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Northern Rockies Conifer Swamp

EVT 7161Northern Rocky Mountain Conifer Swamp

CES306.803GNRTreeRiparian

Summary

This ecological system occurs in the northern Rocky Mountains from northwestern Wyoming north into the Canadian Rockies and west into eastern Oregon and Washington. It is dominated by conifers on poorly drained soils that are saturated year-round or may have seasonal flooding in the spring. These are primarily on flat to gently sloping lowlands, but also occur up to near the lower limits of continuous forest (below the subalpine parkland). It can occur on steeper slopes where soils are shallow over unfractured bedrock. This system is indicative of poorly drained, mucky areas, and areas are often a mosaic of moving water and stagnant water. Soils can be woody peat, muck or mineral but tend toward mineral. Stands generally occupy sites on benches, toeslopes or valley bottoms along mountain streams. Associations present include wetland phases of Thuja plicata, Tsuga heterophylla, and Picea engelmannii forests. The wetland types are generally distinguishable from other upland forests and woodlands by shallow water tables and mesic or hydric undergrowth vegetation; some of the most typical species include Athyrium filix-femina, Dryopteris spp., Lysichiton americanus, Equisetum arvense, Senecio triangularis, Mitella breweri, Mitella pentandra, Streptopus amplexifolius, Calamagrostis canadensis, or Carex disperma.

Source: NatureServe Explorer

Vegetation

Associations present include wetland phases of Thuja plicata, Tsuga heterophylla, and Picea engelmannii forests. The wetland types are generally distinguishable from other upland forests and woodlands by shallow water tables and mesic or hydric undergrowth vegetation; some of the most typical species include Athyrium filix-femina, Dryopteris spp., Lysichiton americanus, Equisetum arvense, Senecio triangularis, Mitella breweri, Mitella pentandra, Streptopus amplexifolius, Calamagrostis canadensis, or Carex disperma.

Source: NatureServe Explorer

Environment

Stands occur on poorly drained soils that are saturated year-round or may have seasonal flooding in the spring. These are primarily on flat to gently sloping lowlands, but also occur up to near the lower limits of continuous forest (below the subalpine parkland). It can occur on steeper slopes where soils are shallow over unfractured bedrock. This system is indicative of poorly drained, mucky areas, and areas are often a mosaic of moving water and stagnant water. Soils can be woody peat, muck or mineral but tend toward mineral. Stands generally occupy sites on benches, toeslopes or valley bottoms along mountain streams.

Source: NatureServe Explorer

Distribution

This system occurs in the northern Rocky Mountains from northwestern Wyoming and central Montana, north into the Canadian Rockies and west into eastern Oregon and 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

Picea engelmannii, Pinus contorta, Thuja plicata, Tsuga heterophylla

Herb (field)

Athyrium filix-femina, Calamagrostis canadensis, Carex disperma, Equisetum arvense, Lysichiton americanus, Mitella breweri, Mitella pentandra, Senecio triangularis, Streptopus amplexifolius

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 (3)

Common Name	Scientific Name	G-Rank
Cinereus Shrew	Sorex cinereus	G5
a dusky shrew	Sorex obscurus	G5
American Water Shrew	Sorex palustris	G5

Source: NatureServe Ecological System assessment

Component Associations (13)

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 - Picea engelmannii / Oplopanax horridus Swamp	G3	NatureServe
Abies lasiocarpa - Picea engelmannii / Streptopus amplexifolius Riparian Forest	G4	NatureServe
Betula glandulosa / Carex spp. Wet Shrubland	GNR	NatureServe
Betula glandulosa / Carex utriculata Shrub Fen	G4	NatureServe
Picea engelmannii / Calamagrostis canadensis Swamp	G4	NatureServe
Picea engelmannii / Caltha leptosepala Swamp	G3	NatureServe
Picea engelmannii / Equisetum arvense Swamp	G4	NatureServe
Picea (x albertiana, engelmannii) / Carex disperma Swamp	G2	NatureServe
Picea (x albertiana, engelmannii) / Lysichiton americanus Swamp	G2	NatureServe
Thuja plicata / Athyrium filix-femina Swamp	G3	NatureServe
Thuja plicata / Carex disperma Swamp	G2	NatureServe
Thuja plicata - Tsuga heterophylla / Lysichiton americanus / Sphagnum spp. Treed Fen	G3	NatureServe
Thuja plicata - Tsuga heterophylla / Oplopanax horridus Rocky Mountain Swamp	G3	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
ID	SNR
MT	SNR
OR	SNR
WA	SNR
WY	SNR

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.