6 American Midland Naturalist Monograph No. 4 



yew (Taxus brevijolta) , bigleaf maple {Acer macro phy Hum), Pacific dog- 

 wood (Cornus Nuttalli), madrone (Arbutus Menziesi), California hazel 



(Corylus rostrata var. calif omica) , redflowering currant (Ribes sangumeum) , 

 and trailing blackberry (Rubus macropetalus) . 



Above the lower belt lodgepole pine (Pinus contorta) and western white 

 pine (Pinus monticola) gradually become dominant. Pinemat manzanita 



(Arctostaphylos nevadensis) is a common species forming a shrubby ground 

 cover over considerable areas. 



Forests surrounding the crater rim, down to about 6,000 feet, are com- 

 posed primarily of mountain hemlock (Tsuga Mertensiana) and Shasta red 

 fir {Abies magnifica var. shastensis) with whitebark pine {Pinus albicauUs) 

 occurring on exposed ridges. Shrubby species common in this forest belt are 

 Crater Lake currant {Rtbes erythrocarpum) , Pacific red elder {Sambucus 

 racemosa), Rocky Mountain maple {Acer glabrum), subalpine spiraea 

 {Spiraea densiflora), low species of Vaccinium, rockspiraea {Holodiscus) , 

 and pinemat manzanita {Arctostaphylos nevadensis). Sitka alder {Alnus 

 sinuata) replaces thinleaf alder of the lower elevations along streams and 

 shrubby willows are common. 



In only a few places, as along Grayback Ridge and on the open slopes 

 above Sun Creek Valley, do shrub types cover extensive areas. Greenleaf 

 manzanita and snowbrush are common in these areas. 



Lassen Volcanic National Park 



Lassen Volcanic National Park includes the region surrounding Lassen 

 Peak from its top at 10,453 feet down to about 5,100 feet elevation. Mount 

 Lassen is the southernmost of a series of volcanic cones extending along the 

 Cascade Mountains and is the only recently active volcano in the continental 

 United States. Although there are magnificent forests clothing the lower 

 sides of the peak, most of the higher country is a barren waste due to rela- 

 tively recent volcanic eruptions. 



The forest, up to about 7,500 feet, is mainly in the Canadian Life Zone 

 with Jeffrey pine {Pinus Jejfreyi), white fir {Abies concolor), and western 

 white pine {Pinus monticola) the dominant species in the lower part of the 

 zone and California red fir {Abies inagnifica) replacing the white fir in the 

 upper part. Lodgepole pine {Pinus contorta) is the common species east 

 of the Cascade Crest. 



In the forest openings and on open hillsides many shrub species are com- 

 mon. The chaparral type composes about one tenth of the vegetation cover 

 of the park with greenleaf manzanita {Arctostaphylos patula) and snow- 

 brush ceanothus {Ceanothus velutinus) as the common species. Other com- 

 mon shrubs are currants and gooseberries {Ribes sp.), serviceberry {Amelan- 

 chier aln folia), bitter cherry {Prunus emarginata), squaw carpet ceanothus 

 {Ceanothus prostratus) , huckleberry oak {Quercus vaccinifolia) , and Califor- 

 nia chinquapin {Castanopsis sempervircns) . Streams are lined with thickets 

 of shrubby willow and alder {Alnus tenuifolia) . Broadleaf trees do not 



