Halsdon

Also within

Devon County

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Carboniferous · Rock Type: Mudstone, Siltstone, Slate

Landscape processes: Karst

Birds & fish recorded

Birds

Description

Halsdon SSSI Description Halsdon is one of the best sections of an outstanding North Devon river and valley system. The special interest lies in a combination of the river, flood-plain meadows and ancient oak woodlands which support many breeding bird species. This 1.5 kilometres stretch of the River Torridge varies in width between 10–15 metres and runs over a varied bed material consisting of boulders, gravel, sand and silt. The several meadows between the river and the woodland overlie a loamy soil derived from sandstones and shales. Rising steeply from the valley floor to approximately 375 metres, the west-facing ridge is of Carboniferous slate with mudstone and siltstone. This provides for a freely drained but mostly very thin soil on which the broad-leaved woodlands are established. Approximately three-quarters of the site is occupied by woodland, the constituent species of which vary according to soil and drainage conditions. On the thinner, more acid soils sessile oak Quercus robur and hybrid oaks dominate and understorey of holly Ilex aquifolium, rowan Sorbus aucuparia and hazel Corylus avellana. Beech Fagus sylvatica is locally abundant in the canopy. The ground flora consists mainly of greater woodrush Luzula sylvatica with some bilberry Vaccinium myrtillus, common cow-wheat Melampyrum pratense, broad buckler-fern Dryopteris dilatata and hard-fern Blechnum spicant. Areas of more nutrient-rich soil support a greater proportion of ash Fraxinus excelsior, pedunculate oak Quercus robur and sycamore Acer pseudoplatanus. hazel becomes more abundant, along with downy birch Betula pubescens, hawthorn Crataegus monogyna and spindle Euonymus europaeus. Wych elm Ulmus glabra occurs in some parts, particularly on the lower slopes. The ground flora is more diverse, with enchanter’s nightshade Circaea lutetiana, bugle Ajuga reptans, bramble Rubus fruticosus, honeysuckle Lonicera periclymenum and wood sedge Carex sylvatica. Alder Alnus glutinosa and willows Salix spp. occur in wet hollows at the foot of the ridge where pendulous sedge Carex pendula forms locally dense patches. There are several small blocks of conifer plantation within the woodland and rhododendron Rhododendron ponticum has invaded some areas. The fields at the foot of the ridge are poorly drained and these marshy areas are dominated by soft rush Juncus effusus with occasional meadowsweet Filipendula ulmaria, greater bird’s-foot trefoil Lotus pedunculatus, purple loosestrife Lythrum salicaria and wild angelica Angelica sylvestris. In the woodland, all three species of woodpecker are breeding, together with sparrowhawk Accipiter nisus, buzzard Buteo buteo, wood warbler Phylloscopus sibilatrix and pied flycatcher Ficedula hypoleuca. Kingfisher Alcedo atthis and dipper Cinclus cinclus nest along this section of the river. Water vole Arvicola amphibius occurs and otters Lutra lutra are resident on the river. Butterflies recorded include purple hairstreak Favonius quercus, silver-washed fritillary Argynnis paphia and speckled wood Pararge aegeria.

Species mentioned

Plant communities