168 Sub-formation of the Chalk 



somewhere about the line marking the present western 

 and northern limits of the chalk beechwoods. 



The equipment of the two trees for such a struggle is 

 very different. The beech, like its relative the oak, is a 

 heavy-seeded tree, and its wide dispersal must depend on 

 the activity of birds and other animals. Many existing 

 beechwoods show signs of failure to regenerate them- 

 selves, and this, as in the case of oakwoods, is often 

 attributed to the disappearance from the woods of the 

 herds of swine which used to feed on the mast and acorns, 

 and incidentally keep the soil open and sow the seeds by 

 trampling them into the ground. The greater production 

 of seed by the ash and its dispersal by the wind clearly 

 gives this species an advantage over the beech in coloni- 

 sation, and 'pro tanto will favour the production of ash- 

 wood rather than beechwood on soils equally favourable 

 for both species. On the other hand, given successful 

 colonisation of an ashwood by the beech, the latter will 

 inevitably beat the former in competition because of the 

 deep shade cast by the beech foliage, so that eventually 

 most of the ashes will be starved and the wood converted 

 into a beechwood. On the borders of the beechwood 

 region in East Hampshire this process may in places be 

 observed. Beechwood has been extensively felled, but 

 enough parent trees were left to furnish a supply of self- 

 sown seedlings, and the ash which has sprung up since 

 the beech was felled is here and there being overshadowed 

 and killed by these self-sown beech seedlings as they 

 grow up. In other places, however, in the same district, 

 the beech is not coming back where it has been cleared, 

 and the ground is occupied either by mixed chalk scrub 

 or mainly by ash. The failure of the beech to regenerate 

 and its replacement by the ash is a parallel phenomenon to 

 the replacement of oak by birch (see pp. 102, 141) ; and it 

 may be stated as a generalisation that extensive clearing 

 tends to handicap the heavy-seeded trees and to lead to 



