Area: 105.15 hectares.
Reasons for Notification:
This site is notified for the extent of south-western dry heath of the type western gorse Ulex galii -- bristle bent Agrostis curlisii and Northern Atlantic wet heaths with cross- leaved heath Erica tetralix and the occurrence of two nationally rare/highly localised types of mire; black bog-rush Schoenus nigricans — bog asphodel Narthecium ossifragum mire and bog asphodel Narthecium ossifragum —Sphagnum papiiosum valley mire. Other reasons for notification are the extent of fen community types; the occurrence of mosaics of fen types; transitions of habitat type from fen through wet heath and humid heath to dry heath; and fen woodland communities in association with open fen. The site also supports the nationally rare, British endemic, Vigur’s eyebright Euphrasia vigursii and the nationally scarce plant species, Cornish moneywort Sibthorpia europaea, marsh fern Thelypteris palustris, pale heath violet Viola lactea and wavy-leaved St John’s wort Hypericum undulatum.
Tregonetha and Belowda Downs are located in mid-Cornwall in the headwaters of the Menalhyl stream and tributaries of the Rivers Fal and Camel. They mainly overlie loamy permeable soils with a wet peaty surface horizon, with well drained, humose, gritty loam soils on higher ground and alluvium deposits along the stream valleys. There is a long history of both underground and surface mineral extraction in the area. Evidence of this can be seen in hummocks, hollows, ditches and other workings throughout the site.
Tregonetha and Belowda Downs is of special interest principally because of the extensive area of lowland south-western heath and the associated range of valley mire, bog and fen communities. The site forms one of the largest remaining tracts of heath and associated fen habitats within the mid-Cornwall moors. It also supports several nationally rare and scarce plants.
On higher ground and drier slopes the heathland is characterised by western gorse Ulex gallii, bristle bent Agrostis curtisii, heather Calluna vulgaris and bell heather Erica cinerea. Cross-leaved heath and purple moor grass Molinia caerulea can be frequent and plants typically associated are tormentil Potentilla erecta, heath milkwort Polygala serpyllifolia, wood sage Teucrium scorodonia and bilberry Vaccinium myrtillus. Bracken Pteridium aquilinum is widespread. The nationally rare, British endemic, Vigur’s eyebright Euphrasia vigursii, the nationally scarce pale heath violet Viola lactea and lesser butterfly orchid Platanthera bifolia, heath spotted orchid Dactylorhiza maculata ssp. ericetorum and the nationally scarce moss, Bryum tenuisetum have been recorded here.
Species typically associated with wet heath are, cross-leaved heath, deergrass Scirpus cespitosus, heather, bog moss Sphagnum spp; and purple moor grass. Species such as bog asphodel Narthecium ossifragum, devil’s bit-scabious Succisa pratensis, common cottongrass Eriophorum angustifolium and carnation sedge Carex panicea occur frequently. Creeping willow Salix repens and mat grass Nardus stricta are common in some areas. Mosses and liverworts associated with the wet heath include the nationally rare liverwort Cladopodiella francisci.
Wetter parts of the site, adjacent to streams, often support taller tussocky fen vegetation in complex mosaics and important transitions to wet heath, south western humid heath, marshy grassland, fen woodland and open water.
One of the maim fen types is characterised by tall tussocks of purple moor grass with black bog rush Schoenus nigricans and bog myrtle Myrica gale. Tormentil, cross- leaved heath, western gorse and other species requiring drier conditions occur frequently in the tussocks. In the water filled hollows between the tussocks bog mosses Sphagnum spp; bog asphodel, common cottongrass and sharp-flowered rush Juncus acutiflorus are locally abundant. Species of particular interest are the nationally rare wavy-leaved St. John’s wort Hypericum undulatum, bog pimpernel Anagallis tenella, pale butterwort Pinguicula lusitanica, heath spotted orchid Dactylorhiza maculata ssp. ericetorum, round-leaved sundew Drosera rotundifolia, lesser skullcap Scutellaria minor and tawny sedge Carex hostiana, flea sedge C. pulicaris and star sedge C. echinata.
Another fen type is dominated by tussocks of purple moor grass with tormentil and cross-leaved heath. Bog asphodel, bog moss Sphagnum spp; creeping willow, devil’s bit scabious, the uncommon Royal fern Osmunda regalis, sweet gale, heather, and saw- wort Serratula tinctoria are commonly associated with this fen type.
In the valley floor permanently waterlogged conditions with more base rich, nutrient poor water has favoured the abundant growth of bog mosses and the formation of a rare type of valley mire. This is characterised by bog asphodel and bog mosses, particularly Sphagnum papillosum; common cottongrass and round-leaved sundew Drosera rotundifolia. Other species which occur are oblong-leaved sundew D. intermedia and pale butterwort.
Marsh fern Thelypteris palustris occurs in a restricted area in association with tall herbs and rushes. Marsh fern is nationally scarce species which has suffered serious decline in recent years. This fern was thought to be extinct in Cornwall until its recent discovery at Tregonetha.
Wet woodland, known as willow carr, has developed along the stream courses. The southern arm of willow carr provides an important wildlife corridor linking the site with the nearby Goss Moor National Nature Reserve. The canopy is dominated by grey willow Salix cinerea, with ash Fraxinus excelsior and downy birch Betula pubescens locally common. The ground is waterlogged and supports a rich flora of herb species, including two nationally rare species, Cornish moneywort Sibthorpia europaea and wavy-leaved St. John’s wort.
Other species which occur cononmonly in the wet woodland include water mint Mentha aquatica, marsh violet Viola palustris ssp. juressii, marsh pennywort Hydrocotyle vulgaris, round-leaved water crowfoot Ranunculus omiophyllus, water horsetail Equisetum fluviatile, shore horsetail E. x litorale, leafy rush Juncus foliosus, smooth stalked sedge Carex laevigata, bogbean Menyanthes trifoliata, ragged robin Lychnis flos-cuculi, yellow pimpernel Lysimachia nemorurm, bog moss Sphagnum spp. and greater tussock sedge Carex paniculata. These wet woodlands exhibit zonation with transitions from standing water, aquatic vegetation to drier woodland and associated fen and heath vegetation.
Broadleaved woodland, dominated by pedunculate oak Quercus robur, with coppiced hazel Corylus avellana, guelder rose Vibernum opulus, ivy Hedera helix bramble Rubus fruticosus and honeysuckle Lonicera periclymenum, also occurs within the site. Wood anemone Anemone nemorosa and bluebell Hyacinthoides non-scripta are locally common in the ground flora. Beech Fagus sylvaticus woodland with holly Ilex aquifolium also occurs. The ground flora is rich in ferns and mosses including royal fern, with bog moss Sphagnum spp. filled wet hollows. The more acid conditions are indicated by the occurrence of bilberry.
Additional habitat diversity is provided by scrub, rivers, streams, springs, pool, ponds and road verges. Royal fern and, a species of local importance, hay-scented buckler fern Dryopteris aemula are abundant, especially along the course of the Menalhyl stream. A small pool, probably connected with past mining activity, supports a large stand of another species of local importance, bottle sedge Carex rostrata. A number of species of interest are associated with the roadside verges, these include wild thyme Thymus polytrichus and southern marsh orchid Dactylorhiza praetermissa.
The site is an important traditional winter roost for the hen harrier Circus cyaneus. Merlin Falco columbarius, short-eared owl Asio lammeus and long-eared owl Asio otus roost and hunt over the site. Barn owl Tyto alba hunt across the site. The diverse habitats provide niches for a range of breeding birds.
Marsh fritillary butterfly, whose larval food plant is devil’s-bit scabious, was recently recorded from the site. There are also records of four species of Odonata, including the black-tailed skimmer Orthetrum cancellatum. The diversity of vegetation types and structure provides habitat for a wide range of invertebrates.
The rivers Menalhyl, Fal and Camel are known to support good populations of otters. The River Camel Valley & Tributaries is designated a cSAC for its otter interest. Situated in the upper catchment of these three rivers the site can play an important role in enabling otters, and other animals, to move between catchments.
This is a new site. It overlaps with the Belowda Beacon SSSI and Geological Conservation review (GCR) site notified for its geological special interest in 1996. The site also includes a Scheduled Ancient Monument (SAM).
In recognition of their international importance Northern Atlantic wet heaths with cross- leaved heath Erica tetralix and dry heaths (all sub types) are listed under Annex I of the EC Habitats & Species Directive 1992. Lowland heathland and fen habitats and Vigur’s eyebright are listed as Priority habitat and Species types in the UK Biodiversity Action Plan 1995.