Salisbury Plain SSSI Integrated Site Assessment 2014-15
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Salisbury Plain SSSI Integrated Site Assessment 2014-15 Wiltshire Conservation Team Natural England, December 2016 Contents Page number A Introduction 1 B Chalk grassland 3 1.1 SAC and SSSI features assessed, units present 3 1.2 Method 3 1.3 Results 5 NVC types, Attributes 8 CG2 Festuca ovina-Avenula pratensis grassland CG3 Bromus erectus grassland CG4 Brachypodium pinnatum grassland CG5 Bromus erectus – Brachypodium pinnatum grassland CG6 Avenula pubescens grassland CG7 Festuca ovina – Hieracium pilosella – Thymus praecox/pulegioides grassland 1.4 Conservation management 13 1.5 Condition status 18 1.6 Condition threats 19 C Juniper 21 2.1 SAC and SSSI features assessed, units present 21 2.2 Method 21 2.3 Results 21 2.4 Conservation management 22 2.5 Condition status 23 2.6 Condition threats 23 D Habitat mosaic 24 3.1 SSSI features assessed, units present 24 3.2 Method 24 3.3 Results 24 3.4 Conservation management 25 3.5 Condition status 25 3.6 Condition threats 25 E Rare plants 26 4.1 SSSI feature assessed, units present – tuberous thistle 26 4.2 Method 26 4.3 Results 26 4.4 Conservation management 27 4.5 Condition status 27 4.6 Condition threats 28 5.1 SSSI feature assessed, units present – vascular plants assemblage 28 5.2 Method 28 5.3 Results 28 5.4 Conservation management 30 Salisbury Plain SSSI Integrated Site Assessment 2014-15. 5.5 Condition status 30 5.6 Condition Threats 31 F Rare mosses and liverworts 32 6.1 SSSI features assessed, units present 32 6.2 Method 32 6.3 Results 32 6.4 Conservation management 33 6.5 Condition status 34 6.6 Condition Threats 34 G Birds 7.1 SPA and SSSI feature assessed, units present – stone-curlew 35 7.2 Method 35 7.3 Results 35 7.4 Conservation management 36 7.5 Condition status 36 7.6 Condition Threats 36 8.1 SPA and SSSI feature assessed, units present – quail 37 8.2 Method 37 8.3 Results 37 8.4 Conservation management 38 8.5 Condition status 38 8.6 Condition Threats 38 9.1 SPA and SSSI feature assessed, units present – hobby 38 9.2 Method 38 9.3 Results 38 9.4 Conservation management 38 9.5 Condition status 39 9.6 Condition Threats 39 10.1 SPA and SSSI feature assessed, units present – hen harrier 39 10.2 Method 39 10.3 Results 39 10.4 Conservation management 40 10.5 Condition status 40 10.6 Condition Threats 40 11.1 SSSI feature assessed, units present – breeding birds assemblage 41 11.2 Method 41 11.3 Results 42 11.4 Conservation management 45 11.5 Condition status 45 11.6 Condition Threats 45 H Invertebrates 46 12.1 SAC and SSSI feature assessed, units present – marsh fritillary 46 12.2 Method 46 12.3 Results 46 12.4 Conservation management 48 Salisbury Plain SSSI Integrated Site Assessment 2014-15. 12.5 Condition status 48 12.6 Condition Threats 48 13.1 SSSI feature assessed, units present – adonis blue butterfly 48 13.2 Method 48 13.3 Results 48 13.4 Conservation management 49 13.5 Condition status 49 13.6 Condition Threats 50 14.1 SSSI feature assessed, units present – brown hairstreak butterfly 50 14.2 Method 50 14.3 Results 50 14.4 Conservation management 53 14.5 Condition status 53 14.6 Condition Threats 53 15.1 SSSI feature assessed, units present – Duke of Burgundy butterfly 54 15.2 Method 54 15.3 Results 54 15.4 Conservation management 56 15.5 Condition status 56 15.6 Condition Threats 57 16.1 SSSI feature assessed, units present – fairy shrimp 56 16.2 Method 56 16.3 Results 56 16.4 Conservation management 57 16.5 Condition status 57 16.6 Condition Threats 57 17.1 SSSI features assessed, units present – invertebrate assemblages 59 17.2 Method 59 17.3 Results 59 17.4 Conservation management 60 17.5 Condition status 60 17.6 Condition Threats 60 I Unit level assessments 62 J Overall results, discussion and conclusions 63 Glossary Appendices Appendix 1 Salisbury Plain SSSI Citation Appendix 2 Location of features by SSSI unit Salisbury Plain SSSI Integrated Site Assessment 2014-15. Appendix 3 Calculated dense and scattered scrub cover by unit (from SUMP 2008/9) and estimated dense and scattered scrub cover by unit (from SP ISA 2014-15). Appendix 4 Tuberous thistle records from Prendergast (2015), sorted by SSSI unit Appendix 5 Condition status of features at unit level Appendix 6 Unit Summary Sheets and NVC maps Appendix 7 Salisbury Plain SSSI Site Condition Plan Appendix 8 Woodland and plantations on Salisbury Plain List of tables Table 1 Number of breeding stone-curlew pairs present on both the SSSI and wider training area, by year. Table 2 Breeding birds assemblage species present on Salisbury Plain SSSI – and their score based on ‘Guidelines for selection of biological SSSIs’ (1989). Table 3 Number of sites or incidences of Duke of Burgundy adults and larval feeding damage, for the West, Centre and East. List of figures Figure 1 Salisbury Plain SSSI, SAC and SPA boundary and units Figure 2 Chalk grassland and other habitats present on Salisbury Plain, from the mid-90s National Vegetation Classification (NVC) survey Figure 3 Decision tree for assigning condition status of chalk grassland features at unit level. Figure 4 Location and type of Condition Threats – West Figure 5 Location and type of Condition Threats - Centre Figure 6 Location and type of Condition Threats - East Figure 7 Condition status change at whole SSSI level Figure 8 Compilation of tuberous thistle records – The West Figure 9 Compilation of tuberous thistle records – The Centre Figure 10 Compilation of tuberous thistle records – The East List of plates Front cover: Chalk grassland on Sidbury Hill Salisbury Plain SSSI Integrated Site Assessment 2014-15. An Introduction Salisbury Plain is an extensive chalk plateau in the middle of Wiltshire, with the biggest area of unimproved chalk grassland in north-west Europe. It is owned, mainly, by the Ministry of Defence (MoD) and managed by Defence Infrastructure Organisation (DIO). Salisbury Plain Site of Special Scientific Interest (SSSI), Special Area of Conservation (SAC) and Special Protection Area (SPA) cover 19,690 hectares (ha), which is about half of the wider military training area – see Figure 1. It is notified for 25 features: chalk grassland, the Nine Mile River, juniper habitat, rare plants, invertebrates including marsh fritillary butterfly and fairy shrimp, and birds including stone curlew and wintering hen harrier. The SSSI Favourable Condition Tables (FCT) list the notified features, with attributes and targets for managing and monitoring each. The FCT has undergone considerable development over the years, including some refinement of the features in 2015, based on the legal document, the Citation (see Appendix 1 – Salisbury Plain SSSI Citation). Condition Assessment, now called Integrated Site Assessment (ISA), of these features, at unit level, was last carried out in 2008; and the aim of this project was to do a representative and robust, fresh, assessment of a significant proportion of the SSSI over two fieldwork seasons in 2014 and 2015. On the Plain, DIO ecologists oversee the grazing, scrub management, stone-curlew plots, juniper exclosures and general conservation management; whilst military training, from a nature conservation perspective, has a big influence on bare ground creation and recovery levels. Natural England is the statutory body and has recently taken on greater responsibility for monitoring on the Plain. All parties have an interest in working towards the Government’s ‘Biodiversity 2020’ target for SSSIs. A core part of this assessment was the chalk grassland, which was carried out, in-house, by the Wiltshire Conservation Team (WCT) and Natural England Field Unit (NEFU), covering two thirds of the SSSI during the summers of 2014 and 2015. The other third is not yet freshly assessed, including much of the Central Impact Area and the Nine Mile River. At the same time, the other notified features were assessed through a variety of surveys and biological records: Natural England specially commissioned surveys – bryophytes (Sharon Pilkington), breeding birds assemblage and quail (Thomson Ecology), Duke of Burgundy butterfly (Martin Townsend), tor-grass (Centre for Ecology and Hydrology (CEH)). Natural England Field Unit – tuberous thistle. DIO commissioned research and management plans - marsh fritillary (CEH), juniper. Wiltshire Botanical Society records, Wiltshire & Swindon Biological Records Centre – rare plant assemblage. Wiltshire Butterfly Conservation and the three Salisbury Plain conservation groups (Imber, Westdown & Larkhill, Bulford) – adonis blue, brown hairstreak and fairy shrimp. Wiltshire Ornithological Society – hen harrier, hobby. Royal Society for Protection of Birds – Wessex Stone-curlew Recovery Programme – annual reports. 1 Salisbury Plain SSSI Integrated Site Assessment 2014-15. Integrated Site Assessment and ‘Bio2020 programme’ reporting is at the SSSI unit level. Within each unit, each notified feature present is given a condition status, along with explanatory text, and reported in Natural England’s Conservation Management System (CMSi). For a unit to achieve overall Favourable condition, all features within that unit must achieve Favourable condition. However, it was not considered possible or necessary to survey everything everywhere, given the scale of the SSSI, rather aim for an appropriate level of survey of each feature, whether at grassland parcel, unit or whole site level; then interpolate to the unit-level condition status judgements. For example, the chalk grassland, a key feature, was surveyed relatively intensively, by randomly selecting an average of four National Vegetation Classification (NVC) polygons or parcels per unit and carrying out a ‘Rapid ISA’. For the notified breeding birds assemblage, a Breeding Birds Survey (BBS, national method) was done in 100 x 1km squares, allowing direct comparison with the previous 2005 and 2000 surveys, using statistical analyses of raw count data and density estimates to demonstrate population trends.