Western Mendip Biodiversity

Cheddar Gorge supports a complex mosaic of valuable semi-natural habitats, which between them are home to a wide range of species, many of which are rare. Limestone grasslands on the gorge slopes are rich in calcicolous (lime-loving) plants, which thrive in the thin dry soils. On slopes with a southern to western aspect these include sheep's-fescue (Festuca ovina), salad burnet (Sanguisorba minor), common bird's-foot-trefoil (Lotus corniculatus), wild thyme (Thymus polytrichus) and common rock-rose (Helianthemum nummularium). Cooler and wetter aspects support an equally rich sward, but the range of species found here includes flea sedge (Carex pulicaris), betony (Stachys officinalis) and lady's bedstraw (Galium veru). Rough grassland with a history of scrub invasion favours coarse species e.g. upright brome (Bromopsis erecta), wood sage (Teucrium scorodonia) and wild marjoram (Origanum vulgare). These grasslands are of outstanding importance for insects and other invertebrates, and in summer many different species of butterfly are abundant on open sunny slopes.

Limestone crags, rocky outcrops and cliff faces support populations of some of the specialities of the gorge, including the rare and protected Cheddar pink (Dianthus gratianopolitanus), slender bedstraw (Galium pumilum) and lesser meadow-rue (Thalictrum minus), and peregrine falcons (Falco peregrinus) can sometimes be seen soaring through the gorge. Scree slopes are frequent below the cliffs and in places support good populations of ferns, including maidenhair spleenwort (Asplenium trichomanes), rustyback (Ceterach officinarum) and the uncommon limestone fern (Gymnocarpium robertianum) and mats of mosses, including Neckera crispa with its shiny, wrinkled leaves and robust, complanate habit. Madder (Rubia peregrina) can often be found scrambling through scrub and over rocks. This normally coastal plant is common in the Cheddar area.

Mixed scrub is an important habitat within the gorge, and is characterised by ash (Fraxinus excelsior), yew (Taxus baccata), hazel (Corylus avellana) and hawthorn (Crataegus monogyna). It also supports whitebeams (Sorbusspecies), including two rare British endemics. In places, mature ash-oak-hazel woodland has developed, and sanicle (Sanicula europaea), dog's-mercury (Mercurialis perennis) and broad-leaved helleborine (Epipactis helleborine) can all be found on the woodland floor.

Plateau soils are deeper and more nutrient-rich, and have an interesting mosaic of flower-rich unimproved grassland within a patchwork of thorn scrub. In places, the large anthills constructed by yellow meadow-ant (Lasius flavus) are prominent, showing holes where green woodpeckers (Picus viridis) have been feeding on the ants inside. In spring, the uncommon green-winged orchid (Orchis morio) is a distinctive feature of these grasslands. Windblown loessic soils have a more neutral-acidic character, and support pignut (Conopodium majus), sweet vernal-grass (Anthoxanthum odoratum), common knapweed (Centaurea nigra) and harebell (Campanula rotundifolia). At Bubwith Acres Nature Reserve, these species co-exist with species-rich calcicolous grassland where underlying limestone reaches the surface, and waxcap fungi (Hygrocybe species) are abundant in the autumn.

Elsewhere, there are small patches of limestone heath, an uncommon and highly distinctive Mendip habitat. Calcifuges (lime-hating species) including ling (Calluna vulgaris) and heath bedstraw (Galium saxatile) co-exist with the typical limestone grassland species.

Caves within the Cheddar Gorge complex are important for roosting and hibernating bat species, including significant numbers of the nationally rare greater horseshoe bat (Rhinolophus ferrumequinum).

SITE: CHARTERHOUSE

Sub-site: Velvet Bottom

The reserve is dominated by extensive areas of rough neutral grassland. Lead contamination of the lower ground over the centuries has prevented tree and scrub growth, and the grassland is relatively species-poor. High levels of lead are toxic to most plants, but over a long period of time, a small but select group has colonised the lead slag heaps that are found in the middle of the reserve. In early spring, mats of common whitlowgrass (Erophila verna) a tiny, white-flowered crucifer, are abundant on dry banks of bare slag, along with herb Robert (Geranium robertianum), and occasionally, spring sandwort (Minuartia verna) which is a rare plant in southern England, and which, on Mendip, is nearly always associated with old lead workings.

Damper ground associated with old settling beds, buddle pits and other depressions are defined by the presence of cuckooflower (Cardamine pratensis), wild angelica (Angelica sylvestris), marsh thistle (Cirsium palustre) and other typical species of marshy grassland.

A more varied vegetation is present on the edges of the reserve, where acidic soils support the uncommon meadow saffron (Colchicum autumnale) the attractive flowers of which can be found in September among the bracken (Pteridium aquilinum). Devil's-bit scabious (Succisa pratensis), ling and other wildflowers attract many insects, especially butterflies and grasshoppers, and dry grassland supports large populations of Adders (Vipera berus) and common lizard (Lacerta vivipara) which may be often seen basking early or late in the day.

Short, rabbit-cropped limestone turf occurs in a few places, and a wide diversity of typical herbs and grasses are present, including carline thistle (Carlina vulgaris), and common spotted orchid (Dactylorhiza fuchsii), which attract many butterflies on warm days. Spring cinquefoil (Potentilla neumanniana) is also found in a few places.

Sub-site: Ubley Warren

The legacy of centuries of opencast lead mining is evident in the uneven gruffy ground and worked-out mineral rakes at this site, and it has been designated as a Site of Special Scientific Interest on account of the intricate and extensive juxtaposition of acidic, lime-loving and lead-tolerant vegetation.

The rakes (characterised by limestone cliffs and exposures within the areas of mining disturbance) are a dominant feature of the reserve, and support important communities of mosses, liverworts, lichens and ferns, some of which are rare. Sheltered and humid conditions within some of the rakes mimic woodland conditions, and a number of typical limestone woodland species can be found.

Acid grassland growing over aeolian loess soils is typified by such plant species as common bent (Agrostis capillaris) and heath bedstraw. Large grassland mosses are a distinctive feature of this sward, and include Hylocomium splendens and Climacium dendroides. Heathland vegetation is also abundant, supporting gorse (Ulex europaeus), western gorse (U. galli), ling, purple moor-grass (Molinia caerulea), bilberry (Vaccinium myrtillus) and heath spotted orchid (Dactylorhiza maculata).

Many of the rare plants at Ubley Warren are associated with the worked-out mineral rakes and limestone outcrops, including the nationally scarce soft-leaved sedge (Carex montana) which is quite frequent, and often grows in association with early purple orchid (Orchis mascula). Hutchinsia (Hornungia petraea) and brittle bladder-fern (Cystopteris fragilis) also favour limestone. Typically, the shallow base-rich soils have developed a rich limestone flora, which also supports common spotted orchid and bee orchid (Ophrys apifera).

Where lead-rich soil is present, the nationally scarce spring sandwort can be found.

Ubley Warren is an important site for reptiles, with slow-worm (Anguis fragilis), adders and common lizards all present.

Sub-site: Black Rock

Steep, south-facing slopes support short herb-rich limestone grassland over thin soils. A very high number of plant and invertebrate species are present in this turf, and many of the plants are very diminutive. Sheep's-fescue, wild thyme and quaking-grass (Briza media) are some of the characteristic species, and more notably, spring cinquefoil can be seen flowering in the spring. Common rock-rose, a prostrate sub-shrub with showy yellow flowers in summer, thrives on these warm slopes. Pollinating insects and nectar-feeders are abundant on warm days, and include such species as the spring-flying brimstone (Gonepteryx rhamni), common blue (Polyommatus icarus), and cinnabar moth (Tyria jacobaea).

Semi-natural woodland clothes the steep and rocky valley slopes close to the top of Cheddar Gorge. This is the typical ash-hazel woodland of the local area. Many ferns and lower plants thrive in the shady and humid conditions, and nearby dry limestone walls are draped with mats of various calcicolous mosses and liverworts. Mosses such as Neckera complanata and Ctenidium molluscum form dense mats, and are well adapted to alternating cycles of dehydration and irrigation. These walls, and the stonework of the disused limestone kiln in the quarry also provide excellent anchorage for several diminutive ferns, such as rustyback, wall-rue (Asplenium ruta-muraria), and maidenhair spleenwort.

Birds are well represented in the nature reserve, and it is possible to hear the distinctive 'cronk' of ravens (Corvus corax), and see sparrowhawks (Accipiter nisus) and a variety of finches and warblers. The woodlands also support badgers Meles meles, foraging bats, and, where honeysuckle (Lonicera periclymenum) is present in the woodland and scrub understorey, the uncommon dormouse (Muscardinus avellanarius).

Sub-site: Long Wood

Long Wood has been woodland since possibly as early as the thirteenth century, and it now supports many plants and animals that are usually restricted to ancient woodland sites. Much of the wood has been traditionally managed as coppice with standards, and evidence of this can be seen close to the path in the valley bottom.

Ash and pedunculate oak (Quercus robur) are the main canopy trees, and stands of beech (Fagus sylvatica) were planted in the 1950s. Below, the understorey is characterised mainly by hazel, field maple (Acer campestre), and in wetter ground, grey willow (Salix cinerea). Fallen wood provides ideal habitat for dead-wood invertebrates and fungi.

In spring, woodland herbs are at their best in Long Wood. Ramsons (Allium ursinum) forms dense white garlic-scented carpets near the stream, with yellow-flowered carpets of opposite-leaved golden-saxifrage (Chrysosplenium oppositifolium) in the wettest places. Large, sharp-edged tussocks of tufted hair-grass (Deschampsia cespitosa) also thrive in this wet, clayey ground, and in summer, send up tall, elegant infloresences. Higher ground favours bluebell (Hyacinthoides non-scripta), wood anemone (Anemone nemorosa) and more uncommonly, herb Paris (Paris quadrifolia) and the curious parasitic toothwort (Lathraea squamaria).

Sub-site: Blackmoor

Blackmoor's long history of lead mining has created a rich mosaic of valuable wildlife habitats. Bare and sparsely vegetated slag heaps contain high levels of toxic heavy metals, especially lead, zinc and cadmium, and very low levels of plant nutrients. Slow colonisation of the heaps by a specialised community of metalliferous specialists has taken place over time, and a low-growing mat of lichens, mosses, and tolerant vascular plants can be found. Alpine penny-cress (Thlaspi caerulescens) is a rare plant which, in Britain, is almost confined to sites rich in lead or zinc. Other unusual plants include sea campion (Silene uniflora). Mats of the tiny white-flowered common whitlowgrass flower in early spring on bare ground. The slag heaps (and large chunks of metalliferous slag) also support a diverse lower plant and lichen community, which includes small lichens of the Cladonia genus and several species that are normally found on siliceous rocks in montane areas (e.g. the small moss Grimmia donniana and the greenish-yellow crustose lichen Rhizocarpon geographicum).

Gruffy ground (uneven and mostly long grassland resulting from opencast lead mining) supports a wide range of plant species, but few are constant and abundant. Several large carpet-forming mosses are however prominent, including the red-stemmed Hylocomium splendens and Pseudoscleropodium purum.

The worked-out rakes are associated with a rich lime-loving flora typical of limestone grassland. Several diminutive mosses and ferns are very characteristic of these outcrops, especially wall-rue Asplenium ruta-muraria and the mosses Fissidens cristatus and Schistidium apocarpum .

Open water, an unusual habitat in this part of the Mendip Hills, is found at Blackmoor in the form of several old ponds lying over the Avon Group mudstones. These ponds, and their associated wetlands, support distinctive flora and fauna, and contribute to the reserve's total of four species of amphibian, and four common species of reptile, including grass snake (Natrix natrix). Deeper water is home to a number of aquatic plants, e.g. Mare's-tail (Hippuris vulgaris), amphibious bistort (Persicaria amphibia) and water-starwort (Callitriche species). Species of the wetland edge include Marsh-marigold (Caltha palustris), brown sedge (Carex disticha) and water-plantain (Alisma plantago-aquatica). The pools are also important for dragonflies and damselflies and a wide range of other invertebrate fauna.

Limestone heath can also be found on higher ground on the reserve. This nationally rare habitat type supports a majority of calcifugous (lime-hating) plants growing alongside some typical calcicolous (lime-loving) species in shallow soil overlying limestone rock. Locally, rainwater has leached carbonate ions away from the root-zone in the surface horizons, allowing shallow-rooted acid-loving plants to grow. At Blackmoor, such communities are typified by ericaceous shrubs and herbs including ling, western gorse, tormentil (Potentilla erecta) and purple moor-grass.

With such a wide range of habitats present at Blackmoor, many birds are resident or frequent visitors, including blackcap (Sylvia atricapilla), swallow (Hirundo rustica) and yellowhammer (Emberiza citrinella).

SITE: BLACKDOWN

Sub-site: GB Gruffy Field

Very uneven ground in the southern half of this reserve is partly due to the presence of a number of caves and swallets in the underlying limestone, as well as being a legacy of past lead mining in the area. Lead-rich waste is present, and whilst poorly vegetated, it supports both Spring Sandwort and alpine penny-cress, which are characteristic of old lead-workings in the Charterhouse area. The vegetation is very species-rich, and forms an intricate mosaic of both acid-loving and calcicolous species, especially where limestone rock forms low outcrops. Some of the more typical species include common bird's-foot-trefoil, fairy flax (Linum catharticum), tormentil, common sorrel (Rumex acetosa) and wild thyme. The nationally scarce dwarf mouse-ear (Cerastium pumilum) and the local hairy rock-cress (Arabis hirsuta) are diminutive herbs that are associated with calcareous bare ground or short grassland in this part of the reserve.

Cave entrances and larger sinkholes provide humid and sheltered conditions which are ideal for a wide range of ferns, including soft shield-fern (Polystichum setiferum), brittle bladder-fern and broad buckler-fern (Dryopteris dilatata).

Loessic soils over shale in the northern half of the site support damp, species-rich neutral-acidic pasture, with some stands of bracken. Rushes indicate impeded drainage in places, with soft-rush (Juncus effusus) being particularly abundant. Common spike-rush (Eleocharis palustris), lady fern (Athyrium filix-femina) and square-stalked St John's-wort Hypericum tetrapterum are other indicators of the damp ground. Colourful summer wildflowers include ragged-robin (Lychnis flos-cuculi), heath spotted orchid, meadow vetchling (Lathyrus pratensis) and greater bird's-foot trefoil (Lotus pedunculatus).

Sub-site: Blackdown Summit

Acidic soils derived from the underlying Portishead Formation (Old Red Sandstone) support one of the largest stands of dwarf shrub heath on Mendip. Land higher than 300 metres is dominated by mature ling, with less abundantly, other heathers (cross-leaved heath Erica tetralix and bell heather E. cinerea), bilberry (Vaccinium myrtillus) and typical heathland grasses. Acid grassland forms a fringing mosaic in places, and is characterised by common bent, western gorse, pill sedge (Carex pilulifera ), green-ribbed sedge (C. binervis) and foxglove (Digitalis purpurea) among other typical plants.

Paths through the heath support opportunistic and/or trample-resistant plants, including the diminutive toad rush (Juncus bufonius), heath rush (J. squarrosus), common yellow-sedge (Carex viridula ssp. oedocarpa) and marsh cudweed (Gnaphalium uliginosum).

A few small mires are also present on Blackdown, providing suitably wet and acidic conditions for Sphagnum mosses and a host of other interesting wetland plants, including the creeping, pink-flowered bog pimpernel (Anagallis tenella) and star sedge (Carex echinata). The summit itself is quite wet, and purple moor-grass can be found with bog asphodel (Narthecium ossifragum) and other bog species.

Dense bracken has become established on the northern side of the hill, a consequence partly of a history of occasional wildfires and reduced grazing pressure on Blackdown, and of thicker soils. Bracken produces thick litter and excludes most other species, so is of low biodiversity interest.

Many ferns, mosses and liverworts flourish in the humid incision of the East and West Twin Brooks, which rise on the northern side of the hill. Here, lady fern, intermediate polypody (Polypodium interjectum) and hard fern (Blechnum spicant) can be found, alongside Dicranum majus and other bryophytes, hairy wood-rush (Luzula pilosa) and bitter-vetch (Lathyrus linifolius).

Blackdown supports many heathland insects and birds, many of which are rare and/or declining. Sharp-eyed visitors may see emperor moths (Saturnia pavonia) or their distinctive cocoons in the heather, meadow pipits (Anthus pratensis), stonechats (Saxicola torquata), skylarks (Alauda arvensis). barn owls (Tyto alba) can also sometimes be glimpsed hunting over the site.

SITE: BURRINGTON COMBE

Sub-site: Burrington Combe

The main ecological interest in the combe lies in the very species-rich limestone grassland and scree that overlies the thin mineral soils. Overall vegetation cover is very sparse, but supports many different calcicolous plants that are typical of such habitats in the area. Perennial herbs help to stabilise the loose stony soil, including salad burnet, small scabious (Scabiosa columbaria), common rock-rose and ploughman's-spikenard (Inula conyzae).

The warm, south-facing slopes of the combe are particularly important for butterflies and other invertebrates.

In past years reduced grazing in the combe has allowed a rich mixed native scrub cover to develop over grassland, scree and on limestone crags and cliffs. Typical species include hawthorn, wild privet (Ligustrum vulgare), yew, ash, wayfaring-tree (Viburnum lantana) and, on more acidic and less steep slopes, rowan (Sorbus aucuparia) gorse and elder (Sambucus nigra). Whilst this heterogeneous habitats provides good cover for birds, much of the scrub has recently been cut back, and grazing resumed to prevent loss of valuable rich grassland.

Thin strips of limestone heath are present on leached soils close to the top of the combe. Here, limestone grassland gives way to vegetation with a heathy character, dominated by western gorse, with bell heather and occasional ling. In turn, this grades into coarse vegetation dominated by bramble (Rubus fruticosus), bracken and hawthorn on Burrington Ham.

Caves within the combe support populations of hibernating bats, including both species of horseshoe bat.

SITE: SOUTH FLANK

Sub-site: Crook Peak to Shute Shelve Hill

On a prominent south and west facing escarpment, this extensive estate comprises a very large area of very rich Mendip downland and includes a very wide range of different habitats, including some that have a restricted distribution.

Immature calcareous soils are dominant on many of the steeper slopes, and a rich limestone flora has developed. Its composition varies, but includes many typical unimproved grassland indicator species including wild thyme, dwarf thistle, dropwort (Filipendula vulgaris), meadow oat-grass and yellow-wort (Blackstonia perfoliata). On parts of Crook Peak and Shute Shelve Hill, sparse, low-growing vegetation is exceptionally rich in places, and supports a number of rarities including honewort (Trinia glauca), somerset hair-grass (Koeleria vallesiana), Cheddar pink and several rare lichens, which are a prominent feature of this sward.

Low craggy limestone outcrops and small areas of limestone pavement offer refuge to small crevice-dwelling ferns, including maidenhair spleenwort, wall-rue and rustyback. More uncommon plants found in this habitat include spring cinquefoil and basil thyme (Clinopodium acinos).

Upslope, for example near the summit of Crook Peak and on the upper parts of Wavering Down, soils give way to acidic loessic material, and limestone grassland is replaced by acid dwarf-shrub heath and bracken. Western gorse is the most common shrub, accompanied by both ling and bell heather. Locally, this is transitional to acid grass-heath, an unusual type of community where dwarf shrubs cover less than 70% of the ground. Here, heathers and gorses are juxtaposed with sweet vernal-grass, heath-grass (Danthonia decumbens), tormentil, sheep's-fescue and red fescue (Festuca rubra). These slopes are unusual in the mosaic that is formed between patches of calcicole and calcifuge vegetation. Locally, a good mixture of scrub is present, with high levels of gorse, hawthorn, blackthorn, roses (Rosa spp.) elder and hazel.

King's Wood is an ancient woodland with a documented history reaching back as early as the 13th century. It is mostly semi-natural in character, and supports a very rich flora and fauna. Ash standards dominate, along with pedunculate oak, and small-leaved lime (Tilia cordata), the latter being especially abundant as standards and pollards near the old boundary banks. Field maple and wild Cherry Prunus avium are less frequent. The understorey is well-developed in King's Wood, with hazel, hawthorn and holly being particularly characteristic. Pollarded trees within the wood suggest that it has been managed as wood-pasture in the past few centuries. A rich ground flora is present in the wood, with ancient woodland indicator species typical of Mendip limestone woods. In spring, bluebells, ramsons and dog's-mercury form dense carpets, with less frequently, toothwort, sanicle, moschatel, wood anemone and woodruff (Galium odoratum).

Limestone boulder scree is also frequent in the upper parts of the wood, and this is covered by dense growth of mosses. King's Wood also supports a number of notable epiphytic lichens.

Many species of invertebrate are found in King's Wood, including ash-black slug (Limax cinereoniger), a characteristic ancient woodland species. Woodland bird species include chiffchaff (Phylloscopus collybita), blackcap, cuckoo (Cuculus canorus), and dormice occur locally.

Sub-site: Axbridge Hill and Fry's Hill

Thin limestone loams overlying limestone and dolomitic conglomerate support a very rich calcareous flora, which varies in composition, but typically includes sheep's-fescue, crested hair-grass, common rock-rose and wild thyme. In places the rare somerset hair-grass can also be found.

Rock bluffs and limestone screes support a distinctive assemblage of species, including slender bedstraw, sea stork's-bill (Erodium maritimum) which is rare so far inland, dwarf mouse-ear and rustyback, wall-rue and maidenhair spleenwort ferns. Saxicolous (rock-dwelling) lichens and bryophytes are very diverse on the bare rock and thin soils associated with rock outcrops.

Locally, leached soils upslope have developed a limestone heath vegetation, characterised by an intimate juxtaposition of lime-loving plants with more calcifugous species, including western gorse, ling, bell heather and tormentil.

Scrub and broadleaved woodland are found on lower slopes, and over scree, and provide a further dimension to the range of habitats.

The combination of rich vegetation and warm, south-facing aspect is highly attractive to butterflies, and the area supports a very rich lepidoptera fauna. Brown argus (Aricia agestis), dark green fritillary (Argynnis aglaja), green hairstreak (Callophrys rubi) and many other butterfly and moth species have been recorded.

The nationally rare Greater and Lesser Horseshoe Bats roost within the SSSI.

SITE: PRIDDY AREA

Sub-site: Priddy Mineries

The biodiversity and habitats of Priddy Mineries reflects the area's past history of lead mining. Valley mire, open water, wetland habitats and lead-rich spoil heaps are all present, and the site supports a very wide range of flora and fauna. It is especially important for its rich wetland flora, supporting good populations of all three British newts, as well as frogs and toads. Common Lizard and Adder are commonly seen, particularly in areas of the site where purple moor-grass forms large tussocks.

Open water (mining pools) support a very rich invertebrate fauna, including many different species of dragonfly.

Bare mining spoil and dams are high in lead and other heavy metals, and this generally deters vegetation growth. The rare alpine penny-cress is one of the early pioneers of bare slag, occurring alongside sea campion Silene uniflora, which is rare so far inland in Somerset. Elsewhere the loose slag is stabilised by rafts of mosses and lichens. Other spoil heaps in the valley bottom have been colonised by a neutral grassland which is moderately diverse. cowslip (Primula veris), yellow-rattle (Rhinanthus minor) and lady's bedstraw can be all be found.

Valley mire is a very uncommon habitat in the Mendip Hills, and it is well-developed at Priddy. Its tussocky appearance is due to an abundance of purple moor-grass, but less frequent associates include hare's-tail cottongrass (Eriophorum vaginatum) which is rare on Mendip, bog asphodel and cross-leaved heath and several species of Sphagnum moss. Nutrient-poor water in the northern pool supports bottle sedge (Carex rostrata), water horsetail (Equisetum fluviatile), and common spike-rush. Submerged plants include broad-leaved pondweed (Potamogeton natans) and the floating form of bulbous rush (Juncus bulbosus).

Elsewhere in the wet valley bottom, greater tussock-sedge (Carex paniculata) forms large and distinctive tussocks a metre or more high, alongside young willow carr and large shuttlecocks of lady fern (Athyrium filix-femina). This species is one of only a few that can tolerate metalliferous soils.

On drier valley slopes, an extensive mosaic of acid grassland and dwarf shrub heath has developed. Bell heather and ling co-exist with gorse and western gorse, whilst wavy hair-grass (Deschampsia flexuosa) and tormentil can be found in the dry grassland.

Sub-site: Stockhill Plantation (Chewton mineries)

Mixed conifer plantation now overlies former lead workings, although evidence of these can still be seen in the form of worked-out rakes and gruffy ground.

In clearings and beside rides on Stockhill, the influence of the underlying Devonian sandstone can be seen in the prominence of heathland and acid grassland plants. Ling and western gorse are frequent, along with purple moor-grass, and other typical calcifuges.

The site is notable for the presence of nightjar (Caprimulgus europaeus) and long-eared owl (Asio otus), as well as a wide range of other birds typical of lowland conifer/heath habitats.

In places, lead contamination in the soil is high, preventing either tree growth or natural regeneration. These open areas are home to a diminutive and very rare moss. Ditrichum plumbicola is endemic to Europe where it is found only in Britain and Germany, and is restricted to lead-mine spoil.

SITE: WESTBURY-SUB-MENDIP

Sub-site: Draycott Sleights

On Mendip, 'sleight' means sheep-pasture, and this site has been managed by traditional sheep-grazing for centuries. Now a nature reserve, Draycott Sleights occupies a steep south-west-facing scarp slope overlooking the Somerset Levels. Its principal habitats are herb-rich limestone grassland with scattered scrub, rocky limestone crags, small cliffs and rock exposures.

The limestone grassland supports a wide range of calcicolous herbs, sedges and grasses. On the slopes the most abundant grasses and sedges include upright brome, crested hair-grass (Koeleria macrantha), sheep's-fescue, quaking-grass and glaucous sedge (Carex flacca). The grassland is rich in herbs supporting squinancywort (Asperula cynanchica), yellow-rattle, kidney vetch (Anthyllis vulneraria) and many other typical species. Orchids that might be seen in summer include pyramidal orchid (Anacamptis pyramidalis) and greater butterfly orchid (Platanthera chlorantha).

Low limestone crags and bluffs provide shelter for small ferns and crustose lichens in shades of yellow, white and grey, and in spring, support the diminutive annual rue-leaved saxifrage (Saxifraga tridactylites) in pockets of bare soil.

The northern part of Draycott Sleights overlies Burrington Oolite and Black Rock Limestone, and supports a slightly different calcareous grassland community, which is dominated by sheep's-fescue and meadow oat-grass (Helictotrichon pratense). Many different, low-growing herbs are also present, including the uncommon green-winged orchid in spring. In summer, many different herbs attract butterflies and other invertebrates. Blue butterflies are especially notable, and include the local adonis blue (Lysandra bellargus) and silver-studded blue (Plebejus argus).

Sub-site: Rodney Stoke (Stoke Woods)

Rodney Stoke National Nature Reserve encompasses broad-leaved woodland, scrub and limestone grassland on two south-facing spurs of the Mendip scarp.

Big Stoke and Little Stoke Woods are mostly ancient in origin, and originally managed as coppice but were almost entirely clear-felled in the 1914–18 war, followed by localised felling in 1939. The canopy is now of two distinct age-classes, with an extensive hazel understorey. The woodland is a good example of a typical Mendip ash wood, and supports three different woodland communities. Stools of coppiced small-leaved lime are frequent in the wood, and pedunculate oak partially replaces ash as the main canopy tree where soils are more neutral in character. Wild service-tree (Sorbus torminalis) is locally distributed in the wood.

Whilst hazel dominates the understorey, a range of other limestone-loving shrubs are also frequent, including buckthorn (Rhamnus cathartica) and guelder rose (Viburnum opulus).

Many typical ancient woodland indicator species are found in the ground flora. Dog's-mercury, bluebell and hart's-tongue (Phyllitis scolopendrium) are abundant. Primroses (Primula vulgaris) wood spurge (Euphorbia amygdaloides) and wood sedge (Carex sylvatica) are frequent along the footpath through the wood. More locally, there is spurge-laurel (Daphne laureola), nettle-leaved bellflower (Campanula trachelium), early purple orchid, herb Paris and toothwort. Purple gromwell (Lithospermum purpureocaeruleum), a nationally rare herb, also occurs at Rodney Stoke; it is not uncommon in old limestone woodlands in the Cheddar area.

Many ferns, bryophytes and fungi flourish in the humid shelter of the woodlands, and boulders and rock outcrops support thick mats of mosses and liverworts. Common large mosses include Thamnobryum alopecurum , and Atrichum undulatum , whilst the leafy liverwort Porella platyphylla is abundant on old limestone walls.

Rich limestone grassland is present locally, and where soils are more leached on higher ground, dwarf-shrub heath occurs locally, with western gorse and ling.

Badgers are frequent in the woodland, and Big Stoke Wood supports roosting populations of bat. Many birds also breed locally and invertebrates are abundant. Purple hairstreak (Quercusia quercus) can sometimes be seen in areas where oaks are present, and marbled white (Melanargia galathea) is a frequent flyer.

SITE: WOOKEY AND WELLS

Sub-site: Ebbor Gorge

Ancient ash woodland dominates the steep rocky limestone slopes of Ebbor Gorge, and is of a varied age structure. It is managed as traditional rotational coppice-with-standards, and is mainly dominated by ash and pedunculate oak. Associated trees include hornbeam (Carpinus betulus), field maple and beech, whilst the understorey is overwhelmingly dominated by coppiced hazel, with lesser amounts of spindle (Euonymus europaeus), dogwood (Cornus sanguinea) and other typical calcicolous shrubs. The ground flora is very rich, with many ancient woodland species, and includes yellow archangel (Lamiastrum galeobdolon), dog's-mercury, wild anemone and bluebell. On wetter ground in the bottom of the gorge, Opposite-leaved golden-saxifrage is abundant, with enchanter's-nightshade (Circaea lutetiana), moschatel (Adoxa moschatellina) and wood sedge.

Butterflies are abundant at Ebbor Gorge, and the site supports some rare species that require a well-developed and complex woodland structure. These include white-letter hairstreak (Strymonidia w-album) and high brown fritillary (Argynnis edippe). Many others are found on the rich limestone grassland.

Cliffs, scree and bluffs in the gorge itself are home to many ferns, lower plants, lichens and fungi, which are favoured by the sheltered, very humid microclimate. More than 150 lichen species have been recorded, in rich communities on the limestone outcrops and older trees, and the gorge also supports more than 100 species of moss and liverwort, including several rarities.

Small caves in the gorge are valuable roosting sites for both greater and lesser horseshoe bats.

Rich, unimproved limestone grassland occurs extensively at the top of the gorge, and supports a range of typical calcicoles, for example common rock-rose, salad burnet, wild thyme and large thyme (Thymus pulegioides). Localised patches of leached soil support limestone heath, with a limited range of calcifuge plants, including bell heather and gorse.

Sub-site: Wookey Hole

Wookey Hole caves support an important roost of the nationally rare greater gorseshoe bat.

North of the cave complex, two large field enclosures lie on steep, south-west-facing slopes. These pastures have escaped agricultural improvement, and support an extensive stand of short calcareous grassland that has developed over Dolomitic Conglomerate. The rich, tightly grazed turf is characterised by relatively low cover of many species, with constant sheep's-fescue and meadow oat-grass. Less frequent graminoids include common bent, heath-grass, spring sedge (Carex caryophyllea) and quaking-grass. Herbs include rough hawkbit (Leontodon hispidus), woolly thistle (Cirsium eriophorum), musk thistle (Carduus nutans), and eyebright (Euphrasia officinalis).

SITE: HARPTREE AREA

Sub-site: Harptree Combe

Distinct habitats within Harptree Combe include old ash woodland, rough grassland, marshy grassland alongside a small stream, and limestone rock exposures. The ash woodland is very rich in woody species, and interesting ground flora plants include dog's-mercury, scaly male-fern (Dryopteris affinis), herb Paris, autumn crocus and yellow archangel. In the upper reaches of the combe, pedunculate oak replaces ash as the dominant canopy tree, with old hazel coppice and drifts of bluebells. Limestone bluffs and crags are frequent on the steep gorge slopes, and here hart's-tongue and broad buckler-fern form large leafy shuttlecocks amongst a lush carpet of bluebells and mosses. Fallen trees decomposing on the valley floor provide a home for many different species of plant, insect and fungus, including the brightly coloured scarlet cups (Sarcoscypha coccinea) .

A fast-flowing small stream flows the length of the gorge, and is fed by various small springs arising in the wood. Extensive mats of opposite-leaved golden-saxifrage carpet the damper ground on the valley floor, along with Ramsons.

The walls of the aqueduct and bare limestone rock faces are home to many different mosses and fern. Species like brittle bladder-fern, and the small mosses Didymodon ferrugineus and Didymodon spadiceus are rare in southern England.