Natural Resources
Conservation Service
Ecological site F021XE238CA
Populus balsamifera ssp. trichocarpa/Salix lucida ssp. lasiandra/Elymus trachycaulus ssp. trachycaulus
Accessed: 08/17/2026
-
Search
Major Land Resource Area or ecological site by name and/or ID.
PreviousSectionsNextGeneral information
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) Populus balsamifera ssp. trichocarpa
Shrub (1) Salix lucida ssp. lasiandra
Herbaceous (1) Elymus trachycaulus ssp. trachycaulus
Physiographic features
This woodland site occurs on stream terraces and floodplains of mountain canyons. Slopes range from 4 to 15 percent. Elevations range from 5000 to 6500 feet.
Table 2. Representative physiographic features
Landforms (1) Stream terrace
(2) Flood plain
Flooding duration Brief (2 to 7 days) Flooding frequency Frequent Elevation 5000 – 6500 ft Slope 4 – 15 % Aspect Aspect is not a significant factor Climatic features
The climate of this site is temperate, 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 16 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) 0 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
This site is associated with perennial mountain streams.
Soil features
The soils associated with this site are deep, somewhat poorly drained and have a thick, dark-colored surface layer high in organic matter. These soils are frequently flooded and have a seasonal water tables at depths between 10 and 20 inches during the early springs and summer. The soil profile is modified with 65 to 85 percent rock fragments. Surface runoff is low to medium depending on slope. These soils are susceptible to gully erosion which intercepts natural overflow patterns resulting in site degradation. Soils are classified as ashy-skeletal Vitriandic Haplocryolls.
Table 4. Representative soil features
Surface texture (1) Extremely cobbly loam
Family particle size (1) Loamy
Drainage class Somewhat poorly drained Permeability class Moderately rapid Soil depth 60 in Surface fragment cover <=3" 10 – 15 % Surface fragment cover >3" 55 – 80 % Available water capacity
(0-40in)6.5 – 7.7 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)6.1 – 7.3 Subsurface fragment volume <=3"
(Depth not specified)10 – 15 % Subsurface fragment volume >3"
(Depth not specified)55 – 80 % 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 insect damage, disease damage or tree harvest. Residual trees left following disturbance have little or no affect on the composition and production of 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 4½ 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.
POLE STAGE: As the canopy closes, trees stratify into crown classes quickly. Cottonwood stands are self-thinning, especially at young ages. This stage is characterized by rapid growth of the cottonwood trees, both in height and canopy. The visual aspect and vegetal structure are dominated by cottonwood trees. Understory vegetation is moderately influenced by a tree canopy of about 15 to over 25 percent.
IMMATURE FORESTLAND: The visual aspect and vegetal structure are dominated by black cottonwood greater than 4½ feet in height. Seedlings and saplings are present in the understory. Understory vegetation is moderately influenced by a tree overstory canopy of about 25 to 35 percent.
MATURE FORESTLAND: The visual aspect and vegetal structure are dominated by cottonwood that have reached or are near maximal heights for the site. Tree canopy cover ranges from 40 to 50 percent. Understory vegetation is strongly influenced by tree competition, overstory shading, duff accumulation, etc. Few seedlings and/or saplings of cottonwood occur in the understory.
OVER-MATURE FORESTLAND: In the absence of naturally occurring disturbances, the tree canopy on this site can become very dense. This stage is dominated by black cottonwood that have reached maximal heights for the site. Understory vegetation is relatively sparse due to tree competition, overstory shading, duff accumulation, etc. Tree canopy cover is commonly greater than 50 percent.
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 a fairly dense, mixed riparian forest of black cottonwood with emergent evergreen ponderosa pine towering to as much as 100 feet. The shrub and herbaceous canopy is well developed, averaging around 50 percent cover. Sapling black cottonwood, willow, dogwood and Wood's rose are the principal understory shrubs. Wildrye, sedges, clover, yarrow and horsetail are also common understory species. Approximate ground cover (basal and canopy) is 35 to 50 percent.
Forest overstory.MATURE FOREST: The visual aspect and vegetal structure are dominated by black cottonwood that have reached or are near maximal heights for the site. Tree canopy cover ranges from 40 to 50 percent. Understory vegetation is strongly influenced by tree competition, overstory shading, duff accumulation, etc. Few seedlings and/or saplings of cottonwood occur in the understory.
Forest understory. Understory composition is approximately 25 percent grasses, 20 percent forbs and 55 percent shrubs and young trees when the average overstory canopy is medium (30 to 40 percent). Average understory production ranges from 1000 to 2000 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)Shrub/Vine 480 720 960 Grass/Grasslike 250 375 500 Forb 200 300 400 Tree 70 105 140 Total 1000 1500 2000 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Primary Perennial Grasses 150–270 sedge CAREX Carex 75–135 – slender wheatgrass ELTRT Elymus trachycaulus ssp. trachycaulus 75–135 – 2 Secondary Perennial Grasses/Grasslikes 69–270 Kentucky bluegrass POPRP2 Poa pratensis ssp. pratensis 15–75 – creeping bentgrass AGST2 Agrostis stolonifera 15–75 – mountain rush JUARL Juncus arcticus ssp. littoralis 15–75 – woodrush LUZUL Luzula 8–15 – bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 8–15 – Indian ricegrass ACHY Achnatherum hymenoides 8–15 – Forb3 Annual 8–15 Forb, annual 2FA Forb, annual 8–15 – 4 Perennial 117–360 western yarrow ACMIO Achillea millefolium var. occidentalis 15–75 – field horsetail EQAR Equisetum arvense 15–75 – clover TRIFO Trifolium 15–75 – American vetch VIAM Vicia americana 8–15 – bedstraw GALIU Galium 8–15 – largeleaf avens GEMA4 Geum macrophyllum 8–15 – common cowparsnip HEMA80 Heracleum maximum 8–15 – starry false lily of the valley MAST4 Maianthemum stellatum 8–15 – slender cinquefoil POGR9 Potentilla gracilis 8–15 – Oregon checkerbloom SIOR Sidalcea oregana 8–15 – western columbine AQFO Aquilegia formosa 8–15 – aster ASTER Aster 8–15 – Shrub/Vine5 Primary Shrubs 300–630 redosier dogwood COSE16 Cornus sericea 150–360 – Woods' rose ROWO Rosa woodsii 75–135 – narrowleaf willow SAEX Salix exigua 75–135 – 6 Secondary Shrubs 61–255 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 15–75 – bitter cherry PREM Prunus emarginata 15–75 – American black elderberry SANIC4 Sambucus nigra ssp. canadensis 15–75 – rubber rabbitbrush ERNAN5 Ericameria nauseosa ssp. nauseosa var. nauseosa 8–15 – white sagebrush ARLU Artemisia ludoviciana 8–15 – Tree7 Deciduous 31–105 black cottonwood POBAT Populus balsamifera ssp. trichocarpa 15–75 – quaking aspen POTR5 Populus tremuloides 8–15 – Pacific willow SALUL Salix lucida ssp. lasiandra 8–15 – 8 Evergreen 16–30 white fir ABCO Abies concolor 8–15 – ponderosa pine PIPO Pinus ponderosa 8–15 – Table 7. Community 1.1 forest overstory composition
Common name Symbol Scientific name Nativity Height ft Canopy cover (%) Diameter in Basal area (square ft/acre) Treeblack cottonwood POBAT Populus balsamifera ssp. trichocarpa Native – 80-100 – 0 Pacific willow SALUL Salix lucida ssp. lasiandra Native – 0-10 – 0 ponderosa pine PIPO Pinus ponderosa Native – 0-5 – 0 ponderosa pine PIPO Pinus ponderosa Native – 0-5 – 0 white fir ABCO Abies concolor Native – 0-3 – 0 quaking aspen POTR5 Populus tremuloides Native – 0-2 – 0 Interpretations
Animal community
Livestock Interpretations:
This site is suited to cattle and sheep grazing during the summer and fall. Livestock will often concentrate on this site taking advantage of the shade and shelter offered by the tree overstory. Harvesting trees under a sound management program for fuelwood or other products can open up the tree canopy to allow increased production of understory species desirable for grazing.
Wildlife Interpretations:
This site provides valuable habitat to mule deer during the summer. It furnishes ideal habitat for a variety of tree and ground nesting birds. Beaver can be sustained by the trees on this site. It is also used by various small mammals and reptiles and their associate predators natural to the area.Hydrological functions
A well stocked black cottonwood stand provides excellent watershed protection. A mixture of herbaceous and woody root systems penetrate and anchor the soil. Erosion producing overland flow is almost non-existent.
Recreational uses
Aesthetic value is derived from the rich hues and textures of the trees, particularly in the fall. The diverse floral and faunal composition and the colorful flowering of wildflowers during the summer enhance the beauty of this site. The site offers rewarding opportunities to photographers and for nature study. It has high value for hunting, camping, picnicking and birdwatching.
Wood products
Black cottonwood has been used for lumber, fence posts, and fuelwood. This tree has a considerable potential for increased utilization. It makes excellent pulp. Some of this wood is used for the production of excelsior, door corestock and boxwood. An undesirable characteristic of black cottonwood is the heavy drain on soil moisture.
This site has fair site quality for tree production. Site index ranges from 30 to 40; production class 1 (Baker and Broadfoot, 1977).
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. Harvest stands in small blocks of 1/5 to 1/2 acre with slash left in place to shelter emerging seedlings from browsing.
3) Selective Tree Removal - Remove selected trees on suitable sites to enhance forage production and manage site reproduction.
4) Spacing Guide - A spacing of about 15 X 15 feet at stand maturity is considered desirable for multiple use management.
c. Pest control - Use necessary and approved control for specific pests and diseases.
d. Fire hazard - Fire is rarely a problem in black cottonwood stands. However, even a light fire may kill black cottonwood seedlings, saplings, and mature trees.Table 8. 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 black cottonwood POBAT 30 40 8 19 – – – Supporting information
Type locality
Location 1: Modoc County, CA Township/Range/Section T43N R15E S34 UTM zone N UTM northing 730991 UTM easting 4603544 Latitude 41° 33′ 0″ Longitude 120° 13′ 49″ General legal description Cedar Creek Trail, Modoc National Forest, Warner Mountains, Modoc County, CA. Other references
Baker, J. B., Broadfoot, W. M. 1977. Site Evaluation for Eight Important Southern Hardwoods. USDA-FS, GTR 50-14.
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
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 - Part 537. Washington, D.C.
USDA-NRCS. 2004 National Forestry Handbook, Title 190. 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
-
Number and extent of rills:
-
Presence of water flow patterns:
-
Number and height of erosional pedestals or terracettes:
-
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
-
Number of gullies and erosion associated with gullies:
-
Extent of wind scoured, blowouts and/or depositional areas:
-
Amount of litter movement (describe size and distance expected to travel):
-
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
-
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
-
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
-
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
-
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:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
-
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:
-
Perennial plant reproductive capability:
Print Options
Sections
Font
AAAAOther
PrintThe 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.
Accessibility statement
