The mountain forests of british columbia and the american northwest: Floristic patterns and syntaxonomy

An overview of the montane and subalpine forests ofAbies lasiocarpa, Picea engelmannii, Abies amabilis andTsuga mertensiana of northwestern North America is provided based on 541 relevés of forest vegetation from coastal and inland British Columbia, Washington and northwestern Montana. A new classification is proposed based on an examination of the floristic patterns across these communities. Owing to their broadscale floristic similarities, coastal subalpineAbies amabilis-Tsuga mertensiana forests and inland forests ofAbies lasiocarpa, Picea engelmannii, P. glauca, Thuja plicata andTsuga heterophylla are combined into a single order,Thujetalia plicatae. The floristic patterns within this order in turn support the recognition of four alliances. These are (1)Tsugion mertensianae, including coastal and inland subalpine forests ofTsuga mertensiana, Abies amabilis, A. lasiocarpa andPicea engelmannii, with deep winter snowpacks and an often luxuriously developed shrub layer; (2)Abieti-Tsugion heterophyllae all. nov., including mesic inland montaneThuja plicata-Tsuga heterophylla andAbies lasiocarpa-Picea engelmannii forests and related southern borealAbies lasiocarpa-Picea glauca communities; (3)Gymnocarpio-Abietion lasiocarpae, including moist coastal and inland forests dominated by a fern-rich understory andOplopanax horridus; and (4)Lysichito-Chamaecyparidion nootkatensis, which includes wet coastal subalpine forests withLysichiton americanum. A total of five new associations are described, bringing the number of recognized associations within the order to twenty-five. An extensive synonymy and crosswalk to other classification systems is provided.