Inlet and Estuary - Gower - page 183

cies is found on these upper fringes of the marsh, especially in the transition zones where it merges with
sand dunes, water meadows or freshwater marsh. Particularly interesting plant communities are found at
Whiteford Point, Llanrhidian and near Loughor.
The major part of the saltmarsh vegetation consists of a relatively small number of salt-tolerant plants
adapted to regular immersion by the tides, and there is a clear zonation according to the frequency of in-
undation. At the lowest level, where pioneer communities are dominated by glasswort Salicornia spp.,
annual sea-blite Suaeda maritima and common cord-grass Spartina anglica , the plants can stand regular
immersion, while the species in the upper marsh can only withstand being occasionally covered by the
tide. Themuddysediments inthisarea alsosupportextensive bedsofthenationally scarce dwarfeelgrass
Zostera noltii .
Common cord-grass is a new species, which originated at the end of the nineteenth century as a result
of hybridisation between the native small cord-grass Spartina maritima and the smooth cord-grass Spar-
tina alterniflora , a naturalised alien introduced from America in the 1820s. Since its introduction on a
small area of marsh west of the Burry Pill in 1935, to aid its 'reclamation' as grazing land, common cord-
grass has colonised substantial areas of the estuary. It now dominates a broad belt of the lower salt marsh
and has also invaded the creeks to the upper salt marsh. Eastwards it extends a considerable way up the
estuary. The vast area of cord-grass below the sea wall at Pen-clawdd did not exist before 1955, but by
1975 it had spread over the whole area. These extensive swards are of little value to wildlife and are con-
sidered to be a threat to bird feeding areas. In Swansea Bay efforts were made to control its spread as it
was thought to be a threat to the tourist industry, but on this side of Gower it was left unchecked. In the
1960s there were calls for the marsh to be sprayed from the air with herbicides, a potentially disastrous
procedure for the other vegetation and intertidal life; thankfully this did not happen.
At the present time nearly 18 per cent of the saltmarsh area is covered by the cord-grass, although
some long-standing areas are contracting for reasons not fully understood. There are similar reports from
other parts of Britain. A number of causes for the decline have been suggested, including a lack of sed-
iment accretion, water-logging, wave damage, oxygen deficiency, pathogenic fungi and a loss of vigour
within the species due its lack of genetic variation. Whatever the future status of the plant in the estuary
there is no doubt that the spread of common cord-grass has dramatically influenced the flora of the lower
salt marsh. Unfortunately there are no published accounts of the vegetation of the inlet prior to its intro-
duction, although there are several tantalisingly brief or introductory descriptions in the literature.
Thelow-ormid-marshcommunitiesare,incontrast,dominatedbyacloselygrazedswardofthecom-
monsaltmarsh-grasswithsea-purslane Atriplexportulacoides frequentalongthecreeksidesandwherever
thereisreducedgrazingpressure.Grazinghasanoticeableeffectonthestructureandcompositionofsalt-
marsh vegetation, most obviously by reducing the height and diversity of plants. The common sea laven-
der Limonium vulgare , for instance, appears to be confined to relatively less-grazed sites such as south of
Loughor and the western side of the Burry Pill. Several other species also occur, usually at low densities,
notably greater sea-spurrey Spergularia media , sea aster Aster tripolium , sea arrowgrass Triglochin mari-
timum , English scurvygrass Cochlearia anglica and sea plantain.
In the mid to upper zones of the marsh there is an extensive sward of common saltmarsh-grass mixed
with red fescue and other species such as thrift and sea milkwort Glaux maritima . The upper edge of the
grazed salt marsh is marked by a belt of the tall unpalatable sea rush in which most of the species of the
red fescue community occur, with the addition of parsley water-dropwort Oenanthe lachenalii , autumn
hawkbit and sedge Carex spp. North of Llanrhidian the sea rush belt is several hundred metres wide and
traditionally it was cut in late summer to provide rushes for bedding and to improve the grazing. This
practice was revived briefly by local farmers during 1975 when bedding straw become prohibitively ex-
pensive. A few of the graziers still cut the rush for bedding, and for young store cattle there is nothing