MOUNT RAINIER The Forest Communities of Mount Rainier National Park

The forests of Mount Rainier National Park are a major natural resource. They extend up the mountain slopes to an elevation of about 1800 m (5,800 ft) and occupy 60% of the Park landscape. This phytosociological study, conducted during 1975-80, has provided a detailed description and classification of these forests for the use of park managers and visitors. The forests lie within three zones based upon the major climax tree species: Tsuga heterophylla, Abies amabilis, and Tsuga mertensiana. A total of 14 plant associations and 5 community types were recognized across the range of environmental conditions represented within the Park. The moist forest types have rich understories that include numerous herbaceous species and shrubs such as Oplopanax horridum. The Abies amabilis/Vaccinium alaskaense Association is typical of modal environments and the most extensive formation within the Park. Dry associations are typified by Gaultheria shallon and Berberis nervosa-dominated understories. High-elevation forest types belong to the cold grouping and are typified by herbaceous understories on better drained sites and by dense understories of ericaceous shrubs on wet sites. Forest types show strong relations with elevation and landform, although details vary in the four Park quadrants. Moisture, temperature, and duration of snowpack appear to be the primary environmental variables. Wildfire has been the major forest disturbance; approximately 90% of the forests have arisen after fire, 7% after avalanche, and 2% after lahars. The natural fire rotation was calculated as being 465 years before white settlement of the region. Climatic episodes appear to have been important in creating-conditions for wildfire. Uses of the forest type classification by managers include interpretations of the potential value of sites for development, productivity and resilience, value for wildlife, and visitor interest. Large color-keyed maps (Plates 1 and 2) are included on the inside back cover to show the distribution of the plant associations and major forest age classes within the Park.