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Home/Ecosystems/ Pacific Northwest Mountain Streamside Forest

Pacific Northwest Mountain Streamside Forest

EVT 7158North Pacific Montane Riparian Woodland
CES204.866GNRTreeRiparian
View on NatureServe Explorer
Summary
This ecological system occurs throughout mountainous areas of the Pacific Northwest coast, both on the mainland and on larger islands. It occurs on steep streams and narrow floodplains above foothills but below the alpine environments, e.g., above 1500 m (4550 feet) elevation in the Klamath Mountains and western Cascades of Oregon, up as high as 3300 m (10,000 feet) in the southern Cascades, and above 610 m (2000 feet) in northern Washington. Surrounding habitats include subalpine parklands and montane forests. In Washington, they are defined as occurring primarily above the Tsuga heterophylla zone, i.e., beginning at or near the lower boundary of the Abies amabilis zone. Dominant species include Pinus contorta var. murrayana, Populus balsamifera ssp. trichocarpa, Abies lowiana, Abies magnifica, Populus tremuloides, Alnus incana ssp. tenuifolia, Alnus viridis ssp. crispa, Alnus viridis ssp. sinuata, Alnus rubra, Rubus spectabilis, Ribes bracteosum, Oplopanax horridus, Acer circinatum, and several Salix species. In western Washington, major species are Alnus viridis ssp. sinuata, Acer circinatum, Salix, Oplopanax horridus, Alnus rubra, Petasites frigidus, Rubus spectabilis, and Ribes bracteosum. This is a disturbance-driven system that requires flooding, scour and deposition for germination and maintenance. It occurs on streambanks where the vegetation is significantly different than surrounding forests, usually because of its shrubby or deciduous character.
Source: NatureServe Explorer
Vegetation
Dominant species include Pinus contorta var. murrayana, Populus balsamifera ssp. trichocarpa, Abies lowiana (= Abies concolor var. lowiana), Abies magnifica, Populus tremuloides, Alnus incana ssp. tenuifolia (= Alnus tenuifolia), Alnus viridis ssp. crispa (= Alnus crispa), Alnus viridis ssp. sinuata (= Alnus sinuata), Alnus rubra, Rubus spectabilis, Ribes bracteosum, Oplopanax horridus, Acer circinatum, and several Salix species. In western Washington, major species are Alnus viridis ssp. sinuata, Acer circinatum, Salix, Oplopanax horridus, Alnus rubra, Petasites frigidus, Rubus spectabilis, and Ribes bracteosum.
Source: NatureServe Explorer
Environment
This ecological system occurs throughout mountainous areas of the Pacific Northwest coast, both on the mainland and on larger islands. It occurs on steep streams and narrow floodplains above foothills but below the alpine environments, e.g., above 1500 m (4550 feet) elevation in the Klamath Mountains and western Cascades of Oregon, up as high as 3300 m (10,000 feet) in the southern Cascades, and above 610 m (2000 feet) in northern Washington. Surrounding habitats include subalpine parklands and montane forests. In Washington, they are defined as occurring primarily above the Tsuga heterophylla zone, i.e., beginning at or near the lower boundary of the Abies amabilis zone.
Source: NatureServe Explorer
Dynamics
This is a disturbance-driven system that requires flooding, scour and deposition for germination and maintenance. It occurs on streambanks where the vegetation is significantly different than surrounding forests, usually because of its shrubby or deciduous character.
Source: NatureServe Explorer
Distribution
This system occurs throughout mountainous areas of the Pacific Northwest Coast, both on the mainland and on larger islands, above 1500 m (4550 feet) elevation in the Klamath Mountains and western Cascades, up as high as 3300 m (10,000 feet) in the southern Cascades, and above 610 m (2000 feet) in northern Washington.
Source: NatureServe Explorer
Ecologically Associated Plant Species

Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.

Tree canopy

Abies amabilis, Abies concolor var. lowiana, Abies magnifica, Pinus contorta var. murrayana, Populus balsamifera ssp. trichocarpa, Populus tremuloides, Pseudotsuga menziesii, Tsuga heterophylla

Shrub/sapling (tall & short)

Acer circinatum, Alnus incana ssp. tenuifolia, Alnus rubra, Alnus viridis ssp. crispa, Alnus viridis ssp. sinuata, Oplopanax horridus, Ribes bracteosum, Rubus spectabilis, Salix scouleriana

Herb (field)

Maianthemum stellatum, Penstemon eriantherus var. whitedii, Petasites frigidus, Sidalcea oregana var. calva

Nonvascular

Rivulariella gemmipara
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (15)

Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.

Mammals (7)

Common NameScientific NameG-Rank
Mountain BeaverAplodontia rufaG5
North American Water VoleMicrotus richardsoniG5
American ErmineMustela richardsoniiG5
Long-tailed WeaselNeogale frenataG5
a dusky shrewSorex obscurusG5
American Water ShrewSorex palustrisG5
Vagrant ShrewSorex vagransG5

Amphibians (2)

Common NameScientific NameG-Rank
Oregon Slender SalamanderBatrachoseps wrightiG3
Oregon Spotted FrogRana pretiosaG2

Insects (3)

Common NameScientific NameG-Rank
Scott's CaddisflyAllomyia scottiG1
Hatch's Click BeetleEanus hatchiG1
Blind Carabid BeetlePterostichus rothiG2?

Molluscs (1)

Common NameScientific NameG-Rank
Broadwhorl Tightcoil SnailPristiloma johnsoniG3

Other (2)

Common NameScientific NameG-Rank
Panther Jumping-slugHemphillia pantherinaG1
Pacific Jumping MouseZapus trinotatusG5
Source: NatureServe Ecological System assessment
At-Risk Species Associated with this Ecosystem (10)

Species with conservation concern that are ecologically associated with this ecosystem type. G-Rank indicates global conservation status: G1 (critically imperiled) through G5 (secure). ESA status indicates U.S. Endangered Species Act listing.

Common NameScientific NameG-RankESA Status
Scott's CaddisflyAllomyia scottiG1--
Oregon Slender SalamanderBatrachoseps wrightiG3--
Hatch's Click BeetleEanus hatchiG1--
Panther Jumping-slugHemphillia pantherinaG1--
Crested-tongue BeardtonguePenstemon eriantherus var. whitediiG4G5T2--
Broadwhorl Tightcoil SnailPristiloma johnsoniG3--
Blind Carabid BeetlePterostichus rothiG2?--
Oregon Spotted FrogRana pretiosaG2Threatened
a liverwortRivulariella gemmiparaG2--
Wanatchee Mountains Checker-mallowSidalcea oregana var. calvaG5T1Endangered
Source: NatureServe Ecological System assessment
Component Associations (18)

Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.

NameG-Rank
Alnus incana / Athyrium filix-femina Wet ShrublandG3 NatureServe
Alnus incana / Cornus sericea Wet ShrublandG3 NatureServe
Alnus incana / Equisetum arvense Wet ShrublandG3 NatureServe
Alnus incana / Mesic Forbs Wet ShrublandG3 NatureServe
Alnus incana / Spiraea douglasii Wet ShrublandG3 NatureServe
Alnus incana / Symphoricarpos albus Wet ShrublandG3 NatureServe
Alnus incana Wet ShrublandGNR NatureServe
Alnus viridis ssp. sinuata / Athyrium filix-femina - Cinna latifolia Wet ShrublandG4 NatureServe
Alnus viridis ssp. sinuata / Oplopanax horridus Shrub SwampG4 NatureServe
Betula glandulosa / Carex utriculata Shrub FenG4 NatureServe
Salix boothii / Carex utriculata Wet ShrublandG4 NatureServe
Salix (boothii, geyeriana) / Carex aquatilis Wet ShrublandG3 NatureServe
Salix boothii - Salix eastwoodiae / Carex nigricans Wet ShrublandG3 NatureServe
Salix boothii - Salix geyeriana / Carex angustata Wet ShrublandG2 NatureServe
Salix boothii - Salix lemmonii Wet ShrublandG3 NatureServe
Salix commutata / Carex scopulorum Wet ShrublandG3 NatureServe
Salix drummondiana / Carex utriculata Wet ShrublandG4 NatureServe
Salix sitchensis / Equisetum arvense - Petasites frigidus Wet ShrublandG4 NatureServe
State Conservation Ranks (2)

Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.

StateS-Rank
ORSNR
WASNR
Roadless Areas (61)

Inventoried Roadless Areas where this ecosystem is present, identified from LANDFIRE 2024 Existing Vegetation Type spatial analysis. Coverage indicates the proportion of each area occupied by this ecosystem type.

California (4)

AreaForestCoverageHectares
Timbered CraterLassen National Forest4.7%78.3
Trail LakeLassen National Forest2.5%11.25
Heart LakeLassen National Forest2.0%75.33
Snow MountainLassen National Forest1.9%16.38

Oregon (36)

AreaForestCoverageHectares
Waldo - LakeWillamette National Forest10.5%127.44
Frog CampWillamette National Forest9.2%18.27
WaldoDeschutes National Forest7.0%140.22
CharltonDeschutes National Forest6.0%171.18
Buck CreekFremont National Forest5.9%234.99
Maiden PeakWillamette National Forest5.0%192.87
Sky Lakes AWinema National Forest4.8%77.22
BadlandsWinema National Forest4.2%14.04
SherwoodUmpqua National Forest3.9%38.34
OlallieMt. Hood National Forest3.7%115.02
HuckleberryWillamette National Forest3.4%10.8
SherwoodRogue River National Forests3.3%94.23
Bend WatershedDeschutes National Forest3.1%185.58
Thirsty Creek AppendageUmpqua National Forest3.1%28.08
AntlerFremont National Forest3.0%66.69
Brown Mt.Winema National Forest2.7%34.56
Rolling Grounds AppendageUmpqua National Forest2.7%21.42
Coleman RimFremont National Forest2.5%108.09
Roaring RiverWillamette National Forest2.4%20.79
Maiden PeakDeschutes National Forest2.2%240.39
Sky Lakes BWinema National Forest2.2%85.59
Mt. JeffersonDeschutes National Forest2.0%18.09
Waldo - FujiWillamette National Forest2.0%121.05
Twin LakesMt. Hood National Forest1.6%39.78
Gordon MeadowsWillamette National Forest1.5%57.69
Bulldog RockUmpqua National Forest1.4%35.1
Wind CreekMt. Hood National Forest1.4%30.33
Roaring RiverMt. Hood National Forest1.2%131.4
DoneganUmpqua National Forest1.2%27.9
Echo MountainWillamette National Forest1.0%33.39
Hanan TrailFremont National Forest1.0%32.94
West - South BachelorDeschutes National Forest1.0%104.04
Three SistersDeschutes National Forest1.0%30.15
Mt. Hood AdditionsMt. Hood National Forest0.9%49.59
Crane MountainFremont National Forest0.8%75.51
Mt. BaileyUmpqua National Forest0.6%48.15

Washington (21)

AreaForestCoverageHectares
South MidwayGifford Pinchot National Forest7.8%74.88
HorseshoeGifford Pinchot National Forest5.3%161.19
ChambersGifford Pinchot National Forest3.0%24.66
ManastashWenatchee National Forest3.0%135.72
Wodouglas Adj.Wenatchee National Forest2.2%162.63
Gotchen CreekGifford Pinchot National Forest2.1%63.18
NaneumWenatchee National Forest2.0%36.54
TiffanyOkanogan National Forest1.7%151.29
Long SwampOkanogan National Forest1.6%423.36
Norse PeakWenatchee National Forest1.0%41.67
Granite MountainOkanogan National Forest0.8%85.05
Glacier Peak IMt Baker-Snoqualmie National Forest0.7%42.12
Thorp Mtn.Wenatchee National Forest0.7%60.03
Dark DivideGifford Pinchot National Forest0.6%138.06
Eagle RockMt Baker-Snoqualmie National Forest0.5%75.15
Alpine Lakes Adj.Wenatchee National Forest0.5%121.05
TeanawayWenatchee National Forest0.5%146.7
Liberty BellOkanogan National Forest0.4%175.77
Glacier Peak KMt Baker-Snoqualmie National Forest0.4%74.7
EntiatWenatchee National Forest0.4%105.21
SawtoothOkanogan National Forest0.3%132.84
Methodology and Data Sources

Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.

Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.

Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.

IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.

Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.

State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.