Home/Ecosystems/ Northern Rockies Avalanche Chute Shrubland

Northern Rockies Avalanche Chute Shrubland

EVT 7168Northern Rocky Mountain Avalanche Chute Shrubland

CES306.801GNRShrubShrubland

Summary

This ecological system occurs in the mountains throughout the northern Rockies, from Wyoming north and west into British Columbia and Alberta. It is composed of a diverse mix of deciduous shrubs or trees, and conifers found on steep, frequently disturbed slopes in the mountains. Occurrences are found on the lower portions and runout zones of avalanche tracks, and slopes are generally steep, ranging from 15-60%. Aspects vary, but are more common where unstable or heavy snowpack conditions frequently occur. Sites are often mesic to wet because avalanche paths are often in stream gullies, and snow deposition can be heavy in the run-out zones. The vegetation consists of moderately dense, woody canopy characterized by dwarfed and damaged conifers and small, deciduous trees/shrubs. Characteristic species include Abies lasiocarpa, Acer glabrum, Alnus viridis ssp. sinuata or Alnus incana, Populus balsamifera ssp. trichocarpa, Populus tremuloides, or Cornus sericea. Other common woody plants include Paxistima myrsinites, Sorbus scopulina, and Sorbus sitchensis. The ground cover is moderately dense to dense forb-rich, with Senecio triangularis, Castilleja spp., Athyrium filix-femina, Thalictrum occidentale, Urtica dioica, Erythronium grandiflorum, Myosotis asiatica, Veratrum viride, Heracleum maximum, and Xerophyllum tenax. Mosses and ferns are often present.

Source: NatureServe Explorer

Vegetation

The vegetation consists of moderately dense, woody canopy characterized by dwarfed and damaged conifers and small, deciduous trees/shrubs. Characteristic species include Abies lasiocarpa, Acer glabrum, Alnus viridis ssp. sinuata or Alnus incana, Populus balsamifera ssp. trichocarpa, Populus tremuloides, or Cornus sericea. Other common woody plants include Paxistima myrsinites, Sorbus scopulina, and Sorbus sitchensis. The ground cover is moderately dense to dense forb-rich, with Senecio triangularis, Castilleja spp., Athyrium filix-femina, Thalictrum occidentale, Urtica dioica, Erythronium grandiflorum, Myosotis asiatica (= Myosotis alpestris), Veratrum viride, Heracleum maximum (= Heracleum lanatum), and Xerophyllum tenax. Mosses and ferns are often present.

Source: NatureServe Explorer

Distribution

This ecological system occurs in the mountains throughout the northern Rockies, from Wyoming north and west into British Columbia and Alberta. It is likely to occur in the Colorado Rockies, but no association from that area have been classified as "avalanche chute" communities.

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 lasiocarpa, Acer glabrum, Populus balsamifera ssp. trichocarpa, Populus tremuloides

Shrub/sapling (tall & short)

Alnus incana, Alnus viridis ssp. sinuata, Cornus sericea, Paxistima myrsinites, Sorbus scopulina, Sorbus sitchensis

Herb (field)

Athyrium filix-femina, Erythronium grandiflorum, Heracleum maximum, Myosotis asiatica, Senecio triangularis, Thalictrum occidentale, Urtica dioica, Veratrum viride, Xerophyllum tenax

Source: NatureServe Ecological System assessment

Ecologically Associated Animals (3)

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 (1)

Common Name	Scientific Name	G-Rank
North American Deermouse	Peromyscus maniculatus	G5

Reptiles (2)

Common Name	Scientific Name	G-Rank
Terrestrial Gartersnake	Thamnophis elegans	G5
Common Gartersnake	Thamnophis sirtalis	G5

Source: NatureServe Ecological System assessment

Component Associations (7)

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.

Name	G-Rank
Abies lasiocarpa - Acer glabrum Avalanche Chute Shrubland	G5	NatureServe
Acer glabrum Avalanche Chute Shrubland	G5	NatureServe
Alnus spp. Avalanche Chute Wet Shrubland	G5	NatureServe
Alnus viridis ssp. sinuata / Athyrium filix-femina - Cinna latifolia Wet Shrubland	G4	NatureServe
Populus balsamifera ssp. trichocarpa / Cornus sericea Riparian Forest	G3	NatureServe
Populus tremuloides / Amelanchier alnifolia Avalanche Chute Shrubland	G3	NatureServe
Populus tremuloides / Cornus sericea Riparian Forest	G4	NatureServe

State Conservation Ranks (5)

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.

State	S-Rank
CO	SNR
MT	SNR
OR	SNR
WA	SNR
WY	SNR

Roadless Areas (12)

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.

Montana (12)

Area	Forest	Coverage	Hectares
Meadow Creek - Upper North Fork	Lolo National Forest	8.8%	244.62
Stevens Peak	Lolo National Forest	3.7%	9.81
Hoodoo	Lolo National Forest	2.7%	1,131.84
Scotchman Peaks (MT)	Kootenai National Forest	1.4%	303.84
Bmss Ra 1485	Flathead National Forest	1.4%	1,844.19
Standard Peak Ra 1129	Flathead National Forest	1.1%	38.25
Sheep Mountain - Stateline	Lolo National Forest	1.1%	172.53
Ten Lakes #683	Kootenai National Forest	1.1%	217.53
Thompson Seton #483	Kootenai National Forest	1.0%	115.65
Thompson Seton RA 1483	Flathead National Forest	0.9%	180.63
Cabinet Face East #671	Kootenai National Forest	0.6%	130.77
Bear - Marshall - Scapegoat - Swan	Lewis and Clark National Forest	0.2%	252.45

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.