Pacific Northwest Wooded Lava Flow

EVT 7173North Pacific Wooded Volcanic Flowage
CES204.883GNRTreeConifer
Summary
This ecological system is found from foothill to subalpine elevations and includes woodland to sparsely vegetated landscapes (generally >10% plant cover) on recent lava flows, excessively well-drained lahars, debris avalanches and pyroclastic flows. The characteristic feature of this system is the substrate limiting characteristic that creates an environment for a more open vegetation than the surrounding closed matrix forest. Examples are recent lava flows (3500-8200 years ago) on the north side of Mount Adams (andecite) and the big lava beds (basalt) south of Indian Heaven west of Mount Adams, Washington, and lahars (200-2000 years old) at Old Maid Flat west of Mount Hood, Oregon. These areas support open to sparse tree cover; characteristic species include Pseudotsuga menziesii, Pinus contorta, Pinus monticola, and Abies lasiocarpa. Tree cover can range from scattered (5%) up to 70% or occasionally even more. There may be scattered to dense shrubs present, such as Acer circinatum, Vaccinium membranaceum, Arctostaphylos uva-ursi (very characteristic), Mahonia nervosa, Amelanchier alnifolia, and Xerophyllum tenax. Soil development is limited, and mosses and lichens often cover the soil or rock surface.
Source: NatureServe Explorer
Distribution
This uncommon system is found in the east and west Cascades of Washington and Oregon, and may occur in small patches in northern California in the vicinity of Mount Lassen or Mount Shasta.
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, Pinus contorta, Pinus monticola, Pseudotsuga menziesii

Shrub/sapling (tall & short)

Acer circinatum, Amelanchier alnifolia, Berberis nervosa, Vaccinium membranaceum

Short shrub/sapling

Arctostaphylos uva-ursi

Herb (field)

Xerophyllum tenax

Nonvascular

Bryoria pikei, Gastroboletus vividus, Rhizopogon atroviolaceus
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (5)

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 NameScientific NameG-Rank
Bushy-tailed WoodratNeotoma cinereaG5

Birds (2)

Common NameScientific NameG-Rank
Common RavenCorvus coraxG5
Rock WrenSalpinctes obsoletusG5

Amphibians (1)

Common NameScientific NameG-Rank
Crater Lake NewtTaricha granulosa mazamaeG5T1Q

Butterflies & Moths (1)

Common NameScientific NameG-Rank
Leona's Little Blue ButterflyPhilotiella leonaG1
Source: NatureServe Ecological System assessment
At-Risk Species Associated with this Ecosystem (4)

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
a fungusGastroboletus vividusG3--
Leona's Little Blue ButterflyPhilotiella leonaG1--
a fungusRhizopogon atroviolaceusG3--
Crater Lake NewtTaricha granulosa mazamaeG5T1QUnder Review
Source: NatureServe Ecological System assessment
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 (13)

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 (3)

AreaForestCoverageHectares
MayfieldLassen National Forest62.2%3,634.11
Timbered CraterLassen National Forest42.2%699.57
LavaLassen National Forest28.3%683.82

Oregon (7)

AreaForestCoverageHectares
Mt. JeffersonDeschutes National Forest3.1%28.53
WaldoDeschutes National Forest3.0%59.4
Brown Mt.Winema National Forest2.1%26.1
SherwoodRogue River National Forests1.7%48.06
West - South BachelorDeschutes National Forest1.4%147.78
Mt. BaileyUmpqua National Forest0.7%52.29
Roaring RiverMt. Hood National Forest0.6%70.29

Washington (3)

AreaForestCoverageHectares
Big Lava BedGifford Pinchot National Forest58.5%4,505.85
HorseshoeGifford Pinchot National Forest2.2%67.59
Gotchen CreekGifford Pinchot National Forest1.4%43.47
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.