ns ag ny Cee ea eee Lem eek eae ee Se 
= aeee Se ae ae 
ES OR, Fee Pee ed re ak ee Te eee Pee 
1913] COOPER—ISLE ROYALE 41 
THE MAPLE FOREST OF ISLE ROYALE AND ITS RELATIONS 
Wherever the sugar maple occurs it forms a part of the climax 
forest, and is usually the dominant species therein. Between the 
two great eastern forest regions there is a transitional belt several 
hundred kilometers wide where the three climax trees of the conifer, 
and the two of the deciduous forest all occur (see map, fig. 14). 
This belt extends from northern Wisconsin through the upper 
peninsula and the northern part of the southern peninsula of Michi- 
gan and eastward to New Brunswick. WHITFORD (59) studied the 
successions in a portion of this belt, and found that the climax 
forest in northern Michigan (both peninsulas) is the beech-maple 
type. The balsam, birch, and spruce are very abundant, but here 
they belong to preliminary stages in the successions. GANONG 
(26, 27) gives an excellent summary of the plant formations of 
New Brunswick. He states that the climatic forest type is the 
“mixed maple-birch-spruce-fir association.” There is no indica- 
tion in his paper that the maple ever supersedes the other trees, 
but the presence of such a possibility must be admitted. The con- 
clusion from the studies of WHITFORD and others seems to be that 
the maple and beech, where not climatically excluded, are able to 
supersede the climax trees of the northeastern forest. 
Coming now to Isle Royale, we find upon the southwestern end, 
occupying the summit of the highest ridge, a mixed growth of 
Acer saccharum Marsh (sugar maple), Betula lutea Michx. f. (yellow 
birch), and B. lenta L. (sweet birch); with the characteristically 
northern trees as a minor element (see ADAMS 4, pp. 30-31, and 
HOLT 33, p. 224). The maple is decidedly the dominant species 
and reaches a large size.‘ At the northern edge of this northernmost 
outpost of the maples we may draw the line that separates the true 
northern forest from the transitional belt (fig. 14). South of this 
line the representatives of the southeastern deciduous forest, 
though not necessarily forming the bulk of the stand, yet have the 
upper hand; north of it the supremacy of the conifers and the paper 
birch is oes 
Pa yor eg es oe sl s% 7 n on the southern side of Michipi- 
coten Island, near the eastern shore of Lake Superior. 
