Chalh Grasslcmd 17 S 



commonly poorer in species than the shrub layer of the 

 corresponding woodland, the scrub association of cal- 

 careous soils is much richer and develops largely on its 

 own account in suitable situations. Sometimes this scrub 

 can be clearly recognised as a progressive association 

 which has colonised open chalky soil and in which such 

 trees as the ash may spring up freely. In such cases an 

 ashwood may develop, with its undergrowth consisting of 

 the shrubs of the chalk scrub and a fairly rich ground 

 vegetation. Whether in these cases the beech normally 

 replaces the ash in succession is doubtful. It is probably 

 generally prevented from doing so by the want of enough 

 adult trees to furnish an adequate supply of seed. 



Chalk grassland association [Chalk pasture] (Fes- 

 tucetum ovinm calcareum) . 



This association, which is the typical association of the 

 South Downs', and has a very wide extension in the 

 southern counties of England, is closely similar to the 

 limestone grassland previously described. It has the same 

 general dominant, the sheep's fescue (Festuca ovina), and 

 a large proportion of the associated species are also the 

 same, but a number of species confined to the south (and 

 particularly the south-east) of England occur in the chalk 

 pasture only. Swamps appear to be entirely absent. 



There is good reason to suppose, as we have already 

 pointed out, that much of the chalk pasture 

 History of ^g extremely old, and much of its area has 

 pasture. possibly never been occupied by a tree 



association — perhaps because of an inade- 

 quate supply of underground water. The chalk grass- 

 land, which forms a very excellent light crisp pasture, 

 has from time immemorial supported considerable flocks 

 of sheep. The smooth curves of the chalk downs are 

 occasionally broken by ancient trackways, camps and 



1 Sussex, Hampshire, Dorset and Wiltshire. The North Downs of 

 Surrey and Kent have much less. 



