830 JOURNAL OP FORESTRY 



Soil 



On the hills the only soil, except in the hollows and on the gentler 

 slopes, is a layer of "duff" or plant remains which has escaped the fre- 

 quent fires. These remains are as yet largely undecomposed and form 

 what Coville* calls "upland peat," which is unlike ordinary peat in that 

 it is not formed in bogs and seems to be due to lack of warmth rather 

 than to lack of air. In the forest, except on recent burns, this "upland 

 peat," or "duff," covers the soil as well as the rock. 



The lower lying portions of the island are covered with a mantle of 

 rocky reddish-brown glacial till of varying thickness. Some of the 

 hollows just above sealevel contain deposits of blue clay which Shaler 

 attributes to sea deposition during the postglacial submergence. 



THE VEGETATION 

 General 



The flora of the island is predominantly northern, with a strong ad- 

 mixture of southern elements. This combination is of unusual interest 

 and affords, as I have said, an excellent opportunity to study the north- 

 ward migration of southern plants if, as some botanists^ have shown, 

 this northward migration is still going on. The question is too large 

 to go into fully here, and will require intensive study covering long 

 periods of time before it can be definitely settled. But observational 

 evidence tends to corroborate the view that there is such a northward 

 movement, and, from the larger viewpoint of time, that this movement 

 is proceeding at a fairly rapid rate. For example, red oak {Quercus 

 rubra) is one of the prominent forest trees of southern New England 

 and comes up into the spruce forests of northern New England only as 

 scattered individuals. Yet there are places on Mt. Desert Island where 

 the red oak occurs as scattered individuals in the main stand, but com- 

 prises a large proportion of the reproduction under the stand. Here 

 the next generation of the forest will probably be largely red oak. 

 Further study is necessary to determine if this increase of oak is tem- 

 porary or is part of a northward migration of the tree. The establish- 

 ment of southern forms is probably favored by the abundance of steep 

 south exposures which receive strong insolation and are protected from 

 rapid fluctuations of temperature by the proximity of the sea. It would 

 be extremely interesting to know why on this island and on Schoodic 

 Point, on the mainland five miles to the east, we find isolated stations 



* Coville, F. V. : "Experiments in blueberry culture." U. S. Dept. Agriculture, 

 Bureau of Plant Industry, Bull. 193, 1910. 

 " See citations given under note 2. 



