Environmental Engineering Reference
In-Depth Information
white, dome-shaped flower heads. Its oblong leaves are finely divided with segments arranged in rings
around the main leaf midrib.
Withinthewetheathlandtherearemanyflushedareaswitharicherflora,includingstalkedspike-rush
Eleocharis multicaulis
, marsh violet
Viola palustris
, round-leaved sundew
Drosera rotundifolia
, lesser
skullcap
Scutellaria minor
,heathspottedorchid
Dactylorhiza maculata
andbogasphodel
Narthecium os-
sifragum
.Scarcerandmorelocalplantsincludesaw-wort
Serratula tinctoria
,bitter-vetch
Lathyrus linifo-
lius
, royal fern
Osmunda regalis
and bog-myrtle
Myrica gale
. In the dampest areas bog-bean
Menyanthes
trifoliata
, bog pondweed
Potamogeton polygonifolius
and marsh cinquefoil
Potentilla palustris
occur.
Rarer species of flushed heathland, such as hare's-tail cottongrass
Eriophorum vaginatum
, oblong-leaved
sundew
Drosera intermedia
and white beak-sedge
Rhynchospora alba
, are known from only a few sites
in Gower.
The brightly patterned marsh fritillary (Fig. 118) is without doubt the best-known invertebrate found
on the commons, and the importance of the Gower colonies has long been recognised. The species is
declining in almost every European country and Britain is now one of the major strongholds, but even
here its numbers have been substantially reduced over the past 150 years. Changes in grazing stock and
practices, afforestation and agricultural 'improvements' are all factors that have contributed towards this
decline. The species, like many others, often occurs in well-separated colonies that form part of a 'meta-
population', within which there is an interchange of individuals. All the colonies are therefore interde-
pendent and have to be protected, rather than just one or two sites. They are often small, however, and
susceptible to extinction, so extensive mosaics of habitats such as those provided by the Gower commons
are essential for the species' long-term survival (Fig. 119).
FIG
118.
Marsh fritillary butterfly, the best-known invertebrate found on the commons. The Gower colonies are na-
tionally important. (Harold Grenfell)
