KENFIG BURROWS: AN ECOLOGICAL STUDY 211 



characteristic of liic "shifting" dunes, with the Marram grass as 

 the dominant species. This species occupies the first seaward line 

 of sand hills, the Agropyretum juncei (sea couch-grass association) 

 of the Somerset and Lancashire dunes being practically absent in 

 this area. It is worthy of notice that Efymus arenarius, which in 

 Norfolk gives rise to low dunes, is entirely absent from this coast. 

 The higher inland dunes, many of them over fifty feet in height, 

 bear on their crests the characteristic tufts of Marram grass. It 

 descends on the leeward sloi)es and colonises the sandy hollows, 

 and in many of the latter, its rhizomic habit of growth is particularly 

 obvious. As a "sand-binder" it is pre-eminent, and it is interesting 

 to note that in the Charters of Kenfig of 1330 special provision was 

 made for its protection and preservation. A7ninophila also occurs 

 in abundance on some of the "fixed" dunes. 



2. The Salix repens association. — Saiix repens occurs on the 

 "shifting" dunes as a "sand-binder," producing a well-marked 

 association. In the sandy dune valleys it forms a carpet of low- 

 growing scrub, but in the more exposed stations it collects around it 

 the blown sand and gives rise to "hummocks" and small dunes. 

 In the damp hollows it forms a fringe round the marshy ground 

 and the dependent species vary accordingly. Salix represents the 

 second stage in succession on the dunes, as Ammophila represents 

 the first. In the more open stations of this association Marram 

 grass is the subdominant species. Salix repens occurs on the 

 Lancashire dunes, but Moss describes it as a comparatively rare 

 plant on the Somerset sand hills. 



3. The Fteris aquilina association. — The bracken covers acres 

 of the " fixed " dunes in this area, and its outliers blend with the 

 willow of the preceding association. Its rhizomic habit of growth 

 makes it likewise a successful sand-binder, and it forms the last stage 

 in succession. According to Massart, Pteris is entirely absent from, 

 or very rare, on the Belgian dunes. It has here undoubtedly 

 adapted itself to life on the dunes and grows luxuriantly. The 

 fronds are regularly harvested for cattle-bedding. Although it is 

 such an abundant type on the " grey " dunes near Kenfig pool, it 

 is sparsely represented on the adjoming boulder clay. This may be 

 due, in part, to the fact that the latter is under cultivation, or perhaps 

 its absence may be accounted for by the more or less calcareous 

 nature of the clay ; the bracken being regarded by some authorities 

 as a calcifuge. 



In these three chief associations the subordinate species vary 

 according to the character of the association. The Marram grass 

 association is essentially an open one, and on the seaward side of 

 the first range of "mobile" dunes it is an almost pure association. 

 As a result of this open character, competition among the associated 

 species is reduced to a minimum. The Salix repens association is 

 of a less open nature. The habit of growth of the Salix affords 

 protection from blowing sand, and excessive insolation, to the types 

 which it shelters. At the same time, a certain amount of humus is 



