'A Nature Conservation Review', D A Ratcliffe (1977), Cambridge.
Site of Special Scientific Interest (SSSI) notified under Section 28 of the Wildlife and countryside Act 1981.
National Grid Reference: SU 895167
Area: 42.2 (ha.) 104.2 (ac.)
This site is included in a 'Nature Conservation Review'.*
Part of the site is managed by the Society of Sussex Downsmen and the site lies within the South Downs Area of Outstanding Natural Beauty. The site contains a group of Bronze age burial mounds with several cross dykes.
Reasons for Notification:
Heyshott Down is an example of unimproved chalk grassland, a nationally rare habitat which has declined in area in recent years. This site has an assemblage of bryophytes (mosses and liverworts) which is not known from any other site on chalk in southern England. It is also nationally important for two groups of Arachnid (spiders).
Heyshott Down lies on the scarp slope of the South Downs on Middle and Lower Chalk. Much of the chalk grassland occurs in and around old chalk pits, with scattered scrub occurring in parts. These areas support the richest community of bryophytes. The rest of the site consists of semi-natural mixed and deciduous woodland. This combination of woodland, scrub, damp coombes and open grassland provides habitats for numerous invertebrate species.
The chalk grassland is rich in plant species. It consists of a short turf dominated by sheep's fescue Festuca ovina and upright brome Bromus erectus with taller patches of tor grass Brachypodium pinnatum and cock’s foot Dactylis glomerata. The community includes species such as round-headed rampion Phyteuma tenerum, musk orchid Herminium monorchis and fly orchid Ophrys insectifera.
There is a wide range of bryophytes, including several subalpine species that are more usually restricted to north and northwest Britain. These include Hylocomium brevirostre, Rhytidiadelphus loreus and of particular
interest Antitrichia curtipendula, Rhacomitrium lanuginosum and Jungermannia atrovirens, a species known from only one other site in southeast England.
Ash Fraxinus excelsior is dominant in many parts of the woodland, with beech Fagus sylvatica, field maple Acer campestre, hazel Corylus avellana coppice and in places yew Taxus baccata. There are several species in the shrub layer, with hawthorn Crataegus monogyna, blackthorn Prunus spinosa, sweet briar Rubus rubiginosa and whitebeam Sorbus aria among the most frequent species. The shrub layer is dense throughout much of the wood and occurs as patches of scrub outside the woodland.
The site is nationally important for spiders and harvestmen: Tapinocyboides pygmaea has
been recorded in Britain from here and one Scottish site, while Pelecopsis radicicola is known at only one other West Sussex site.
The calcareous grassland and woodland also support rich communities of woodlice (Isopoda) and bugs (Hemiptera). The site is a locality of the rufous grasshopper Gomphocerippus rufus which is uncommon in the county.
* 'A Nature Conservation Review', D A Ratcliffe (1977), Cambridge.
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