial grasses and shrubs, thereby perpetuating the fire cycle.
Resilience Management:
Within the natural range of variability under a normal distribution regime this site is resistant to disturbance, but has low resilience when disturbance occurs. Physiographic characteristics including proximity to rock outcrops, shallow soils, and low fine fuel loads make this site very fire resistant. The site is also capable of withstanding extended drought with limited plant mortality. Disturbances outside of shifts in climate are not common, resulting in a very stable site.
When disturbance occurs outside the normal range of variability the plant community shifts quickly and is very susceptible to invasion by non-native annual species. This low resilience is a result of the site’s limited resources (arid soil moisture regime and sandy soils) and warmer climate (mesic soil temperature regime). Changes in disturbance regimes of surrounding sites also jeopardize this site. The adjacent sites are highly susceptible to infill and encroachment of juniper. Infill across sites creates fuel continuity at a landscape scale and increases the probability of large scale fires that carry through previously fire resistant sites.
The Reference state is representative of the natural range of variability under pristine conditions. No introduced species occur in this state and disturbance has not fundamentally altered soil quality or plant community composition. This state represents a persistent old growth juniper woodland and has two general plant communities; a grass – shrub dominant community and a grass – forb dominated community. Both support an open stand of old growth juniper.
Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups and low fine fuel loads. Plant community phase changes are primarily driven by climate. Warm, dry cycles resulting in severe drought stresses plants and increases susceptibility to insects and disease. Cooler, wetter cycles that are conducive to tree establishment may result in woodland infill, and fine fuel accumulations may result in single tree or small area fires. Fire return interval is centuries.
Characteristics and indicators. • Lack of introduced plant species
• Presence of all functional and structural groups
• High plant vigor and reproductive capacity in most years
Resilience management. Management should focus on preservation of old growth juniper and prevention of non-native species establishment. Removal of infill trees to maintain pre-European infill rates can prevent transition to State 2.
Community 1.1 Old Growth Juniper, Bitterbrush, Mountain Big Sagebrush, and Bluebunch Wheatgrass
This community is characterized by an open stand of old growth juniper. Spacing of trees is variable based on the amount of soil and rock. The understory is sparse. It is dominated by mountain big sagebrush, antelope bitterbrush, and bluebunch wheatgrass, with widely varying amounts of other grasses such as Sandberg bluegrass, Thurber’s needlegrass and Idaho fescue. Idaho fescue commonly dominates under the trees and within influence of the tree crowns. Pockets of deeper soils with coarser surface textures also provide a niche for needlegrasses and Indian ricegrass. This community is very stable and the most common community in this state.
Figure 9. 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
340
470
600
Shrub/Vine
80
115
150
Forb
45
65
80
Tree
35
50
70
Total
500
700
900
Figure 10. Plant community growth curve (percent production by month). OR4051, B10A Mesic, Mid Elev., N/A, Stony, Good Condition. HCPC Growth Curve B10A Mesic, Mid Elev., N/A, Stony, Good Condition - Cindery Hills & Lava Blisters.
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
5
30
55
10
0
0
0
0
0
0
Community 1.2 Old Growth Juniper, Perennial Grasses, and Forbs
Juniper overstory has experienced isolated mortality as the result of small, single tree or small area fire; or drought and disease. This community is limited to the extent of the disturbance (usually a small, isolated area). Site is still characterized by an open stand of old growth juniper. Young trees (<150 years old) and/or shrubs are reduced or removed from the site. Perennial forbs and grasses expand.
Insects (e.g. aroga moth), drought stress, and/or small isolated fire reduces sagebrush and young juniper trees. Disturbance from drought and disease may be more widespread than fire.
Pathway 1.2A Community 1.2 to 1.1
Time and favorable climatic conditions (cooler/wetter climatic cycles) facilitate increase in shrub overstory.
State 2 Current Potential
This state is similar to the reference state yet some amount of introduced species occur and/or infill rates are exceeding pre-European settlement rates. Ecological function is largely intact, however the resiliency of the state has been reduced. This state represents a persistent old growth juniper woodland and has two general plant communities; a grass – shrub dominant community and a grass – forb dominated community. Both support an open stand of old growth juniper. Non-natives may increase in abundance but will not become dominant within this State.
Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups and low fine fuel loads. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, residual dry matter accumulation, and adaptations for seed dispersal.
Plant community phase changes are primarily driven by climate. Warm, dry cycles resulting in severe drought stresses plants and increases susceptibility to insects and disease. Cooler, wetter cycles that are conducive to tree establishment may result in woodland infill, and fine fuel accumulations may result in single tree or small area fires. Fire return interval is centuries.
Characteristics and indicators. • Presence of all functional and structural groups
• High plant vigor and reproductive capacity in most years
Resilience management. Management should focus on preservation of old growth juniper and prevention of non-native species expansion. Removal of infill trees to maintain pre-European infill rates can prevent transition to State 3; or restore to Reference (State 1) if non-native species are not present.
Community 2.1 Old Growth Juniper, Bitterbrush, Mountain Big Sagebrush, and Bluebunch Wheatgrass
This community is characterized by an open stand of old growth juniper. Spacing of trees is variable based on the amount of soil and rock. The understory is sparse. It is dominated by mountain big sagebrush, antelope bitterbrush, and bluebunch wheatgrass, with widely varying amounts of other grasses such as Sandberg bluegrass, Thurber’s needlegrass and Idaho fescue. Idaho fescue commonly dominates under the trees and within influence of the tree crowns. Pockets of deeper soils with coarser surface textures also provide a niche for needlegrasses and Indian ricegrass. This community is very stable and the most common community in this state.
Community 2.2 Old Growth Juniper, Perennial Grasses, and Forbs
Juniper overstory has experienced isolated mortality as the result of small, single tree or small area fire; or drought and disease. This community is limited to the extent of the disturbance (usually a small, isolated area). Site is still characterized by an open stand of old growth juniper. Young trees (<150 years old) and/or shrubs are reduced or removed from the site. Perennial forbs and grasses expand. If annual non-native species are present, they may increase with disturbance but will not become dominant.
Insects (e.g. aroga moth), drought stress, and/or small isolated fire reduces sagebrush and bitterbrush. Disturbance from drought and disease may be more widespread than fire.
Pathway 2.2A Community 2.2 to 2.1
Time and favorable climatic conditions (cooler/wetter climatic cycles) facilitate increase in shrub overstory.
State 3 Western Juniper Infill
In this state western juniper dominates the overstory and site resources. Young juniper (<100 years old) is co-dominant with old growth juniper and increasing. Bitterbrush, mountain 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.
Increased pace of tree recruitment results in a multi-age class overstory. As tree density increases, shrub mortality increases, and deep-rooted perennial grasses are reduced. Bare ground interspaces are large and connected, allowing for establishment and expansion of cheatgrass, annual forbs, mustards, and granite prickly phlox.
Characteristics and indicators. • Western juniper infill trees are co-dominant with old growth trees or dominant in the overstory
• Presence of all functional and structural groups, though diversity may be reduced
• Bare ground patches are large and connected
Resilience management. Management should focus on preservation of old growth juniper and promoting native understory vigor and expansion. Removal of infill trees to release resources and reduce competition for native understory vegetation can help maintain State 3; or restore to Current Potential (State 2) if all functional groups and understory species are present.
Community 3.1 Western Juniper, Bitterbrush, Mountain Big Sagebrush, and Bluebunch Wheatgrass
Western juniper dominates the overstory and site resources. Young trees are actively growing with noticeable leader growth. Shrubs and bunchgrasses are still present in the understory, but production has been reduced. Shallow rooted perennial grasses increase while deep rooted decrease. Gaps between perennial plants have increased. Annual non-native species and perennial increasers are present, particularly in the interspaces.
Western juniper dominates the site. Trace amounts of bitterbrush and sagebrush may be present however dead skeletons will be more numerous than living brush. Deep-rooted bunchgrasses may or may not be present in the interspaces. Idaho fescue may still be present under the canopy of large trees. Bare ground interspaces are large and connected. Soil redistribution may be increasing, especially by wind . Annual non-native species and perennial increasers are present and increasing, particularly in the interspaces.
Time allows for maturation of the tree community. Additional disturbances such as recreational vehicle use, repeated heavy grazing, and pressure from the urban interface that stress understory species accelerate this pathway.
Pathway 3.2A Community 3.2 to 3.1
Removal of disturbances such as recreational vehicle use, repeated heavy grazing, and pressure from the urban interface may allow understory species to increase vigor and expand in the understory if infill trees are not utilizing all site resources. Mechanical treatment of infill trees (non-old growth juniper) can also facilitate this pathway.
State 4 Annual
In this state, perennial bunchgrasses and non-sprouting shrubs are greatly reduced or missing on the site. The understory has been replaced by non-native annual grasses and forbs, sprouting shrubs, and native increasers. Competition with the tree overstory and/or repeated disturbances such as fire, heavy grazing, and recreational use has allowed non-resprouting shrubs and perennial grasses to be replaced by cheatgrass, an invasive annual grass, and introduced annual forbs like pale madwort (Alyssum alyssoides). Forbs (e.g. granite prickly phlox , Linanthus pungens and tansymustard, Descurainia species) and sprouting shrubs (e.g. rabbitbrush species) also increase and fill open spaces in the understory.
This state may still support a western juniper overstory. If the site has not had a stand replacement fire, it will be a mix of old growth and young juniper. Following a stand replacement fire, the tree overstory will be temporarily lost. Time without disturbance will allow trees to reestablish. However, fuel continuity typical of annual dominated systems causes fires to become more frequent and widespread making replacement of old growth trees unlikely. Reestablishment of old growth trees would take centuries without disturbance (primarily fire), and feasibility of this pathway is currently unknown.
Characteristics and indicators. • Understory is dominated by cheatgrass and introduced annual forbs
• Perennial grasses are greatly reduced or missing
Annual non-native plants, native increaser forbs, and sprouting shrubs dominate this site. This community has a western juniper overstory that still supports old growth trees. Young trees (<100 years old) are co-dominant or dominant. Non-resprouting shrubs may be present in trace amounts.
This community occurs after stand replacement fire. Annual non-native plants, native increaser forbs, and sprouting shrubs dominate this site. Scattered juniper or patches of juniper may persist, but the western juniper overstory has been removed.
Annual non-native plants, native increaser forbs, and sprouting shrubs dominate this site. Western juniper has re-established in the overstory following a stand replacing fire.
Time and lack of fire allows for sprouting shrubs such as rabbitbrush to increase, and potentially bitterbrush and sagebrush to establish. The probability of bitterbrush/sagebrush establishment is extremely low. Young juniper reestablishes.
Pathway 4.3A Community 4.3 to 4.2
Fire.
Transition T1A State 1 to 2
Introduction of non-native species, altered fire regimes, repeated heavy grazing by domestic livestock, and/or increased CO2 levels.
Context dependence. The combination of multiple triggers increases likelihood of this transition.
Restoration pathway R2A State 2 to 1
Mechanical treatment of infill trees (non-old growth juniper); non-native species are not present.
Context dependence. Non-native species are not present.
Transition T2A State 2 to 3
Time and favorable conditions for tree expansion allow trees to become dominant.
Restoration pathway R3A State 3 to 2
Mechanical treatment of infill trees (non-old growth juniper).
Context dependence. Depleted understories may be slow to recover. Understory recovery may not be possible if anthropogenic disturbances are still stressing understory species. Restoration to State 2 is possible from Community 3.1 when all functional groups are still present, and site has maintained understory species diversity. Restoration from Community 3.2 is unlikely due to depleted understory.
Transition T3A State 3 to 4
Time allows for maturation of the tree community and loss of understory species; or stand replacement fire .
Context dependence. Additional disturbances such as recreational vehicle use, repeated heavy grazing, and pressure from the urban interface that stress understory species accelerate this transition.
Additional community tables
Table 6. Community 1.1 plant community composition
The unique morphological structure of old growth western juniper trees including hollows and cavities provide habitat for cavity nesting birds. A study in Central Oregon found cavity nesting birds were 2.7 times more abundant in old growth juniper woodlands than post settlement stands (Waichler et al. 2001).
Hydrological functions
The soils of this site have high infiltration rates and low runoff potential.
Supporting information
Inventory data references
Prineville District BLM Ecological Site Inventory
NASIS component and pedon data
Range Site Descriptions
Field knowledge of range-trained personnel
Other references
Anderson, E. J., M. M. Borman, and W. C. Krueger. 1998. The Ecological Provinces of Oregon: a Treatise on the Basic Ecological Geography of the State., Oregon Agricultural Experiment Station. Special Report 990. (Oregon State University: Corvallis.)
Miller, R.F.; Bates, J.D.; Svejcar, T.J.; [et al.] E. Eddleman. 2005. Biology, ecology, and management of western juniper (Juniperus occidentalis). Tech. Bul. 152. Corvallis, OR: Oregon State University Agricultural Experiment Station. 82 p.
Miller, Richard F.; Chambers, Jeanne C.; Evers, Louisa; Williams, C. Jason; Snyder, Keirith A.; Roundy, Bruce A.; Pierson, Fred B. 2019. The ecology, history, ecohydrology, and management of pinyon and juniper woodlands in the Great Basin and Northern Colorado Plateau of the western United States. Gen. Tech. Rep. RMRS-GTR-403. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 284 p.
Waichler, W.S.; Miller, R.F.; Doescher, P.S. 2001. Community characteristics of old-growth western juniper woodlands. Journal of Range Management. 54(5): 518-527.
Contributors
Bob Gillaspy Cici Brooks E Ersch K.Kennedy S.F. Greenfield Jennifer Moffitt - 2025 Ecological dynamics and STM updates
Approval
Kirt Walstad, 3/26/2025
Acknowledgments
Dr. Richard Miller, Professor Emeritus Oregon State University - Thank you for reviewing this ecological site, providing feedback, and sharing photos for use in this document.
Rangeland 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)
Jeff Repp and Bruce Franssen
Contact for lead author
State Rangeland Management Specialist for NRCS - Oregon
Date
04/24/2003
Approved by
Kirt Walstad
Approval date
Composition (Indicators 10 and 12) based on
Annual Production
Indicators
Number and extent of rills:
None to some.
Presence of water flow patterns:
None to some.
Number and height of erosional pedestals or terracettes:
None.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are
not bare ground):
10 - 20%
Number of gullies and erosion associated with gullies:
None.
Extent of wind scoured, blowouts and/or depositional areas:
None to some.
Amount of litter movement (describe size and distance expected to travel):
Fine - limited movement.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range
of values):
Moderately to slightly resistant to erosion: aggregate stability = 2-4.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Shallow and very shallow, well drained, sandy loams and stony loamy sands dominated by volcanic ash: Weak thin and medium platy to single grain structure, dry color value of 5, 3-4 inches thick; Low OM (1-2%).
Effect of community phase composition (relative proportion of different functional groups) and spatial
distribution on infiltration and runoff:
Moderate ground cover (40-50%) and slight to severe slopes (0-15% with some as high as 60% on sides of blisters) moderately limit rainfall impact and overland flow.
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:
Perennail, deep-rooted bunch-grasses
Sub-dominant:
Evergreen shrubs = deciduous shrubs
Other:
Evergreen trees = perennial forbs > other shrubs
Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or
decadence):
Normal decadence and mortality expected.
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-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:
Cheatgrass and Medusahead invade sites that have lost deep rooted perennial grass functional groups.
Perennial plant reproductive capability:
All species should be capable of reproducing annually.
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.
Click on box and path labels to scroll to the respective text.
