PSPC ena A OMe eee eae ee eee 
oa eee Pee ed RE nS Ee tc SRE RER eae ge 
met up ee rep cee aA GN ane Opa ean nee OR? gk ae aie ree MPa s Se SRE R pe ee Rian Ba ea A iterse dy Se Migr Sa: sen ee a a ie igh De NM ge ee A ee dee A at tere ER Se 
NaS ST aaa a has 
1913] COOPER—ISLE ROYALE 43 
ecologically unimportant on account of its scarcity. Germination 
in the forest is less abundant than in the case of Betula. It is not 
liable to fungus attacks and withstands severe winds. Birth-rate 
and mortality are both low. Taxus canadensis is the most impor- 
tant species of the undergrowth, its influence lying in the complete- 
ness with which it occupies and shades the ground, preventing tree 
reproduction over large areas. 
III. Intensive study of selected areas (quadrats) yielded the 
following facts concerning the dynamics of the forest. 
The forest is a complex of windfall areas of differing ages, the 
youngest made up of dense clumps of small trees, and the oldest 
containing a few mature trees with little young growth beneath. 
The history of a windfall area is as follows. After the débris 
has disintegrated sufficiently to allow abundant light to reach the 
ground, a new generation of trees springs up, approximately even- 
aged, composed of the three dominant species, Abies always greatly 
preponderant. During the continued development of this group 
most of the individuals are at various times eliminated, A dies suffer- 
ing most for the causes enumerated in section II. Because of the 
dense shade no new individuals can start beneath them, and the 
final outcome is a group composed of a few large trees, approxi- 
mately even-aged, in which Adzes has nearly or quite lost its posi- 
tion of dominance to Betula. In situations sheltered from wind 
all species live to a greater age and windfalls are less frequent. The 
processes though less rapid are nevertheless the same as in more 
exposed situations. The result in the forest in general is a mosaic 
or patchwork which is in a state of continual change. The forest as 
a whole remains the same, the changes in various parts balancing 
each other. 
’ IV. The following evidences that the dominant forest of Isle 
Royale is also the climax have been derived from the studies sum- 
marized above and from those dealing with the successions. 
1. The dominant forest is the most mesophytic of the plant 
societies. 
2. It is uniform upon all soils and upon areas that have passed 
through very different lengths of subaerial history. 
3. All the successions culminate in the establishment of this as 
q the final stage. 
