A preliminary classification of forest communities in the central portion of the western Cascades in Oregon

Forest communities in the central portion of Oregon's western Cascades are arrayed along moisture and temperature gradients. With the aid of reconnaissance data and a computerized ordination technique, 23 forest communities have been provisionally recognized in two distinct forest zones, the Tsuga heterophylla (300 to 1050 m in elevation) and the Abies amabilis (1050 to 1550 m). The location of these zones is largely a function of temperature (elevation), while distribution of individual communities within a zone is controlled mainly by moisture availability.\ud Eleven climax or near-climax associations and three seral communities were recognized within the Tsuga heterophylla zone. Associations range from the Pseudotsuga/Holodiscus on very dry sites to the Tsuga/Polystichum-Oxalis on wet sites. In the Abies amabilis zone, nine units were identified--seven climax or near-climax associations and two seral communities.\ud Driest habitats in the zone are occupied by the Abies--Tsuga mertensiana/\ud Xerophyllum association and wettest sites support the Chamaeeyparis/Oplopanax association. Characteristics of all 23 forest communities are described and relationships among them are discussed