A Common Resource - Gower - page 211

ticular it keeps the streams and runnels across the commons open, and this provides ideal conditions for
many insect populations, particularly dragonflies and damselflies.
The natural vegetation of the commons was probably a mixed woodland of sessile oak Quercus pet-
raea and downy birch Betula pubescens , with alder in wetter sites and broad buckler-fern Dryopteris
dilatata , bluebell and creeping soft-grass Holcus mollis abundant in the field layer. A few bog-moss
Sphagnum spp. mires probably existed in the wettest sites, but open heathland and moorland would have
been restricted to the exposed slopes of Rhossili Down and Cefn Bryn. Today the commons occupy the
more infertile, stony and ill-drained areas of acid soil, and they have mixed open heath vegetation in-
terspersed with areas of marsh and bog, with a few surviving oak-birch and alder woods around the
edges. The abundance of common cottongrass Eriophorum angustifolium , heath rush Juncus squarrosus ,
purple moor-grass, mat-grass Nardus stricta and deergrass gives the commons an upland character des-
pite their lowland position (Fig. 116). Rocky outcrops and scree on the commons form a valuable habitat
for lower plants and there is a particularly notable bryophyte and lichen flora on and around the boulder
field on Rhossili Down, with mosses including drooping thread-moss Bryum alpinum , arctic fork-moss
Campylopus atrovirens , squirrel-tail moss Pterogonium gracile and fringed hoar-moss Hedwigia ciliata ,
the latter at its only site in Glamorgan.
FIG 116. Common cottongrass on Cefn Bryn Common. The presence of cottongrass and other species, such as heath
rush and purple moor-grass, gives the commons an upland character. (Jonathan Mullard)
Although at first sight the vegetation of the Gower commons may appear to be uniform there is in
fact a complex pattern of vegetation types, including wet heath, dry heath and acidic grassland and scrub,
and the proportions of these habitats vary markedly from common to common. The Biological Survey
of Common Land, for example, recorded ten different habitats on Cefn Bryn alone (Table 11). Although
this is the largest and one of the most complex commons in the peninsula the mosaic of habitats is typ-
ical of many of the Gower commons. Nearly half of Cefn Bryn is covered in continuous bracken, which