Populus trichocarpa Forest & Woodland Alliance
Black cottonwood forest and woodland

USDA Ecological Section Map

Summary Information

  • Primary Life FormTree
  • Elevation0-2800 m
  • State RarityS3
  • Global RarityG5
  • DistributionCAN: AB, BC. USA: AK, CA, ID, MT, NV, OR, WA, WY (NatureServe)
  • Endemic to CaliforniaNo
  • Endemic to California Floristic Province and DesertsNo
  • Date Added1995/11/01

Characteristic Species

Populus trichocarpa is dominant or co-dominant in the tree canopy with Abies concolor, Acer macrophyllum, Acer negundo, Alnus incana, Alnus rhombifolia, Alnus rubra, Fraxinus latifolia, Juniperus occidentalis, Morella californica, Pinus contorta ssp. murrayana, Pinus jeffreyi, Platanus racemosa, Populus fremontii, Populus tremuloides, Quercus agrifolia, Salix exigua, Salix hookeriana, Salix laevigata, Salix lasiolepis, Salix lucida ssp. lasiandra, Salix lutea and Salix scouleriana.

Vegetation Layers

Trees < 30 m; canopy is intermittent or continuous. Shrub layer is open to continuous. Herbaceous layer is sparse or abundant, especially with forbs.

Membership Rules

  • Populus trichocarpa conspicuous with > 5% absolute cover and > 30% relative cover in the tree canopy (Potter 2005).


Seasonally flooded and permanently saturated soils on stream banks and alluvial terraces. The USFWS Wetland Inventory (1996 national list) recognizes Populus balsamifera ssp. trichocarpa as a FACW plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) Black cottonwood series
NVCS (2009) Populus balsamifera ssp. trichocarpa temporarily flooded forest alliance, Populus balsamifera ssp. trichocarpa temporarily flooded woodland alliance
Calveg Black cottonwood
Holland North Coast black cottonwood riparian forest, Montane black cottonwood riparian forest
Munz Not treated
WHR Montane riparian, Valley foothill riparian
CDFW CA Code 61.120.00

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