Il] WOODLAND ASSOCIATIONS 41 



The distinction between the oak and birch woods on the 

 one hand and the ash woods on the other hand is very sharp 

 and clear in the Peak District, where most of the woods 

 may without difficulty be referred to the oak and birch woods 

 or to the ash association. It is true that a number of the 

 woods are exploited for timber. However, in many of these, no 

 re-planting takes place; and the indigenous trees spring up 

 again quite spontaneously, either from the cut stools or from 

 self-sown seed. In other cases, non-indigenous trees, such as 

 beech (*Fagus sylvatica^), sycamore {*Acer Pseudoplatanus), 

 larch {*Larix decidua=* L.europaea), and pine {*Pinus sylvestris) 

 are planted where the native trees have been felled ; but, even 

 in these cases, unless the shade cast by the planted species 

 differs greatly from that cast by the original ones, the ground 

 flora usually affords a fairly conclusive test as to whether or 

 not the original wood belonged to the oak and birch woods or 

 to the ash wood. A few of the woods of the district may indeed 

 be said to be really primitive, as human interference with them 

 is confined to the occasional cutting down of one or two trees 

 by the occupier of some upland farm. 



Many of the woods, however, are in a degenerate condition ; 

 and there is in this district no sharply dividing line between 

 degenerate woodland on the one hand and scrub (considered 

 in the next chapter) on the other. The questions relating to 

 existing plantations and to reafforestation are discussed in the 

 last chapter of the book. 



Factors related to the Distribution of the 

 Woodland Associations 



Sufficient examples of woodland have now been examined in 

 this and other districts to enable one to judge, in a general way 

 at least, which are the principal ecological factors related to the 

 present distribution of the various woodland associations. The 

 oak and birch woods of the Pennines, as contrasted with the ash 

 woods of the same region, are related to a difference in the 

 chemical nature of the soil ; for the former woods are here 

 strictly confined to non-calcareous soils, and the latter, with 



1 Throughout this book, the species which are not indigenous are preceded 

 by an asterisk. 



