10 



NORTH AMERICAN FAUNA 70 



menziesii, Pinus lambertiana, P. ponderosa, Libocedrus decurrens, and 

 Abies concolor. Ornithological investigations in these areas, especially 

 the Siskiyou Mountains, are insufficient to compare the ecological 

 aspects between these two plant communities. 



True Fir Forest. — True firs occupy a narrow band of the Cascade 

 Mountains above 1,372 m to about timberline (Fig. 6). Dominant 

 species are Abies magnijica shastensis, A. concolor, and A. procera. 

 Associated species are Tsuga mertensiana, Pinus contorta, Sorbus occi- 

 dentalis, and Viburnum pauciflorum. Abies magnijica shastensis is a 

 dominant species in the Siskiyou Mountains (Fig. 7) from about 1,798 

 to 2,012 m (Waring 1969). 



Timberline Forest. — The highest elevations of Jackson County 

 are typically forested by small subalpine forests; two Cascade 

 Mountain peaks (Mount McLoughlin and Brown Mountain) are 

 above timberline (Fig. 6). Pinus albicaulis, Tsuga mertensiana, Abies 

 lasiocarpa, Cassiope spp., and Phyllococe spp. are the dominant plants 

 above about 1,829 m. Juniperus communis, Pinus monticola, Cassiope 

 spp., and Phyllodoce spp. are dominant plants in the higher Siskiyou 

 Mountains. The Timberline Forest includes the Tsuga mertensiana 

 Zone and the Alpine Zone of Franklin and Dyrness (1973). 



Fig. 6. True Fir Forest near Lake of the Woods (Klamath County) at 1,524 m. 

 The summit of Mount McLoughlin is in the background. 



