92 The Plant-formation of Sandy Soil 



certainly degenerated into heathland during the last few 

 centuries, while yet others are only now beginning to 

 show the changes preparatory to this transformation. 



It is generally admitted that the process is greatly 

 accelerated by the extensive felling of trees and clearing 

 of woodland on these soils. Clearing leads to the rapid 

 destruction of the mild woodland humus, and thus 

 facilitates the entrance of the pioneers of the heath vege- 

 tation. This factor has certainly been fully operative 

 in the conversion of many of the British woodlands to 

 heath. 



We will now see how far the plant-associations of our 

 sandy soils can be interpreted in the light of these general 

 considerations. 



The Plant-formation of Sandy Soil 



Dry sandy oakwood association (Quercetum arenosum 

 Roburis et sessiliflorm). This association is developed on 

 many of the sands and sandstones mentioned. The soil 

 is much poorer in humus than that of the damp oakwood 

 on clays and loams, and the association is much poorer 

 floristically. The following is a list of the more charac- 

 teristic and commoner species. ' ' ^' 



