Area: 276.7 hectares.
Other Information:
Part of the site comprises Holton Heath NNR. The site adjoins Poole Harbour SSSI and lies partly within the Dorset Area of Outstanding Natural Beauty and Heritage Coast. The site consolidates three sites previously notified as Holton Heath SSSI, Sandford Heath SSSI and Black Hill (Holton) SSSI and has been amended by extension at this revision.
Description and Reasons for Notification:
Holton and Sandford Heaths is one of a collection of sites which together comprise the Dorset heathlands. Although these heathlands have declined in extent and now occupy only 14% of their original area they show a high degree of ecological cohesion and clear ecological trends and patterns. The Dorset heaths complex is one of the major lowland heathland areas in Britain and is of international importance for its plant and animal communities.
The site lies to the north west of Poole Harbour and consists of the remaining heathlands of a once continuous heathland block between the Sherford River to the north and the Piddle Valley to the south, together with wetland habitats along the Sherford and fringing Poole Harbour. Sands and clays of the Bagshot beds underlie most of the site with more recent local deposits of alluvium, valley and plateau gravels. Most of the site is low lying with the highest point at Holton Heath only some 25 metres above sea level. Parts of the site were once used for the wartime manufacture of ammunitions which has left a network of deep cuttings. The site is important for a number of plant communities and their associated species; for heath and mire plant communities; for dry acid grasslands; for river valley and coastal wetlands as well as for a number of rare or scarce species associated with all of these habitats.
On dry free-draining soils the vegetation is dominated by heather Calluna vulgaris with bell heather Erica cinerea, bristle bent Agrostis curtisii and dwarf gorse Ulex minor also frequent. Western gorse Ulex gallii is also found occasionally on dry heathland in this part of the Dorset heaths. Locally there are stands of bracken Pteridium aquilinum and common gorse Ulex europaeus and areas with mature Scots pine Pinus sylvestris and maritime pine Pinus pinaster. Very locally, on former trackways, the Nationally Rare plant Jersey cudweed Gnaphalium luteoalbum1occurs.
Dry heath succeeds to humid heath on moister, peatier soils where there is slight impedance of drainage. This Nationally Scarce community is restricted to Dorset and the New Forest. Purple moor-grass, cross-leaved heath Erica tetralix and heather are the most abundant plants, with dwarf gorse and bristle bent also present. Locally on Sandford Heath the Nationally Rare plant Dorset heath Erica ciliaris, here at the north eastern edge of its range, forms a significant component of the humid heath.
Wet heath is found on permanently waterlogged soils. Here cross-leaved heath is abundant and occurs with the bog mosses Sphagnum compactum and S. tenellum, deergrass Trichophorum cespitosum and purple moor-grass Molinia caerulea. The Nationally Scarce plant, marsh gentian Gentiana pneumonanthe occurs abundantly in this habitat on extensive grazed wet heathland at east Keysworth.
The site also includes smaller areas where valley mire vegetation has developed on permanently waterlogged deep peat. Here purple moor-grass and bog-myrtle Myrica gale and locally common cottongrass Eriophorum angustifolium are dominant. Bog mosses are common including Sphagnum auriculatum, S. papillosum and at Holton Heath the Nationally Scarce Sphagnum pulchrum.
Reedswamp, fen and wet woodland are features of the Sherford River Valley in the north where there is also some remaining neutral grassland. In wetter areas the flora includes marsh marigold Caltha palustris, yellow iris Iris pseudacorus and marsh cinquefoil Potentilla palustris. In slightly drier conditions the herb-rich turf is dominated by red fescue Festuca rubra and common bent Agrostis capillaris with carnation sedge Carex panicea, common sedge C. nigra, star sedge C. echinata and many herbs, including ragged-robin Lychnis flos-cuculi, marsh pennywort Hydrocotyle vulgaris, marsh valerian Valeriana dioica and meadow thistle Cirsium dissectum. Two plants which are local in Dorset occur here, bulbous foxtail Alopecurus bulbosus and yellow bartsia Parentucellia viscosa.
Grazed acid grassland occurs south of Sandford. In a dry sandy sward with much bare ground, common bent and squirreltail fescue Vulpia bromoides are the most abundant grasses. Other common plants include sheep’s sorrel Rumex acetosella, bird’s-foot Ornithopus perpusillus, cat’s-ear Hypochoeris radicata and the moss Polytrichum juniperinum. In slightly wetter areas the composition of the grassland changes. Other grasses such as the bristle bent and purple moor-grass become common with pill sedge Carex pilulifera and lousewort Pedicularis sylvatica also present. Several Nationally Scarce plant species occur in these areas; clustered clover Trifolium glomeratum, mossy stonecrop Crassula tillaea, smooth cat’s-ear Hypochaeris glabra and hairy bird’s-foot-trefoil Lotus subbiflorus are found in the drier, sandy habitats while pale
dog-violet Viola lactea occurs in damper habitat near areas of grazed rushy pasture. The flora also includes bird’s-foot clover Trifolium ornithopodioides, subterranean clover Trifolium subterraneum and allseed Radiola linoides, species local in Dorset. A grazed seasonal pond is a feature of this area and here soakaway vegetation, characterised by the occurrence of marsh St John’s-wort Hypericum elodes and bog pondweed Potamogeton polygonifolius, has developed. Other typical plants of this community – bog pimpernel Anagallis tenella, many-stalked spike-rush Eleocharis multicaulis and marsh pennywort – are also found here.
The invertebrate fauna of mire and heath includes a number of Nationally Rare and Scarce species. Exposed sand provides habitat for solitary bees and wasps with many rare and scarce species recorded including four Nationally Rare species from acid grassland south of Sandford and three from heathland elsewhere. Grasshoppers and crickets include the Nationally Scarce bog bush-cricket Metrioptera brachyptera and several colonies of the Nationally Scarce butterfly silver-studded blue Plebejus argus are present on humid and wet heath. Streams and ponds support a variety of dragonflies and damselflies with more than 17 breeding species recorded including two Nationally Scarce species, small red damselfly Ceriagrion tenellum and scarce Ischnura Ischnura pumilio.
The site is particularly important for rare heathland reptiles with both of Britain’s endangered and protected reptiles, sand lizard Lacerta agilis2and smooth snake Coronella austriaca2present. L. agilis has an extremely restricted range in Britain with some 85% of the national population occurring on the Dorset heaths. There are populations of sand lizard on dry heathland throughout the site and it is estimated that together these comprise some 4% of the national population. At Black Hill, the natural south-facing slopes of hillocks in the north of the site together with the slopes and banks of artificial cuttings in the south provide particularly favourable topographical conditions for these lizards. These conditions have allowed an unusually dense colony of sand lizards to become established; only a few other sites in Britain approach or exceed the population density found at Black Hill. Smooth snake is also widely distributed and one particularly large population is known.
The heathland birds Dartford warbler Sylvia undata3,4, nightjar Caprimulgus europaeus3and woodlark Lullula arborea3,4are all present in numbers which make a contribution to the internationally important populations of these birds on the Dorset heathlands. Reedswamp and associated scrub support several pairs of the nationally rare Cetti’s warbler Cettia cetti.
1. Specially protected species listed in Schedule 8 of the Wildlife and Countryside Act 1981 (as amended).
2. European protected species listed on Schedule 2 of the Habitats Regulations 1994.
3. Species listed in Annex 1 of the EC Birds Directive.
4. Specially protected species listed in Schedule 1 of the Wildlife and Countryside Act 1981 (as amended).