Natural Resources
Conservation Service
Ecological site R021XY418OR
WET LOAMY TERRACE
Accessed: 12/03/2024
General information
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.
Figure 1. Mapped extent
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.
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
Not specified |
Physiographic features
This site occurs on alluvial terraces and fans. Slopes range from 1 to 12 percent. Elevations typically range from 4000 to 4500 feet on the east side of the Cascade Mountains. Minor occurrences may range as low as 2500 feet on the west side in the Butte Falls or Prospect area.
Table 2. Representative physiographic features
| Landforms |
(1)
Terrace
(2) Alluvial fan |
|---|---|
| Elevation | 4,000 – 4,500 ft |
| Slope | 1 – 12% |
| Aspect | Aspect is not a significant factor |
Climatic features
The annual precipitation ranges from 20 to 40 inches. It occurs mainly between the months of October and June in the form of both rain and snow. The soil temperature regime is primarily frigid (east side). The average annual air temperature is about 47 degrees F. The frost free period is less than 120 days. The optimum period for plant growth is from April through July.
Table 3. Representative climatic features
| Frost-free period (average) | 120 days |
|---|---|
| Freeze-free period (average) | 0 days |
| Precipitation total (average) | 40 in |
Influencing water features
Soil features
The soils of this site are moderately deep to a hardpan, loamy textured and moderately well drained or well drained. Seasonally wet conditions in the subsoil are great enough, however, to significantly affect the plant community. They are generally formed in alluvium. Permeability is moderate about the hardpan and very slow below. The avialable water holding capacity is 2 to 4 inches for the profile. The potential for water erosion is slight.
Table 4. Representative soil features
| Family particle size |
(1) Loamy |
|---|---|
| Drainage class | Moderately well drained to well drained |
| Soil depth | 40 in |
| Available water capacity (0-40in) |
2 – 4 in |
Ecological dynamics
Overstory removal is likely to initiate ponderosa pine regeneration and an increase in plants such as Oregon grape, dewberry, serviceberry, and snowberry.
Composition of the plant community is closely correlated to soil wetness and aeration since this site has a temporary seasonal watertable. An increase in lodgepole pine and water loving species occurs as wetness increses. This often occurs adjacent to lodgepole pine meadow areas which are intermingled with this site. The dry margins will have an increase in Douglas-fir, white fir and/or incense cedar, and less Douglas-fir or spirea.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 1
HCPC, FEID/SPDO-SYAL/PIPO
Community 1.1
HCPC, FEID/SPDO-SYAL/PIPO
The potential native plant community is dominated by ponderosa pine. Minor occurrences of lodgepole pine, incense cedar, white fur and Douglas-fir may also be present. Douglas spirea dominates the shrub layer and is well adapted to the seasonal water table of this site. Depending on the degree of wetness, common snowberry and western dewberry are also abundant along with minor amounts of other shrubs such as willow, oceanspray, rose, Saskatoon serviceberry, squaw carpet, tall Oregongrape and pinemat manzanita. Idaho fescue is somewhat common and there are sparse occurrences of western fescue, Junegrass and orcutt brome. The most common forbs include strawberry, yarrow, wooly eriophyllum, mountain sweetroot, tall potentilla and avens (old man's beard).
Figure 2. 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 | 192 | 276 | 360 |
| Grass/Grasslike | 90 | 129 | 168 |
| Tree | 54 | 90 | 126 |
| Forb | 12 | 21 | 30 |
| Total | 348 | 516 | 684 |
Figure 3. Plant community growth curve (percent production by month). OR5556, D21 Mid Elev., NA, Meadow. HCPC Growth Curve.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 0 | 10 | 30 | 40 | 15 | 5 | 0 | 0 | 0 |
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Dominant deep rooted perennial grasses | 72–120 | ||||
| Idaho fescue | FEID | Festuca idahoensis | 60–90 | – | ||
| western fescue | FEOC | Festuca occidentalis | 12–30 | – | ||
| 2 | Sub-dominant deep rooted perennial grasses | 12–30 | ||||
| Orcutt's brome | BROR2 | Bromus orcuttianus | 6–18 | – | ||
| Ross' sedge | CARO5 | Carex rossii | 6–12 | – | ||
| 4 | Sub-dominant shallow rooted perennial grasses | 6–18 | ||||
| prairie Junegrass | KOMA | Koeleria macrantha | 6–18 | – | ||
|
Forb
|
||||||
| 9 | Other perennial forbs | 12–30 | ||||
| common yarrow | ACMI2 | Achillea millefolium | 0–5 | – | ||
| blue eyed Mary | COLLI | Collinsia | 0–5 | – | ||
| trumpet | COLLO | Collomia | 0–5 | – | ||
| common woolly sunflower | ERLA6 | Eriophyllum lanatum | 0–5 | – | ||
| strawberry | FRAGA | Fragaria | 0–5 | – | ||
| avens | GEUM | Geum | 0–5 | – | ||
| white hawkweed | HIAL2 | Hieracium albiflorum | 0–5 | – | ||
| desertparsley | LOMAT | Lomatium | 0–5 | – | ||
| western sweetroot | OSOC | Osmorhiza occidentalis | 0–5 | – | ||
| tall cinquefoil | POAR7 | Potentilla arguta | 0–5 | – | ||
|
Shrub/Vine
|
||||||
| 12 | Sub-dominant evergreen shrubs | 18–36 | ||||
| pinemat manzanita | ARNE | Arctostaphylos nevadensis | 6–12 | – | ||
| prostrate ceanothus | CEPR | Ceanothus prostratus | 6–12 | – | ||
| hollyleaved barberry | MAAQ2 | Mahonia aquifolium | 6–12 | – | ||
| 13 | Dominant deciduous (or 1/2 shrubs) shrubs | 150–240 | ||||
| rose spirea | SPDO | Spiraea douglasii | 120–180 | – | ||
| common snowberry | SYAL | Symphoricarpos albus | 30–60 | – | ||
| 14 | Sub-dominant deciduous (or 1/2 shrubs) shrubs | 24–84 | ||||
| Saskatoon serviceberry | AMAL2 | Amelanchier alnifolia | 6–30 | – | ||
| Pacific dewberry | RUVI4 | Rubus vitifolius | 6–30 | – | ||
| oceanspray | HODI | Holodiscus discolor | 6–12 | – | ||
| rose | ROSA5 | Rosa | 6–12 | – | ||
|
Tree
|
||||||
| 16 | Dominant evergreen trees | 30–60 | ||||
| ponderosa pine | PIPO | Pinus ponderosa | 30–60 | – | ||
| 17 | Sub-dominant evergreen trees | 24–48 | ||||
| white fir | ABCO | Abies concolor | 6–12 | – | ||
| incense cedar | CADE27 | Calocedrus decurrens | 6–12 | – | ||
| ponderosa pine | PIPO | Pinus ponderosa | 6–12 | – | ||
| Douglas-fir | PSME | Pseudotsuga menziesii | 6–12 | – | ||
| 18 | Dominant deciduous trees | 6–30 | ||||
| willow | SALIX | Salix | 6–30 | – | ||
Interpretations
Supporting information
Contributors
E Ersch
Hickman, Borine
K.Kennedy
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 |
|---|---|
| Contact for lead author | Oregon NRCS State Rangeland Management Specialist |
| Date | 09/05/2012 |
| Approved by | Bob Gillaspy |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
None, slight sheet & rill erosion hazard -
Presence of water flow patterns:
None -
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):
<5% -
Number of gullies and erosion associated with gullies:
None -
Extent of wind scoured, blowouts and/or depositional areas:
None, slight wind erosion hazard -
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):
Significantly resistant to erosion: aggregate stability = 4-6 -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Moderately deep (to a hardpan), moderately well drained or well drained loams (seasonally wet subsoil limits plant growth): Moderate OM (1-3%) -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Significant vegetative cover of over 110% and gentle slopes (1-12%) effectively limit rainfall impact and overland flow; infiltration is moderate -
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:
Rose spirea > Idaho fescue > Snowberry = Ponderosa Pine > Western fescue = forbs > other forbs > other shrubs > other grassesSub-dominant:
Other:
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):
Favorable: 700, Normal: 600, Unfavorable: 500 lbs/acre/year at high RSI (HCPC) -
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:
Lodgepole pine and other water loving species will increase with increased wetness. Douglas fir, white fir, and incense cedar will increase with decreasing wetness. Cheatgrass and Medusahead invade sites that lost deep rooted perennial grass functional groups. -
Perennial plant reproductive capability:
All species should be capable of reproducing annually
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