Natural Resources
Conservation Service

Ecological site F003XD805OR

Frigid Udic Maritime Mountain Slopes
40-60 PZ

Last updated: 4/01/2025
Accessed: 07/13/2026

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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.

MLRA notes

Major Land Resource Area (MLRA): 003X–Olympic and Cascade Mountains

This area includes the west slope and parts of the east slope of the Cascades Mountains in Washington and Oregon. The Olympic Mountains in Washington State are also included. These mountains are part of a volcanic arc located at a convergent plate boundary. Volcanic rocks predominate but metamorphic and sedimentary rocks occur in the North Cascades and Olympic Mountains. Topography is generally dissected and steep, but some areas consist of constructional volcanic platforms and isolated stratovolcanoes. Elevation is usually 500 to 6000 feet but reaches to 14,410 ft at the summit of Mount Rainier. Many areas hosted alpine glaciers or ice sheets during the Pleistocene, and a few remain today.

Climate becomes cooler and moister with increasing elevation and latitude. Low elevations experience a long growing season and mild temperatures. High elevations can accumulate snowpack lasting into summer and frost may occur in any month. Average annual precipitation ranges from 60 to 180 inches in most areas. Most precipitation falls during the fall, winter, and spring during low-intensity frontal storms. Summers are relatively dry. Average annual temperature is 27 to 50 degrees F. The frost-free period is 10 to 180 days.

Classification relationships

Forested Plant Associations of the Oregon East Cascades (Simpson 2007)
CWF431 – white fir–grand fir/queencup beadlily
Plant association group – White fir / Grand fir, wet

Plant Associations of the Commercial Forest of the Warm Springs Indian Reservation (Marsh 1987)
Grand fir / Snowberry
Grand fir / Oregon Boxleaf
Grand fir / Vine Maple

Landfire biophysical settings model (Landfire 2007)
0710180 East Cascades Mesic Montane Mixed-Conifer Forest and Woodland.

Ecological site concept

This site encompasses a broad group of forest communities encompassed by the wet, modified maritime influenced, mixed conifer zone at middle elevations on the east slope of the Oregon Cascades. In reference condition, this site supports a forest canopy dominated by Douglas-fir (Pseudotsuga menziesii) and grand fir (Abies grandis), with western larch (Larix occidentalis) and understory reproduction of Douglas-fir and grand fir common. Plant community diversity is high with many wet site indicator species present such as bigleaf huckleberry (Vaccinium membranaceum), Oregon boxwood (Paxistima myrsinites), vine maple (Acer circinatum), vanilla leaf (Achlys triphylla), twinflower (Linnaea borealis) and beadlilly (Clintonia uniflora).

Sites at higher elevations than this site receiving cooler temperatures, higher precipitation, and in many cases more favorable aspects that result in increased effective soil moisture, support codominance of western hemlock (Tsuga heterophylla) due to its greater moisture requirements. In comparison to the associated mixed conifer sites receiving less precipitation, the maritime influence of this site results in a udic rather than xeric soil moisture regime with greater available moisture during the summer season. The higher soil moisture conditions of this site, as well as cooler temperatures, result in a less frequent fire rotation in comparison to these drier sites. This site has a fire regime characterized by moderately frequent, low and mixed severity fire (Landfire fire regime group 3).

This is a provisional ecological site that groups characteristics at a broad scale with little to no field verification and is subject to extensive review and revision before final approval. All data herein was developed using existing information and literature and should be considered provisional and contingent upon field validation prior to use in conservation planning.

Associated sites

F003XD806OR	Frigid Udic Maritime Mountain Slopes 60-90 PZ Occupying landforms upslope or landscape positions with greater precipitation and/or soil moisture accumulation and retention.

F003XD806OR

Frigid Udic Maritime Mountain Slopes 60-90 PZ

Occupying landforms upslope or landscape positions with greater precipitation and/or soil moisture accumulation and retention.

Similar sites

F003XD806OR	Frigid Udic Maritime Mountain Slopes 60-90 PZ Higher precipitation, dominated by western hemlock

F003XD806OR

Frigid Udic Maritime Mountain Slopes 60-90 PZ

Higher precipitation, dominated by western hemlock

Table 1. Dominant plant species

Tree	(1) Abies grandis (2) Pseudotsuga menziesii
Shrub	Not specified
Herbaceous	(1) Clintonia uniflora

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Physiographic features

This site is largely found occupying middle elevations on the east slope of the Cascades in Oregon. Its range is largely restricted to areas outside of the pumice plateau where deep pumice soils preclude the persistence of Douglas-fir. Within this range the site is primarily found on benches and slopes of mountains and glacial moraines. This site is commonly found occupying elevations between 3,000 – 5,400 ft (900 – 1,650 m). Slopes are most often 6 – 50% but can range from 0 - 65%. This site is found on all aspects. This site does not experience flooding or ponding and no water table is present within the upper two meters of soil.

Table 2. Representative physiographic features

Landforms	(1) Mountains > Mountain slope (2) Mountains > Bench (3) Mountains > Moraine
Flooding frequency	None
Ponding frequency	None
Elevation	3000 – 5400 ft
Slope	6 – 50 %
Water table depth	100 in
Aspect	W, NW, N, NE, E, SE, S, SW

Table 3. Representative physiographic features (actual ranges)

Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	0 ft
Slope	0 – 65 %
Water table depth	0 in

Climatic features

The average annual precipitation ranges from 40 - 60 in (100 – 150 cm) which occurs mainly between the months of November and June, mostly in the form of rain and snow. The average annual air temperature ranges from 39 - 43° F (4 - 6 °C) and the frost-free period ranges from 50 to 80 days. The soil temperature regime is frigid, soil moisture regime is udic. This climate is influenced by maritime weather patterns emerging from the pacific coast which bring greater precipitation and higher winter temperatures. These patterns are somewhat modified by the Cascade crest, which due to orographic uplift, buffers the site from the greater maritime impacts experienced by forests in the Western Cascades. The graphs below are populated from the closest available weather station to representative site locations and are provided to indicate general climate patterns.

Table 4 Representative climatic features

Frost-free period (characteristic range)	50-80 days
Freeze-free period (characteristic range)	90-140 days
Precipitation total (characteristic range)	40-60 in
Frost-free period (average)	70 days
Freeze-free period (average)	100 days
Precipitation total (average)	50 in

Characteristic range

Actual range

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

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Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6 Annual average temperature pattern

Climate stations used

(1) SANTIAM JUNCTION [USC00357554], Blue River, OR
(2) SISTERS [USC00357857], Sisters, OR
(3) MARION FRKS FISH HATCH [USC00355221], Willamette Natl Forest, OR

Soil features

The soils that typify this site concept are moderately deep to very deep over paralithic bedrock. Soil parent materials are commonly colluvium and residuum weathered from andesite and glacial till, both of which are either mixed or mantled (topped) with volcanic ash. Soil drainage and available water content are influenced by ash content and rock fragments throughout the profile. These are primarily well drained to somewhat excessively drained soils that often contain substantial subsurface rock fragments. Surface textures commonly range from sandy loams and fine sandy loams to gravelly, very stony and very cobbly sandy loams.

A representative soil complex associated with this site:

Howash very cobbly sandy loam, low precipitation, 12 to 30 percent slopes

Table 5. Representative soil features

Parent material	(1) Colluvium – andesite (2) Residuum – andesite (3) Till (4) Volcanic ash – volcanic rock
Surface texture	(1) Sandy loam (2) Gravelly sandy loam (3) Very cobbly sandy loam (4) Very stony sandy loam (5) Fine sandy loam
Family particle size	(1) Ashy-skeletal (2) Ashy
Drainage class	Well drained
Permeability class	Moderate to rapid
Depth to restrictive layer	20 – 80 in
Soil depth	20 – 80 in
Surface fragment cover <=3"	0 – 45 %
Surface fragment cover >3"	0 – 45 %
Available water capacity (0-40in)	1.6 – 6.3 in
Soil reaction (1:1 water) (0-40in)	5.1 – 7.3
Subsurface fragment volume <=3" (4-60in)	5 – 35 %
Subsurface fragment volume >3" (4-60in)	5 – 60 %

Table 6. Representative soil features (actual values)

Drainage class	Well drained to somewhat excessively drained
Permeability class	Not specified
Depth to restrictive layer	0 in
Soil depth	0 in
Surface fragment cover <=3"	0 %
Surface fragment cover >3"	0 %
Available water capacity (0-40in)	0 in
Soil reaction (1:1 water) (0-40in)	0
Subsurface fragment volume <=3" (4-60in)	0 %
Subsurface fragment volume >3" (4-60in)	0 %

Ecological dynamics

As a wet mixed conifer site, this site is often situated above the moist mixed conifer zone and below the wet western hemlock/grand fir and cold mountain hemlock (Tsuga mertensiana)/silver fir (Abies amabilis) forests. The reference plant community for this site is characterized by a diverse canopy dominated by Douglas-fir and grand fir, with western larch common and incense cedar (Calocedrus decurrens), lodgepole pine (Pinus contorta), ponderosa pine (Pinus ponderosa), western hemlock (Tsuga heterophylla) and western white pine (Pinus monticola) often also occurring depending on more localized site conditions. Of the true firs, grand fir is more common on this site north of the Metolius drainage, with hybrids between grand fir and white fir more common to the south (Simpson 2007). Overstory composition in mature forests is largely dominated by shade tolerant species but variability may be dependent on factors such as aspect, with ponderosa and incense cedar increasing on some southern exposures with less effective moisture. Plant community diversity is high across this broad site concept with many species present. Some consistently dominant species include snowbrush (Ceanothus velutinus), golden chinkapin (Chrysolepis chrysophylla), bigleaf huckleberry (Vaccinium membranaceum), Oregon boxwood (Paxistima myrsinites), Vine maple (Acer circinatum), vanilla leaf (Achlys triphylla), twinflower (Linnaea borealis) and bride’s bonnet (Clintonia uniflora).

Disturbance:

Historically, wet grand fir forests were likely subject to a fire regime characterized mainly by moderately frequent, mixed severity fire (Landfire fire regime group 3) (Simpson 2007, Landfire 2007). This is in contrast to drier grand fir, Douglas-fir and ponderosa forests that were subject to more frequent, low intensity fires (Hessberg et al. 2005). This fire regime combined with high precipitation, favors the development of closed canopy conditions and the infill of shade tolerant true fir species, incense cedar and Douglas-fir in the understory of these forests. While ponderosa pine may be present on these sites, it will be outcompeted overtime by more shade-tolerant species, and is often only present in the canopy of late successional forests as scattered mature individuals (Franklin and Dyrness 1973). Snowbrush, golden chinkapin and vine maple will increase following fire and often form shrubfields on favorable sites following stand replacing fires. These shrubfields may persist for decades and may inhibit the reestablishment of tree species (Franklin and Dyrness 1973).

These sites are often of high productivity and attractive for commercial timber harvesting which will have varying effects on stand structure and composition depending on harvest practices. Dense shrub cover following fire or logging may delay stand regeneration (Marsh et al 1987). Livestock grazing potential is limited on this site due to closed canopy conditions and high shrub cover.

The state and transition model below represents a generalized and simplified version of forest change in response to fire in this ecological site. It does not attempt to model the complex effects of forestry practices or insect outbreaks on ecosystem change. It is largely based on Landfire biophysical settings model: 0710180 East Cascades Mesic Montane Mixed-Conifer Forest and Woodland (Landfire 2007).

State and transition model

Custom diagram

Standard diagram

More interactive model formats are also available. View Interactive Models

More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Historic Reference

2. Managed

T1A	-	Extensive Timber Harvest
R2A	-	Forest restoration, stand replacing fire

State 1 submodel, plant communities

1.1. Shrub and Stand Initiation

1.2. Young Closed Forest

1.3. Mature Closed Forest

1.1A	-	Lack of fire for ~20 years
1.2B	-	High severity, stand replacing fire occurs
1.2A	-	Lack of fire for ~65 years
1.3A	-	High severity, stand replacing fire occurs

State 1
Historic Reference

A wet forest community, this site occurs across the landscape as a mosaic of plant community phases characterized by variation in forest structural stage (tree age, density and cover) and plant community. This mosaic pattern is highly influenced by a mixed fire regime approximated by Landfire fire regime group 3: 35 - 200 Year Fire Return Interval, Low and Mixed Severity. As a highly productive forest community, this site will persist in closed canopy conditions represented by communities 1.2 and 1.3 most often. The mature, closed forest community represented by 1.3 is the reference community. Open stand conditions are possible due to insect outbreak or disease but rarely persist given site productivity. A minor amount of exotic species may be present on this site. However, site productivity and diversity likely bolster resilience to invasion for this site and exotic species are not known to significantly alter plant community dynamics as of writing.

Dominant plant species

grand fir (Abies grandis), tree
Douglas-fir (Pseudotsuga menziesii), tree
bride's bonnet (Clintonia uniflora), other herbaceous

Community 1.1
Shrub and Stand Initiation

Community dominated by shrubs. These shrubfields may persist for decades yet are likely important for providing shade to young conifers, cycling nutrients and providing wildlife forage. Forest reestablishment will depend on seed sources and may require longer intervals if available sources are no longer onsite and must depend on wind or animal transport from adjacent forests. Fire with high enough severity to remove shrub cover will maintain this community. All other communities may transition to this phase after stand replacing fires.

Community 1.2
Young Closed Forest

Closed canopy forest, densely stocked with young to intermediate aged Douglas-fir, western larch and grand fir. Western hemlock may be locally present in the subcanopy, which is otherwise dominated by shrubs with little herbaceous cover due to lack of light.

Community 1.3
Mature Closed Forest

The reference community is characterized by a mature, closed canopy forest. It is an uneven aged stand with large grand fir, Douglas-fir and western larch in the overstory. Western hemlock may be present in some areas more locally that receive more moisture. It is densely stocked, with a limited cover of herbaceous species or shrubs, species present will be primarily shade-tolerant species.

Pathway 1.1A
Community 1.1 to 1.2

Lack of fire for ~20 years

Pathway 1.2B
Community 1.2 to 1.1

High severity, stand replacing fire occurs

Pathway 1.2A
Community 1.2 to 1.3

Lack of fire for ~65 years

Pathway 1.3A
Community 1.3 to 1.1

High severity, stand replacing fire occurs

State 2
Managed

This alternative state represents the many variations of timber harvesting that can occur in this site. This may result in a number of manipulated community types and pathways depending on strategies surrounding harvest, shrub control, weed control and replanting. Following harvest, some sites with adequate moisture and shrub seed source may be dominated by early seral shrubs. These may persist for decades yet are likely important for providing shade to young conifers, cycling nutrients and providing wildlife forage and cover.

Dominant plant species

Douglas-fir (Pseudotsuga menziesii), tree

Transition T1A
State 1 to 2

Extensive timber harvest followed by continual management for timber production that has significantly altered species compositions and resulting disturbance responses.

Restoration pathway R2A
State 2 to 1

Alterations of forest tree species composition, as well as soil compaction and surface disturbances due to large machine usage may hinder passive forest reestablishment. Forest reestablishment may require shrub control and tree replanting if the desired goal is regaining a forest structure within a desired timeframe. Ecological forestry practices may promote a return to reference state. Stand replacing fire may lead to a transition to community 1.1 of the reference state if soil compaction is not severe, species composition has not been significantly altered and tree seed source is available.

Additional community tables

Table 7. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Table 8. Community 1.2 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Table 9. Community 1.3 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Supporting information

References

1980. Fire Effects Information System. http://www.fs.fed.us/database/feis/.
. 2021 (Date accessed). USDA PLANTS Database. http://plants.usda.gov.

Other references

Agee, J.K., 1993. Fire Ecology of Pacific Northwest Forest. Island Press, Washington, DC.

Franklin, J., & Dyrness, C. 1973 Natural vegetation of Oregon and Washington. : Portland, Or., Pacific Northwest Forest and Range Experiment Station, Forest Service, U.S. Dept. of Agriculture.

Fryer, Janet L. 2018. Pinus ponderosa var. benthamiana, P. p. var. ponderosa: Ponderosa pine. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: www.fs.fed.us/database/feis/plants/tree/pinponp/all.html

Hessburg, P.F., Agee, J.K., & Franklin, J.F. (2005). Dry forests and wildland fires of the inland Northwest USA: Contrasting the landscape ecology of the pre-settlement and modern eras.

Hopkins, W. 1979. Plant associations of the Fremont National Forest. Portland, Or. U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Region.

LANDFIRE, 2007, Biophysical Settings Model Descriptions, LANDFIRE 1.1.0, U.S. Department of the Interior, USDA Forest service, Accessed 20 April 2020 at https://www.landfire.gov/bps-models.php

Marsh, Frank; Helliwell, Richard; Rodgers, Jean. 1987. Plant Association Guide for the Commercial Forest of the Warm Springs Indian Reservation. Portland, Or. U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Region.

Ritchie, Martin W.; Maguire, Douglas A.; Youngblood, Andrew, Technical Coordinators. 2005. Proceedings of the Symposium on Ponderosa Pine: Issues, Trends, and Management. 2004 October 18-21; Klamath Falls, OR. Gen. Tech. Rep. PSW-GTR-198. Albany CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 281 p.

Scher, Janette S. 2002. Larix occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/tree/larlya/all.html [2020, June 5].

Simpson, M. 2010. Forested plant associations of the Oregon East Cascades. Portland, Or. U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Region.

Tollefson, Jennifer E. 2008. Calocedrus decurrens. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us /database/feis/plants/tree/caldec/all.html [2020, May 28].

Volland, L. 1985 Plant associations of the central Oregon pumice zone. Portland, Or. U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Region.

Contributors

Andrew Neary - Concept developed for 2020 PES initiative

Approval

Kirt Walstad, 4/01/2025

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	05/10/2024
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:

Download reference sheet

Natural ResourcesConservation Service

Ecological site F003XD805OR

Frigid Udic Maritime Mountain Slopes 40-60 PZ

Last updated: 4/01/2025 Accessed: 07/13/2026

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General information

MLRA notes

Classification relationships

Ecological site concept

Associated sites

Similar sites

Table 1. Dominant plant species

Natural Resources
Conservation Service

Frigid Udic Maritime Mountain Slopes
40-60 PZ

Last updated: 4/01/2025
Accessed: 07/13/2026