Environmental Engineering Reference
In-Depth Information
centlywychelm
Ulmusglabra
wasalsopresentinlargenumbers,butitsoccurrencehasbeenreduceddra-
matically byDutchelmdisease. Sometimes thewoodsalsocontain considerable amountsofsmall-leaved
lime
Tilia cordata
, field maple
Acer campestre
and sycamore. Where there is sufficient light reaching
the ground the invasive sycamore is often abundant in the shrub layer, along with large numbers of ash
seedlings, but it only occurs occasionally as a canopy species. Although present almost everywhere it is
generally more abundant on the deeper, heavier soils, which it appears to prefer. Spindle
Euonymus euro-
paeus
and wild privet
Ligustrum vulgare
are frequent as well, although other plants which might gener-
ally beexpected tooccurinsuchconditions, especially buckthorn
Rhamnus catharticus
andspurge-laurel
Daphne laureola
, are rare in the shrub layer.
FIG
143.
Ash woodland on the north Gower cliffs. Looking north along the escarpment from Cilifor Top in winter.
(Harold Grenfell)
The ground flora of the ash woods is again rich and is usually dominated by ramsons and dog's mer-
cury
Mercurialis perennis
, together with hart's-tongue fern
Phyllitis scolopendrium
and soft shield-fern
Polystichum setiferum
,whichisveryabundantonshadedslopes.Fernssuchasmale-fern
Dryopteris filix-
mas
, lady-fern
Athyrium filix-femina
and broad buckler-fern are also locally frequent and in places dom-
inant. In Parkmill Woods and Llethrid Valley there are populations of the locally uncommon royal fern,
a dramatic plant that sometimes grows up to 3 metres high, hence its name (Fig. 144). This fern of wet
woods was one of the species most heavily affected by the Victorian collectors. Several woods have dra-
matic spring displays of bluebells. Other notable species include wood spurge
Euphorbia amygdaloides
,
toothwort
Lathraeasquamaria
,herbParis
Parisquadrifolia
,butcher'sbroom
Ruscusaculeatus
andstink-
ing hellebore, all ofwhich are most abundant in eastern orsouthern Britain and, like the trees themselves,
are nearly at the western or northwestern limits of their ranges in Gower.
Stinking hellebore, a perennial of woods and scrub on calcium-rich soils, was first recorded in Glam-
organ around 1803 by Dr Turton, who discovered it between Parkmill and Pennard Castle. It was still
there in abundance in 1840, when it was noted by Gutch, but it is now very rare in the Parkmill area even
though the woodland appears to have changed little since Turton's day. Although individual plants are
