SOME PHYTOGEOGKArHICAL OBSERVATIONS IN LAKE COUNTY, 



MICHIGAN. 



BY LEROY H. HARVEY. 



The northern half of the Southern Peninsula represents to the phyto- 

 geographer an interestmg prohlem in classification. Viewed in the main from 

 the floristic standpoint, it has received various disposition. Ti'anseau ('05) 

 considers it a part of the northern coniferous forest; Harshbei'ger ('11) in- 

 cludes it in his Interlacustrine Area of the Lake District; vs^hile Shreve ('12) 

 maps this area in his Northern Mesophytic Evergreen Forest, concerning which 

 he states : "This extensive region is characterized throughout by a pure or 

 nearly pure stand of needle-leaved evergreen trees, among which deciduous 

 trees are often present either as minor components of the forest or else as 

 trees of minor stature. * * * in the eastern portion of the area the white 

 pine (P. strobus), the hemlock {Tsuga canadensis), the jack-pine (P. divari- 

 cata), and the balsam fir (Abies balsamea) are the most common species." 



This phytogeographic area he delimits as distinct from his Northeastern 

 Evergreen-Deciduous Transition Forest. 



To one at all familiar with the region under discussion the inadequacy 

 of such a classification from the standpoint of ecological plant — geography is 

 strikingly apparent. AVithin the history of man the needle-leaved evergreen 

 forest probably never did predominately occupy very extensvie unbroken areas 

 within this region. Limited stands of the big pines were interrupted by more 

 extensive areas of the jack-pine, the mixed jack-pine oak, and the black-white 

 oak formations. All along the eastern and western boundaries of the southern 

 peninsula and scattered throughout the central area there existed extensive 

 stands of the hardwood or mixed hardwood formation. It is thus evident that 

 ecological conditions permit in certain widely distributed areas over the entire 

 region the development of the deciduous climax forest type for eastern North 

 America, either as the pure maple-beech or mixed hardwood association. 



Our region thus represents a great tension zone in which the northern 

 outposts of the deciduous climax forest formation and the southern relicts of the 

 northeastern evergreen forest formation overlap and intermingle, thus becom- 

 ing competitors for occupation. So nicely balanced are the controlling factors 

 that in many areas one fails to find any evideiace of the usual successful 

 sequence, while factorial interpretation of present distributional conditions is 

 well nigh impossible. If considered, however, in light of the postglacial migra- 

 tions (Adams '02) and with an eax'ly pre-occupation of the several enviromental 



21st Mich. Acad. Sci. Kept., 1919. 



