Alnus incana Shrubland Alliance
Mountain alder thicket

USDA Ecological Section Map

Summary Information

  • Primary Life FormShrub
  • Elevation1200-2925 m
  • State RarityS3
  • Global RarityG4
  • DistributionCAN: BC, MB, NB, NS, ON, PE, QC. USA: CA, CO, CT, IA, ID, IL, IN, MA, ME, MI, MN, MT, ND, NH, NJ, NM, NV, NY, OH, OR, PA, RI, UT, VT, WA, WI, WV, WY. Mexico (NatureServe)
  • Endemic to CaliforniaNo
  • Endemic to California Floristic Province and DesertsNo
  • Date Added1995/11/01

Characteristic Species

Alnus incana is dominant or co-dominant in the shrub canopy with Acer glabrum, Cornus sericea, Salix jepsonii, Salix lemmonii, Salix melanopsis, Salix planifolia, Salix prolixa and Salix scouleriana. Emergent trees may be present at low cover, including Abies concolor, Pinus contorta ssp. murrayana, Pinus jeffreyi, Pinus ponderosa, Populus spp. or Salix spp.

Vegetation Layers

Shrubs < 10 m; canopy is intermittent to continuous. Herbaceous layer is variable and usually includes forbs, ferns, and grasses.

Membership Rules

  • Alnus incana > 25% absolute cover in the small tree layer, where it usually dominates (Manning and Padgett 1995).
  • Alnus incana > 5% absolute cover in the shrub layer where it dominates (Potter 2005).


Montane streamsides, seeps, springs, and pond and lake margins. The USFWS Wetland Inventory (1996 national list) recognizes Alnus incana spp. tenuifolia as an OBL+ plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) Montane wetland shrub habitat, Mountain alder series
NVCS (2009) Alnus incana seasonally flooded shrubland alliance, Alnus incana temporarily flooded shrubland alliance
Calveg Riparian mixed shrub, Mountain alder
Holland Montane riparian scrub
Munz Not treated
WHR Montane riparian
CDFW CA Code 63.210.00

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 Western North American montane-subalpine riparian scrub