The forest communities of Mount Rainier National Park

The forests of Mount Rainier National Park are a major natural re-source. They extend up the mountain slopes to an elevation of about1800 m (5,800 ft) and occupy 60% of the Park landscape. This phy-tosociological study, conducted during 1975-80, has provided a de-tailed description and classification of these forests for the use of parkmanagers and visitors. The forests lie within three zones based uponthe major climax tree species: Tsuga heterophvlla, Abies amabilis, andTsuga mertensiana. A total of 14 plant associations and 5 communitytypes were recognized across the range of environmental conditionsrepresented within the Park. The moist forest types have rich understo-ries that include numerous herbaceous species and shrubs such as
Oplopanax horridum. The Abies amabilislVaccinium alaskaense
Association is typical of modal environments and the most extensiveformation within the Park. Dry associations are typified by Gaultheriashallon- and Berberis nervosa-dominated understories. High-elevationforest types belong to the cold grouping and are typified by herbaceousunderstories on better drained sites and by dense understories ofericaceous shrubs on wet sites. Forest types show strong relations withelevation and landform, although details vary in the four Park quad-rants. Moisture, temperature, and duration of snowpack appear to bethe primary environmental variables. Wildfire has been the major forestdisturbance; approximately 90% of the forests have arisen after fire, 7%after avalanche, and 2% after lahars. The natural fire rotation was cal-culated as being 465 years before white settlement of the region. Cli-matic episodes appear to have been important in creating conditions forwildfire. Uses of the forest type classification by managers include in-terpretations of the potential value of sites for development, productiv-ity and resilience, value for wildlife, and visitor interest. Large color-keyed maps (Plates 1 and 2) are included on the inside back cover toshow the distribution of the plant associations and major forest ageclasses within the Park.