This tall shrubland system occurs throughout mountainous regions of the Pacific Northwest, from the southern Cascades and Coast Ranges north into the mountains of British Columbia. This system occurs on sideslopes of mountains on glacial till or colluvium. These habitats range from moderately xeric to wet and occur on snow avalanche chutes at montane elevations. In the mountains of Washington, talus sites and snow avalanche chutes very often coincide spatially. On the west side of the Cascades, the major dominant species are Acer circinatum, Alnus viridis ssp. sinuata, Rubus parviflorus, and small trees, especially Chamaecyparis nootkatensis. Forbs, grasses, or other shrubs can also be locally dominant. Prunus virginiana, Amelanchier alnifolia, Vaccinium membranaceum or Vaccinium scoparium, and Fragaria spp. are common species on drier avalanche tracks on the east side of the Cascades. The main feature of this system is that it occurs on steep, frequently disturbed (snow avalanches) slopes. Avalanche chutes can be quite long, extending from the subalpine into the montane and foothill toeslopes.
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