Pewsey Downs SAC Conservation

European Site Conservation Objectives: Supplementary advice on conserving and restoring site features

Pewsey Downs Special Area of Conservation (SAC) Site Code: UK0012552

Photo: Ben Cooke Natural England

Date of Publication: 21 January 2019

Page 1 of 22 About this document

This document provides Natural England’s supplementary advice about the European Site Conservation Objectives relating to Pewsey Downs SAC.

This advice should therefore be read together with the SAC Conservation Objectives available here.

You should use the Conservation Objectives, this Supplementary Advice and any case-specific advice given by Natural England when developing, proposing or assessing an activity, plan or project that may affect this site.

This Supplementary Advice to the Conservation Objectives presents attributes which are ecological characteristics of the designated species and habitats within a site. The listed attributes are considered to be those that best describe the site’s ecological integrity and which, if safeguarded, will enable achievement of the Conservation Objectives. Each attribute has a target which is either quantified or qualitative depending on the available evidence. The target identifies as far as possible the desired state to be achieved for the attribute.

The tables provided below bring together the findings of the best available scientific evidence relating to the site’s qualifying features, which may be updated or supplemented in further publications from Natural England and other sources. The local evidence used in preparing this supplementary advice has been cited. The references to the national evidence used are available on request. Where evidence and references have not been indicated, Natural England has applied ecological knowledge and expert judgement. You may decide to use other additional sources of information.

In many cases, the attribute targets shown in the tables indicate whether the current objective is to ‘maintain’ or ‘restore’ the attribute. This is based on the best available information, including that gathered during monitoring of the feature’s current condition. As new information on feature condition becomes available, this will be added so that the advice remains up to date.

The targets given for each attribute do not represent thresholds to assess the significance of any given impact in Habitats Regulations Assessments. You will need to assess this on a case-by-case basis using the most current information available.

Some, but not all, of these attributes can also be used for regular monitoring of the actual condition of the designated features. The attributes selected for monitoring the features, and the standards used to assess their condition, are listed in separate monitoring documents, which will be available from Natural England.

These tables do not give advice about SSSI features or other legally protected species which may also be present within the European Site.

If you have any comments or queries about this Supplementary Advice document please contact your local Natural England adviser or email [email protected]

Page 2 of 22 About this site

European Site information

Name of European Site Pewsey Downs Special Area of Conservation (SAC)

Location Wiltshire

Site Map The designated boundary of this site can be viewed here on the MAGIC website

Designation Date 1 April 2005

Qualifying Features See section below

Designation Area 153.87 ha

Designation Changes None

Feature Condition Status Details of the feature condition assessments made at this site can be found using Natural England’s Designated Sites System

Names of component Pewsey Downs SSSI Sites of Special Scientific Interest (SSSIs)

Relationship with other Not Applicable European or International Site designations

Site background and geography

Pewsey Downs SAC lies on the southern edge of the Marlborough Downs close to the village of Alton Barnes. It is located within the North Wessex Downs AONB and Berkshire and Marlborough Downs National Character Area (NCA Profile 116)

The site lies on the Cretaceous chalk which forms the high ground of the Marlborough Downs and is part of the south facing chalk escarpment on the northern edge of the Vale of Pewsey. The steep chalk escarpment is indented by a number of impressive coombes and dry valleys which provide a varied topography. The topography provides a variety of micro climates and aspects which is reflected in the diversity of wildflowers and other species found on the site. Milk Hill is the highest point in Wiltshire at 294 metres above sea level.

Soils vary across the site from deep rich neutral soils in the Coombes and base of the escarpment and clay with flints on the hill tops giving rise to a mosaic of acid and neutral grassland. The chalk redzina soils on the escarpment support extensive areas of species rich chalk grassland.

Pewsey Downs has a wealth of significant archaeological and historic features dating back to Neolithic Bronze Age, Iron Age and Saxon times including several designated as Scheduled Monuments such as the Wansdyke, Adams Grave Neolithic long barrow on Walkers Hill and the impressive causewayed camp on Knapp Hill. Pewsey Downs is also designated as an SSSI and National Nature Reserve (NNR). Consisting of three hills on the southern edge of the Marlborough Downs the reserve is famous for the Alton Barnes or Pewsey White Horse, one of several iconic chalk horse carvings characteristic of the wider landscape. The NNR is used extensively for recreation. Views from the reserve stretch across the Page 3 of 22

Vale of Pewsey all the way to Salisbury Plain. There are a number of well used bridle paths and other Rights of Way.

The scarp slope supports extremely rich chalk grassland flora, considered to be one of the best examples in the UK. Much of the turf is dominated by a sheep’s-fescue – meadow oat-grass (Festuca ovina – Helictotrichon pratense) CG2 National Vegetation Classification (NVC) community, although in some areas upright brome Bromopsis erecta CG3 grassland is the dominant type. There are also fragments of acid grassland communities with rare dwarf mouse ear Cerastium pumilum. Grazing with cattle and sheep is important to maintain the diversity of species.

The site also supports a rich butterfly community including scarce species such as marsh fritillary Euphydryas aurina chalk hill Polyommatus coridon and Adonis blue Polyommatus bellargus. The SAC is part of the larger Pewsey Downs SSSI also designated for its chalk grassland communities and butterflies. The SAC is at the centre of a landscape scale farmer group project which aims to link areas of chalk grassland and increase connectivity for the marsh fritillary butterfly and other species.

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About the qualifying features of the SAC

The following section gives you additional, site-specific information about this SAC’s qualifying features. These are the natural habitats and/or species for which this SAC has been designated.

Qualifying habitats:

• H6210/ H6211. Semi-natural dry grasslands and scrubland facies: on calcareous substrates (Festuco-Brometalia) (important orchid sites); Dry grasslands and scrublands on chalk or limestone (important orchid sites) *

These grasslands are typically found on thin, well-drained, lime-rich soils associated with chalk and limestone. They occur predominantly at low to moderate altitudes in England and Wales, extending locally into upland areas in northern England, Scotland and Northern Ireland. Most of these calcareous grasslands are maintained by grazing.

A large number of rare plants are associated with this habitat, including, on Pewsey Downs SAC: Burnt tip orchid Neotina ustulata, bastard-toadflax Thesium humifusum, field fleawort Tephroseris integrifolia, dwarf mouse ear Cerastium pumilum, and the early gentian Gentianella anglica. The invertebrate fauna is also noteworthy, and includes rarities such as the marsh fritillary butterfly, adonis blue butterfly and chalk hill blue.

It supports extensive examples of CG2 Festuca ovina-Avenula pratensis grassland with areas of CG3 Bromus erectus grassland. Many herbs characteristic of Wiltshire downland are widespread such as devil’s-bit scabious Succisa pratensis, saw-wort Serratula tinctoria, ox-eye daisy Leucanthemum vulgare and chalk milkwort Polygala calcarea.

This SAC is also distinctive in hosting the priority habitat type "orchid rich sites". This priority habitat type comprises calcareous grasslands which contain either a rich suite of orchid species, important populations of at least one nationally uncommon orchid species or one or several orchid species considered to be rare, very rare or exceptional in the UK. In addition to burnt tip orchid, the uncommon green-winged orchid Anacamptis morio, autumn lady’s-tresses Spiranthes spiralis and frog orchid Coeloglossum viride are also present, together with a rich assemblage of more widespread species, including bee orchid Ophrys apifera, fragrant orchid Gymnadenia conopsea and pyramidal orchid Anacamptis pyramidalis.

Qualifying Species:

• S1654. Gentianella anglica; Early gentian

Early gentian is an annual plant occurring in calcareous grassland, mainly on steep, south-facing slopes. It grows on bare ground or in thin turf that is kept open by a combination of rabbit or sheep grazing and trampling by livestock on thin droughty soils. In dense turf it becomes shaded out and unable to compete with other more vigorous species. This species can undergo significant population fluctuations, both regionally due to weather conditions and on individual sites as a reflection of grazing levels.

Early gentian occurs mainly on chalk escarpments in central southern England, but its range extends to Cornwall and south west Wales and northwards to Lincolnshire. Pewsey Down is one of three sites selected in the central part of the range. It holds very significant populations of plants in high quality chalk grassland.

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Table 1: Supplementary Advice for Qualifying Features: H6210. Semi-natural dry grasslands and scrubland facies: on calcareous substrates (Festuco-Brometalia) (important orchid sites); Dry grasslands and scrublands on chalk or limestone (important orchid sites) *

Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Extent and Extent of the Maintain the total extent of the There should be no measurable reduction (excluding any trivial Wiltshire Chalk Grassland NVC distribution feature within feature at 107.7 ha (75.7 loss) in the extent and area of this feature, and in some cases, Survey 1989. (Archived internal of the feature the site hectares CG2 and 31.9 ha CG3.) the full extent of the feature may need to be restored. The Natural England survey data baseline-value of extent given has been generated using data available on request.) gathered from the listed site-based surveys. NATURAL ENGLAND 2009 / Area measurements given may be approximate depending on 2012 Definitions of Favourable the methods, age and accuracy of data collection, and as a Condition: Pewsey Downs SSSI result this value may be updated in future to reflect more (Available on request from accurate information. The extent of an Annex I habitat feature Natural England) covers the sum extent of all of the component vegetation communities present and may include transitions and mosaics This attribute will be periodically with other closely-associated habitat features. Where a feature monitored as part of Natural is susceptible to natural dynamic processes, there may be England’s SSSI Condition acceptable variations in its extent through natural fluctuations. Assessments

Where a reduction in the extent of a feature is considered necessary to meet the Conservation Objective for another Annex I feature, Natural England will advise on this on a case- by-case basis. Extent and Spatial Maintain the distribution and A contraction in the range, or geographic spread, of the feature Wiltshire Chalk Grassland NVC distribution distribution of configuration of the feature, (and its component vegetation and typical species, plus Survey 1989 (Archived internal of the feature the feature including where applicable its transitional communities) across the site will reduce its overall Natural England survey data within the site component vegetation types, area, the local diversity and variations in its structure and available on request.) across the site composition, and may undermine its resilience to adapt to future environmental changes. This may also reduce and break NATURAL ENGLAND 2009/ up the continuity of a habitat within a site and how well its 2012 Definitions of Favourable typical species are able to move around the site to occupy and Condition: Pewsey Downs SSSI use habitat. Such fragmentation can impact on their viability (Available on request from and the wider ecological composition of the Annex I habitat. Natural England)

Smaller fragments of habitat can typically support smaller and PAYNE K, 1987 NVC Survey and more isolated populations which are more vulnerable to Pewsey Downs Management extinction. These fragments also have a greater amount of Plan. Nature Conservancy open edge habitat which will differ in the amount of light, (Archived internal Natural

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

temperature, wind, and even noise that it receives compared to England document available on its interior. These conditions may not be suitable for some of request.) the typical and more specialist species associated with the Annex I habitat feature. This attribute will be periodically monitored as part of Natural England’s SSSI Condition Assessments

Structure and Vegetation Ensure the component This habitat feature will comprise a number of associated semi- Wiltshire Chalk Grassland NVC function community vegetation communities of the natural vegetation types and their transitional zones, reflecting Survey 1989. (Archived internal (including its composition feature are referable to and the geographical location of the site, altitude, aspect, soil Natural England survey data typical characterised by the following conditions (especially base-status and drainage) and available on request.) species) National Vegetation vegetation management. In the UK these have been Classification types categorised by the National Vegetation Classification (NVC). PAYNE K 1985 NVC Survey and • CG2 Festuca ovina - Avenula Maintaining or restoring these characteristic and distinctive 1987 Pewsey Downs pratensis grassland vegetation types, and the range of types as appropriate, will be Management Plan Nature important to sustaining the overall habitat feature. This will also Conservancy. (Archived internal • CG3 Bromus erectus help to conserve their typical plant species (i.e. the constant Natural England document grassland and preferential species of a community), and therefore that of available on request.) the SAC feature, at appropriate levels (recognising natural fluctuations). McSWEENEY P, 1991 Chalk grassland survey, English Nature Detailed NVC surveys (dated 1985 and 1991) show a complex (Archived internal Natural mosaic of vegetation communities due to varied soils, England survey data available on topography, aspect, and past management history. Areas of request.) CG2 and CG3a may oscillate between the two communities without loss of conservation interest depending on grazing This attribute will be periodically pressure and season, as communities are distinguished by monitored as part of Natural quantity of Bromus erectus present and this is highly England’s SSSI Condition susceptible to grazing. Assessments

Structure and Vegetation: Maintain the proportion of A high cover of characteristic herbs, including sedges (Carex NATURAL ENGLAND 2009/ function proportion of herbaceous species within the species) is typical of the structure of this habitat type. 2012 Definitions of Favourable (including its herbs range 40%-90% Condition: Pewsey Downs SSSI typical (including (Available on request from species) Carex spp ) Natural England)

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

HEWINS, E. 2015, Habitat Surveillance data project Pewsey Downs results for Unit 5 Knapp Hill results (Survey on behalf of Natural England available on request from Natural England)

This attribute will be periodically monitored as part of Natural England’s SSSI Condition Assessments

Structure and Key Maintain the abundance of the Some plant or animal species (or related groups of such NATURAL ENGLAND 2009/ function structural, typical species listed below to species) make a particularly important contribution to the 2012 Definitions of Favourable (including its influential enable each of them to be a necessary structure, function and/or quality of an Annex I Condition: Pewsey Downs SSSI typical and/or viable component of the Annex 1 habitat feature at a particular site. These species will include; (Available on request from species) distinctive habitat; Natural England) species • Structural species which form a key part of the Annex I Constant and preferential plant habitat’s structure or help to define that habitat on a particular species of the CG2 Festuca SAC (see also the attribute for ‘vegetation community HEWINS, E. 2015, Habitat ovina - Avenula pratensis composition’). Surveillance data project Pewsey grassland and CG3 Bromus Downs results Unit 5 Knapp Hill erectus grassland NVC • Influential species which are likely to have a key role (Survey on behalf of Natural vegetation types at this SAC affecting the structure and function of the habitat (such as England available on request bioturbators (mixers of soil/sediment), grazers, surface borers, from Natural England) Important orchid spp: burnt predators or other species with a significant functional role orchid Orchis ustulata, green- linked to the habitat) WILSON, P and PRICE, D winged orchid Orchis morio, (Species Recovery Trust), 2017. autumn lady’s-tresses Spiranthes • Site-distinctive species which are considered to be a Early gentian Gentianella anglica: spiralis, frog orchid particularly special and distinguishing component of an Annex I Sample Survey of Sites in Coeloglossum viride, bee orchid habitat on a particular SAC. England (Survey on behalf of Ophrys apifera, lesser butterfly Natural England. Report available orchid Platanthera bifolia, There may be natural fluctuations in the frequency and cover of on request from Natural England) fragrant orchid Gymnadenia each of these species. The relative contribution made by them conopsea and pyramidal orchid to the overall ecological integrity of a site may vary, and Natural This attribute will be periodically Anacamptis pyramidalis. England will provide bespoke advice on this as necessary. monitored as part of Natural The list of species given here for this Annex I habitat feature at England’s SSSI condition this SAC is not necessarily exhaustive. The list may evolve, assessments and species may be added or deleted, as new information

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Important invertebrate about this site becomes available. Detailed locations and grid assemblage including: Adonis references found in Pewsey blue Polyommatus belargus, Downs SSSI Wiltshire Botanical marsh fritillary Euphydryas Society Survey (2007/08). aurinia, chalkhill blue Distribution maps also available. Polyommatus coridon, small blue This report also includes Cupidio minimus dingy skipper historical records from the NNR Erynnis tages, brown argus (Keith Payne maps dated 1984 Aricia agestis, dark green fritillary and 1986). (NNR data is held by dark green fritillary Argynnis NATURAL ENGLAND, 2007/8 aglaja, Duke of Burgundy Data held by NE, BSBI and Hamearis lucina yellow meadow Wiltshire Botanical Society. ant Lasius flavus Wiltshire Biological Records Centre also hold data.

More recent post 2007/8 occasional records by Wilts Botanical Society and Natural England are held by Natural England and available on request. Butterfly transect records also held by Natural England and local Butterfly Conservation group. (Available on request from Natural England)

Structure and Vegetation: Maintain the frequency/cover of There will be a range of undesirable or uncharacteristic species NATURAL ENGLAND 2009/ function undesirable the following undesirable species which, if allowed to colonise and spread, are likely to have an 2012 Definitions of Favourable (including its species to within acceptable levels and adverse effect on the feature's structure and function, including Condition: Pewsey Downs SSSI typical prevent changes in surface its more desirable typical species. These may include invasive (Available on request from species) condition, soils, nutrient levels or non-natives such as Cotoneaster spp, or coarse and Natural England) hydrology which may encourage aggressive native species which may uncharacteristically their spread; dominate the composition of the feature. This attribute will be periodically monitored as part of Natural Undesirable species include: Creeping thistle Cirsium England’s SSSI Condition arvense, spear thistle Cirsium vulgare, curled dock Rumex Assessments crispus, broad leaved dock Rumex obtusifolius, common ragwort Senecio jacobaea, common nettle Urtica dioica; tor grass Brachypodium pinnatum, upright brome Bromopsis

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

erecta

Structure and Vegetation Maintain the pattern of natural Transitions/zonations between adjacent but different vegetation NATURAL ENGLAND 2009/ function community vegetation zonations/transitions communities are usually related to naturally-occurring changes 2012 Definitions of Favourable (including its transitions in soil, aspect or slope. Such 'ecotones' retain characteristics of Condition: Pewsey Downs SSSI typical each bordering community and can add value in often (Available on request from species) containing species not found in the adjacent communities. Natural England) Retaining such transitions can provide further diversity to the habitat feature, and support additional flora and fauna. PAYNE, K.R. 1987. Management Plan for Pewsey Downs NNR. As well as calcicolous grassland the site includes species-rich Nature Conservancy Council. neutral grassland (MG5) and areas which exhibit a transition (Available on request from between CG2, CG3 and MG5. In addition, species-poor Natural England) grassland is found on deeper soils at the top and bottom of slopes. Vegetation transitions are associated with differences in MASSEN, D & CASHMAN, P. soil depth, slope, aspect and microclimatic conditions. 2003. Management Plan for Pewsey Downs NNR. English Detailed NVC surveys (dated 1985 and 1990) show a complex Nature. (Available on request mosaic of vegetation communities due to varied soils, from Natural England) topography, aspect, and past management history. There is also a complicated relationship with non-notified grassland Wiltshire Chalk Grassland NVC communities e.g. MG5, MG6, MG7. The site includes areas of Survey 1989, Nature MG5b Cynosurus cristatus – Centaurea nigra grassland (found Conservancy Council. (Archived over deeper soils and on north facing slopes) survey data available on request from Natural England)

PAYNE K 1985 NVC Survey Nature Conservancy Council. (Unpublished archived survey data available on request from Natural England)

McSWEENEY P, 1991 Chalk grassland survey, English Nature (Unpublished archived document available on request from Natural England)

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Structure and Soils, Maintain the properties of the Soil is the foundation of basic ecosystem function and its CRITCHLEY et al 2002 Biol. function substrate and underlying soil types, including properties strongly influence the colonisation, growth and Conserv., 105, 199-215, Defra (including its nutrient structure, bulk density, total distribution of those plant species which together form commissioned research projects typical cycling carbon, pH, soil nutrient status vegetation types, and therefore provides a habitat used by a BD1451 (DIGFOR) and BD5001 species) and fungal: bacterial ratio, to wide range of organisms. Soil biodiversity has a vital role to (soil compaction) within typical values for the recycle organic matter. Changes to natural soil properties may habitat. therefore affect the ecological structure, function and processes associated with this Annex I feature. Structure and Supporting Maintain the extent, quality and The structure and function of the qualifying habitat, including RAGGETT, L. & LARGE, R., function off-site spatial configuration of land or its typical species, may rely upon the continued presence of 2013. Mapping connectivity of (including its habitat habitat surrounding or adjacent areas which surround and are outside of the designated site species-rich grassland habitat in typical to the site which is known to boundary. Changes in surrounding land-use may adversely the Wiltshire Chalk landscape. A species) support the feature (directly/indirectly) affect the functioning of the feature and its collaboration between the component species. This supporting habitat may be critical to Stepping Stones project and Where appropriate there should the typical species of the feature to support their feeding, Natural England’s Vale of be buffer strips adjacent to the breeding, roosting, population dynamics ('metapopulations'), Pewsey Landscape-scale NNR site to protect the species-rich pollination or to prevent/reduce/absorb damaging impacts from Project. Natural England and grassland from the effects of adjacent land uses e.g. pesticide drift, nutrient enrichment. Wiltshire Wildlife Trust report. pesticide drift and nutrient (Available on request from enrichment. Corridors of suitable habitat will help link the site to nearby Natural England) areas of species-rich grassland and facilitate movement of invertebrates, notably Lepidoptera. The site is part of the wider CLARKE, S. & GREEN, D. 2015. Pewsey Downs SSSI. There are also opportunities to link to Pewsey Downs Landscape other chalk grassland SSSIs such as Morgan’s Hill and Marsh Fritillary and Duke of Calstone and Cherhill Downs and other species rich grassland Burgundy breeding habitat survey via the Wansdyke linear Scheduled Monument. Unpublished report for Natural England. GI database includes maps of existing chalk grassland.

Structure and Functional Maintain the overall extent, This recognises the potential need at this site to maintain or RAGGETT, L. & LARGE, R., function connectivity quality and function of any restore the connectivity of the site to its wider landscape in 2013. Mapping connectivity of (including its with wider supporting features within the order to meet the conservation objectives. These connections species-rich grassland habitat in typical landscape local landscape which provide a may take the form of landscape features, such as habitat the Wiltshire Chalk landscape. A species) critical functional connection with patches, hedges, watercourses and verges, outside of the collaboration between the the site. Important also for Marsh designated site boundary which are either important for the Stepping Stones project and Fritillary butterfly and other migration, dispersal and genetic exchange of those typical Natural England’s Vale of species supported by the SAC species closely associated with qualifying Annex I habitat Pewsey Landscape-scale NNR grassland. features of the site. These features may also be important to Project. Natural England and the operation of the supporting ecological processes on which Wiltshire Wildlife Trust report

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

the designated site and its features may rely. In most cases CLARKE, S. & GREEN, D. 2015. increasing actual and functional landscape-scale connectivity Pewsey Downs Landscape would be beneficial. Where there is a lack of detailed Marsh Fritillary and Duke of knowledge of the connectivity requirements of the qualifying Burgundy breeding habitat survey feature, Natural England will advise as to whether these are Unpublished report for Natural applicable on a case by case basis. England. GI database includes maps of existing chalk grassland.

Structure and Adaptation Maintain the feature's ability, and This recognises the increasing likelihood of natural habitat Climate Change adaptation function and resilience that of its supporting processes, features to absorb or adapt to wider environmental changes. literature and manual; European (including its to adapt or evolve to wider Resilience may be described as the ability of an ecological Union 2013. Guidelines on typical environmental change, either system to cope with, and adapt to environmental stress and climate change and Natura 2000; species) within or external to the site change whilst retaining the same basic structure and ways of functioning. Such environmental changes may include NATURAL ENGLAND, 2015. changes in sea levels, precipitation and temperature for Climate Change Theme Plan and example, which are likely to affect the extent, distribution, supporting National Biodiversity composition and functioning of a feature within a site. The Climate Change Vulnerability vulnerability and response of features to such changes will assessments (‘NBCCVAs’) for vary. SACs and SPAs in England [Available at Using best available information, any necessary or likely http://publications.naturalengland. adaptation or adjustment by the feature and its management in org.uk/publication/495459459137 response to actual or expected climatic change should be 5360]. allowed for, as far as practicable, in order to ensure the feature's long-term viability.

The overall vulnerability of this SAC to climate change has been assessed by Natural England (2015) as being low, taking into account the sensitivity, fragmentation, topography and management of its habitats.

This means that this site is considered to be vulnerable overall but is a lower priority for further assessment and action. Individual species may be more or less vulnerable than their supporting habitat itself. In many cases, change will be inevitable so appropriate monitoring would be advisable.

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Supporting Air quality Maintain the concentrations and This habitat type is considered sensitive to changes in air More information about site- processes deposition of air pollutants to at quality. Exceedance of these critical values for air pollutants relevant Critical Loads and Levels (on which the or below the site-relevant Critical may modify the chemical status of its substrate, accelerating or for this SAC is available by using feature relies) Load or Level values given for damaging plant growth, altering its vegetation structure and the ‘search by site’ tool on the Air this feature of the site on the Air composition and causing the loss of sensitive typical species Pollution Information System Pollution Information System associated with it. (www.apis.ac.uk ). (www.apis.ac.uk). Critical Loads and Levels are recognised thresholds below which such harmful effects on sensitive UK habitats will not occur to a significant level, according to current levels of scientific understanding. There are critical levels for ammonia (NH3), oxides of nitrogen (NOx) and sulphur dioxide (SO2), and critical loads for nutrient nitrogen deposition and acid deposition. There are currently no critical loads or levels for other pollutants such as Halogens, Heavy Metals, POPs, VOCs or Dusts. These should be considered as appropriate on a case-by-case basis.

Ground level ozone is regionally important as a toxic air pollutant but flux-based critical levels for the protection of semi- natural habitats are still under development. It is recognised that achieving this target may be subject to the development, availability and effectiveness of abatement technology and measures to tackle diffuse air pollution, within realistic timescales. Supporting Conservation Maintain the management Active and ongoing conservation management is needed to NATURAL ENGLAND, 2005. processes measures measures (either within and/or protect, maintain or restore this feature at this site. Further Pewsey Down SSSI - Views (on which the outside the site boundary as details about the necessary conservation measures for this site About Management feature relies) appropriate) which are necessary can be provided by contacting Natural England. to maintain the structure, NATURAL ENGLAND, 2015. Site functions and supporting This information will typically be found within, where applicable, Improvement Plan: Pewsey Down processes associated with the supporting documents such as Natura 2000 Site Improvement SAC feature Plan, Site Management Strategies or Plans, the Views about Management Statement for the underpinning SSSI and/or NATURAL ENGLAND, 2016. management agreements. Pewsey Down National Nature Reserve (NNR) Management Plan (Available on request from Natural England)

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

PAYNE, K.R. 1987. Management Plan for Pewsey Downs NNR. Nature Conservancy Council. (Available on request from Natural England)

MASSEN, D & CASHMAN, P. 2003. Management Plan for Pewsey Downs NNR. English Nature. (Available on request from Natural England)

Version Control Advice last updated:

Variations from national feature-framework of integrity-guidance: N/A

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Table 2: Supplementary Advice for Qualifying Features: S1654. Gentianella anglica; Early gentian

Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Population Population Maintain the abundance of the Populations may fluctuate considerably from year to year, NATURAL ENGLAND 2009/ (of the abundance population at a level which is depending on habitat condition, weather, etc. Flowering 2012 Definitions of Favourable feature) above the baseline population- performance may also vary between years, affecting the plant's Condition: Pewsey Downs SSSI size known or estimated at or visibility. This will ensure there is a viable population of the (Available on request from soon after the time of SAC feature which is being maintained at or increased to a level that Natural England) designation, whilst avoiding contributes as appropriate to its Favourable Conservation deterioration from its current level Status across its natural range in the UK. as indicated by the latest mean NATURAL ENGLAND, 2016. peak count or equivalent. Due to the dynamic nature of population change, the target- Pewsey Down National Nature value given for the population size or presence of this feature is Reserve (NNR) Management The baseline figure given at the considered to be the minimum standard for conservation/ Plan (Available on request from time of the Standard Data Form restoration measures to achieve. This minimum-value may be Natural England) in 1995-06 was 1001-10000 but revised where there is evidence to show that a population’s the population has never been size or presence has significantly changed as a result of natural surveyed comprehensively. One factors or management measures and has been stable at or WILSON, P and PRICE, D subsite has been surveyed in above a new level over a considerable period (generally at (Species Recovery Trust), 2017. 2017 as part of a resurvey, but least 10 years). The values given here may also be updated in Early gentian Gentianella anglica: only holds a small part of the future to reflect any strategic objectives which may be set at a Sample Survey of Sites in total population. There are NNR national level for this feature. England. (Available on request records of 398 individuals on from Natural England) Walkers Hill and 70 individuals Given the likely fluctuations in numbers over time, any impact- on Milk Hill in 1997. assessments should focus on the current size of the site’s population, as derived from the latest known or estimated level PAYNE, K.R, Nature established using the best available data. This advice accords Conservancy Council. 1987. with the obligation to avoid deterioration of the site or significant Management Plan for Pewsey disturbance of the species for which the site is designated, and Downs NNR and botanical survey seeks to avoid plans or projects that may affect the site giving data (Available on request from rise to the risk of deterioration. Similarly, where there is Natural England) evidence to show that a feature has historically been more abundant than the stated minimum target and its current level, the ongoing capacity of the site to accommodate the feature at such higher levels in future should also be taken into account in any assessment.

Unless otherwise stated, the population size or presence will be that measured using standard methods, such as peak mean counts or breeding surveys. This value is also provided recognising there will be inherent variability as a result of Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

natural fluctuations and margins of error during data collection.

Whilst we will endeavour to keep these values as up to date as possible, local Natural England staff can advise that the figures stated are the best available. Population Population Maintain the presence of both G. Intermixed populations have been recorded from many sites, WILSON, P and PRICE, D (of the structure: anglica and G. amarella. The with the hybrid recorded especially from sites near edge of (Species Recovery Trust), 2017. feature) presence of putative hybrid between the two range of G. anglica. Phenological differences (flowering time) Early gentian Gentianella anglica: Gentianella (G. x davidii) is not known from usually helpful in distinguishing between G. anglica and autumn Sample Survey of Sites in amarella, the site gentian G. amarella. England Gentianella x davidii and Note: there is still some uncertainty about the extent to which Wiltshire Botanical Society 'intermediates these two species hybridise, or indeed whether the two species (2007/08), Pewsey Downs SSSI. ' are actually one. Survey of rare plants for Natural England (Available on request from Natural England or Wiltshire Botanical Society)

Supporting Distribution of Maintain the distribution and A contraction in the range, or geographic spread, of the feature WILSON, P and PRICE, D habitat: supporting continuity of the feature and its (and its component vegetation) across the site will reduce its (Species Recovery Trust), 2017. extent and habitat supporting habitat, including overall area, the local diversity and variations in its structure Early gentian Gentianella anglica: distribution where applicable its component and composition, and may undermine its resilience to adapt to Sample Survey of Sites in vegetation types and associated future environmental changes. Contraction may also reduce England (Available on request transitional vegetation types, and break up the continuity of a habitat within a site and how from Natural England) across the site. well the species feature is able to occupy and use habitat within the site. Such fragmentation may have a greater amount of Detailed locations and grid Early gentian is associated with open edge habitat which will differ in the amount of light, references found in Pewsey the CG2 grassland community temperature, wind, and even noise that it receives compared to Downs SSSI Wiltshire Botanical (particularly sub-community its interior. These conditions may not be suitable for this feature Society Survey (2007/08). CG2a) and this may affect its viability. Distribution maps also available. This report also includes historical records from the NNR (Keith Payne maps dated 1984 and 1986). (Data available on request from Natural England)

This attribute will be periodically monitored as part of Natural England’s SSSI condition

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

assessments.

More recent Wiltshire Botanical Society records and NNR team surveillance records may be available

NATURAL ENGLAND, 2016. Pewsey Down National Nature Reserve (NNR) Management Plan (Available from Natural England on request)

Supporting Extent of Maintain the total extent of the In order to contribute towards the objective of achieving an WILSON, P and PRICE, D habitat: supporting habitats which support the overall favourable conservation status of the feature at a UK (Species Recovery Trust), 2017. extent and habitat feature, associated with CG2 / level, it is important to maintain or if appropriate restore the Early gentian Gentianella anglica: distribution well grazed CG3 Habitat = extent of supporting habitats and their range within this SAC. Sample Survey of Sites in approx. 75 ha: suitable locations The information available on the extent and distribution of England. (Data available on within this will depend on aspect, supporting habitat used by the feature may be approximate request from Natural England) sward height and bare ground. depending on the nature, age and accuracy of data collection, and may be subject to periodic review in light of improvements Detailed locations and grid in data. references found in Pewsey Downs SSSI Wiltshire Botanical The early gentian population is found on Pewsey Downs East Society Survey (2007/08). and West. It grows on bare ground or in thin turf that is kept Distribution maps also available. open by a combination of rabbit or sheep-grazing and trampling This report also includes by livestock on thin droughted soils. In dense turf it becomes historical records from the NNR shaded out and unable to compete with other more vigorous (Keith Payne maps dated 1984 species. and 1986). (Data available on request from Natural England)

This attribute will be periodically monitored as part of Natural England’s SSSI condition assessments.

More recent Wiltshire Botanical Society records and NNR team

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

surveillance records may be available from the local Natural England Area team or Wiltshire Botanical Society. Wiltshire botanical Society records are also held by the Botanical Society of the British Isles (BSBI) and Wilts Biological Records Centre.

Supporting Habitat Maintain patches of bare ground Patches of suitable vegetation often occur in mosaics with less habitat: structure and and an open-textured sward to suitable areas, and generally associated with steeper slopes, structure/ bare ground: provide creating suitable more southerly aspects, thinner soils, heavier grazing or function regeneration/ regeneration/colonisation niches. trampling. All available evidence points to need for there being colonisation Bare ground should be in range plenty of bare ground in a short/tightly grazed open-textured niches c.5-10%. sward. Many sites best described as 'sparsely vegetated').

Some evidence suggests that G. anglica tends to occur in microsites recovering after disturbance (whereas G. amarella may also occur as a pioneer in recently disturbed sites). Supporting Soils, Maintain the properties of the Soil supports basic ecosystem function and is a vital part of the habitat: substrate and underlying soil types, including natural environment. Its properties strongly influence the structure/ nutrient structure, bulk density, total colonisation, growth and distribution of those plant species function cycling carbon, pH, soil nutrient status which together form vegetation types, and therefore provides a and fungal:bacterial ratio, within habitat used by a wide range of organisms. Soil biodiversity typical values for the supporting has a vital role to recycle organic matter. Changes to natural habitat soil properties may therefore affect the ecological structure, function and processes associated with the supporting habitat of this Annex II feature. Supporting Substrate Maintain a substrate of skeletal See above for floristic indicators that may indicate changes in habitat: drought-prone relatively infertile soil nutrient status (increase in fertility). structure/ soils overlying calcareous function bedrock (chalk or limestone), occasionally overlying lime-rich sand on coastal sand dunes, with a generally SE, S or SW aspect. Supporting Vegetation Maintain/ reduce the This feature can be adversely affected by changes to the grass: This attribute will be periodically habitat: composition: frequency/cover of the following herb ratio (increased grassiness), often in tandem with sward monitored as part of Natural structure/ negative undesirable species at or to becoming 'thicker' (less bare ground) or more rank. England’s SSSI Condition function indicators acceptable levels which are not Assessments

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

encouraged by changes in Undesirable species include: Brachypodium pinnatum, surface condition, soils, nutrient Bromopsis erecta, Avenula pubescens, Arrhenatherum elatius, levels or changes to hydrology.; Cirsium arvense, Cirsium vulgare, Urtica dioica, Rumex Crispus and Rumex obtustifolius. Cover of tall grasses, should typically not exceed about 10% Tall grasses e.g. Brachypodium pinnatum, Bromopsis erecta, Avenula pubescens, Arrhenatherum elatius, Dactylis Species favoured by increased glomerata, may be an indication of undergrazing and should soil fertility / agricultural typically not exceed about 10%. The first two may locally occur improvement should be rare or at higher cover in stands of CG4a and CG3a respectively. absent. Other species may be favoured by increased soil Agricultural weeds should be rare fertility/agricultural improvement, e.g. Lolium perenne, Holcus or absent. lanatus, Cynosurus cristatus, Trisetum flavescens, Trifolium repens

'Agricultural weeds' such as Cirsium arvense, Cirsium vulgare, Galium aparine, Plantago major, Rumex obtusifolius, Senecio jacobaea and Urtica dioica, can be be indicators of bad management and loss/degradation of suitable habitat. Supporting Vegetation Maintain a sward typically in the Swards usually require moderate to heavy grazing and/or This attribute will be periodically habitat: height range of 2-5cm, but may also trampling to keep them sufficiently short and open; but on some monitored as part of Natural structure/ occur in slightly taller swards (5- coastal sites, drought and exposure may be sufficient on their England’s SSSI Condition function 20cm) as long as these still have own to maitain suitable sward conditions. Grazing may be by Assessments plenty of bare ground and an rabbits, deer, sheep or cattle. absence of 'grassy' dominants. Generally, rabbits and/or sheep preferred to cattle (see, e.g. Telfer 1994), although Wilson (2000) suggests for sites in Wilts that summer (April-October) cattle grazing at 1 animal/ha, plus less intensive grazing in the winter, is suitable for many sites, with sheep used in late summer to remove any excess grass growth. Sward height may vary from year to year, depending not only on stocking rates and timing but also on the weather. Supporting Vegetation Maintain the area of suitable Vegetation composition of this feature can be variable, WILSON, P and PRICE, D habitat: structure and supporting habitat which is short depending on habitat, aspect, management regime and (Species Recovery Trust), 2017. structure/ composition (2-5 cm), tightly-grazed and underlying geology/soils, but the frequent presence of the Early gentian Gentianella anglica: function trampled calcicolous grassland following species tend to be positive indicators of suitable early Sample Survey of Sites in with typically 5-10% bare ground gentian habitat in its usual CG2 NVC community: Poterium England (Data available on which corresponds to the sanguisorba, Cirsium acaule, Thymus praecox, Polygala request from Natural England)

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

following NVC communities: vulgaris, Carex flacca, Hippocrepis comosa, Blackstonia CG 2a, 2b. Most frequent in perfoliata, Linum catharticum, Leontodon hispidus, Pilosella Detailed locations and grid short species-rich CG2 and officinarum, Ranunculus bulbosus. references found in Pewsey CG2b. Downs SSSI Wiltshire Botanical Grasses such as Avenula pratensis, A. pubescens, Society Survey (2007/08). Brachypodium pinnatum, B. sylvaticum and Bromopsis erecta Distribution maps also available. may be frequent as an open grassy 'overstorey', but never This report also includes abundant or dominant. Early gentain may often occur with historical records from the NNR autumn gentian Gentianella amarella, but the two species (Keith Payne maps dated 1984 usually occupy different microsites and seasonal timings, and 1986). (Data available on although there may be considerable overlap on some sites. request from Natural England)

This attribute will be periodically monitored as part of Natural England’s SSSI Condition Assessments

Supporting Adaptation Maintain the feature's ability, and This recognises the increasing likelihood of natural habitat processes and resilience that of its supporting habitat, to features to absorb or adapt to wider environmental changes. (on which the adapt or evolve to wider Resilience may be described as the ability of an ecological feature and/or environmental change, either system to cope with, and adapt to environmental stress and its supporting within or external to the site change whilst retaining the same basic structure and ways of habitat relies) functioning. Such environmental changes may include changes in sea levels, precipitation and temperature for example, which are likely to affect the extent, distribution, composition and functioning of a feature within a site. The vulnerability and response of features to such changes will vary.

Using best available information, any necessary or likely adaptation or adjustment by the feature and its management in response to actual or expected climatic change should be allowed for, as far as practicable, in order to ensure the feature's long-term viability.

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

Supporting Air quality Maintain or, where necessary, The supporting habitat of this feature is considered sensitive to More information about site- processes restore concentrations and changes in air quality. Exceedance of these critical values for relevant Critical Loads and Levels (on which the deposition of air pollutants to at air pollutants may modify the chemical status of its substrate, for this SAC is available by using feature and/or or below the site-relevant Critical accelerating or damaging plant growth, altering its vegetation the ‘search by site’ tool on the Air its supporting Load or Level values given for structure and composition (including food-plants) and reducing Pollution Information System habitat relies) this feature of the site on the Air supporting habitat quality and population viability of this feature. (www.apis.ac.uk). Pollution Information System (www.apis.ac.uk). Critical Loads and Levels are recognised thresholds below which such harmful effects on sensitive UK habitats will not occur to a significant level, according to current levels of scientific understanding. There are critical levels for ammonia (NH3), oxides of nitrogen (NOx) and sulphur dioxide (SO2), and critical loads for nutrient nitrogen deposition and acid deposition. There are currently no critical loads or levels for other pollutants such as Halogens, Heavy Metals, POPs, VOCs or Dusts. These should be considered as appropriate on a case-by-case basis.

Ground level ozone is regionally important as a toxic air pollutant but flux-based critical levels for the protection of semi- natural habitats are still under development. It is recognised that achieving this target may be subject to the development, availability and effectiveness of abatement technology and measures to tackle diffuse air pollution, within realistic timescales. Supporting Conservation Maintain the management Active and ongoing conservation management is needed to NATURAL ENGLAND, 2005. processes measures measures (either within and/or protect, maintain or restore this feature at this site. Further Pewsey Down SSSI - Views (on which the outside the site boundary as details about the necessary conservation measures for this site About Management feature and/or appropriate) which are necessary can be provided by contacting Natural England. its supporting to maintain the structure, NATURAL ENGLAND, 2015. Site habitat relies) functions and supporting This information will typically be found within, where applicable, Improvement Plan: Pewsey Down processes associated with the supporting documents such as Natura 2000 Site Improvement SAC

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Attributes Targets Supporting and Explanatory Notes Sources of site-based evidence (where available)

feature and/or its supporting Plan, site management strategies or plans, the Views about habitats. Management Statement for the underpinning SSSI and/or NATURAL ENGLAND, 2016. management agreements. Pewsey Down National Nature Reserve (NNR) Management Plan (Available on request from Natural England)

PAYNE, K.R, Nature Conservancy Council. 1987. Management Plan for Pewsey Downs NNR. (Available on request from Natural England)

MASSEN, D & CASHMAN, P. 2003. Management Plan for Pewsey Downs NNR. English Nature. (Available on request from Natural England)

Supporting Grazing Maintain a grazing regime to Swards usually require moderate to heavy grazing and/or processes pressure keep the sward short (preferably trampling to keep them sufficiently short and open; but on some (on which the 2-5cm) coastal sites, drought and exposure may be sufficient on their feature and/or own to maintain suitable sward conditions. its supporting habitat relies) Grazing may be by (any combination of) rabbits, deer, sheep or cattle. Generally, rabbits and/or sheep preferred to cattle (see, e.g. Telfer 1994), although Wilson (2000) suggests for sites in Wilts that summer (April-October) cattle grazing at 1 animal/ha, plus less intensive grazing in the winter, is suitable for many sites, with sheep used in late summer to remove any excess grass growth. Version Control Advice last updated: Variations from national feature-framework of integrity-guidance: water quality attribute removed as not relevant to this feature.

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