VII] MOORLAND ASSOCIATIONS 193 



SUB-ALPINE GRASSLAND 



In the end, the retrogressive changes outlined above result 

 in the complete disappearance of the peat ; and on the surface 

 thus laid bare, a new set of species begins to invade. In this 

 invasion the ordinary inhabitants of the surrounding peat- 

 moors can take no part; and the successful invaders are the 

 more hardy members of the Nardus grassland. As has been 

 stated (see page 185), such plants follow the streams of the 

 peat-moors almost to their sources ; and hence they are the 

 plants which one would expect to be the first to establish 

 themselves in the newly formed habitat. The summit of 

 Bleaklow Hill, four miles north of the Peak, is tenanted by 

 an open plant association which has almost certainly originated 

 in the way just described. On the summit of Great Whernside 

 and other hills of the mid-Pennines, Smith and Rankin describe 

 an association which seems to be capable of a similar interpre- 

 tation : " the summit-ridge from the edge of the peat-bog 

 upwards is rocky, with a scanty soil which supports a meagre 

 vegetation consisting of grasses. Here and there are patches 

 or islands of peat" (Smith and Rankin, 1903: 154). 



The following species were observed on the summit of 

 Bleaklow Hill:- 



Nardus stricta Rumex Acetosella 



Deschampsia flexuosa Potentilla erecta 

 Festuca ovina ( = P- Tormentilla) 



Agrostis vulgaris Calluna vulgaris 



Juncus squarrosus Vacciniuin Myrtillus 



Luzula erecta Qalium saxatile 



On Great Whernside, Smith and Rankin (loc. cit.) record 

 Festuca ovina forma vivipara and Poa alpina ; and it is not 

 impossible that a careful search on Bleaklow Hill would reveal 

 these plants, although they have not yet been recorded for 

 Derbyshire. 



The case of this sub-Alpine Pasture illustrates the im- 

 portant principle that a succession of plant associations, once 

 initiated, may lead from one plant formation to another (cf. Moss, 

 19106: 37). In the case under discussion, the retrogressive 

 succession began in the closed cotton-grass association, continued 



M. 13 



