912 NINETEENTH REPORT. 



by trees of any kind. The black oak forest meets the prairie so formed 

 at a sharp line. The area covers nearly three square miles. Sand has so 

 drifted as to form knolls, reaching above the level of the prairie, and there 

 occur islands of black oak forests on these sand knolls, surrounded by 

 prairie. The absence of all trees, even seedlings, on the prairie, indicates 

 little or no advance of trees over the peat. This and many similar areas 

 seem to have been treeless from the start. The peat is reported to be not 

 over ten feet deep and in dry seasons is likely to take fire and burn to 

 the bottom. 



The aspen (Populus tremuloides ) is social, showing a tendency to form 

 stands of pure growth. The best example of this type begins on a 

 swampy area, northwest of Wayne, and follows two miles northward 

 along the Wayne-Plymouth electric line on both sides of the track. The 

 aspen forest is totally unlike any other of the region in appearance, and 

 is one of the most noticeable features to be seen in the vegetation along 

 this route. It is one of the best examples of a like-commensal forest. 

 The total area of pure aspen in the county, however, is not large, although 

 it is larger than that of any other gregarious species. Like the birch, it 

 commonly mixes with other species. Portions of the aspen forest north 

 of Wayne contain red maple, pin oak, Populus deltoides, and other trees, 

 evidently pioneers of other associations, which are very slowly encroach- 

 ing on the aspen. 



A forest of exceptional interest begins well within the city limits of 

 Detroit and extends northwestward and north, covering about forty 

 square miles. It is characterized by paper birch which often forms over 

 65 per cent of the woods, as in the S. W. 14? S. E. 14, Sec. 16, Greenfield. 

 Palmer Park and the west side of the Grand Lawn Cemetery wood 

 preserve a portion of this association. The soil is sandy, of good to fair 

 productiveness. 



II. Species tending to form both like- and unlike-commensal forests. 



The black oak (Quercus velutina) forms a thin forest sometimes called 

 oak openings, upon sand which is light and dry and is blown by the 

 wind. It is too poor for agriculture, at least under present methods. The 

 people should plant poplar windbreaks and forest planting should be 

 undertaken. The Norway pine (Pinus resinosa) should do well here. 



An intimate relation exists between the black oak forest and the 

 people and type of agriculture which has sprung up over the extensive 

 area from which this forest association has been cleared. Here we find 

 the barb-wire fence, the primitive log house and small barns. The 

 people are generally Polish and distinct socially from those who farm 

 where maple, beech, or any of the other forest associations described, 

 have been removed. The conditions of soil which have supported begin- 



