Natural Resources
Conservation Service
Ecological site F021XE230CA
Pinus ponderosa/Symphoricarpos rotundifolius/Achnatherum
Accessed: 08/25/2026
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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
Table 1. Dominant plant species
Tree (1) Pinus ponderosa
Shrub (1) Symphoricarpos rotundifolius
Herbaceous (1) Achnatherum
Physiographic features
This site occurs on all aspects of mountain sideslopes. Elevations range from 5300 to 7500 feet. Slopes range from 15 to 50 percent.
Table 2. Representative physiographic features
Landforms (1) Mountain slope
Elevation 5300 – 7500 ft Slope 15 – 50 % Aspect Aspect is not a significant factor Climatic features
The climate of this site is subhumid, characterized by warm, dry summers and cold, moist winters. The area's precipitation comes mostly from winter Pacific cyclonic storms, with a very slight summer monsoonal season that is erratic but can be locally significant. Average annual precipitation ranges from 20 to 30 inches with most occurring during the winter months. Approximately half the precipitation falls as snow; half as rain.
Table 3 Representative climatic features
Frost-free period (average) 80 days Freeze-free period (average) 0 days Precipitation total (average) 30 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
There are no influencing water features associated with this site.
Soil features
The soils associated with this site are moderately deep, well drained soils that formed in volcanic ash and colluvium over residuum derived from glassy tuff. These soils have high amounts of vitric volcanic ash and glass throughout the profile which enhances the waterholding capacity. The soil profile is modified with 35 to 70 rock fragments, mainly gravels and cobbles. These soils have a mollic epipedon to 18 inches and an argillic horizon from 13 to 31 inches. Soil series associated with this site include Lyonman.
Table 4. Representative soil features
Parent material (1) Colluvium – tuff
(2) Residuum – tuff
Surface texture (1) Ashy sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate Soil depth 22 – 40 in Surface fragment cover <=3" 15 – 20 % Surface fragment cover >3" Not specified Available water capacity
(0-40in)4 – 6 in Calcium carbonate equivalent
(0-40in)Not specified Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)5.6 – 7.3 Subsurface fragment volume <=3"
(Depth not specified)50 – 60 % Subsurface fragment volume >3"
(Depth not specified)3 – 6 % Ecological dynamics
Major Successional Stages of Forestland Development:
HERBACEOUS: Vegetation is dominated by grasses and forbs under full sunlight. This stage is experienced after a major disturbance such as crown fire. Skeleton forest (dead trees) remaining after fire or residual trees left following harvest have little or no affect on the composition and production of the herbaceous vegetation.
SHRUB-HERBACEOUS: Herbaceous vegetation and woody shrubs dominate the site. Various amounts of tree seedlings (less than 20 inches in height) may be present up to the point where they are obviously a major component of the vegetal structure.
SAPLING: In the absence of disturbance the tree seedlings develop into saplings (20 inches to 4.5 feet in height) with a range in canopy cover of about 5 to 10 percent. Vegetation consists of grasses, forbs and shrubs in association with tree saplings.
IMMATURE FORESTLAND: The visual aspect and vegetal structure are dominated by ponderosa pine greater than 4.5 feet in height. The young ponderosa pine are still very susceptible to fire at this stage. Seedlings and saplings of ponderosa pine are common in the understory. Dominants are the tallest trees on the site; co-dominants are 65 to 85 percent of the highest of dominant trees. Understory vegetation is moderately influenced by a tree overstory canopy of about 15 to 25 percent.
MATURE FORESTLAND: This stage is dominated by ponderosa pine that have reached or are near maximal heights for the site. Tree canopy cover ranges from 30 to 40 percent. Understory vegetation is strongly influenced by tree competition, overstory shading, duff accumulation, etc. Infrequent, yet periodic, wildfire is presumed to be a natural factor influencing the understory of mature ponderosa pine forests. Ponderosa pine trees, at this stage of growth, are relatively resistant to cool, slow burning, wildfires through the understory because of their thick, insulating bark. Ground fires affect understory vegetal structure and composition leaving an open grass-forb community with scattered mountain big sagebrush and associated mountain browse species. This stage of community development is assumed to be representative of this site in the pristine environment.
OVER-MATURE FORESTLAND: This stage is dominated by ponderosa pine that have reached maximal heights for the site. Understory vegetation is reduced due to tree competition, overstory shading, duff accumulation, etc. Few seedlings or saplings of ponderosa pine are found in the understory.
Wildfire is recognized as a natural disturbance that strongly influenced the structure and composition of the climax vegetation of this forest site. Studies have shown that prior to 1900, most Pacific ponderosa pine stands experienced low-severity surface fires at intervals ranging from 1 to 40+ years. Crown fires were rare in most stands. Fire also shaped the composition of Pacific ponderosa pine stands. In the late 1800's ponderosa pine stands exhibited open parklike appearances with well-stocked overstories and relatively few understory trees and shrubs. Frequent and mild surface fires created openings for pine seedling establishment, thus maintaining its persistence. These fires also thinned saplings and maintained the relatively open understories. Fire suppression, however, has allowed the unnatural buildup of forest fuels which has increased the occurrence of stand-replacing fires. Over the last 100 years of fire suppression, seral Pacific ponderosa pine stands have been replaced by shade-tolerant species such as white fir. White fir is very shade tolerant and will regenerate under shade as where ponderosa pine will not.
Pacific Ponderosa pine is fire-adapted in all stages of its life history and is especially well adapted to light, regular surface fires. This species has evolved with a thick bark and open crown structure that allows it to survive most fires. Mature trees will self-prune, leaving a smooth bole which reduces aerial fire spread. Other fire adaptations include deep roots, high foliar moisture content, insulated bud scales, and medium to light lichen growth. Seedlings prefer the mineral-soil seedbeds created by fire.
Pacific ponderosa pine's response to fire will vary according to fire severity, tree age, and season. High-severity fires that occur during periods of high stress will generally result in death. Low- to medium-severity fires will generally restrict the growth and regeneration of the tree, but recovery is usually evident the following year. Immediately following fire, Pacific ponderosa pine may experience a large needle drop as a reaction to hot convectional air movement through the canopy.
Pacific ponderosa pine is shade intolerant and grows most rapidly in near full sunlight. There is a strong tendancy for climax pine stands to be even-aged in small groups rather than being truly uneven-aged. Heavy grazing induces effects opposite those of fire. Removal of the grass cover by grazing tends to favor shrub communities.
Fire Ecology:
Creeping barberry is moderately tolerant of fire. It is a vigorous sprouter following fire and may be favored by intense fire. Little specific information is available on adaptations of Letterman's needlegrass to fire. It is morphologically similar to Columbia needlegrass, which is only slightly to moderately damaged by fire. Season of burn affects the plant's ability to survive a fire. Post-fire regeneration is through seeding and tillering. Western needlegrass is moderately damaged by fire. The recovery time is between 3 and 5 years. Ross’ sedge survives fire through buried seed with long-term viability. These seeds germinate after heat treatment. Ross’ sedge’s rhizomes survive low- to moderate-severity fires. Historically, surface fires were most common in Ponderosa pine stands, with occasional flare-ups occurring in brush patches. Crown fires were unlikely in most stands. Long, loosely packed pine needles and herbaceous species maintained frequent and mild surface burns. These fires created opening for pine seedling establishment, thus maintaining its persistence. These fires also thinned saplings and maintained the relatively open understories. The recent increase in understory density has been attributed to the current longer fire intervals.
Ponderosa pine is fire-adapted in all stages of its life history and is especially well adapted to light, regular surface fires. The seeds prefer openings with mineral soil usually prepared by fire for seedbed. For the seedlings and young trees, early development of insulative bark, shielded meristems, high moisture content in living needles, and rapid extension of taproots reduce their mortality from fire. For mature trees, thick bark, deep roots, and low- flammability crown structures help them survive most fires. Following a stand-replacement fire, the succesional sequence in these types’ proceeds from herbaceous species to shrub and hardwood, and finally ponderosa pine stages.
State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Reference StateCommunity 1.1
Reference Plant CommunityThe reference plant community is dominated by an open park-like appearance with an overstory of ponderosa pines and relatively few understory trees. White fir occurs infrequently in the overstory. The understory is dominated by perennial grasses and forbs with scattered shrubs, such as roundleaf snowberry, creeping barberry and needlegrasses. Other important species include Ross' sedge and Wheeler's bluegrass. An overstory canopy cover of 30 to 35 percent is assumed to be representative of tree dominance on this site.
Forest overstory.MATURE FORESTLAND: This stage is dominated by ponderosa pine that have reached or are near maximal heights for the site. Tree canopy cover ranges from 30 to 40 percent. Overstory tree canopy composition is approximately 95 percent ponderosa pine. Mature tree heights range from 80 to 125 feet tall. White fir, Jeffrey pine, Washoe pine and western juniper may comprise up to 5 percent of the overstory.
Forest understory. Understory vegetation is approximately 50 percent grasses and grass-like plants, 20 percent forbs and 30 percent shrubs and young trees. Average understory production ranges from 200 pounds per acre to 500 pounds per acre with a medium canopy cover. Understory production includes the total annual production of all species within 4.5 feet of the ground surface.
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 100 175 250 Shrub/Vine 50 87 125 Forb 40 70 100 Tree 10 18 25 Total 200 350 500 Table 6. Soil surface cover
Tree basal cover 0% Shrub/vine/liana basal cover 0-10% Grass/grasslike basal cover 0-0% Forb basal cover 0-0% Non-vascular plants 0% Biological crusts 0% Litter 50-60% Surface fragments >0.25" and <=3" 20-20% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 10-20% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – 1-3% 1-3% >0.5 <= 1 – – 2-5% 1-3% >1 <= 2 – – 10-15% 5-10% >2 <= 4.5 0-1% 2-5% – – >4.5 <= 13 2-5% 1-2% – – >13 <= 40 3-5% – – – >40 <= 80 10-15% – – – >80 <= 120 5-10% – – – >120 – – – – Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Primary Perennial Grasses/Grasslikes 72–128 Letterman's needlegrass ACLE9 Achnatherum lettermanii 18–32 – western needlegrass ACOCO Achnatherum occidentale ssp. occidentale 18–32 – Ross' sedge CARO5 Carex rossii 18–32 – Wheeler's bluegrass POWH2 Poa wheeleri 18–32 – 2 Secondary Perennial Grasses 14–58 mountain brome BRMA4 Bromus marginatus 4–18 – squirreltail ELEL5 Elymus elymoides 4–18 – blue wildrye ELGL Elymus glaucus 4–18 – tall trisetum TRCA21 Trisetum canescens 4–18 – Forb3 Perennial 30–100 wavyleaf Indian paintbrush CAAP4 Castilleja applegatei 4–18 – tapertip hawksbeard CRAC2 Crepis acuminata 4–18 – prickly hawkweed HIHO Hieracium horridum 4–18 – tailcup lupine LUCAC3 Lupinus caudatus ssp. caudatus 4–18 – sweetcicely OSBE Osmorhiza berteroi 2–4 – lambstongue ragwort SEINM Senecio integerrimus var. major 2–4 – American vetch VIAM Vicia americana 2–4 – woolly mule-ears WYMO Wyethia mollis 2–4 – ballhead waterleaf HYCAC Hydrophyllum capitatum var. capitatum 2–4 – fireweed CHANA2 Chamerion angustifolium ssp. angustifolium 2–4 – heartleaf arnica ARCO9 Arnica cordifolia 2–4 – Shrub/Vine4 Primary Shrubs 36–64 creeping barberry MARE11 Mahonia repens 18–32 – roundleaf snowberry SYRO Symphoricarpos rotundifolius 18–32 – 5 Secondary Shrubs 18–66 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 4–18 – snowbrush ceanothus CEVE Ceanothus velutinus 4–18 – currant RIBES Ribes 4–18 – chokecherry PRVI Prunus virginiana 2–4 – antelope bitterbrush PUTR2 Purshia tridentata 2–4 – Utah serviceberry AMUT Amelanchier utahensis 2–4 – Tree6 Evergreen 12–34 ponderosa pine PIPO Pinus ponderosa 4–18 – white fir ABCO Abies concolor 2–4 – western juniper JUOC Juniperus occidentalis 2–4 – Jeffrey pine PIJE Pinus jeffreyi 2–4 – Table 9. Community 1.1 forest overstory composition
Common name Symbol Scientific name Nativity Height ft Canopy cover (%) Diameter in Basal area (square ft/acre) Treeponderosa pine PIPO Pinus ponderosa Native – 95-100 – 0 Jeffrey pine PIJE Pinus jeffreyi Native – 0-2 – 0 white fir ABCO Abies concolor Native – 0-1 – 0 western juniper JUOC Juniperus occidentalis Native – 0-1 – 0 Interpretations
Animal community
Livestock Interpretations:
This site is suited to cattle and sheep grazing during the spring, summer, and fall. Grazing management should be keyed to needlegrass production. New plants of these grasses are established entirely from seed and grazing practices should allow for ample seed production and seedling establishment periodically. Letterman’s needlegrass begins growth early in the year and remains green throughout the relatively long growing season, thus, making it valuable forage for livestock. Western needlegrass has a spreading and deeply penetrating root system, which makes it resistant to trampling. Ross' sedge may be a poor to good forage plant depending on the site. Palatability of Ross' sedge has been rated "fair" for domestic sheep, horses, cattle, and small mammals. Creeping barberry browse contains toxic alkaloids and is slightly poisonous and unpalatable to livestock.
Livestock will often concentrate on this site taking advantage of the shade and shelter offered by the tree overstory. Many areas are not used because of steep slopes or lack of adequate water. Attentive grazing management is required due to steep slopes and erosion hazards.
Ponderosa pine needles can cause abortion and associated complications in cattle, however, this site can be safely grazing if timing and intensity of use are closely monitored. Sheep and goats can be used for control of noxious and invasive weeds. One considerable advantage of prescribed livestock grazing over chemical or mechanical controls is that unwanted, competitive vegetation may be removed while marketable animal products are simultaenously produced. Prescribed grazing can also be used to promote establishment and growth of conifer seedlings when numbers, distribution and timing are controlled.
Harvesting trees under a sound management program can open up the tree canopy to allow increased production of understory species desirable for grazing.
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:
Letterman's needlegrass provides valuable forage for many species of wildlife. It is consumed by mule deer and is most palatable early in the season before the foliage becomes coarse and wiry. Western needlegrass provides valuable forage for many species of wildlife. Ross' sedge is important summer elk forage, particularly in the first half of the growing season. It has been rated "good" for elk and "poor" for mule deer and pronghorn antelope. Creeping barberry is an important forage species for many wildlife species. Pacific ponderosa pine provides numerous species of birds and mammals with cover. As seedlings, they provide low ground cover for small birds and mammals. Upon reaching pole size, stands provide good windbreaks and thickets important as hiding cover for elk and mule deer. Mature trees and standing snags house arboreal species, while fallen logs and stumps provide many cavity-dwelling species with adequate shelter. Mature trees also provide thermal and escape cover for elk and mule deer. Fallen logs and stumps are used as cover by cottontails, small rodents, and reptiles. Pacific ponderosa pine needles, cones, buds, pollen, twigs, seeds, and associated fungi and insects provide food for many species of birds and mammals. Small mammals that eat stems and roots include deer mice, chipmunks, shrews, voles, and tree and ground squirrels. Large browse mammals include elk, mule deer, porcupines, hares, and rabbits. Many bird species eat Pacific ponderosa pine seeds.Hydrological functions
Runoff is medium to high depending on the slope. Lyonman is in Hydrologic Group B. The hydrologic cover condition of this site is fair in a representative stand. The average runoff curve is about 60 for group B soils. There is 50 to 60 percent cover of litter which includes needles and pine cones.
Recreational uses
Pacific ponderosa pine stands offer year-round recreation and aesthetic scenery. Hiking, backpacking, hunting, and bird watching are common uses.
Wood products
Ponderosa pine is prized for its quality wood, which has versatility in framework, sheathing, subflooring, siding, window sash, doors, interior trim, pulp, poles and timbers. Although no longer harvested, the oleoresin, or pitch, of ponderosa pine has been a source of turpentine in the past.
This forest site is of low site quality for tree production. Site index ranges from 70 to 80 (Meyer, 1938).
PRODUCTIVITY CAPACITY
Fuelwood Production: 30 to 35 cords per acre for stands averaging 50 to 60 feet in height and 90 years of age with a medium canopy cover. There are about 213,750 gross British Thermal Units (BTUs) heat content per cubic foot of ponderosa pine wood. Solid wood volume in a cord varies but usually ranges from 65 to 90 cubic feet. Assuming an average of 75 cubic feet of solid wood per cord, there are about 16 million BTUs of heat value in a cord of ponderosa pine wood.
Posts (7 foot): 25 to 50 per acre in stands of medium canopy.
MANAGEMENT GUIDES AND INTERPRETATIONS
1. LIMITATIONS AND CONSIDERATIONS
a. Potential for sheet and rill erosion is moderate to severe depending on slope.
b. Moderate to severe equipment limitations on steeper slopes and moderate to severe equipment limitations on sites having extreme surface stoniness.
c. Proper spacing is the key to a well managed, multiple use and multi-product woodland.
2. ESSENTIAL REQUIREMENTS
a. Adequately protect from wildfire.
b. Protect soils from accelerated erosion.
c. Apply proper grazing management.
3. SILVICULTURAL PRACTICES
a. Harvest cut selectively or in small patches size dependent upon site conditions) to enhance forage production.
1) Thinning and improvement cutting - Removal of poorly formed, diseased and low vigor trees for fuelwood.
2) Harvest cutting - Selectively harvest surplus trees to achieve desired spacing. Save large, healthy, full-crowned trees for cone (fruit) producers. Do not select only "high grade" trees during harvest.
3) Slash Disposal - broadcasting slash improves reestablishment of native understory herbaceous species and establishment of seeded grasses and forbs after tree harvest.
4) Spacing Guide - D+9
b. Prescription burning program to maintain desired canopy cover and manage site reproduction.
c. Pest control - Porcupines can cause
extensive damage and populations should be controlled.
d. Fire hazard - Fire usually not a problem in well-managed, mature stands.Other products
Bareroot stock of ponderosa pine can be used for soil stabilization. Needlegrass has been used successfully in revegetating mine spoils and also has good potential for erosion control.
Other information
Letterman’s needlegrass has been used successfully in revegetating mine spoils. This species also has good potential for erosion control. Native Americans used the inner cambial layer of ponderosa pine as food. They also converted the pine resin into medicinal salve for rheumatism, backaches, and dandruff.
Table 10. Representative site productivity
Common name Symbol Site index low Site index high CMAI low CMAI high Age of CMAI Site index curve code Site index curve basis Citation ponderosa pine PIPO 70 80 55 69 – – – Supporting information
Type locality
Location 1: Modoc County, CA Township/Range/Section T42N R15E S3 UTM zone N UTM northing 731577 UTM easting 4599565 Latitude 41° 30′ 51″ Longitude 120° 13′ 29″ General legal description Modoc National Forest - in the Warner Mountains approximately 2.5 miles up the Deep Creek Road from Modoc County Road 1 about 1.5 miles south of Cedarville, Modoc County, California. Other references
Habeck, R. J. 1992. Pinus ponderosa var. ponderosa. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2006, January 12].
Lanner, R.M. 1984. Trees of the Great Basin. University of Nevada Press, Reno NV.
Miles, S.R. and C.B. Goudey. 1997. Ecological Subregions of California Section and Subsection Descriptions. United States Department of Agriculture Forest Service, Pacific Southwest Region R5-EM-TP-005. Subsection M261Gf-Warner Mountains.
USDA-NRCS 2000. National Forestry Manual, Washington D.C.
USDA-NRCS. 2004 National Forestry Handbook, Title 190. Washington, D. C.
USDA-SCS 1997. National Engineering Manual, Washington D.C.
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).Contributors
P Novak-Echenique
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) Contact for lead author Date Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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