Fraxinus latifolia Forest & Woodland Alliance
Oregon ash groves

USDA Ecological Section Map

Summary Information

  • Primary Life FormTree
  • Elevation0-1700 m
  • State RarityS3.2
  • Global RarityG4
  • DistributionCAN: BC. USA: CA, OR, WA (NatureServe) (USDA Plants)
  • Endemic to CaliforniaNo
  • Endemic to California Floristic Province and DesertsNo
  • Date Added2009/09/01

Characteristic Species

Fraxinus latifolia is dominant or co-dominant in the tree canopy with Acer macrophyllum, Alnus rhombifolia, Calocedrus decurrens, Pinus ponderosa, Quercus kelloggii, Quercus wislizeni and Salix laevigata.

Vegetation Layers

Trees < 25 m; canopy is open to continuous. Shrub layer is sparse to intermittent. Herbaceous layer is variable.

Membership Rules

  • Fraxinus latifolia > 5% absolute cover and > 30% relative cover in the tree canopy (Klein et al. 2007).
  • Fraxinus latifolia > 5% absolute cover in the tree canopy (Potter 2005).
  • Fraxinus latifolia > 50% relative cover in the tree canopy, or > 30% relative cover with Alnus rhombifolia or Umbellularia californica (Buck-Diaz et al. 2021).
  • Fraxinus latifolia > 50% relative cover in the tree canopy, or > 30% relative cover with Acer negundo, Umbellularia californica, or Salix laevigata (Sikes et al. 2023).


Riparian corridors, incised canyons, seeps, stream banks, terraces. Soils are alluvial. The USFWS Wetland Inventory (1996 national list) recognizes Fraxinus latifolia as a FACW plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) White alder series
NVCS (2009) Fraxinus latifolia temporarily flooded forest alliance
Calveg Riparian mixed hardwood, White alder, Red alder
Holland North Coast riparian forests, Great Valley mixed riparian forest, White alder riparian forest, Southern sycamore-alder riparian woodland
Munz Foothill woodland
WHR Montane riparian
CDFW CA Code 61.960.00

National Vegetation Classification Hierarchy

Formation Class Mesomorphic Tree Vegetation (Forest and Woodland)
Formation Subclass Temperate Forest
Formation Temperate Flooded and Swamp Forest
Division Western North America Flooded and Swamp Forest
Macro Group Western Cordilleran montane-boreal riparian scrub
Group Vancouverian riparian deciduous forest