Bailey a: Bailey: Woody Plants of National Parks 17 



ramosissima), ephedra {Ephedra viridis and E. Torreyana), desert almond 

 (Prunus fasciculata) and mescal (Agave utahensis) . Along the Colorado 

 River and tributaries there occur such species as seepwillow (Baccharis glu- 

 titiosa), Emory baccharis (B. Emoryi) , arrow-weed (Pluchea sertcea), and 

 mesquite (Prosopis glandulosa) on the slopes above. 



Great Lakes Region 



Isle Royale National Park 



Isle Royale National Park includes within its boundaries a group of 

 islands in northwestern Lake Superior near the Canadian border, our only 

 entirely insular national park. The main island, which is about 45 miles 

 long and 7 miles wide, has adjacent to it many smaller islands. Although 

 lying in the Great Lakes Region, the vegetation has some features in common 

 with the more northern of our western national parks. 



The forest cover of Isle Royale is made up principally of balsam (Abies 

 balsamea) , white spruce (Picea glatica) , and paper birch (Bettda papyrijera) 

 with mountain ash (Sorhus americana) and pin cherry (Primus pennsyhantca) 

 often found in the understory. The trees are in very dense stands in the 

 flats and hollows which lie between the several long ridges running length- 

 wise of the island, but considerable underbrush is found in openings or at 

 the edges of the forest. A few of the characteristic shrubby associates are 

 western thimbleberry (Rubiis parviflorus) , red raspberry (Rubus idaeus var. 

 aculeatissimus) , alder (Alnus crispa and A. incajia) , several species of service- 

 berry (Amelanchier), and dogwood (Cornus canadensis and C. stolonifera) . 

 Above the Lake Superior shore line at the edge of the forest lowbush blue- 

 berry (Vaccinium angustijoliiim) is common and often bearberry (Arctosta- 

 phylos iiva-ursi) or mats of the dwarf juniper (Juniperus communis var. de- 

 pressa) . Jack pine (Pmus Banksiana) is common in places but with very 

 little undercover. Aspen (Populus tremuloides) is also frequent. 



Moose have had a considerable effect upon the shrubby vegetation in the 

 park. This is particularly evident when one compares records of vegetation 

 found today on the main island with records of the past.-^ 



Canada yew (Taxits canadensis) was at one time an important shrub over 

 a considerable part of the island. Today it can scarcely be found except 

 on the outlying islands where moose have not been to any great extent. 

 Beaked filbert or hazelnut (Corylus rostrata) was also at one time more wide- 

 spread than it is now since it has been overbrowsed by the moose. 



Along the ridges red maple (Acer rubrum) is common and patches of red 

 pine (Pinus resinosa) frequent. At the southeast end of the island along the 

 flats on top of Greenstone Ridge may be found groves of sugar maple (Acer 

 saccharum) and yellow birch (Betula lenta) . This is a hardwood forest 

 type more typical of those further south. 



In the bottoms of the depressions between the ridges are found many 

 3 Brown. C. A., Ferns and Flowering Plants of Isle Royale, Michiaan, pp. 18-20. 



1933. 



