Forest/Environment Relationships in Lassen Volcanic National Park, California, U.S.A.

Abstract

Forest types of Lassen Volcanic National Park (LVNP), California, were defined by cluster analysis and related to environmental gradients by detrended correspon- dence analysis (DCA) and mosaic diagrams. In addition, re- gression models relating basal area of common tree species to environmental variables were developed. Six forest types, largely differentiated by elevation (and secondarily by topographic setting), included Pinus jeffreyi Grev. & Balf./Abies concolor (Gord. & Glend.) Lindl. forests on rel- atively xeric sites from 1600 to 1900 m; Abies concolorl Abies magnifica A. Murr. forests on somewhat more mesic settings from 1700 to 2000 m; Chaos Jumbles/Devastated Area sites dominated by Pinus contorta Dougl. and other pines on recently geologically disturbed terrain from 1800 to 2000 m; Abies magnificalPinus monticola Dougl. forests from 2000 to 2400 m on a wide variety of topographic uplands; Pinus contorta forests from 1900 to 2200 m on lower slopes, valley bottoms, and meadow/lake margins; and Tsuga mertensiana (Bong.) Carr. woodlands from 2400 to 2600 m on the flanks of Lassen Peak. Elevation was strongly correlated with the first DCA axis (r = 0.92) and species regression models included elevation as the primary variable in five of six cases. Topographic variables were in- corporated in four species models and soil chemical proper- ties in three models, reflecting their secondary importance in controlling tree species distributions in LVNP.