Betula occidentalis Shrubland Alliance
Water birch thicket

USDA Ecological Section Map

Summary Information

  • Primary Life FormShrub
  • Elevation600-2500 m
  • State RarityS2.2
  • Global RarityG4
  • DistributionCAN: AB. USA: CA, CO, ID, MT, NM, NV, OR, SD, UT, WA, WY (NatureServe)
  • Endemic to CaliforniaNo
  • Endemic to California Floristic Province and DesertsNo
  • Date Added1995/11/01

Characteristic Species

Betula occidentalis is dominant or co-dominant in the tall shrub or low tree canopy with Acer negundo, Alnus spp., Artemisia tridentata ssp. vaseyana, Cornus sericea, Pinus jeffreyi, Pinus monophylla, Populus fremontii, Populus tremuloides, Populus trichocarpa, Prunus virginiana, Rosa woodsii and Salix spp. If B. occidentalis is shrubby, emergent trees may be present at low cover.

Vegetation Layers

Otherwise, low trees < 30 m; canopy is intermittent to continuous. Shrubs are typically sparse if the birch forms a low tree canopy. Herbaceous layer is sparse.

Membership Rules

  • Betula occidentalis > 25% cover in the tall shrub or short tree canopy (NatureServe 2007).


Intermittently, seasonally, temporarily flooded, saturated stream banks, alluvial terraces, and seeps. Soils are bouldery and gravelly sands and loams. The USFWS Wetland Inventory (1996 national list) recognizes Betula occidentalis as a FACW plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) Water birch series
NVCS (2009) Betula occidentalis intermittently flooded shrubland alliance, Betula occidentalis seasonally flooded shrubland alliance, Betula occidentalis temporarily flooded shrubland alliance
Calveg Water birch, Riparian mixed shrub, Riparian mixed hardwood, Cottonwood-Alder, Willow
Holland Modoc-Great Basin riparian forest, Modoc-Great Basin riparian scrub
Munz Not treated
WHR Montane riparian
CDFW CA Code 63.610.00

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 Great Basin montane riparian scrub