CHAPTER II 



WOODLAND ASSOCIATIONS 



Distribution of the woods. "Woodland associations of Great Britain. 

 Woodland associations of the southern Pennines. Factors related 

 to the distribution of the woodland associations. Oak woods of 

 Qziercus Robur. Transitional woods of Quercus Robur and Q. sessili- 

 jlora. Oak woods of Quercus sessiliflora ; trees and shrubs ; variation 

 of vegetation in the oak woods ; influence of shade on the ground 

 vegetation. Alder- willow thickets. Birch woods of Betula pubescens ; 

 the primitive birch forest. Ash woods of Fraxinus excelsior ; semi- 

 natural woods and plantations on the limestone slopes ; trees and 

 shrubs ; herbaceous vegetation. Comparison of the woodland plants 

 of the southern Pennines. 



Distribution of the Woods 



The great majority of the woods occur on the slopes of the 

 hills, where they ascend, on an average, to about 1000 feet 

 (305 m.). Occasionally, they reach an altitude of 1250 feet 

 (381 m.). On the Coal-measure rocks, which do not, as a rule, 

 reach so high an elevation as the Pendleside, Millstone Grit, 

 and Mountain Limestone rocks, the woods occasionally extend 

 on to the flatter plateaux. In such situations, woods seldom 

 occur at altitudes higher than 800 feet (244 m.). On the whole, 

 the woods are of small size ; and they by no means cover the 

 whole of the hill slopes. In fact, as a rule, the hill-sides are 

 occupied by uncultivated grassland (see Chapter IV) or scrub 

 (see Chapter III), where they are not cultivated as permanent 

 pasture (see Chapter VIII). 



