Area: 13,413.2 hectares.
The site boundary has been amended by extension and deletion.
The extensions include the formerly separate Gidleigh Common SSSI and Black Tor Copse Forest Nature Reserve.
This Copse and the former North Dartmoor SSSI are Nature Conservation Review sites; the SSSI also contains a site listed in the Geological Conservation Review and it lies wholly within Dartmoor National Park.
Description and Reasons for Notification:
North Dartmoor contains one of the largest areas of upland semi-natural habitat in southern Britain. It is particularly important for western blanket bog and mixed valley mire communities, but also supports a diverse upland breeding bird community. Within the site lies Black Tor Copse, of national importance for lichens, and also Black Ridge Brook, of national geological importance.
The site is located on the northern part of the Dartmoor granite. It comprises a plateau lying between 300 and 600 metres, cut by many valleys and the headwaters of many of the major rivers of Devon are found here. The highest areas are capped by tors and rocky buttresses, often flanked by granite clitter. The area receives a high rainfall of 1.50–2.30 metres per year and experiences strong prevailing southwesterly winds. The soils are very acidic. Higher areas are covered with raw peat deposits, several metres thick in places, while on the lower slopes thinner gleyed soils and podzols with much organic matter occur.
Western blanket bog occupies parts of the highest ground, characterised by abundant bog-mosses, principally Sphagnum capillifolium, S. papillosum and S. auriculatum. Typical associated plants are purple moor grass Molinia caerulea, hare’s-tail cottongrass Eriophorum vaginatum, common cottongrass E. angustifolium, deergrass Trichophorum cespitosum, cross-leaved heath Erica tetralix, heather Calluna vulgaris, round-leaved sundew Drosera rotundifolia and bog asphodel Narthecium ossifragum. Many pools containing Sphagnum cuspidatum and S. auriculatum occur within this blanket bog, while on the drier banks and rocks and moss Racomitrium lanuginosum is abundant.
The valley mires within the site are of two types. Where water movement is restricted, a plant community similar to that of the blanket bog occurs, although with Sphagnum pulchrum often a major constituent. Where water movement is greater, the mires have abundant S. fallax, S. auriculatum and Polytrichum commune, along with soft rush Juncus effusus, sharp-flowered rush J. acutiflorus, bottle sedge Carex rostrata, star sedge C. echinata, white-beak sedge Rhyncospora alba and bogbean Menyanthes trifoliata.
Large areas of both wet and dry heathland are also found within the SSSI, dominated by heather, purple moor grass and cross-leaved heath, together with western gorse Ulex gallii and bilberry Vaccinum myrtillus. In amongst this heathland patches of acidic grassland are frequent, the main components of which are bristle bent Agrostis curtisii, sheep’s fescue Festuca ovina, mat-grass Nardus stricta, heath rush Juncus squarrosus and green-ribbed sedge Carex binervis. Both these heathland and grassland communities are restricted to south-west Britain. Occasionally bilberry alone is the dominant shrub and here mosses such as Pleurozium schreberi, Rhytidiadelphus loreus, Racomitrium lanuginosum, Hylocomium splendens, Thuidium tamariscinum and Hypnum jutlandicum are abundant, while lichen-rich patches with Cladonia arbuscula, C. uncialis and C. impexa also occur.
Among the more unusual species recorded on site are cranberry Vaccinium oxycoccus on the open moor, fir clubmoss Huperzia selago, lemon-scented fern Oreopteris limbosperma, Tunbridge filmy-fern Hymenophyllum tunbrigense and Wilson’s filmy-fern H. wilsonii in wet shaded crevices in scree slopes, bog orchid Hammarbya paludosa in a few mires, and the liverwort Anastrepta orcadensis on the highest tors.
The bird community includes the only regular breeding populations of golden plover Pluvialis apricaria and dunlin Calidris alpina in southern Britain. Also present are breeding populations of whinchat Saxicola rubetra, wheatear Oenanthe oenanthe and ring ouzel Turdus torquatus, a species which breeds here in greater numbers than anywhere else in southern England.
Black Tor Copse is one of three high altitude stunted pedunculate oak Quercus robur woodlands on Dartmoor. It has developed on thin humic and podzolic soils with extensive granite clitter on a south-west facing slope above the West Okement River. The vascular plant community is limited to strict acid-loving species such as Bilberry, but the moss and lichen floras are rich. Many of the granite boulders are covered with a carpet of mosses, with species such as Rhytidiadelphus loreus, Thuidium tamariscinum and Plagiothecium undulatum being abundant. The Copse is nationally important for the lichens which clothe the trees, mosses and rocks, with exceptionally well-developed Parmelietum laevigatae and Usneion communities. Many species present are rarely found outside the uplands of Scotland and Wales, including Mycoblastis affinis, Usnea filipendula, Sphaerophorus melanocarpus, Arthonia stellaris, Micaria botyroides, M. cinerea, M. violacea and Gyalideopsis muscicola, and also Bryoria smithii known from only two other sites in Britain. Notable species growing on rocks in the vicinity include Massalongia carnosa, Ochrolechia tartarea, Pilophorus strumaticus and Parmelia discordans.
Black Ridge Brook provides an important palynological record of the Flandrian vegetation history and environmental change on north Dartmoor. The pollen sequence covers the whole period from the late Devensian/Flandrian boundary almost to the present day and is supported by radiocarbon dating. In addition to the relatively long record, the site provides pollen evidence for local tree cover and relatively early burning.