Halnaker Chalk Pit

Site of Special Scientific Interest · 50.8728, -0.6924

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Also within

West Sussex County SOUTH DOWNS National Park

Condition (Natural England)

Favourable (1)
UnitFeatureConditionArea (ha)Assessed
SU921089 — Favourable 6.37 2011-07-27

Habitats

Mixed scrub, Montane scrub

Geology & landscape

Rock Type: Chalk

Description

Description The site consists of a partly vegetated pit in the Upper Chalk with peripheral areas of scrub and woodland. Halnaker Chalk Pit is important as the joint location of the largest population of a nationally rare* plant species in great Britain. The floor of the chalk pit has a very thin layer of soil providing comparatively few nutrients. In addition, the chalk is freely draining and these factors combine to result in a relatively harsh environment. The pit is characterised by areas of bare chalk and a patchy stunted vegetation including such species as creeping bent grass Agrostis stolonifera, hoary plantain Plantago media and scarlet pimpernel Anagallis arvensis. This site is most significant for its population of the nationally rare and vulnerable + broad leaved cudweed Filago pyramidata with 10,000 plants 1990 figures comprising approximately 50 percent of the total British population. The only other site with a comparable population is at Cuxton, Kent. This plant is typically found as a cornfield flower but as a result of modern agricultural practice has been almost extirpated. However the chalk pit provides a sufficiently suitable habitat for the plant to reach a height of a few centimetres and seed freely. Other flowering plant species found on the pit floor include wild basil Clinopodium vulgare and wild parsnip Pastinaca sativa. As the soils become a little deeper around the edge of the pit typical chalk grassland species such as yellow wort Blackstonia perfoliata, autumn gentian Gentianella amarella and marjoram Origanum vulgare become more common. This area of the pit also supports a colony of bee orchids Ophrys apifera. The scrub beyond the top of the pit is dominated by elder Sambucus nigra and dogwood Cornus sanguinea. As the scrub grows into mature woodland English oak Quercus robur and ash Fraxinus excelsior are the dominant species. Notes *nationally rare species are those occurring in 1 15 of the 10 x 10 kilometres squares in Britain +classified as 'vulnerable' in the British Red Data Book of Vascular Plants Perring and Walters, 1983. second edition

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
creeping bent Agrostis stolonifera LC grass poaceae
scarlet pimpernel Anagallis arvensis Not listed in GB list herb primulaceae
yellowwort Blackstonia perfoliata LC herb gentianaceae
wild basil Clinopodium vulgare LC herb lamiaceae
broad leaved cotton rose Filago pyramidata EN herb asteraceae
autumn gentian Gentianella amarella LC herb gentianaceae
bee orchid Ophrys apifera LC herb orchidaceae
wild marjoram Origanum vulgare LC herb lamiaceae
wild parsnip Pastinaca sativa LC herb apiaceae
hoary plantain Plantago media LC herb plantaginaceae
dogwood Cornus sanguinea LC shrub cornaceae
elder Sambucus nigra LC shrub caprifoliaceae
ash Fraxinus excelsior LC tree oleaceae
common oak Quercus robur LC tree fagaceae

Plant communities

W20 — Montane scrub

Salix lapponum-Luzula sylvatica scrub

Salix arbuscula, Salix cinerea, Salix lapponum, Salix myrsinites, Salix phylicifolia, Salix reticulata, Empetrum nigrum, Calluna vulgaris, Salix lanata, Vaccinium myrtillus, Vaccinium uliginosum, Carex atrata, Carex bigelowii, Carex binervis, Carex flacca, Luzula multiflora, Luzula sylvatica, Huperzia selago, Selaginella selaginoides, Aulacomnium palustre, Mnium hornum, Philonotis fontana, Plagiomnium undulatum, Rhizomnium punctatum, Dicranum bonjeanii, Dicranum majus, Dicranum scoparium, Fissidens adianthoides, Racomitrium lanuginosum, Calliergonell cuspidatum, Ctenidium molluscum, Hylocomium splendens, Hypnum callichroum, Hypnum cupressiforme, Palustriella commutatum, Plagiothecium denticulatum, Plagiothecium undulatum, Pleurozium schreberi, Ptilium crista-castrensis, Rhytidiadelphus loreus, Rhytidiadelphus squarrosus, Rhytidiadelphus triquetrus, Sanionia uncinata, Scorpidium revolvens, Thuidium tamariscinum, Atrichum undulatum, Polytrichastrum alpinum, Sphagnum capillifolium, Sphagnum fallax, Sphagnum girgensohnii, Sphagnum palustre, Sphagnum russowii, Sphagnum squarrosum, Sphagnum subnitens, Sphagnum teres, Barbilophozia barbata, Chiloscyphus polyanthos, Diplophyllum albicans, Lophocolea bidentata, Plagiochila porelloides, Ptilidium ciliare, Scapania undulata, Cladonia squamosa, Peltigera canina, Angelica sylvestris, Caltha palustris, Hieraclium spp., Saussurea alpina, Solidago virgaurea, Campanula rotundifolia, Succisa pratensis, Valeriana officinalis, Rhodiola rosea, Vaccinium vitis-idaea, Thymus praecox, Epilobium anagallidifolium, Dactylorhiza viridis, Euphrasia officinalis, Rhinanthus minor, Oxalis acetosella, Oxyria digyna, Polygonum viviparum, Rumex acetosa, Anemone nemorosa, Ranunculus acris, Thalictrum alpinum, Alchemilla alpina, Alchemilla glabra, Filipendula ulmaria, Geum rivale, Galium boreale, Galium saxatile, Saxifraga aizoides, Saxifraga hypnoides, Saxifraga oppositifolia, Saxifraga stellaris, Viola riviniana, Agrostis canina, Agrostis capillaris, Anthoxanthum odoratum, Deschampsia cespitosa, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Nardus stricta, Dryopteris dilatata, Phegopteris connectilis

W21 — Hedgerow scrub, Mixed scrub

Crataegus monogyna-Hedera helix scrub

Hedera helix, Salix cinerea, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Corylus avellana, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Malus sylvestris, Sorbus aria, Taxus baccata, Ulmus glabra, Ulmus procera, Sambucus nigra, Viburnum lantana, Euonymus europaeus, Cornus sanguinea, Juniperus communis, Ligustrum vulgare, Clematis vitalba, Rhamnus cathartica, Crataegus laevigata, Crataegus monogyna, Prunus spinosa, Juncus effusus, Plagiomnium undulatum, Brachythecium rutabulum, Kindbergia praelonga, Rhynchostegium confertum, Tamus communis, Heracleum sphondylium, Torilis japonica, Arum maculatum, Arctium minus, Cirsium arvense, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Stellaria graminea, Stellaria holostea, Stellaria media agg., Calystegia sepium, Mercurialis perennis, Geranium robertianum, Iris foetidissima, Glechoma hederacea, Lamium purpureum, Origanum vulgare, Stachys sylvatica, Teucrium scorodonia, Allium ursinum, Hyacinthoides non-scripta, Circaea lutetiana, Rumex sanguineus, Anemone nemorosa, Ranunculus repens, Fragaria vesca, Geum urbanum, Potentilla sterilis, Poterium sanguisorba, Rosa arvensis, Rosa canina, Rubia peregrina, Rubus fruticosus agg., Galium aparine, Urtica dioica, Viola riviniana, Anisantha sterilis, Arrhenatherum elatius, Brachypodium pinnatum, Brachypodium sylvaticum, Bromopsis erecta, Dactylis glomerata, Elytrigia repens, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris filix-mas

W22 — Hedgerow scrub, Mixed scrub

Prunus spinosa-Rubus fruticosus scrub

Hedera helix, Acer campestre, Corylus avellana, Ulex europaeus, Prunus spinosa, Plagiomnium undulatum, Brachythecium rutabulum, Eurhynchium striatum, Kindbergia praelonga, Thuidium tamariscinum, Atrichum undulatum, Lophocolea bidentata, Achillea millefolium, Cardamine flexuosa, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Silene uniflora, Stellaria media agg., Mercurialis perennis, Geranium robertianum, Stachys sylvatica, Teucrium scorodonia, Hyacinthoides non-scripta, Oxalis acetosella, Digitalis purpurea, Plantago lanceolata, Veronica chamaedrys, Armeria maritima, Rumex acetosa, Filipendula ulmaria, Geum urbanum, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Urtica dioica, Viola riviniana, Agrostis capillaris, Brachypodium sylvaticum, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris borreri, Dryopteris filix-mas