National Character Area 110 Chilterns
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National Character Area 110 Chilterns The National Character Area (NCA) following the Chilterns (110) is particularly rich in arable plants: 82 out of 121 rare and threatened plants have been recorded since 1987, giving a total Important Arable Plant Area (IAPA) score of 389. This is one of the highest scores in the country; thus the Chilterns NCA should be prioritised for conservation measures. Twenty of the 23 Section 41 (S41) arable plants listed under the NERC Act 2006 have been recorded in the Chilterns. Of these, eleven plants have post-2000 recorded populations. The Chilterns are the hotspot for wild candytuft in the UK, but there are fewer recent records when compared with the historical distribution. Red hemp-nettle, corn buttercup, shepherd’s-needle and annual knawel were historically widespread across the Chilterns, but there are very few recent records; particularly red hemp-nettle which is only present at one location in the hills. However, this species could be brought back from the soil seed bank, as the seed is known to survive a long time when buried. However, corn buttercup and shepherd’s-needle are thought to have short seed longevity and many of the historical and mid-date recorded populations might have been lost. The north east end of the Chilterns has a couple of recent records of ground-pine, and it is likely that these are some of the most northerly populations in England as the species prefers warmer climates and very calcareous soils, usually associated with the North Downs. However, there are a few populations in the Hampshire Downs. There is an unusual record of grass-poly from the south west end of the Chilterns as this species is more associated with the landscape of the East Anglian chalk to the east of the Chilterns. However, it would survive at any locations where there is seasonal inundation of water reducing the competition by plants and crops. Records of cornflower are scattered across the NCA. In recent years cornflower, along with Austrian chamomile, corn marigold and corncockle, has been included in cornfield flower seed mixtures, and it is not always possible to differentiate which populations are naturally occurring and which are introduced. The coincidence of S41 species indicates that the richest location is near Marsworth and Harpenden. The latter is the Rothamstead Research Station and it is not known whether the species are naturally occurring or have been introduced as part of the arable trial experiments. However, the records date from the 1970s, prior to the origin of the experimental plots, and the species have been considered to be naturally occurring from the soil seed bank for the purposes of this mapping (until proven otherwise). Corn cleavers which is known to be reintroduced at the Research Station has not been included in the IAPA score. The IAPA mapping indicates that in the Chilterns there are six tetrads of European Importance, 67 of National Importance, and 87 of County Importance for arable plants. It is not known whether these locations have been a focus for survey, but further monitoring and baseline surveys of agricultural holdings would increase our knowledge of the distribution of arable plants within this NCA. This is the case particularly for farms undertaking conservation measures to identify whether there are rare arable plants located within the managed areas and how the populations are faring. In summary, the IAPA tetrad map does provide a good baseline for targeting agri-environment scheme measures and voluntary conservation measures, particularly cultivated margins. However, it is not a complete picture, and it is likely that there are undiscovered populations of rare and threatened arable plants in this particularly rich NCA. There is a need for additional surveys on holdings with historical and current populations of arable plants and feedback to land managers and Natural England Advisers suggesting changes in management to help sustain populations of threatened plants and potentially restore populations from buried seed. Holdings that have agri-environment options suitable for arable plants should be surveyed to find out whether the management is suitably targeted, particularly if the farms are entered into higher-level options or going to continue into Countryside Stewardship. Chilterns Soils For the purpose of this mapping, soil has been categorised using the broad soil category dominant in the tetrad. The mapping does not show the finer changes in soils throughout the fields, and this can misrepresent particular hotspots of very chalky soil that may be locally dominant where it is close to the soil surface. The most common soils in the Chilterns NCA are within the clay category and is the dominate substrate for 472 tetrads. Soils derived from chalky substrates are scattered along the ridge of the Chilterns and are the dominant soil for 62 tetrads. None of the tetrads were classified as ‘free-draining sandy, gravel or shale substrates’ or ‘other’ soil types which includes peaty soils, soils under river beds that have not been classified and coastal habitats such as saltmarsh. Contains Ordnance Survey data © Crown copyright and database right 2016. ± Kilometers 10 Pheasant’s-eye Adonis annua There are five locations with pheasant- eye records. None of the records are recent except for an introduced population near Marsworth (SP91H). Populations in High Wycombe (SU89G) and Dunsden Green (SU77N) were recorded in the mid-date range and were both last recorded in 1994. The records near Ibstone (SU79R) and Pegsdon (TL13F) are historical. Data maintained by the Contains Ordnance Vice-County Recorder and Survey data © Crown provided by the Botanical copyright and database Society of the British Isles right 2016. and Ireland and accessed ± from the BSBI Distribution Kilometers 10 Database 2015. Contains Plantlife Important Arable Plant Area database data 2015. Ground-pine Ajuga chamaepitys The most recent populations of ground- pine from the Chilterns were recorded from the chalk ridge between Barton-le- Clay and Hitchin from 2007 (TL02Z, TL03V and TL13F). However, there are also records of a reintroduction of ground-pine in the latter tetrad and some of the more recent records could be confused with this population. There is also a mid-date record from Harpenden (TL11G) and a mid-date range introduction north east of Tring (SP91H). Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2016. Society of the British Isles and Ireland and accessed ± from the BSBI Distribution Kilometers 10 Database 2015. Interrupted Brome Bromus interruptus All of the naturally occurring records of interrupted brome within the Chilterns are historical. However, there has been a recent introduction of interrupted brome near Aston Rowant (SU79I) in 2004. Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2016. Society of the British Isles and Ireland and accessed ± Kilometers from the BSBI Distribution 10 Database 2015. Thorow-wax Bupleurum rotundifolium All of the naturally occurring records of thorow-wax within the Chilterns are historical. However, there has been a recent introduction of thorow-wax north of Tring (SP91H) in 2000. Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2016. Society of the British Isles and Ireland and accessed ± Kilometers from the BSBI Distribution 10 Database 2015. Cornflower Centaurea cyanus Parts of the Chilterns have recent records of cornflower which are thought to be naturally occurring from the soil seed bed. However, in more recent years cornflower has been included in amenity planting. This has made it difficult to differentiate which records are naturally occurring from the soil seed bank or introduced from sown mixtures. Much effort has been placed into determining the outcome of this distinction when the records have been collated by the vice- county recorder. There is the possibility that no known origin of the seed exists, particularly if it is a newly recorded population on farmland. Recently recorded cornflower records that are thought to be naturally occurring are present around: Purley on Thames (SU67T and SU67S), between Reading and Maidenhead (SU77M, SU77T, SU78V, SU88A and SU88K). Beaconsfield (SU99A). Harpenden (TL11G). Langley (TL22F). Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2016. Society of the British Isles and Ireland and accessed ± Kilometers from the BSBI Distribution 10 Database 2015. Upright Goosefoot Chenopodium urbicum There is one mid-date record of upright goosefoot from Naphill (SU89N) from 1992. Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2016. Society of the British Isles and Ireland and accessed ± Kilometers from the BSBI Distribution 10 Database 2015. Red-tipped Cudweed Filago lutescens There are four records of red-tipped cudweed in the Chilterns. The most recent record is from Cockpole Green (SU78V) and there are historical records from Crowmarsh Gifford (SU68I), Lower Assendon (SU78H) and Cookham Dean (SU88S). Contains Ordnance Data maintained by the Survey data © Crown Vice-County Recorder and copyright and database provided by the Botanical right 2015. Society of the British Isles and Ireland and accessed ± from the BSBI Distribution Kilometers 10 Database 2015. Broadleaved Cudweed Filago pyramidata There is one recent naturally occurring population of broadleaved cudweed recorded in the Chilterns from Dunsdon Green (SU77N), which was last recorded in 2009. There is one population recorded in the mid-date range at Hurley (SU88G). The other naturally occurring populations are all historical. In addition, there are two introduced populations at Northchurch (SP90P) and Marsworth (SP91H) both recorded in the mid-date range.