Pacific Northwest Alpine Dry Grassland

EVT 7171North Pacific Alpine and Subalpine Dry Grassland
CES204.099GNRHerbGrassland
Summary
This high-elevation, grassland system is dominated by perennial grasses and forbs found on dry sites, particularly south-facing slopes, typically imbedded in or above subalpine forests and woodlands. Disturbance such as fire also plays a role in maintaining these open grassy areas, although drought and exposed site locations are primary characteristics limiting tree growth. It is most extensive in the eastern Cascades, although it also occurs in the Olympic Mountains. Alpine and subalpine dry grasslands are small openings to large open ridges above or drier than high-elevation conifer trees. In general, soil textures are much finer, and soils are often deeper under grasslands than in the neighboring forests. These grasslands, although composed primarily of tussock-forming species, do exhibit a dense sod that makes root penetration difficult for tree species. Typical dominant species include Festuca idahoensis ssp. idahoensis, Festuca viridula, and Festuca idahoensis ssp. roemeri (the latter occurring only in the Olympic Mountains). This system is similar to Northern Rocky Mountain Subalpine-Upper Montane Grassland (CES306.806), differing in its including dry alpine habitats, more North Pacific floristic elements, greater snowpack, and higher precipitation.
Source: NatureServe Explorer
Distribution
This system occurs only in the Pacific Northwest mountains (Coastal and westside Cascadian).
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.

Herb (field)

Astragalus australis var. olympicus, Boechera horizontalis, Eriophyllum lanatum var. lanatum, Festuca idahoensis, Festuca roemeri, Festuca viridula, Synthyris lanuginosa

Nonvascular

Ramaria coulterae, Rhizopogon atroviolaceus
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (6)

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 (5)

Common NameScientific NameG-Rank
Snowshoe HareLepus americanusG5
Long-tailed VoleMicrotus longicaudusG5
Montane VoleMicrotus montanusG5
North American DeermousePeromyscus maniculatusG5
Northern Pocket GopherThomomys talpoidesG5

Amphibians (1)

Common NameScientific NameG-Rank
Crater Lake NewtTaricha granulosa mazamaeG5T1Q
Source: NatureServe Ecological System assessment
At-Risk Species Associated with this Ecosystem (6)

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
Cotton's MilkvetchAstragalus australis var. olympicusG5T1--
Crater Lake RockcressBoechera horizontalisG1--
a fungusRamaria coulteraeG3--
a fungusRhizopogon atroviolaceusG3--
Cutleaf SynthyrisSynthyris lanuginosaG2--
Crater Lake NewtTaricha granulosa mazamaeG5T1QUnder Review
Source: NatureServe Ecological System assessment
Component Associations (4)

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
Festuca rubra Montane MeadowG2 NatureServe
Festuca viridula - Eucephalus (engelmannii, ledophyllus) MeadowG4 NatureServe
Festuca viridula - Festuca idahoensis MeadowG2 NatureServe
Festuca viridula - Lupinus latifolius MeadowG4 NatureServe
State Conservation Ranks (1)

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
WASNR
Roadless Areas (44)

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.

Oregon (4)

AreaForestCoverageHectares
OlallieMt. Hood National Forest16.1%495.09
Three SistersDeschutes National Forest4.4%136.08
Waldo - FujiWillamette National Forest0.9%55.71
Mt. Hood AdditionsMt. Hood National Forest0.7%38.43

Washington (40)

AreaForestCoverageHectares
Gotchen CreekGifford Pinchot National Forest15.2%461.52
Wodouglas Adj.Wenatchee National Forest10.4%755.01
Pasayten RimOkanogan National Forest10.2%701.82
EntiatWenatchee National Forest9.2%2,697.66
ChelanWenatchee National Forest8.4%2,548.53
SawtoothOkanogan National Forest8.4%4,143.87
Myrtle LakeWenatchee National Forest8.2%370.35
Long SwampOkanogan National Forest8.0%2,134.53
Glacier Peak AMt Baker-Snoqualmie National Forest7.4%11.7
Canyon CreekWenatchee National Forest7.4%237.87
TiffanyOkanogan National Forest7.2%643.86
Norse PeakMt Baker-Snoqualmie National Forest6.3%234.27
Hidden LakeMt Baker-Snoqualmie National Forest4.2%110.07
Lion RockWenatchee National Forest4.1%77.58
Stormy Mtn.Wenatchee National Forest4.0%531.81
Liberty BellOkanogan National Forest3.7%1,610.91
Rock CreekWenatchee National Forest3.6%472.68
NaneumWenatchee National Forest3.4%62.37
Granite MountainOkanogan National Forest3.0%333.81
ManastashWenatchee National Forest2.7%122.04
Mt. Baker MaMt Baker-Snoqualmie National Forest2.6%261.54
Glacier Peak HMt Baker-Snoqualmie National Forest2.4%99.63
Nason RidgeWenatchee National Forest2.2%174.51
TeanawayWenatchee National Forest2.0%589.95
Alpine Lakes Adj.Wenatchee National Forest1.8%416.61
Blue SlideWenatchee National Forest1.7%119.25
Heather LakeWenatchee National Forest1.6%70.38
Jefferson RidgeOlympic National Forest1.6%41.22
Glacier Peak JMt Baker-Snoqualmie National Forest1.4%152.73
Twin LakesWenatchee National Forest1.4%129.24
Goat Rocks AdjWenatchee National Forest1.4%33.75
Glacier Peak BMt Baker-Snoqualmie National Forest1.3%100.44
Norse PeakWenatchee National Forest1.2%50.85
Alma CopperMt Baker-Snoqualmie National Forest1.2%39.06
Eagle RockMt Baker-Snoqualmie National Forest1.1%153.63
Glacier Peak GMt Baker-Snoqualmie National Forest0.9%30.42
Mt. Baker NorthMt Baker-Snoqualmie National Forest0.8%54.81
Mt. Baker Noisy - DiobsudMt Baker-Snoqualmie National Forest0.7%168.3
Mt. Baker WestMt Baker-Snoqualmie National Forest0.6%65.79
Boulder RiverMt Baker-Snoqualmie National Forest0.6%74.16
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.