Environmental Engineering Reference
In-Depth Information
FIG
40
. An aerial view of the remarkable conical rock known as the Knave. (Peter R. Douglas-Jones)
Royal Commission on the Ancient and Historical Monuments of Wales for Figures
PLANT COMMUNITIES
The coastline is particularly noted for the range of habitats that occur, from intertidal rocks and the ex-
posed maritime grasslands in the west, to blackthorn
Prunus spinosa
and hazel scrub within the more
sheltered valleys in the east. In addition there is an interesting mosaic of habitats on the cliffs, the gentler
slopes being covered by acidic soils while the limestone outcrops, containing crevice, ledge and scree
communities,aresurroundedbydrygrasslandwhichgradesintoneutralgrasslandandthenintoacidheath
vegetation, often within a few metres of the outcrop. In comparison to other areas of coastal limestone,
however, the maritime influence on the cliff vegetation is quite limited, due to the very high relict cliffs
and the presence of extensive rocky beaches at the base of the cliffs that act as wave breaks. The large
tidalrangealsoreducestheamountofthrownsprayreachingthecliffs,asthewavesobviouslybreakwell
away from the cliffs when the tide is out. The least maritime communities are the gorse and limestone
heaths, acid grasslands, bracken and bramble, and the blackthorn scrub of the inland part of the cliffs.
Salt-tolerant plants on the lower part of the cliffs typically include spring squill
Scillia verna
, golden
samphire
Inula crithmoides
(Fig. 41), rock sea lavender
Limonium procerum
, buck's horn plantain
