Area: 45.84 hectares.
Site name changed from Carrine Common, to Carrine Common and Penwethers. Boundary amended by extension and minor deletion.
Description and Reasons for Notification:
Carrine Common and Penwethers is situated approximately 1.5 km south west of Truro. The site is underlain by Devonian slates and sandstones of the Mylor Series.
Well-drained shallow Brown Earths underlie the dry heath and drier meadows. Lower lying mire vegetation has developed over waterlogged cambic stagnogley soils, often displaying a wet, peaty surface horizon. Alluvial deposits occur along the stream valleys.
The site supports a variety of habitats, ranging from western lowland heath, scrub and mesotrophic, herb-rich hay meadows on drier slopes, to low-lying areas with impeded drainage, which support wet heath, willow carr, streamside and mire vegetation.
Carrine Common supports dry dwarf shrub heath, dominated by heather Calluna vulgaris, bell heather Erica cinerea, western gorse Ulex gallii and bristle bent Agrostis curtisii. The nationally rare plant, Dorset heath Erica ciliaris (*1), is locally dominant in the south-east of the Common. This is the largest population of Dorset Heath in Cornwall, and is unusual in that it occurs here in dry rather than wet heath.
Other plant species of note within the heathland include the hybrid heath Erica x watsonii, pale dog-violet Viola lacteal, a sub-species of the common violet, Viola riviniana spp. minor, and the endemic bramble species, Rubus daveyi, R.dumnoniensis, R.rilstone and R.cornubiensis.
A series of herb-rich hay meadows lie immediately east of the common, forming the most extensive unimproved mesotrophic grassland known in Cornwall. The species rich sward supports over 50 plants species, with abundant sweet vernal-grass Anthoxanthum odoratum, crested dog’s tail Cynosurus cristatus, common bent Agrostis capillaris, heath-grass Danthonia decumbens and common knapweed Centaurea nigra, together with yellow rattle Rhinanthus minor, southern marsh-orchid Dactylorhiza praeternissa, great bird’s-foot-trefoil Lotus pedunculatus, lousewort Pedicularis sylvatica and the nationally scarce yellow bartsia Parentucellia viscosa.
The adjacent hedgerows support a rich variety of shrub species, including the nationally rare Plymouth pear Pyrus cordata (*2), which occurs at several locations within the main site and in hedgerows to the east. This is the second British location for this species, recently discovered here, completely separate from the Devon population.
The lower-lying meadows support a variety of wetland habitat types including fen-type meadows, wet-heath/bog, and mire communities. More base-rich heath/bog communities are dominated by purple moor-grass Molinia caerulea, and black bog-rush Schoenus nigricans; together with a rich wetland flora including Dorset heath, bog asphodel Narthecium ossifragum, bog pimpernel Anagallis tenella, round-leaved sundew Drosera rotundifolia, marsh lousewort Pedicularis palustris, devil’s-bit scabious Succisa pratensis and bogbean Menyanthes trifoliata. Royal fern Osmunda regalis is locally abundant.
The lowest lying, permanently water-logged meadows support mire communities largely dominated by purple moor-grass, together with abundant tormentil Potentilla erecta, sharp-flowered rush Juncus acutiflorus, meadowsweet Filipendula ulmaria, wild angelica Angelica sylvestris, hemp-agrimony Eupatorium cannabinum and Sphagnum bog mosses. The rich sedge flora includes star sedge Carex echinata and tawny sedge Carex hostiana. Bog-myrtle Myrica gale is locally dominant. An additional species of particular note is the nationally scarce plant species, wavy-leaved St. John’s wort Hypericum undulatum. The uncommon oblong-leaved sundew Drosera intermedia and pale butterwort Pinguicula lusitanica also occur here.
(*1) These plant species are included in the Red Data Book listing of rare and endangered species.
(*2) These plants are Red Data Book species, and in addition are afforded special protection under Schedule 8 of the 1981 Wildlife and Countryside Act (as amended 1985).