270 THE FORESTS OF ALLEGANY COUNTY 



ranges of tree species, but within general limits, at which there is 

 more or less overlapping or mingling of two or more species, it may 

 be noticed that finally one kind of tree disappears and another ap- 

 pears. For example, in ascending one side of a mountain, Beech, 

 Maple, Basswood, etc., may appear at the base of the mountain. 

 Above these a succeeding zone may contain Chestnut, Sweet Birch, 

 etc.; and the next higher zone, Chestnut Oak, Table-mountain Pine, 

 Wild Red Cherry, etc. These zones blend into each other more or 

 less by the mingling of the trees peculiar to each zone. Similarly 

 defined areas of tree growth of still other species may be met with 

 on the opposite slope of the same mountain. Or in passing from 

 deep valleys on a mountain side to adjoining ridges or benches at the 

 same altitude, often there may be found an assemblage of trees 

 peculiar to each of these dissimilar localities. 



The explanation of these phenomena is believed to lie in the fact 

 that certain trees have become so completely adapted to a given kind 

 or condition of soil (dry, moist, loose or compact), or climate, that 

 they cannot exist where the required soil and climate are wanting. 

 Thus the presence of a northern climate in portions of this region 

 appears to account for the presence, by extension, of northern trees 

 into this county which are prevalent in their wider northern range 

 under the same conditions. The more cosmopolitan trees of this 

 region are conspicuous over a greater area, while the less widely 

 adapted kinds appear within narrower limits. 



The part also which some trees and shrubs play by taking first 

 possession of denuded lands, thus rendering the soil favorable by 

 protection of moisture for the introduction of still other trees, is a 

 most interesting and practical consideration in the distribution of 

 trees. This is especially true where fire and the axe have destroyed 

 a part or the whole of an original forest. The full value of all the 

 trees in a region cannot be determined without a knowledge of the 

 relationship of species in their natural succession. 



DISTRIBUTION OF PRINCIPAL TIMBER TREES. 



The most conspicuous of the timber species are the White Oak, 

 Chestnut Oak, Eed Oak, Chestnut and White Pine. They form 



