2018-19 Soil Policy Evidence Programme
Habitat Suitability Modelling Scoping Study
12th September 2019 Report code: SPEP2018/19-08
Mae’r ddogfen yma hefyd ar gael yn y Gymraeg. This document is also available in Welsh.
© Crown copyright 2020 WG41030
ADAS GENERAL NOTES
Project No.: 1021091-1(01)
Title: Habitat Suitability Modelling Scoping Study
Client: Welsh Government – Soil Policy Unit, Department for Environment, Energy & Rural Affairs
Date: 12th September 2019
Office: Wolverhampton
Status: Final
Chris Forster-Brown, Dave Skirvin & Lucy Authors Wilson Technical reviewer Lucy Wilson
Date: 12th Sept 2019 Date: 12th Sept 2019
ADAS Project manager Lucy Wilson
Date: 12th Sept 2019
Welsh Government James Cooke Project Manager
RSK ADAS Ltd (ADAS) has prepared this report for the sole use of the client, showing reasonable skill and care, for the intended purposes as stated in the agreement under which this work was completed. The report may not be relied upon by any other party without the express agreement of the client and ADAS. No other warranty, expressed or implied, is made as to the professional advice included in this report. Where any data supplied by the client or from other sources have been used, it has been assumed that the information is correct. No responsibility can be accepted by ADAS for inaccuracies in the data supplied by any other party. The conclusions and recommendations in this report are based on the assumption that all relevant information has been supplied by those bodies from whom it was requested. No part of this report may be copied or duplicated without the express permission of ADAS and the party for whom it was prepared. Where field investigations have been carried out, these have been restricted to a level of detail required to achieve the stated objectives of the work. This work has been undertaken in accordance with the quality management system of RSK ADAS Ltd.
CONTENTS
1 INTRODUCTION ...... 1 1.1 Objectives ...... 1 2 RESTORATION/ ESTABLISHMENT REQUIREMENTS OF THE MAIN TERRESTRIAL PRIORITY HABITATS IN WALES ...... 2 2.1 Lowland meadows ...... 2 2.2 Lowland calcareous grassland ...... 2 2.3 Lowland dry acid grassland ...... 3 2.4 Upland calcareous grassland ...... 4 2.5 Coastal and floodplain grazing marsh ...... 4 2.6 Purple moor-grass and rush-pasture ...... 5 2.7 Arable field margins...... 6 2.8 Lowland heathland ...... 7 2.9 Upland heathland ...... 8 2.10 Blanket bog ...... 9 2.11 Reedbeds ...... 9 2.12 Upland oakwood ...... 10 2.13 Upland mixed ashwood ...... 10 2.14 Wet woodland ...... 10 3 LINKING PRIORITY HABITAT REQUIREMENTS TO ALC LIMITING FACTORS ...... 12 3.1 Methodology ...... 12 3.2 Results ...... 17 4 GAPS IN ALC DATA FOR DESCRIBING ENVIRONMENTAL CONDITION REQUIREMENTS...... 32 4.1 Gaps in biophysical requirements of priority habitats ...... 32 4.1.1 Historical extent of habitats ...... 32 4.1.2 Multiple NVC types ...... 32 4.1.3 Additional analysis of soil data ...... 33 4.1.4 Geology ...... 33 4.2 ALC Data Gaps & Additional Technical Information / Evidence...... 34 5 SCOPING A MODELLING PROJECT THAT COULD UTILISE SUCH A FRAMEWORK ...... 36 5.1 Work Package 1: Habitat requirements scoring ...... 36 5.1.1 Datasets required ...... 37
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5.1.2 Resource estimates...... 37 5.2 Work package 2: Development of a desktop-based tool for assessing land area suitability for priority habitats ...... 38 5.2.1 Key steps ...... 38 5.2.2 Outputs ...... 39 5.2.3 Resource estimates...... 39 5.3 Additional cost option ...... 39 5.3.1 Combing ALC with plan species niche modelling tool ...... 39 5.3.2 Tasks required for the development of this approach ...... 40 5.3.3 Datasets required ...... 41 5.3.4 Resource estimates...... 42 6 POTENTIAL USES FOR SUCH A MODELLING SYSTEM ...... 43 6.1 Support for agri-environment scheme development ...... 43 6.1.1 Flood risk reduction ...... 43 6.1.2 Decarbonisation ...... 43 6.1.3 Habitat ...... 43 6.2 Support for agri-environment management option selection ...... 44 6.3 Assessment of the implications of climate change ...... 44 6.4 To inform land use choice ...... 44 6.5 To help target expansion and restoration of the priority habitat network ...... 45 6.6 Area Statements ...... 45 7 REFERENCES ...... 47
Tables Table 1. Notes on Priority Habitat requirement tables...... 12 Table 2. ALC soil texture class abbreviations ...... 15 Table 3. Definition of soil wetness class in the ALC ...... 16 Table 4. Lowland meadows ...... 17 Table 5. Lowland calcareous grassland ...... 18 Table 6. Lowland dry acid grassland ...... 19 Table 7. Upland calcareous grassland ...... 20 Table 8. Coastal and floodplain grazing marsh ...... 21 Table 9. Purple moor-grass and rush pasture ...... 22 Table 10. Arable field margins ...... 23
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Table 11. Lowland heathland ...... 24 Table 12. Upland heathland ...... 25 Table 13. Blanket bog...... 26 Table 14. Reedbeds ...... 27 Table 15. Upland oakwood ...... 28 Table 16. Upland mixed ashwood ...... 29 Table 17. Wet woodland ...... 30
Appendices APPENDIX 1 ...... 49 APPENDIX 2 – GLOSSARY ...... 50
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1 INTRODUCTION
A scoping study was carried out to explore an approach to modelling potentially suitable locations to restore and / or establish different priority habitat types in Wales. This involved an assessment of soil, site and climatic property data underpinning the Predictive Agricultural Land Classification (ALC) Map (Wales) and the methods being developed to model potential suitable locations to grow agricultural and forestry crops as part of the Welsh Government’s “Capability, Suitability & Climate Programme” (CSC). The approach for assessing priority habitat requirements was to be analogous to the approach used for recent work to generate crop bio-physical requirements based on soil, agro-climatic and ALC parameters (ADAS, 2019). The focus was on the main terrestrial priority habitats (PHs) listed under Section 7 of the Environment Act.
1.1 Objectives
The objectives of this study were to answer the following questions. 1. Can the ALC data on soil, climate, slope, wind / frost exposure, flood risk be used with a habitat requirement report to model potential suitable locations for different habitats given appropriate management? 2. Are there data gaps? If so what needs to be developed? 3. What would a project like this look like? 4. What steps would be involved? 5. What expertise would be required? 6. What is the estimated cost range for each project step? 7. What is the estimated time range to complete each project step? 8. What are the potential uses for such a modelling system? These objectives were achieved through a series of tasks:- Task 1. Research restoration/ establishment requirements of the main terrestrial priority habitats in Wales. Task 2. Link these requirements to the ALC limiting factors and determine suitable thresholds if possible. Task 3. Identify gaps in ALC data for describing environmental condition requirements. Task 4. Scope out a modelling project that could utilise such a framework. Task 5. Research potential uses for such a modelling system.
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2 RESTORATION/ ESTABLISHMENT REQUIREMENTS OF THE MAIN TERRESTRIAL PRIORITY HABITATS IN WALES
This section provides a review of the restoration requirements for the principal terrestrial Priority Habitats in Wales (Task 1). Wherever possible, it seeks to provide the main edaphic, topographical and climatic conditions suitable for restoring/re-creating each of the Priority Habitats. Restoration for each habitat should be targeted at areas that already hold more of the relevant resource, particularly where additional habitat would join up fragmented stands or increase the area of established examples. The maps presented in the Priority Habitats of Wales (Jones et al, 2003) give an excellent guide to targeting restoration effort. It is suggested that these are used in conjunction with the soils, climate and site data held by Welsh Government in order that restoration effort can be most appropriately applied. The NRW networks and revised networks report may also be a valuable resource, when considering how likely restoration efforts are supported by neighbouring seedbanks.
2.1 Lowland meadows
Properties of the underlying soil type: MG5, is characteristic of infertile to moderately fertile, deep loamy to clayey, brown earths. However, there is a degree of variation from lighter textured, somewhat calcareous soils to superficially acidic (but non-podzolic) soils. MG4 and MG8 community types tend to occur on, respectively, deep alluvial silts that are frequently gleyed, and deep moderately calcareous brown earths, which are seasonally to periodically inundated. Soil chemical properties of Lowland Meadows include: P less than 10 mg l-1 (Index 0), K less than 200 mg l-1 (Index 2+), pH 5.4-6.3 for Lowland Meadows. Topographical context: Typically found on flat or shallow sloping land up to approximately 300m above sea level. Climatic context: Lowland Meadows occur within a wide range of climatic variation. Distribution in Wales: MG5 widely distributed, though much declined and degraded. Greater occurrence in southern half, with particular concentrations in Glamorgan, Carmarthenshire and the northern half of Pembrokeshire. MG4 and MG8 much more restricted, and at western limit of their UK distribution. MG4 (floodplain meadow) occurs as handful of small sites near English border in Powys and Wrexham. MG8 (flood-pasture) occurs as tiny example in Dee floodplain. Restoration potential: Relatively diverse stands of semi-improved grassland (MG6b) likely to be most suitable precursor, not highly improved situations (MG7).
2.2 Lowland calcareous grassland
Properties of the underlying soil type: All NVC types in Wales (CG1 – CG3, CG6 and CG7) occur on shallow soils (e.g. rendzinas and calcareous brown earths), overlying limestone and other lime-rich rocks. They are therefore found on free-draining, dry soils. In Wales, they are primarily confined to Carboniferous Limestone in the north and south of the country. Soil chemical properties of Lowland calcareous grassland include: Low P levels (mean levels of around 5 mg l-1), pH > 7 (in range 7.7–7.9). Calcareous grasslands have lower available Phosphorus than all other Priority Habitat grasslands and heathlands.
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Topographical context: Remaining examples are typically confined to distinct topographic features – coastal headlands, inland escarpments and dry valley slopes. Found up to approximately 300m above sea level. Climatic context: Lowland calcareous grassland occurs largely in areas with less than 1000mm rainfall per annum. Distribution in Wales: South coast of Gower peninsula, Vale of Glamorgan coast, southern edge of Brecon Beacons National Park, Great Orme and Denbighshire/Conwy border. Restoration potential: The greatest opportunity for restoration of calcareous grasslands is where semi-improved neutral grassland overlies thin brown earths and rendzina soils overlying limestone. The highest priority for restoration would be semi-improved Calcareous grassland (recorded by Phase 1); improved grassland in suitable locations reverts within a reasonable timescale.
2.3 Lowland dry acid grassland
Properties of the underlying soil type: Four NVC types in Wales (U1 – U4). Lowland dry acid grassland characteristically occurs on base-poor and frequently heavily leached soils, overlying pervious parent materials such as acid rocks and/or sand and gravels. Soils are liable to summer drought, and the vegetation is open in character, with frequent bare patches. Though brown earths are most typical, soil types range from rankers through brown earths to podzols. Soil chemical properties of Lowland dry acid grassland include: P less than 10 mg l1, K less than 200 mg l1, pH between 4 and 5. Each soil type tends to result in distinctive NVC communities. Topographical context: U2 and U4 are still frequent, juxtaposed with ‘ffridd’ vegetation (including lowland heathland) in the upland fringes. U3 is found on moister soils in Glamorgan. U1 is found, often on steep slopes towards the English border. Found between 150m and 500m above sea level. Climatic context: The commonest types of Lowland dry acid grassland in Wales (U2 and U4) occur in areas where precipitation exceeds 800mm/year and mean annual maximum mean temperature is <27oC i.e. all of Wales. U1 is more exacting climatically, and only occurs where annual rainfall is <1000mm/year and mean annual maximum temperature is >26oC Distribution in Wales: U2 and U4 are widespread in the upland fringes, associated with ‘ffridd’ vegetation. The largest areas in descending rank order, each with >2000 hectares are: Snowdonia National Park, Gwynedd, Powys, Ceredigion, Brecon Beacons National Park and Neath Port Talbot. The highest density occurs in Blaenau Gwent and Merthyr Tydfil in the south and Snowdonia and Gwynedd in the north. U3 is only found in areas of Glamorgan. U1 is found in the east of Wales, close to the English border (e.g. Breidden Hill, Stanner Rock). Restoration potential: The greatest opportunity for restoration of lowland dry acid grassland is where semi-improved grassland overlies soils that are naturally podzolic and ranker-like in character. Reversion of arable land to lowland dry acid grassland is not feasible in Wales as very little arable land overlies naturally acidic soils. Semi-improved acid grassland would be the highest priority; improved areas revert quickly.
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2.4 Upland calcareous grassland
Properties of the underlying soil type: Three NVC types in Wales (CG10, CG12 and CG14). As with lowland calcareous grassland, upland CG12 occurs on shallow soils (e.g. rendzinas and moist, calcareous brown earths), overlying Carboniferous Limestone. It is also found on Old Red Sandstone. It is found on free-draining, dry soils. CG12 and CG14 are ledge communities, associated with the above rock types, though also with basic igneous and metamorphic rocks. Soil chemical properties of Upland calcareous grassland include: Generally low P levels (mean levels of around 5 mg l-1), pH > 7 (in range 7.7–7.9). Topographical context: Stands of CG10 are small and linked to the presence of base-rich rock, often juxtaposed with other habitat types such as base-rich flushes. It is usually found in relatively inaccessible areas and often associated with steep or medium slopes. CG12 and CG14 are ledge communities, associated with base-rich rock in the mountains (i.e. on cliffs and other faces). Climatic context: Upland calcareous grassland in Wales (CG10) occurs in mountainous areas and therefore tends to be present where there is > 1000mm rainfall per annum. Distribution in Wales: Upland calcareous grassland has a somewhat different distribution to its lowland counterpart. It is not coastal and is confined to areas of Snowdonia, limestone in Denbighshire and the southern edge of Brecon Beacons National Park. This last is a particularly important area and here, it is found in the Black Mountains, Brecon Beacons, Fforest Fawr, Mynydd Llangatwg, Mynydd Llangynydir and Mynydd Du. Restoration potential: In order for restoration to be successful, there would ideally be areas of unimproved calcareous grassland already present and the emphasis should be on re- uniting fragmented examples.
2.5 Coastal and floodplain grazing marsh
Properties of the underlying soil type: Three NVC types in Wales. Coastal grazing marsh largely comprises MG11 and MG12. Floodplain grain marsh is MG13. Coastal and floodplain grazing marsh has usually derived from saltmarsh and/or freshwater swamp habitats. This is reflected in its relatively high pH (6 +) and high levels of available Phosphorus, Potassium and Nitrogen compared to other Priority Habitats. Coastal grazing marsh undergoes periodic inundation with brackish or salt waters. Floodplain grazing marsh similarly undergoes periodic inundation from river water. Soil types tend to be light-textured brown earths and alluvial soils that experience fairly frequent superficial wetting and drying processes. Most coastal grazing marsh is formed on reclaimed coastal land and occurs behind sea defences. Where defences are intact it supports neutral grassland MG5, MG6, MG7, MG9, MG10 and M23. Areas of frequent inundation can contain MG11 and very rarely MG12 and can grade into saltmarsh. Flood plain grassland consists mainly of MG4, MG5 and MG8 (with improvement MG6 and MG7). MG9, MG10, MG13, M22 and M23 are also found on floodplains.
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Topographical context: Coastal grazing marsh is found in flat, coastal situations, often behind sea defences or, more occasionally, dunes. It is usually drained by a series of ditches. Floodplain grazing marsh tends to occur in inland, flat, valley-floor scenarios. It too is usually ditched or bordered by flood banks. Climatic context: Many of the coastal and floodplain grazing marshes in Wales are found in the drier districts, corresponding with their locations along the coasts and major river valleys in the south-west, west and north-east. Distribution in Wales: The main areas of coastal grazing marsh are found in the south-east (Gwent Levels), south (Margam Moors) and Anglesey (Malltraeth Marsh). Floodplain grazing marsh is associated with the main watercourses, particularly the Conwy, Clwyedog and Dee in the north, the River Severn and its major tributaries in the east, the Usk in the south east and the Tywi in Carmarthenshire. Other major rivers with large concentrations of floodplain grassland are the Neath, the Loughor (Swansea and Carmarthenshire), and the Teifi (Ceredigion and Carmarthenshire). Restoration potential: Many of the above examples contain large areas of improved and semi-improved grassland. These areas should be targeted, particularly where areas of semi- improved grassland support species that can act as a seed source for adjacent improved grassland. It is often the smaller sites (e.g. around Carmarthen Bay and Cardigan Bay) that are the least impacted by grassland improvement and therefore improved or semi-improved sites adjacent to these should also be targeted for restoration/re-creation. Notes: There seems to be a general ambiguity about coastal grazing marsh. It is different from saltmarsh, but is inundated from time to time by brackish water, the extent to which depends how modified it is or how solid any sea defences are, preventing salt water incursion.
2.6 Purple moor-grass and rush-pasture
Properties of the underlying soil type: Five NVC types in Wales (M22 – M26). The Purple moor-grass and rush-pasture Priority Habitat encompasses a number of soil types, each of which are reflective of a particular NVC community. Of the two most common community types, M23 is found on moderately acid to neutral soils that are kept moist for most of the year. There is a strong correlation of the occurrence of this community to areas of impeded drainage, and soils are usually stagnogleys or ground water gleys. M25 is also found on water-logged soils but, in contrast to M23, a greater degree of water movement is apparent in these situations, and soils tend to be well aerated. Of the rarer community types, M24 is inclined to strongly humic soils that are generally intermediate in terms of moisture regime, base status and nutrient content. There is usually no marked seasonal fluctuation in water level. M22 occurs on a variety of moist base-rich and moderately mesotrophic soils; predominately on alluvial soils and gleys of mineral origin. M26 is a very local community of moist base-rich and calcareous peats and peaty mineral soils. Soil chemical properties of Purple moor-grass and rush-pasture include: P less than 10 mg l1, K less than 200 mg l1 and pH 4.7-5.4. Topographical context: Soil moisture is fundamental to Purple moor-grass and rush-pasture communities, with both the mean water table height and the timing and duration of water
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logging affecting wetland plant communities. Many plants are adapted to wet conditions and this adaptation to soil wetness varies between species. It is useful to think of a wetness gradient with plants able to thrive under water-logged conditions for most or all of the year at one end of the gradient and those only able to tolerate a high water-table for part of the year at the other end. Drainage of wetland soils leads to changes in their properties with increased oxidation, mineralisation of nitrogen, compaction and wastage of organic matter and potentially reduced water storage capacity. Climatic context: Climatically, Purple moor-grass and rush-pasture encompasses a multiplicity of variables. The most common NVC types of M23 and M25 are predominately of western distribution within Wales and therefore occur where the mean annual maximum temperature is <26oC. However, it does not penetrate to areas where the February minimum mean temperature is <0.50C below freezing. Consequently, most is situated at below 200m. With regard to rainfall, these communities are restricted to areas that receive respectively 1200mm and 1000mm mean annual rainfall per year, and >160 and >140 wet days/year. M24 and M22 can be regarded as representing the opposite climatic extreme to M23. Consequently, in UK terms they tend to be of a south eastern distribution. Within the UK, M22 predominantly occurs within the 29oC mean annual maximum isotherm and M24 occurs in areas that receive between 120-140 wet days/year. Conversely, M26 is a sub- montane community between 250m – 450m, where the climate is typically cold and wet. Annual rainfall in these situations is approximately 1600mm, and with 160 wet days/year. Distribution in Wales: Purple moor-grass and rush-pastures largely occur in areas of high rainfall and over a wide altitudinal range. Nevertheless, there is a bias in favour of the west of Wales. In descending rank order, the largest areas of the commoner communities (M23 and M25) occur in Ceredigion, Snowdonia National Park, Powys, Gwynedd, Pembrokeshire, Brecon Beacons National Park and Anglesey. The highest density is found in Gwynedd with 3.7ha/km2. The South Wales Coalfield, encompassing Glamorgan and Carmarthenshire, is also particularly important for this habitat and especially for examples of the M24 community. M22 is much more localised, occurring in fen-like situations in Anglesey, Gwynedd and Glamorgan. M26 is even more restricted and has only been recorded in Snowdonia. Restoration potential: In general, recreation and restoration should be targeted at the more restricted forms of Purple moor-grass and rush-pasture (M24 in particular). It is unlikely that it will be possible to establish examples of M22 and M26, due to their more exacting soil chemical requirements. Ranker forms of M25, comprising virtual monocultures of Purple moor-grass should not be encouraged. Some forms of M23 are relatively species-rich and these should be targeted where there are damp slopes in the uplands (with some through flow of water). The key conditions are usually the presence of a high water table and impeded drainage on gley soils. MG9 and MG10 would be the highest priority for restoration.
2.7 Arable field margins
Properties of the underlying soil type: Wide range of NVC OV (open vegetation) communities. Similarly wide range of soil types, with more neutral soils on Anglesey and the
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Lleyn Peninsula and more base-rich soils in parts of Gower, Vale of Glamorgan and Monmouthshire. Topographical context: Usually found in flat or gently sloping conditions. Climatic context: Comparatively low rainfall areas. Often above average temperatures for Wales as a whole. Distribution in Wales: The main areas of arable field margins are in the lowlands of Pembrokeshire, Powys, Monmouthshire, Gower (Swansea), Vale of Glamorgan, Denbighshire, Flintshire and Wrexham. Significant areas are found on Anglesey and Lleyn. Restoration potential: The re-introduction of arable cropping should be considered for areas of improved and semi-improved grassland, particularly where these lie within the areas outlined above. Other: This habitat will be revised under Section 7 updates. Currently it is based on management only. There is interest in the rich plant communities (both bryophytes and vascular) that are supported by long-term (ancient) traditional arable management. The different communities are strongly linked to soil type and climate. NRW has distribution maps of arable communities and extrapolated maps of Important Arable Plant Areas. The IAPA’s could be used to guide restoration effort, alongside historic species records.
2.8 Lowland heathland
Properties of the underlying soil type: Four dry lowland heath NVC types in Wales (H4, H8 – H10). Two wet lowland heath NVC types in Wales (M15 and M16). All occur in base-poor situations. The dry heaths are frequently on heavily leached soils, overlying pervious parent materials such as acid rocks and/or sand and gravels. Soils supporting dry heath are liable to summer drought and brown earths and podzolic soils are most typical. Wet heaths are on damper acid soils, where either shallow peat or mineral soils are seasonally waterlogged. Humid heaths (found in Glamorgan) are found on intermediate soils (i.e. damp, though not impeded drainage). Soil chemical properties of Lowland heath include: P less than 10 mg l1, K less than 200 mg l1, pH < 5. Topographical context: H8 and H10 dry lowland heaths are relatively frequent, juxtaposed with ‘ffridd’ vegetation (including lowland dry acid grassland) in the upland fringes. They are therefore principally confined to slopes. H4 is found on moister soils in Glamorgan. H8 and H10 are found between 150m and 500m above sea level. H4 is at lower levels. H9 is a rare community in Wales. Wet heaths tend to be found in flatter situations, corresponding to the more impeded drainage conditions. Both wet and dry heath, as well as lowland dry acid grassland and marshy grassland are frequently found in close proximity, often in mosaics. Climatic context: The commonest types of Lowland heath in Wales (H8, H10, M15) tend to occur in areas where precipitation exceeds 800mm/year and mean annual maximum temperature is <27oC. H4 is rather more exacting climatically, and only occurs where annual rainfall is <1000mm/year and mean annual maximum temperature is >26oC. Distribution in Wales: H8 and H10 are widespread in the upland fringes, associated with ‘ffridd’ vegetation. Particular concentrations are found in Ceredigion, Snowdonia National Park and in the Brecon Beacons. The humid H4 is only found in south Wales (principally
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Glamorgan); however, NRW identified a form of H4 Ulex gallii-Agrostis curtisii heath without Agrostis curtisii found in Pembrokeshire and the Gower and may also occur much further north on Llŷn and Anglesey (Sherry, 2007). Wet heaths are particularly well represented in Swansea, Pembrokeshire, Snowdonia National Park, Gwynedd and Ceredigion. Restoration potential: The greatest opportunity for restoration of lowland heathland is where acid grassland overlies soils that are naturally podzolic and ranker-like in character. Grazing levels are the key factor in heathland recreation and various studies have shown how, when grazing is restricted, heathland may be restored. An assessment should be made, taking into account relative mixtures of existing heath and grassland, to assess which is more desirable to recreate. Reversion of arable land to lowland heathland is not feasible in Wales as very little arable land overlies naturally acidic soils.
2.9 Upland heathland
Properties of the underlying soil type: Six main upland heath NVC types in Wales (H8 – H10, H12, H18, H21). Wet upland heath NVC types in Wales are the same as for lowland heath (M15 and M16). All occur in base-poor situations. The dry upland heaths are frequently on heavily leached soils, overlying pervious parent materials such as acid rocks. Soils supporting dry upland heath are liable to summer drought and brown earths and podzolic soils are most typical. Wet heaths are on damper acid soils, where either shallow peat or mineral soils are seasonally waterlogged Soil chemical properties of upland heath are in line with those for lowland heath and include: P less than 10 mg l1, K less than 200 mg l1, pH < 5. Topographical context: Upland heaths follow a well-marked altitudinal sequence in the western Welsh hills. Thus, H8 is found at moderate elevations, with H10 on higher slopes and H12 tending to dominate higher again. H21 is occasionally prominent in the most extreme conditions, being found on north and north-east facing slopes. H18 tends to be found where heavy grazing is prominent. The dry heather moors in the east of Wales is the main locus for H12. In the west, upland heathland is found more on steeper slopes and less heavily grazed sites. Wet heaths tend to be found in flatter situations, corresponding to the more impeded drainage conditions. Climatic context: Most of the commoner types of Upland heath in Wales (H8, H10, H18) tend to occur in areas where precipitation exceeds 800mm/year and mean annual maximum temperature is <27oC. H12 is found in both dry wet situations and also as the predominant heathland type in the drier east of Wales. Distribution in Wales: H8 and H10 are widespread in the upland fringes, associated with ‘ffridd’ vegetation. Particular concentrations are found in Ceredigion, Snowdonia National Park and in the Brecon Beacons. H12 heath is particularly prominent in the east, in Denbighshire, Blaenau Gwent and the eastern half of the Brecon Beacons National Park. Upland wet heaths are particularly well represented in Snowdonia National Park, Gwynedd and Ceredigion. Restoration potential: The greatest opportunity for restoration of upland heathland, as with other heathland types, is where acid grassland overlies soils that are naturally podzolic and ranker-like in character. Grazing levels are the key factor in heathland recreation and various studies have shown how, when grazing is restricted, heathland may be restored. An
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assessment should be made, taking into account relative mixtures of existing heath and grassland, to assess which is more desirable to recreate. The main focus should be on re- uniting fragmented blocks of existing heathland. The restoration of upland forestry to upland heathland should also be considered.
2.10 Blanket bog
Properties of the underlying soil type: Encompasses four main NVC types in Wales (M17 – M20). In addition, there are three bog pool NVC types (M1 – M3). Blanket bog occurs in acidic waterlogged conditions, on thin and thicker layers of peat. It has a low pH (sometimes as low as 3) and correspondingly low nutrient levels. Topographical context: blanket bog reaches its greatest extent on poorly-drained upland plateaux. It is usually found over 250m. Climatic context: Blanket bog in Wales is found in the wettest areas, where annual precipitation exceeds 1200mm. Annual mean temperatures are also low compared to most other Priority Habitats. Distribution in Wales: This Priority Habitat is associated particularly with the main mountain massifs. These include the Brecon Beacons National Park, Elenydd and Pumlumon in Ceredigion, Llanbrynmair in Powys, Berwyn and Mynydd Hiraethog in the north-east, the Rhinogs, Migneint and Carneddau. Restoration potential: A key focus for blanket bog restoration should be the large areas of wet modified bog that exist. This is often dominated by Purple moor-grass and is found in the mountains throughout mid and north Wales. There is also significant potential in targeting blanket bog restoration to areas in which young or failed conifers have been planted. First and foremost, the potential for restoration or re-creation should take into account the presence of deep peat, altitude, rainfall, the presence of upland plateaux conditions and impeded drainage.
2.11 Reedbeds
Properties of the underlying soil type: Reedbeds establish in areas where the water table lies at or above the ground surface for much of the year. They can be naturally nutrient-rich systems though have often been made more eutrophic through the contamination of ground waters from agricultural run-off, sewage or some industrial effluents. Topographical context: Flat, river and coastal floodplains, lake fringes. Climatic context: Largely coastal and associated with the main river valleys in Wales. Therefore tending to exist in drier locations. Distribution in Wales: This Priority Habitat is associated particularly with the coastal areas of the south, south-west and north-west. Anglesey, Pembrokeshire, Carmarthenshire and Swansea hold significant areas of reedbed. Restoration potential: Focus should be on the improved coastal and river floodplain grasslands. Additionally, abandoned mineral workings and former industrial sites are potentially good target locations. Newly established reedbed should not be encouraged in areas of deep peat or on coastal dune land.
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2.12 Upland oakwood
Properties of the underlying soil type: Encompasses four main NVC types in Wales (W17, W11, W10e and W16b). These all occur in base-poor, to acidic conditions, generally in areas of high rainfall. W17 and W11 are found in the wettest conditions, whereas W10e is found as a transition habitat between these types and the driest community (W16b). Topographical context: W11 and W17 are the classic western sessile oakwoods and are found on steep slopes and ‘hanging’ valley sides. W17 often features significant amounts of associated rocks. Climatic context: Most examples of this habitat are found in conditions of high rainfall, typically > 1000mm per annum. Distribution in Wales: Upland oakwood is concentrated in Snowdonia, Powys, Ceredigion and Carmarthenshire. Restoration potential: Restoration should be targeted at areas that already support relatively high cover of upland oakwood. This would allow already significant areas of this habitat to be consolidated and linkages made between existing woods.
2.13 Upland mixed ashwood
Properties of the underlying soil type: Encompasses two main NVC types in Wales (W8 and W9). These occur in neutral to base-rich conditions on relatively dry soils. Wetter areas (flush-lines) within these woodlands will often support small areas of W7 woodland. Here, the water table is higher and the dominant species tends to be alder. Topographical context: Generally on steep slopes, though also present on the lower, shallower slopes of valleys. Climatic context: Most examples of this habitat are found in conditions of high rainfall, typically > 900mm per annum. It is likely that Wales provides the optimal climatic conditions for this woodland type in an international context. Distribution in Wales: The largest concentrations of Upland mixed ashwood are found in the limestone areas of Conwy, Denighshire, Flintshire, Monmouthshire, central Carmarthenshire and south-east and west Glamorgan. Restoration potential: Restoration should be targeted at areas that already support relatively high cover of upland mixed ash woodland. There are a relative lack of locations outside the core areas that are suitable for expansion of this woodland type. Therefore, expansion should be targeted at areas contiguous or near existing stands.
2.14 Wet woodland
Properties of the underlying soil type: Poorly-drained or seasonally wet soils. Topographical context: Found in three situations: (1) as successional developments on terrestrial wetlands; (2) alder-dominated stands in seepages and spring lines and (3) floodplains and along river edges. Climatic context: Found throughout Wales and not particularly influenced by specific climactic conditions.
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Distribution in Wales: Found throughout Wales, with notable concentrations in Powys, Carmarthenshire, the Brecon Beacons and Snowdonia National Parks, Gwynedd and parts of Glamorgan. Restoration potential: upland and valley-side alder woods should establish relatively easily on open ground, adjacent to existing alder woodland (ensure light grazing). Therefore, expansion should be targeted at areas contiguous or near existing stands. These woodlands are more difficult to establish within areas of upland oak and ashwood as soil conditions prevent expansion.
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3 LINKING PRIORITY HABITAT REQUIREMENTS TO ALC LIMITING FACTORS
This assessment (Task 2) considers the climate (e.g. temperature and rainfall), site limitations (e.g. aspect and gradient), and soil factors (e.g. soil depth, stone content, wetness/drainage or soil pH status) for the different Priority Habitats (PH) found in Wales. The section covers both land capability (i.e. the general assessment of, for example, climatic and soil factors without taking into consideration land use) and suitability (i.e. the fitness for restoration or creation of a specific PH). This approach follows a similar methodology to that used to identify land suitability for crop production as part of the Capability, Suitability & Climate Programme, but applied to priority habitats.
3.1 Methodology
For each priority habitat, a requirements table for each of the attributes in the ALC, along with other non-ALC biophysical constraints was produced using information from the review in Task 1. These requirements could then be mapped to the ALC sub-grades for each of the attributes, and compared with the sub-grades in the predictive ALC map to identify those areas that would be suitable for each priority habitat. The example Table 1 below, supplemented with the information in Table 2 and Table 3 is designed to facilitate understanding of the tables in the results section, which details the requirements of each PH and in a tabular summary.
Table 1. Notes on Priority Habitat requirement tables
Requirements Min (e.g.) Max (e.g.) Notes
Climate 500 1000 This is the annual rainfall which is optimum or Rainfall (mm) Optimum & [tolerable] for the PH, unless otherwise stated. [tolerable] range [300] [2500]
Mean annual maximum 15 24 This is the range of mean annual maximum temperature (°C). Optimum temperatures which are optimum or [tolerable] for [7] [32] & [tolerable] range the PH, unless otherwise stated.
Note that this temperature metric is different to that used in the ALC classification for crop suitability, but is used here as it is more relevant to semi-natural habitat constraints. ALC accumulated 1150 ≥1300 For the Agricultural Land Classification (ALC) temperature (day °C) system the period January to June is considered
the critical growth period. Accumulated temperature (AT0) January to June is a measure of the relative warmth of a locality and is the excess of daily air temperature above 0°C (for the ALC system).
The AT0 ranges from c.600-800°C where the altitude is highest (c. 600-800 m) to >1200°C at
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Requirements Min (e.g.) Max (e.g.) Notes altitudes of ≤200 m in, for example, Pembrokeshire. Where there is no specific information on PH requirements, the minimum and maximum AT0 are based on the limit values for the appropriate ALC grades. Air or ground frost An 'air frost' occurs when the temperature at 1.25 -3 0 metres above the ground falls below 0°C, whereas
'ground frost' refers to a temperature below 0°C measured on a grass surface. The minimum temperature is the temperature furthest from 0°C and the maximum temperature is the temperature closest to 0° at which freezing damage occurs.
Site Gradient (°) 0 7 The gradient limit for each PH is given based on the categorisation used in the ALC: grade 1 to 3a 7°; grade 3b 11°; grade 4 18° and grade 5 >18°. Altitude (m) Altitude (above mean sea level), affects, for example, soil wetness and temperature. For the AT0, the lapse rate for temperature is 1.14 day °C/m (MAFF, 1988). For example, for two points which had the same National Grid easting and northing but a difference of 50 m in altitude the AT0 would be 57°C higher at the lower altitude.
Rainfall and frost risk increase at higher altitudes. Aspect The compass direction in which the land/slope faces (e.g. south or west). The south side of a slope will receive more direct solar radiation than the north side (in the northern hemisphere). Daily and accumulated temperatures are higher on slopes with a southerly aspect than those facing in a northerly direction. Flooding (freq, duration) Occasional, Rare, short The incidence of flooding is strongly influenced by medium topography but the extent, duration, frequency and timing can be difficult to establish precisely. The ALC takes account of frequency, duration and timing of flooding applied to soils of good or moderate permeability. Values for frequency are:- 1. very rare – not more than once in 15 years 2. rare – once in 10 to once in 14 years
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Requirements Min (e.g.) Max (e.g.) Notes 3. occasional – once in 3 to once in 9 years 4. frequent – more than once in 3 years Values for duration are:- 1. short – not more than 2 days (48 hours) 2. medium – more than 2 but not more than 4 days 3. long – more than 4 days
Soil Soil pH 7.0 7.5 This is the soil pH which is optimum or [tolerable] Optimum & [tolerable] for the PH, unless otherwise stated. range [5.0] [8.3] Topsoil texture S C This indicates the range of suitable soil textures for the PH, e.g. min S to max C means that the PH can be established on S, LS, SL, SZL, ZL, MZCL, MCL, SCL, HZCL, HCL, SC, ZC & C. Abbreviations for topsoil texture are listed in Table 2, below. Topsoil texture should also include peaty and organic soils for the assessment of habitat suitability. Depth (cm) 20-50 50-100 Soil depth is an important factor in determining the available water capacity of a soil. ALC soil wetness class III II For ALC purposes, soil wetness is assessed by a combination of the climatic regime, the soil water regime and the texture of the top 25 cm of the soil. There are six soil wetness classes (I-VI) (Table 3) which are used in combination with topsoil texture and field capacity days to grade according to soil wetness. A range of soil wetness classes are given for each PH as suitable classes depending on both soil texture and field capacity days. The most important is the minimum (i.e. wettest) soil wetness class. Undrained state needs to be identified to show potential for drained sites. Cranfield University – J. Hollis Conversion. Moisture balance (mm) +5 +30 [+10] Droughtiness limits for ALC grades are defined in terms of moisture balances-MB (mm) for wheat and [-10] [potatoes], calculated as crop available water capacity-AP- moisture deficit-MD. The moisture balance limits given are based on the ALC classes considered suitable for the PH, unless indicated otherwise. Drought characteristics are required.
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Requirements Min (e.g.) Max (e.g.) Notes Field capacity (days) >225 151-175 Field capacity days (FCD) is a meteorological parameter which estimates the number of days when the soil moisture deficit is zero. The FCD categories in the ALC for assessing the climatic component of the wetness assessment are, <126, 126-150, 151-175, 176-225 and >225 days. For Wales, most sites will be in the highest two categories.
Other (non-ALC) Existing land use Semi- Highly- Ranging from natural to intensively altered, the improved improved existing land use types that have potential for grassland grassland conversion to the PH if other conditions are met. Underlying geology Lime-rich Limestone Some Priority Habitats must overly certain rock types Adjacent habitats Some Priority Habitats must be adjacent to other habitat types Soil chemical requirements Some Priority Habitats have exacting soil chemical requirements
Table 2. ALC soil texture class abbreviations
Abbreviation Soil textural class Notes
S Sand
LS Loamy sand
SL Sandy loam
SZL Sandy silt loam
ZL Silt loam
MZCL Medium silty clay loam <27% clay content
MCL Medium clay loam <27% clay content
SCL Sandy clay loam
HSCL Heavy silty clay loam <27% clay content
HCL Heavy clay loam <27% clay content
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Abbreviation Soil textural class Notes
SC Sandy clay
ZC Silty clay
C Clay
P Peat
SP Sandy peat
LP Loamy peat
PL Peaty loam
PS Peaty sand
MZ Marine light silts
Table 3. Definition of soil wetness class in the ALC
Wetness Class Duration of Waterlogging (not necessarily continuous period)
I The soil profile is not wet within 70 cm depth for more than 30 days in most years
II The soil profile is wet within 70 cm depth for 31-90 days in most years or, if there is no slowly permeable layer within 80 cm depth, it is wet within 70 cm for more than 90 days, but not wet within 40 cm depth for more than 30 days in most years.
III The soil profile is wet within 70 cm depth for 91-180 days in most years or, if there is no slowly permeable layer within 80 cm depth, it is wet within 70 cm for more than 180 days, but only wet within 40 cm depth for between 31 and 90 days in most years.
IV The soil profile is wet within 70 cm depth for more than 180 days but not within 40 cm depth for more than 210 days in most years or, if there is no slowly permeable layer within 80 cm depth, it is wet within 40 cm depth for 91-210 days in most years.
V The soil profile is wet within 40 cm depth for 211- 335 days in most years.
VI The soil profile is wet within 40 cm depth for more than 335 days in most years.
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3.2 Results
Table 4. Lowland meadows
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 900 1200 Lowland Meadows can tolerate a wide range of [tolerable] range [700] [1500] climatic variations. Rainfall and temperature do Mean annual maximum air not appear to be major determinants. However, temperature (°C). Optimum & since the MG5 community occurs below 300m, it [tolerable] range suggests that rainfall would not be that high ALC accumulated temperature (perhaps ideally less than 1200mm) and that (day °C) temperature would be in the moderate category. Air or ground frost In cooler, wetter climates MG5 would succeed to MG3 (upland meadow). Site Gradient (°) 0 7 Typically found on flat or shallow sloping land.
Altitude (m) 0 300 Aspect No limitations Flooding (freq, duration) Rare, Frequent, Drier MG5 hay meadows in min. category to short long MG4 and MG8 grasslands as periodically inundated. Most of Welsh examples at drier end of scale. Soil Soil pH 5.4 6.3 Optimum & [tolerable] range Topsoil texture MZCL C MG5, is characteristic of infertile to moderately fertile, deep loamy to clayey, brown earths. However, there is a degree of variation from lighter textured, somewhat calcareous soils to superficially acidic (but non-podzolic) soils. Topsoil textures given are the range for MG5 hay meadow vegetation (not including the very driest end). Depth (cm) 50 100 Classic MG5 hay meadow vegetation tends to be on relatively deep to deep soils. Other lowland meadow types such as MG4 and MG8 community types also occur on, respectively, deep alluvial silts that are frequently gleyed, and deep moderately calcareous brown earths, which are seasonally to periodically inundated. These are however rare types in Wales. Drainage ALC soil wetness class IV II MG5 in category II; MG4/MG8 in category IV Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Improved Semi- Relatively diverse stands of semi-improved grassland improved grassland (MG6b) likely to be most suitable grassland precursor, not highly improved situations (MG7). Underlying geology MG5b on calcareous bedrock – counties in north Wales; MG5c on more siliceous bedrock in upland margins in borders areas. One third of
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Requirements Min Max Notes MG5a in Pembrokeshire (particularly Catelmartin Range) Adjacent habitats Often surrounded by improved or at best, semi- improved grassland Soil chemical requirements
Table 5. Lowland calcareous grassland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 800 1000 [tolerable] range Mean annual maximum air 25 35 High compared to most other habitats, temperature (°C). Optimum & [20] [40] particularly when in south-facing situations. [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) 0 >18 No limitations; CG1 on very steep slopes, CG2 (the commonest type in Wales) also tends to be on steeper slopes. Altitude (m) 0 300 Aspect Tend to be south-facing, though other aspects are encountered, particularly west-facing Flooding (freq, duration) Very Rare, short rare, short Soil Soil pH 6 7.5 Optimum pH > 6 Optimum & [tolerable] range [5] [8.1] Topsoil texture All NVC types in Wales (CG1 – CG3, CG6 and CG7) Depth (cm) 20 50 occur on shallow soils (e.g. rendzinas and calcareous brown earths), overlying limestone and other lime-rich rocks. Often very little topsoil and some communities exist as pockets of protorendzinas over largely rock-dominated landscape. Drainage Most very free-draining ALC soil wetness class II I Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Improved Semi- The greatest opportunity for restoration of grassland improved calcareous grasslands is where semi-improved neutral neutral grassland overlies thin brown earths and grassland rendzina soils overlying limestone. Underlying geology Lime-rich Limestone In Wales, they are primarily confined to Carboniferous Limestone in the north and south of the country. This habitat is particularly dictated by underlying geological conditions. It occurs in the north in Anglesey, Conwy,
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Requirements Min Max Notes Denbighshire and Flintshire, and in the south in Brecon Beacons NP, the Gower and the Vale of Glamorgan. Smaller stands are found in Merthyr Tydfil and Bridgend areas. Lowland calcareous grassland in coastal situations included in maritime cliff and slope. Adjacent habitats Tend to be less isolated than lowland meadows; often associated with other forms of grassland (dry neutral and acidic), dry dwarf shrub heath and rock and scree habitat. Soil chemical requirements
Table 6. Lowland dry acid grassland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 800 1600 The commonest types of Lowland dry acid [tolerable] range grassland in Wales (U2 and U4) occur in areas Mean annual maximum air >220C <270C where precipitation exceeds 800mm/year and temperature (°C). Optimum & mean annual maximum temperature is <27°C i.e. [tolerable] range all of Wales. U1 is more exacting climatically, and ALC accumulated temperature only occurs where annual rainfall is (day °C) <1000mm/year and mean annual maximum Air or ground frost temperature is >26°C
Site Gradient (°) 11 >18 U1 often found on steep slopes; U2 and U4 found particularly on moderate slopes in the upland fringes. Altitude (m) 150 800 Most frequently between 150 and 500m Aspect No limitations Flooding (freq, duration) Very Rare, short rare, short Soil Soil pH 4 5 Optimum & [tolerable] range Topsoil texture Though brown earths are most typical, soil types Depth (cm) 20 50 range from rankers through brown earths to podzols. Drainage ALC soil wetness class III II Soils are liable to summer drought and frequently heavily leached. Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Semi- The greatest opportunity for restoration of improved lowland dry acid grassland is where semi- neutral improved grassland overlies soils that are grassland naturally podzolic and ranker-like in character.
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Requirements Min Max Notes Underlying geology Pervious parent Reversion of arable land to lowland dry acid materials such as acid grassland is not feasible in Wales as very little rocks and/or sand and arable land overlies naturally acidic soils. Many gravels examples characteristic of commons. Adjacent habitats Often adjacent to lowland heath; upland fringe ‘ffridd’ landscapes Soil chemical requirements
Table 7. Upland calcareous grassland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 1000 2000 Upland calcareous grassland in Wales (CG10) [tolerable] range occurs in mountainous areas and therefore tends to be present where there is > 1000mm rainfall per annum. Mean annual maximum air <230C <260C temperature (°C). Optimum & [tolerable] range ALC accumulated No limitations temperature (day °C) Air or ground frost No limitations
Site Gradient (°) 11 >18 Often associated with steep or medium slopes, especially where sub-surface irrigation occurs Altitude (m) 300 750 [850] Figures apply to CG10. Other NVC types (CG12 and CG14) tend to be at higher end of range on base-rich rock in the uplands Aspect No limitations Flooding (freq, duration) Rare, short Very rare, short Soil Soil pH 6 7.5 Optimum range is 6 – 7.5 Optimum & [tolerable] [5] [8] range Topsoil texture SL MZCL As with lowland calcareous grassland, upland Depth (cm) CG12 occurs on shallow soils (e.g. rendzinas and moist, calcareous brown earths). Drainage ALC soil wetness class v III Usually found on free-draining, dry soils. However, CG10, the most common upland calcareous community, tends to be kept moist through sub-surface irrigation. This is also true of the CG12 and CG14 communities. Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Patches of CG10 tend to be small and often grazed. Ideally, grazing would be very light.
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Requirements Min Max Notes Underlying geology Old Red Carboniferous CG12 and CG14 are ledge communities, Sandstone limestone associated with these rock types, though also with basic igneous and metamorphic rocks. CG10 occurs on exposures of calcareous soil parent materials, often set within landscapes dominated by more acidic rocks and widespread thick drift. Adjacent habitats Unimproved calcareous In order for restoration to be successful, grassland there would ideally be areas of unimproved calcareous grassland already present and the emphasis should be on re-uniting fragmented examples. Soil chemical requirements
Table 8. Coastal and floodplain grazing marsh
Requirements Min Max Notes Climate Rainfall (mm) Optimum & Many of the coastal and floodplain grazing [tolerable] range marshes in Wales are found in the drier districts, corresponding with their locations along the coasts and major river valleys in the south-west, west and north-east. Rainfall not an important criterion for this habitat Mean annual maximum air temperature (°C). Optimum & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) 0 0 Coastal grazing marsh is found in flat, coastal situations. Floodplain grazing marsh tends to Altitude (m) 0 occur in inland, flat, valley-floor scenarios. Aspect N/A Flooding (freq, duration) Frequent, Frequent, long Coastal grazing marsh undergoes periodic long inundation with brackish or salt waters. Floodplain grazing marsh similarly undergoes periodic inundation from river water. Soil Soil pH 7.9 8.7 pH figures given for Thames Estuary marshes. Optimum & [tolerable] Coastal grazing marshes are ideally brackish range and alkaline. On re-wetting however, pH can drop considerably (as low as 2.7). Topsoil texture LS ZC (MZ) Soil types tend to be light-textured brown Depth (cm) earths and alluvial soils Drainage
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Requirements Min Max Notes ALC soil wetness class VI IV Experience fairly frequent superficial wetting and drying processes. Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Semi- Improved These areas should be targeted, particularly improved grassland where areas of semi-improved grassland grassland support species that can act as a seed source for adjacent improved grassland. Underlying geology Adjacent habitats Rivers or coast Often derived from saltmarsh (coastal grazing marsh) or freshwater swamp (floodplain grazing marsh). These habitats may persist nearby. Arable land adjacent to rivers and/or coastal levels also potential for reversion. Soil chemical requirements
Table 9. Purple moor-grass and rush pasture
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 1000 1200 For the most common NVC types of M23 and [tolerable] range [800] [1400] M25. M24 occurs in situations where rainfall is around 100mm. Annual rainfall in situations where M26 occurs is approximately 1600mm. Mean annual maximum air 26 The most common NVC types of M23 and temperature (°C). Optimum [29] M25 are predominately of western & [tolerable] range distribution within Wales and therefore occur ALC accumulated where the mean annual maximum temperature temperature is <26°C. Within the UK, M22 (day °C) predominantly occurs within the 29°C mean annual maximum isotherm. Air or ground frost -0.5 The most common NVC types of M23 and M25 do not penetrate to areas where the February minimum mean temperature is <0.5°C below freezing. Site Gradient (°) 0 7 Tend to be flat or slightly sloping situations.
Altitude (m) 0 200 Optimal figures given for the most common [400] NVC types of M23 and M25, though M23 can extend to 400m. Conversely, the rare M26 is a sub-montane community between 250m – 450m, where the climate is typically cold and wet. Aspect No limitations Flooding (freq, duration) Frequent, long Soil Soil pH 4.7 5.4 Figures given for M25. M23 occurs in range 4 Optimum & [tolerable] [<4] [5.5] – 6; M24 tends to occur in range 5 – 6.5 and range
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Requirements Min Max Notes M22 at highest pH end of 6 – 8 (usually between 6.5 and 7.5). Topsoil texture M23 soils are usually stagnogleys or ground Depth (cm) water gleys. M25 soils tend to be well aerated. Of the rarer community types, M24 is inclined to strongly humic soils that are generally intermediate in terms of moisture regime, base status and nutrient content. M22 occurs on a variety of moist base-rich and moderately mesotrophic soils; predominately on alluvial soils and gleys of mineral origin. M26 is a very local community of moist base-rich and calcareous peats and peaty mineral soils. Drainage ALC soil wetness class V VI Of the two most common community types, M23 is found on moderately acid to neutral soils that are kept moist for most of the year. There is a strong correlation of the occurrence of this community to areas of impeded drainage. M25 is also found on water-logged soils but, in contrast to M23, a greater degree of water movement is apparent in these situations (particulalry in the upper horizons). M24 is intermediate in terms of moisture regime. There is usually no marked seasonal fluctuation in water level. Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Underlying geology High water table Adjacent habitats Soil chemical requirements – 10 P (mg l-1) Soil chemical requirements – 200 K (mg l-1)
Table 10. Arable field margins
Requirements Min Max Notes Climate Rainfall (mm) Optimum & Comparatively low rainfall areas [tolerable] range Mean annual maximum air Often above average temperatures for Wales temperature (°C). Optimum & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) 0 7 Flat or gently sloping
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Requirements Min Max Notes
Altitude (m) Aspect Flooding (freq, duration) Soil Soil pH Variable, though arable land tends to be Optimum & [tolerable] found in Wales in areas with generally higher range pH levels (e.g. Pembrokeshire, Monmouthshire, Gower, Vale of Glamorgan an lowland of north-east Wales Topsoil texture Depth (cm) Drainage ALC soil wetness class Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Arable Semi- The re-introduction of arable cropping should crops improved be considered for areas of improved and grassland semi-improved grassland, particularly where these lie within the areas outlined above. Underlying geology Tends to be found in areas of more neutral or base-rich soils in lowlands of Wales. Adjacent habitats Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
Table 11. Lowland heathland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 800 1200 Minimum for most common types (H8, H10, [tolerable] range [1600] M15); maximum for H4. Mean annual maximum air 25 28 H8, H10, M15 mean annual maximum temperature (°C). Optimum [23] [30] temperature <27°C. H4 mean annual & [tolerable] range maximum temperature >26°C. ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) Dry heaths principally confined to slopes. Wet heaths tend to be found in flatter situations. Altitude (m) 150 500 H8 and H10. H4 is at lower levels. Aspect No limitations. Flooding (freq, duration) Soil Soil pH 3.5 5 Optimum & [tolerable] [6] range
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Requirements Min Max Notes Topsoil texture Soils supporting dry heath are liable to Depth (cm) summer drought and brown earths and podzolic soils are most typical. Wet heaths are on damper acid soils, where either shallow peat or mineral soils are seasonally waterlogged. Humid heaths (found in Glamorgan) are found on intermediate soils (i.e. damp, though not impeded drainage). Drainage ALC soil wetness class V II Wet heath (M15) in wetness class V, drier heaths (H8, H10) in drier classes Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Low grazing pressure acid grassland Underlying geology Acid rocks Sand and gravels Adjacent habitats Soil chemical requirements – 10 P (mg l-1) Soil chemical requirements – 200 K (mg l-1)
Table 12. Upland heathland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 1000 1600 Optimum figures given for H12; H18 similar, [tolerable] range though slightly higher; H10 likely to be at lower end; also found in drier situations Mean annual maximum air 22 26 Mean annual maximum temperature <27°C. temperature (°C). Optimum & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) Dry heaths principally confined to slopes. Wet heaths tend to be found in flatter situations. Altitude (m) H8 found at moderate elevations, H10 on higher slopes and H12 higher again. H21 occasionally prominent in most extreme conditions. Aspect N/NE facing for H21 Flooding (freq, duration) Soil Soil pH 3.5 5 Optimum & [tolerable] [6] range
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Requirements Min Max Notes Topsoil texture PL LP (or mineral The dry upland heaths are frequently on soil) heavily leached soils, overlying pervious Depth (cm) parent materials such as acid rocks. Wet heaths are on damper acid soils, where either shallow peat or mineral soils are seasonally waterlogged. Drainage ALC soil wetness class IV II Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Low Upland grazing forestry pressure acid grassland Underlying geology Acid rocks Sand and gravels Adjacent habitats Existing heathland Soil chemical requirements – 10 P (mg l-1) Soil chemical requirements – 200 K (mg l-1)
Table 13. Blanket bog
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 1200 2000 Optimum range given for M19 blanket bog; [tolerable] range [2200] this is also range for M17 blanket bog, though that tends to be in areas where rainfall is around 2000mm and can exceed this. Mean annual maximum air 23 25 Annual mean temperatures are low temperature (°C). Optimum [21] compared to most other Priority Habitats. & [tolerable] range M19 is generally found at lower end of range, ALC accumulated with M17 at higher (due to lower elevation) temperature (day °C) Air or ground frost
Site Gradient (°) 0 4 Upland plateaux; flat or gently sloping
Altitude (m) 250 400 Optimal figures given for M17; M19 is a [600] community of higher altitudes, usually over 550m Aspect Flooding (freq, duration) Soil Soil pH 3 4 Both M17 and M19 within this tolerable [5] range
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Requirements Min Max Notes Optimum & [tolerable] range Topsoil texture LP P Thin and thick layers of peat Depth (cm) Drainage ALC soil wetness class V VI Waterlogged conditions, especially M17 Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Wet Young or modified failed conifer bog e.g. plantations purple moor-grass Underlying geology Adjacent habitats Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
Table 14. Reedbeds
Requirements Min Max Notes Climate Rainfall (mm) Optimum & Rainfall not an important factor though most [tolerable] range stands are, by default, in drier areas (largely confined to lowlands) Mean annual maximum air Generally few limitations, though high temperature (°C). Optimum summer temperatures are essential & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost Not suited to long spring frosts
Site Gradient (°) 0 0
Altitude (m) 0 <150 [500] Aspect N/A Flooding (freq, duration) Soil Soil pH Phragmites seems to show few substrate Optimum & [tolerable] preferences, growing equally well on wholly range organic and wholly mineral material. Topsoil texture No limitations Depth (cm) Drainage ALC soil wetness class V VI Establish in areas where the water table lies at or above the ground surface for much of the year. Ideal conditions are provided where
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Requirements Min Max Notes the water table is +50cm to -20cm and where flooding for several months of the year Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Improved Abandoned coastal and mineral river workings & floodplain former grasslands industrial sites Underlying geology Phragmites seems to show few substrate preferences, growing equally well on wholly organic and wholly mineral material. Adjacent habitats Coasts and rivers Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
Table 15. Upland oakwood
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 800 3000 W16e and W10 at lower end, with W11 [tolerable] range consistently over 1000mm and W17 often twice this level. Mean average maximum air 25 Humidity often an important ‘feature’ of W17 temperature (°C). Optimum woodlands (and to a lesser extent W11 and & [tolerable] range W10). This forms ideal conditions for ALC accumulated luxuriant growth of oceanic bryophytes temperature (day °C) Air or ground frost
Site Gradient (°) >18 W11 and W17 are the classic western sessile oakwoods and are found on steep slopes and ‘hanging’ valley sides. Altitude (m) 180 450 W11 generally below 180m. Aspect Aspect does not appear to be generally important, many examples of W11 and W17 on north-facing slopes Flooding (freq, duration) Very rare, Rare, short These woodlands are not subject to flooding short due to steep conditions in which they grow. Soil Soil pH 3.5 5.5 Base-poor to acidic conditions. W17 at lower Optimum & [tolerable] end of range with W10 at higher end. range Topsoil texture Generally on brown earths or brown podzolic Depth (cm) soils (W11); humic rankers and brown podzols (W17); brown earths (W10) Drainage Moist but free draining
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ALC soil wetness class W17 and W11 are found in the wettest conditions, whereas W10e is found as a transition habitat between these types and the driest community (W16b). Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Underlying geology Ordovician and Silurian shales Adjacent habitats Upland mixed ashwood Where this occurs adjacent to upland oakwood, it is generally fragmentary Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
Table 16. Upland mixed ashwood
Requirements Min Max Notes Climate Rainfall (mm) Optimum & 600 1600 W8 at lower end of range; W9 at higher end [tolerable] range Mean annual maximum air <25 >26 W9 found at lower end of range; W8 at temperature (°C). Optimum higher end & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) 7 >18 Generally on steep slopes, though also present on the lower, shallower slopes of valleys. Altitude (m) 0 200 W8 woodland generally below 180m Aspect Generally not important Flooding (freq, duration) Rare, short Occasional, medium Soil Soil pH 4.5 7 Neutral to base-rich conditions Optimum & [tolerable] (sometimes range more) Topsoil texture MZCL C W8 Gleyed brown soils through to Depth (cm) stagnogleys; W9 brown soils Drainage ALC soil wetness class IV II W8 can occur in conditions of impeded drainage, and, especially in the winter, can be subject to a high water table; W9 soils also moist for much of year Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Underlying geology
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Requirements Min Max Notes Adjacent habitats Upland oakwood (particularly W9) Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
Table 17. Wet woodland
Requirements Min Max Notes Climate Rainfall (mm) Optimum & No limitations [tolerable] range Mean annual average air No limitations temperature (°C). Optimum & [tolerable] range ALC accumulated temperature (day °C) Air or ground frost
Site Gradient (°) Found in three situations: (1) as successional developments on terrestrial wetlands; (2) alder-dominated stands in seepages and spring lines and (3) floodplains and along river edges. Altitude (m) 0 400 Most examples are at lower end of scale. W3 at higher altitude. Aspect 0 Flat for wetland and floodplain examples; relatively steep for seepages/spring line examples Flooding (freq, duration) Rare, short Frequent, Many of the NVC communities occur in long standing water for most of year (though also require short periods of below surface water table). Those examples on slopes not subject to much flooding. Soil Soil pH No limitations Optimum & [tolerable] range Topsoil texture No limitations Depth (cm) Drainage ALC soil wetness class VI III Poorly-drained or seasonally wet soils. Moisture balance (mm) Field capacity (days) Other (non-ALC) Existing land use Open ground Underlying geology Adjacent habitats Existing alder woodland; upland oakwood and
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ashwood in seepage examples Soil chemical requirements – P (mg l-1) Soil chemical requirements – K (mg l-1)
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4 GAPS IN ALC DATA FOR DESCRIBING ENVIRONMENTAL CONDITION REQUIREMENTS.
The review in Section 2 and analysis in Section 3 successfully identified a number of constraints to priority habitat establishment along with estimated ranges that can be aligned with parameters in the ALC. Those most commonly identified include annual rainfall and mean annual maximum temperature from the climate requirements; gradient, altitude and flooding from the site requirements; and soil pH, topsoil texture, depth and soil wetness class from the soil requirements. No constraints on priority habitat establishment were found for some of the ALC parameters that are more specific to growing crops (e.g. accumulated temperature; drainage; moisture balance; field capacity days). Whilst the amount of information that was available for many of the priority habitats reviewed, certain key requirements were missing for specific communities (although listed for most others) so these seem to be genuine gaps in knowledge.
4.1 Gaps in biophysical requirements of priority habitats
We therefore recommend that the first stage in the development of a modelling approach is to update the list of biophysical requirements for each priority habitat to fill a number of gaps in the data regarding the requirements for the habitats. These would need to be filled through consultation with specialist ecologists and a comprehensive literature search combined with using a GIS approach similar to that used by Burnside et al (2002) for calcareous grasslands in the South Downs. Existing GIS layers on key ALC and non-ALC biophysical parameters (slope, aspect, soil type, soil pH, rainfall, etc.) would be overlayed with the locations of existing priority habitat and the association of the habitat with each of the biophysical parameters used to identify the biophysical requirements of the habitat.
4.1.1 Historical extent of habitats A limitation of a spatial analysis with the current distribution of PH are that this does not necessarily describe all of the situations in which the PH may have occurred in the past and therefore where it may be possible to establish them in the future. Indeed this was a key finding of a recent (unpublished) study by Natural England who used soil mapping data to inform habitat network re-creation. They observed that the remaining resource of purple moor grass and rush pasture within the case study area was fragmented and associated with small pockets of particular soil types that are not well represented more widely. If this approach were used alone, large areas of suitable soils for the habitat could be missed. It would therefore also be advantageous to include historic vegetation maps in this analysis to see if habitat has ever existed in an area (at least as far back as records allow). The 1930s Geoffrey Rees vegetation work on Lleyn, the Second Land Utilisation survey, Phase 1 / 2 etc. and historic OS maps could all be useful in this exercise.
4.1.2 Multiple NVC types The review of priority habitat requirements in Section 2 is a useful overarching description, however, many habitats incorporate multiple NVC types, as identified in Section 2 and Tables 4-17. It is also the case some habitats in Wales do not fall easily into one NVC category, and instead are somewhere between the two (NRW recognised problems in Wales with the original lowland heath NVC classifications (Sherry, 2007)). Some habitats appear to be sufficiently distinct from the standard NVC to warrant their own community description e.g.
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species-poor Molinia. Others, such as ‘ffridd’ and ‘rhos pastures’, tend to be particularly favoured in a Welsh context and to feature a particularly Welsh combination of species (alongside local cultural references). As part of the process above, Table 1 should be further developed by NVC type and key indicator species (e.g. rare arable plants communities) to help refine the modelling approach and take full advantage of the UKCP18 climate change scenarios. It is important to develop habitat requirements with specialist ecologists experienced in Wales to ensure subtle differences are recognised.
4.1.3 Additional analysis of soil data Further alignment between soil type and habitat types is required. At a very broad level ‘soilscapes’ (Cranfield University) mapping gives an overview of the habitats associated with the major soil groups which is also reproduced in English Nature Report 7121. This EN publication also makes reference to work by Gilbert and others (1996) on a MAFF funded habitat creation model2 developed as a decision support tool to identify those vegetation communities that could be created on ex-arable land using soil and climatic data extracted from the Land Information System (LandIS) database held by Cranfield University. These data were used in conjunction with the tolerance ranges of vegetation communities for a number of parameters (pH, fertility, wetness, droughtiness and temperature) to enable suitable communities to be selected for a specific grid reference or site. It would be worth studying the parameters contained within this habitat creation model and whether it could be adapted/expanded upon.
4.1.4 Geology Whilst formal soil type classification is not needed for ALC (nor knowledge of the underlying geology), most strategic scale reconnaissance ALC mapping has used a knowledge of soil types (e.g from the National Soil Map) to help develop the ALC system and inform the ALC mapping. Whilst underlying geology is often also a useful component to an understanding of ALC, geological maps do not record the uppermost 1-2m of land surface and so often miss the thin superficial deposits from which the soils (and vegetation communities) are derived. For example, thin glacial or periglacial deposits, loess, peat, alluvium, sand and gravel plateau drifts etc. which means the soils may be quite different in character to the underlying geology (e.g. non calcareous drifts over chalk or limestone). So for this reason, and because soil maps are likely to provide a ‘shorthand’ for many of the required environmental conditions (including soil chemistry such as natural fertility and pH) for different habitats, they should be included in the spatial datasets required. Section 3.2 of the report identifies the need for information on permeability, gleying, porosity and water movement which can be provided in the LandIS (Cranfield University) soil data. A review of the following data sources and publications would be beneficial: NRW distribution maps of arable communities and extrapolated maps of Important Arable Plant Areas.
1 Guidance on understanding and managing soils for habitat restoration projects 2 For more information, contact Natural England
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Grime et.al. (1988) as a source of information on individual species responses to likely variables. Tir Gofal agri-environment monitoring results (~c twenty years of data) for key habitat responses. NVC Types and Welsh context by specialist ecologists (Sherry, 2007) to provide validation and confidence. Soil and habitat relationship from; o Soilscapes (Cranfield University) o English Nature Report 712 Guidance on understanding and managing soils for habitat restoration projects. o Gilbert et al. (2002)
4.2 ALC Data Gaps & Additional Technical Information / Evidence
Some potential constraints to the establishment of priority habitat were identified that were not part of the ALC and could therefore be considered gaps in the ALC data for describing environmental condition requirements of these habitats. These additional constraints included existing land-use, which for some habitats is a key factor when assessing the likely success of establishment; underlying geology, which is related to soils and drainage but not explicitly characterised in the ALC; adjacent habitats, which can affect establishment and successful colonisation by key species; and soil chemical requirements for some PHs. Additional spatial datasets would need to be identified to represent each of these and some suggestions are provided in Table 18.
Table 18. Additional spatial datasets that could potentially be used to supplement ALC sub- grade data in the habitat suitability modelling
Data gap Possible datasets for filling gap
Existing land use - NRW Phase 1 & Phase 2 surveys - WG Environmental Impact Assessment habitat surveys - Basic Payment Scheme crop code data - EO-derived land use mapping
Underlying geology - Geological maps (BGS)
Adjacent habitats - NRW Phase 1 (50m raster) - Latham J. and Rothwell J - A Handbook on Habitat Networks: Practical Application for Improving Connectivity and building Ecosystem Resilience NRW Evidence report 275 - April 2019
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Soil chemical requirements - The Advanced Soil Geochemical Atlas of England and Wales (BGS).
Additional soil properties - LandIS soil mapping (Cranfield University)
Seasonality of flooding - NRW Flood Maps (In Development) – frequency and duration.
Other ‘intermediate’ climatic - ALC median field capacity days (measure of parameters overall climatic wetness), average summer rainfall, and summer accumulated temperature (Met Office).
Impacts of nitrogen deposition on Environment Systems Wind Risk Model certain habitats (e.g. calcareous grasslands)
Whilst this study focuses on determining condition requirements for PHs, forming a network of connected habitat that aids dispersal and colonisation is also an important consideration when targeting habitat creation or restoration. Natural Resources Wales have done much work in this area (Latham, Sherry & Rothwell, 2013), and have recently produced habitat network maps that should complement the modelling approach scoped out in the current study. Intellectual Property Rights will need to be considered for existing data sets.
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5 SCOPING A MODELLING PROJECT THAT COULD UTILISE SUCH A FRAMEWORK
The aim of this task was to scope out a modelling project that could utilise the ALC framework to assess the suitability of land for restoration or establishment of the main terrestrial priority habitats in Wales. This section of the report considers the steps that would be required, the software tools and expertise that would be required, the data requirements, and the choices that would need to be made such as spatial unit and level of user control. A time and cost is also estimated for each step. The approach outlined below is based on recent work done by ADAS in a project entitled “Identifying optimal locations for land use change to biodiversity and woodland habitats to deliver maximum environmental outcomes”, which was funded by the Environment Agency in collaboration with Natural England and the Forestry commission as key stakeholders in the project. The project developed a prototype framework for targeting land use change from agriculture. Data used in the framework all had national coverage, and many were open source; however many could be replaced with local data if available. A scoring system was developed based around the national datasets, considering three environmental outcomes (water quality, flood risk and biodiversity) separately but with the option of aggregating them to give an overall benefit score. Costs were also estimated for each land- use change option to enable a cost-benefit analysis to be undertaken. A bespoke software tool was developed that took fine scale gridded data as inputs, applied the scoring system in a bottom-up manner to produce a set of gridded outputs in terms of environmental outcomes, costs and benefits, which could then be mapped using standard GIS software. We propose two work packages; the first with the objective of scoring habitat requirements against ALC sub-grades and any other limiting factors for which data were available; and the second to develop a desktop tool for assessing land area suitability for priority habitats. The resulting model will be useable by WG and NRW to input the requirements for new habitats or modify requirements to generate new maps.
5.1 Work Package 1: Habitat requirements scoring
This work package would take the information on habitat requirements presented in Section 3 and classify these with respect to ALC grades to provide a scoring for the habitat of suitable, limited suitability or unsuitable. The same classification would also be applied to other ALC biophysical requirements (e.g. frost exposure, flooding, etc.), with bespoke classifications for these factors based on those used in the crop requirements work (ADAS, 2019) or developed as part of this work package (e.g. existing land use, soil chemical properties). An example framework that could be utilised for the scoring system is that developed in the work done by ADAS and Environment Systems for crop suitability (Appendix 1). In this approach, each PH would be assessed for suitability against each of the ALC grades & sub- grades plus each of the other ALC biophysical suitability constraints identified as being important for the habitat. A three point scoring system will be used (suitable, limited, unsuitable) plus a categorical variable for certainty in this assessment (high, medium, low). Expert judgement would be used to assign scores based on the work done in the current study, plus the additional gap-filling research recommended. As mentioned in Section 4, there are some gaps in the information on the biophysical requirements that make up the ALC for some of the PHs. These gaps would need to be filled via a combination of further literature review and consultation with specialists, and a GIS
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analysis of current distribution of PHs in relation to the new predictive ALC map – for which there is a version now available that covers non-agricultural as well as agricultural land. This is important as much of the existing PH will fall outside of agricultural land areas. As part of the scoring process it may be necessary to revise the formulae used to link the two different temperature attributes to provide an overall climate suitability grade, as the ALC climate grades are based on temperatures during the growing season (January to June), whereas for habitats maximum and minimum temperatures across the whole year or in specific months may be more relevant. Testing of the appropriateness of the existing ALC climate classification would be required to determine whether a revision would improve the scoring. Using an appropriate spatial resolution, a score for the suitability for restoration or establishment of each priority habitat will be calculated based on the individual attribute scores within the predictive ALC and the non-ALC biophysical constraints data layers. The resulting suitability scores will then be used to produce suitability maps for each priority habitat.
5.1.1 Datasets required The following GIS layers and datasets will be required for this workpackage (see Table 18 for further detail): Attributed predictive ALC (including sub-grades for the component factors) Exposure maps for frost, wind & salt spray (Environment Systems) Soil biochemical properties (K status, P status) Phase 1 habitats (or PH habitat inventories if available) Geology maps (solid / drift) Existing land cover/use NRW habitat network maps Soil Series Map (2019) & associated attributed data WG Rock outcrop layer
5.1.2 Resource estimates Estimated Staff time required: 30 days Estimated Cost: £18,000 Expertise required: Specialist ecologist for each of the PHs; expert on ALC calculations; soil scientist and GIS analyst. Software tools required: GIS software (e.g. ARCGIS, QGIS) Choices to be made: Spatial resolution of mapped scores; which non-ALC constraints to include; which datasets to use to represent these additional constraints.
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5.2 Work package 2: Development of a desktop-based tool for assessing land area suitability for priority habitats
To allow easy access to the model we recommend developing a windows-based desktop tool for production of gridded data assessments of the suitability of land areas for priority habitat restoration or establishment. The tool would be suitable for use by non-experts and would be based around a set of windows to allow users to do the following: Select the priority habitats of interest Select current or future ALC classifications Select other constraints Modify constraints and scores if required Run the scoring framework for each selected priority habitat Export output as gridded data of a file type directly readable by ArcGIS (consideration of Government and Agency systems required). Specify requirements for new habitats (using the requirements framework described in Section 3) The tool would be written using the Microsoft .NET framework.
5.2.1 Key steps The key tasks in the development of the web tool would be: 1. Design of desktop tool In this task, a design for the tool interface would be developed, including location of menus, the theme and colours for the interface. This would be done in consultation with key stakeholders, through the collection of “user stories” to identify a prioritise set of user needs. This process would ensure that the tool interface was clear and easy to use and that the core functionality required by the stakeholders was included in the tool. Based on the consultation and design, a full specification for the tool would be written and used as the blueprint for the development of the code for the tool. 2. Development of code to provide core functionality Using the specification from Task 1, the code required for the tool would be developed using the Microsoft .NET framework. Core functionality would be expected to include selection of locations of gridded input data (e.g. the Attributed Agricultural Land Class data, biophysical data), the selection of priority habitats to be assessed, running of the model and export of the gridded output data. Code would also be written for administrative functions that would be accessible from the menus. These functions would allow selection of different ALC input layers (current or future ALC) and the uploading of data requirements for new priority habitats). As part of the development process, all code would be tested using a Unit Testing approach to ensure that each of the components function as expected, before being added as functionality within the tool. 3. Development of code to implement the model using inputs specified on interface To allow the scoring framework to be used in the tool, the scoring framework developed in work package 1 would be developed into an algorithm that would run when triggered by the
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user within the tool interface. This algorithm would calculate the score for each habitat based on the selection made by the user, and produce a set of gridded output data (e.g. comma –separated value files) for the selected habitats. This output data would then be able to be saved and exported form the tool for conversion to maps using GIS software. 4. Testing of the interface On completion of the coding, and successful unit testing, the entire tool would be trialled with key users to ensure that it provided the functions required and that the outputs were as expected. The aim would be to have a sub set of the key stakeholders to act as testers and to provide feedback on the tool and suggestions for improvement, which would be implemented as allowed by time and budget constraints. 5. Documentation and Training A full set of documentation on how to use the tool would be produced giving step-by-step instructions on how to use the tool, with descriptions of the functionality included in the tool and the scoring framework used within the tool. In addition, a training course would be run for the key users of the tool to ensure that they were happy with how to use the tool, and the outputs of the tool. Support via email and phone would be provided for a defined fixed period after the handover of the tool.
5.2.2 Outputs A desktop-based tool to allow users to score land according to its suitability for conversion to or restoration of key habitats, based on a scoring framework linked to ALC attributes. A set of user documentation for the tool.
5.2.3 Resource estimates Estimated Staff time required: 52 days Estimated Cost: £38,000 Expertise required (for development of scoring framework and tool): Environmental modeller, C# developer Software tools required (for tool development): Integrated Development Environment (e.g. Visual Studio) Software tools required (for use of tool outputs): GIS Software (e.g. ArcGIS, Q-GIS) Choices to be made: Functionality to be included in tool; level of ongoing support and maintenance
5.3 Additional cost option
Another possible modelling approach has been identified that could confer additional advantages to the approach presented above. This alternative approach is based on using a plant niche modelling approach (for which an open source tool called MultiMOVE currently exsits) and is described below.
5.3.1 Combing ALC with plan species niche modelling tool This approach would adapt the ALC grading information, plus other non-ALC biophysical parameters to fit the inputs required for the MultiMOVE niche model (Henrys et al., 2015)
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to predict the suitability of a location (land parcel or area) for identification of locations that would be suitable for establishment or restoration of priority habitats. These locations would then be filtered through a set of additional constraints (e.g. proximity to existing priority habitat, existence of pollutants such as heavy metals) to provide suggested areas for the restoration or establishment of priority habitats. For this additional cost option, Tasks 1-5 detailed below could replace work package 1, if required, and Task 6 below is additional to the tool development detailed in work package 2 above.
5.3.2 Tasks required for the development of this approach 1. Development of linkages between Ellenberg scores and ALC attributes relating to soil pH, wetness and temperatures The MultiMove model requires inputs for pH, wetness, soil fertility, rainfall, canopy height, maximum July temperature and minimum January temperature. The pH, wetness and fertility inputs are based on Ellenberg scores, and so there would be a need to map the ALC attribute scores for pH and wetness to match the Ellenberg scores required as inputs. The fertility input is a measure of Nitrogen and Phosphorous status of the soil, which is not included in the ALC, and would need to be sourced from other data, possibly based on British Survey of Fertiliser Practice. For the rainfall input the ALC rainfall classes would need to be converted to actual annual rainfall, which might be better sourced from rainfall data layers. For temperature, MultiMOVE uses the maximum temperature in July and the minimum temperature in January, which are not directly available from the ALC attributes. There would therefore be a need to either obtain the required inputs from temperature data linked to the ALC attributes or to find a method for mapping the ALC temperature attributes to the required inputs in the MultiMove model. The canopy height input would need to be derived from current land use and the priority habitat that is intended to be restored.
2. Identification of key indicator plant species for priority habitats (from the list of plant species in the MultiMove model) As MultiMOVE is based on individual species and not habitats, to enable MultiMOVE to be used to indicate suitability for priority habitat restoration or establishment, there is a need to identify a set of key indicator plant species for each of the priority habitats to allow the MultiMOVE model to be used to predict suitability for priority habitats. This would be done through consultation with ecologists and other stakeholders. This task would produce a list of key indicator species for each priority habitat.
3. Development of suitability lookup table for priority habitats based on indicator species using MultiMove model For each priority habitat, the MultiMOVE model would be used to develop a lookup table of potential suitability. From the model, a prediction of the suitability for each individual indicator species (based on the attributes required by the species) would be derived at an appropriate spatial resolution using the spatially explicit input data produced in Task 1. The predicted suitabilities for the individual species would then be combined (using the habitat suitability scaling functions within the MultiMove model) to provide an overall suitability probability for each priority habitat, based on the suitability of the location for each of the
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indicator species for a given habitat.
4. Development of constraints layers for factors constraining the restoration and establishment of priority habitats, not included within the ALC classification Since MultiMOVE uses a restricted set of input data, there may be other factors that would constrain the restoration or establishment of priority habitats that need to be accounted for. This task would create a set of data layers for other constraints (e.g. proximity to existing priority habitat, heavy metal pollution, flooding, management constraints) based on ALC attributes and other non-ALC biophysical characteristics.
5. Production of suitability score for land parcels The outputs from tasks 3 and 4 would be combined using GIS to produce a gridded data layer containing the suitability of land (at an appropriate spatial scale) for restoration or establishment of priority habitat. The constraints layer from task 4 would be used to filter the land areas selected as suitable from the MultiMOVE model using an appropriate weighting system for each of the constraints associated with the priority habitat.
6. Enhancement of modelling tool The MultiMOVE model allows the outputting of the parameters for the fitted models for each species, and it would potentially be possible to produce a database of fitted parameters for all of the species in the MultiMOVE model. This would then make it possible for the desktop-based tool to be enhanced so that it would allow users to: a. select their own indicator species for the priority habitats and re-assess suitability using the selected indicator species rather than the default set produced in Task 2, b. take the data layers produced in Tasks 1-5 above as inputs to the tool.
This enhancement would be achieved by writing code to apply the model equations using the selected indicator species and produce the suitability data layer from the MultiMOVE model output.
5.3.3 Datasets required The following GIS layers and datasets will be required for this option (see Table 18 for more detail): Attributed predictive ALC (including sub-grades for the component factors) Exposure maps for frost, wind, salt spray (Environment Systems) Soil biochemical properties (K status, P status) Phase 1 habitats (or PH habitat inventories if available) Geology maps Land cover/ land use maps NRW habitat network maps British Survey of Fertiliser Practice (BSFP aims to use a sample size of 1300 farms across the UK, which is deemed to be statistically representative at a national level. Therefore,
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the values would be average values assumed to apply to all farms, and would not necessarily relate to local conditions.).
5.3.4 Resource estimates Estimated staff time: 72 days Estimated cost: £44,000 Expertise required (for development of scoring framework and tool): Specialist ecologists; environmental modeller; GIS analyst, C# developer Software tools required (for tool development): Integrated Development Environment (e.g. Visual Studio); R for running MultiMOVE model Software tools required (for use of tool outputs): GIS Software (e.g. ArcGIS, Q-GIS) Choices to be made: Methodology for associating ALC sub-grades to Ellenberg scores; additional constraints to be included and the datasets to be used to represent these; the set of key indicator plant species to be used for each PH; the spatial scale at which the model should operate; the level of user control and functionality for the tool.
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6 POTENTIAL USES FOR SUCH A MODELLING SYSTEM
Potential uses for the proposed modelling system are discussed below.
6.1 Support for agri-environment scheme development
In July 2018, Welsh Government put forward a proposal for a new post-Brexit land management programme for Welsh farming in place of the Common Agricultural Policy. A subsequent consultation closed in July 2019 and sets out proposals for a Sustainable Farming Scheme, which will offer active farmers in Wales an annual payment for carrying out actions to deliver desired economic, social and environmental outcomes. Unlike the previous proposals from Welsh Government, which set out two separate schemes – the Public Goods Scheme and Economic Resilience Scheme – this plan aims to bring together all environmental and economic aims under the single umbrella of ‘sustainability’. Key areas of support are proposed to be for reduction in flood risk, decarbonisation and habitat. The proposed modelling system could help Welsh Government scope out the potential impact of the Public Goods elements related to habitat creation on farmland.
6.1.1 Flood risk reduction Landscape features and mitigation measures that increase infiltration and slow the flow of water will be supported under this key area. This includes planting trees, and restoring bogs and marshy grasslands. Creation of priority habitat on agricultural land, particularly habitats that have natural flood risk management benefits such as woodland, wetlands, coastal habitats and floodplain habitats, will likely be supported under this priority area, particularly if they are located in the right places. A recent study carried out for the EA, NE and FC in England (ADAS, 2019b) developed a pilot tool to provide decision support for the location of priority areas for agricultural land use change to priority habitat, plus the choice of priority habitat that would maximise benefits to flood risk reduction, water quality and biodiversity. Inclusion of modelled maps of suitability for each of these habitats in this type of approach would help target agricultural land use change to those areas in which the greatest flood risk benefit would be obtained and also where successful establishment of good quality habitat is most likely.
6.1.2 Decarbonisation Restoration of certain habitats that sequester carbon, such as woodlands, peat bogs, coastal grasslands and acid grasslands would be supported under this priority area. Location of these habitats is not as important as for flood risk reduction, but the quality of the restored habitat is a key factor. Habitat quality could be strongly influenced by the site suitability as informed by the proposed modelling approach.
6.1.3 Habitat This priority area would again support the creation of good quality semi-natural habitats that provide other environmental benefits as well as biodiversity value. Again, habitat quality could be strongly influenced by the site suitability as informed by the proposed modelling approach. The likely magnitude of environmental function of any priority habitat created could be semi-quantified using the proposed modelling approach if site suitability were used as a proxy for habitat quality.
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6.2 Support for agri-environment management option selection
If the proposed Public Goods Scheme described above were implemented, applicants to the scheme could benefit from knowing whether or not any parts of the land under their ownership could support establishment or restoration of a priority habitat. This could help them select the options that were most likely to be successful on their farm. The modelling outputs could also be used by the administrators of the scheme to help inform payment rates based on the likely quality and therefore function of the newly created habitat. This could be considered a type of Payment for Ecosystem Services approach.
6.3 Assessment of the implications of climate change
Basing a suitability model on the parameters in the ALC brings with it the possibility for assessing the predicted potential extent of priority habitats under future climate scenarios. A project for Defra and the Welsh Government (Keay et al, 2013) assessed how future changes in climate may affect agriculture in England and Wales using the Agricultural Land Classification (ALC) system as a surrogate measure. The study focused on the time period 1961-1990 to generate a baseline from which relationships were derived to apply to the future climate change scenarios. Twelve UKCP09 climate change scenarios were investigated namely the medium, high and low emissions scenarios for 2020 (2010-2039), 2030 (2020- 2049), 2050 (2040- 2069) and 2080 (2070-2099) time periods. A current study for Welsh Government is updating these future ALC maps for the UKCP18 climate change scenarios. Predicting the potential extent of priority habitats under future climate could help assess the climate sensitivity of different plant communities and identify those that are likely to have a more restricted range in the future. These insights could be used to refine habitat sensitivities to develop climate vulnerability models for Wales similar to that developed by the University of Southampton GeoData Institute and Natural England (Harfoot et al, 2014).
6.4 To inform land use choice
Planning Policy Wales (PPW) paragraph 4.10 outlines national policy towards conserving Wales’ Best and Most Versatile (BMV) agricultural land. BMV agricultural land is defined in Planning Policy Wales as Grades 1, 2 and 3a. This is excellent to good quality land which is able to best deliver the food and non-food crops. The Predictive ALC map plus targeted survey work is used to determine the ALC grade of land parcels that have been identified for possible development so that Local Planning Authorities, Developers, Surveyors and Land Use Managers can make informed decisions regarding the best use of the land. A similar approach could be taken if a BMV-equivalent were developed for priority habitats. This could be used in a similar way; for example if there were two parcels of land that could be used for a development, the PH potential maps could be used to determine which has the higher potential biodiversity value and therefore should be conserved. Habitat potential maps would also be useful for developers and ecological consultants to identify suitable sites for biodiversity offsetting.
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6.5 To help target expansion and restoration of the priority habitat network
The Nature Recovery Plan for Wales sets out the ambition to ‘To reverse the decline in biodiversity, for its intrinsic value, and to ensure lasting benefits to society’. One of the objectives of this plan (Objective 3) is to increase the resilience of the natural environment by restoring degraded habitats and habitat creation. This will build the resilience of the natural environment of Wales. The Well-being of Future Generations (Wales) Act 2015 makes public bodies take a more joined up approach to improving the environmental, as well as the economic, cultural and social well-being of Wales. The Act requires public bodies to set objectives to achieve a biodiverse natural environment with healthy functioning ecosystems, and to take all reasonable steps to achieve those objectives. Key interventions set out in the Plan under Objective 3 are;
Identify critical priorities for restoration through expert advice, mapping of Ecosystem Services, opportunity mapping, to inform strategies, policies and guidance, for example Area Statements under the Environment Bill. Use the measures under the Rural Communities - Rural Development Programme to develop and deliver habitat restoration initiatives, through the Co-operative measure and piloting new schemes. Welsh Government’s Peatland Restoration Project - Wales has a commitment to develop a National Peatland Restoration Programme in addition to supporting LIFE and Sustainable Management Scheme funded restoration activities. These habitat creation and restoration interventions could be targeted to areas of land where they are most likely to succeed and provide the most biodiversity benefits using the modelling system presented here.
6.6 Area Statements
The Environment (Wales) Act 2016 made it a duty for NRW to produce Area statements. Area statements will help coordinate NRW’s work and the work of others, to build the resilience of ecosystems and enhance the benefits they provide. They will bring together data, information and ways of engaging others to help better understand the state and trends of natural resources in an area, the pressures on them and their benefits.
Area Statements will use evidence to consider the relevance of the National Resources Policy priorities in an area. Drawing on the understanding of the local pressures on natural resources and the impact on well-being.
Focusing and prioritising actions that have multiple benefits, will deliver across the wellbeing goals, build resilience of ecosystems and stocks of natural resources, and identify ways of using natural resources which are more efficient.
Habitat potential mapping may be an important evidence base to assess future outputs, options and trade-offs.
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There are strong links to NRW deliverables under the Environment (Wales) Act and Well- being of Future Generations (Wales) Act including the building of ‘Resilient Ecological Networks’ and assessing the ‘Ecosystem Resilience’ attributes of Diversity, Extent, Condition and Connectivity. ‘Reverse-engineering’ the model to assess the resilience of ecosystems based on underlying soil properties and climatic vulnerability may provide a more informed focus to wider environmental threats.
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7 REFERENCES
ADAS (2019) Crop Requirements – Part 2: Capability, Suitability & Climate Programme. Final Report to Welsh Government. ADAS (2019b) Agricultural Land Use Change Project: Identifying optimal locations for land use change to biodiversity and woodland habitats to deliver maximum environmental outcomes. Final project report to Environment Agency. Ardeshir, D. and Shepherd, S. 2019. Favourable Conservation Status in England. Lowland Meadows. Natural England Ardeshir, D. and Shepherd, S. 2015. EIA Remediation Guidelines. Tasks 1 and 2. A report to Welsh Government Burnside, N. G., Smith, R. F. & Waite S. (2002) Habitat suitability modelling for calcareous grassland restoration on the South Downs, United Kingdom. Journal of Environmental Management 65: 2019-221. Critchley, C. N. R., Chambers B. J., Fowbert, J. A., Bhogal, A., Rose, S. C., and Sanderson, R. A. (2002). Plant species richness, functional type and soil properties of grasslands and allied vegetation in English Environmentally Sensitive Areas. Grass and Forage Science Critchley, C. N. R., Chambers B. J., Fowbert, J. A., Bhogal, A., Rose, S. C., and Sanderson, R. A. (2002). Association between lowland grassland plant communities and soil properties. Biological Conservation 105 (2002) 199–215 Gilbert, J.C., Gowing, G.J.G., Higginbottom, P.R.G. & Godwin, R.J. (2002) The habitat creation model: a decision support system to assess the viability of converting arable land into semi-natural habitat. Computers and Electronics in Agriculture, 28(1): 67-85. Grime, J.P., Hodgson, J.G. & Hunt, R (1988) Comparative Plant Ecology. A Functional Approach to Common British Species. Springer, Netherlands. Harfoot, A., Hill, C., Taylor, S. & Knight, M. (2014) National Biodiversity Climate Change Vulnerability Model: Technical Report for Natural England. Henrys, P.A.; Butler, A.; Jarvis, S.; Smart, S.M.; Fang, Z. (2015). MultiMOVE Model: Ensemble niche modelling of British vegetation v2.0.1. NERC Environmental Information Data Centre. https://doi.org/10.5285/94ae1a5a-2a28-4315-8d4b-35ae964fc3b9 Jones, P.S., Stevens, D.P., Blackstock, T.H., Burrows, C.R. and Howe, E.A. (2003). Priority Habitats of Wales a technical guide. Countryside Council for Wales Keay, C.A.; Jones, R.J.A.; Procter, C.; Chapman, V.; Barrie, I.; Nias, I.; Smith, S.; Astbury, S. (2013). SP1104 the Impact of climate change on the capability of land for agriculture as defined by the Agricultural Land Classification, DEFRA 138pp. Latham J. and Rothwell J – A Handbook on Habitat Networks: Practical Application for Improving Connectivity and building Ecosystem Resilience. NRW Evidence report 275, April 2019. Latham, J., Sherry, J. & Rothwell, J. (2013) Ecological Connectivity and Biodiversity Prioritisation in the Terrestrial Environment of Wales. CCW Staff Science Report No. 13/3/3 Natural England Technical Information Note (TIN037). 2008. Soil Texture. Rodwell, J.S., (1991). British Plant Communities Vol 1. Woodlands and scrub. Cambridge University Press: Cambridge Rodwell, J.S., (1991). British Plant Communities Vol 2. Mires and heaths. Cambridge University Press: Cambridge
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Rodwell, J.S., (1992). British Plant Communities Vol 3. Grasslands and montane communities. Cambridge University Press: Cambridge Rodwell, J.S., (1995). British Plant Communities Vol 4. Aquatic communities, swamps and tall-herb fens. Cambridge University Press: Cambridge Rodwell, J.S., (2000). British Plant Communities Vol 5. Maritime communities and vegetation of open habitats. Cambridge University Press: Cambridge Sherry, J. 2007. Lowland heathland in Wales - a review and assessment of National Vegetation Classification survey data 1993-2002. CCW Staff Science Report 07/3/1 Wilson, P.J. and Wheeler, R. B. 2016. A survey and assessment of soil pH and nutrient status on sites of high botanical value, 2014. Report to Natural England.
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APPENDIX 1
Table A1. Example scoring framework for priority habitats based on crop requirements work (updates currently being made to this framework).
Theme Factor Grade/class LowlandMeadows LowlandMeadows_CERT ALC suitability CLIMATE (ALC grade) 1 suitable high ALC suitability CLIMATE (ALC grade) 2 suitable high ALC suitability CLIMATE (ALC grade) 3a limited high ALC suitability CLIMATE (ALC grade) 3b limited high ALC suitability CLIMATE (ALC grade) 4 unsuitable high ALC suitability CLIMATE (ALC grade) 5 unsuitable high ALC suitability DEPTH (ALC grade) 1 suitable high ALC suitability DEPTH (ALC grade) 2 suitable high ALC suitability DEPTH (ALC grade) 3a limited high ALC suitability DEPTH (ALC grade) 3b unsuitable high ALC suitability DEPTH (ALC grade) 4 unsuitable high ALC suitability DEPTH (ALC grade) 5 unsuitable high ALC suitability DROUGHT (ALC grade) 1 suitable high ALC suitability DROUGHT (ALC grade) 2 suitable high ALC suitability DROUGHT (ALC grade) 3a limited high ALC suitability DROUGHT (ALC grade) 3b unsuitable high ALC suitability DROUGHT (ALC grade) 4 unsuitable high ALC suitability DROUGHT (ALC grade) 5 unsuitable high ALC suitability Rock (ALC grade) 5 unsuitable high ALC suitability Rock (ALC grade) NA (no rock present) suitable high ALC suitability SLOPE (ALC grade) 1 suitable high ALC suitability SLOPE (ALC grade) 2 suitable high ALC suitability SLOPE (ALC grade) 3a suitable high ALC suitability SLOPE (ALC grade) 3b limited high ALC suitability SLOPE (ALC grade) 4 unsuitable high ALC suitability SLOPE (ALC grade) 5 unsuitable high ALC suitability STONES (ALC grade) 1 suitable high ALC suitability STONES (ALC grade) 2 suitable high ALC suitability STONES (ALC grade) 3a suitable high ALC suitability STONES (ALC grade) 3b unsuitable high ALC suitability STONES (ALC grade) 4 unsuitable high ALC suitability STONES (ALC grade) 5 unsuitable high ALC suitability WETNESS (ALC grade) 1 suitable high ALC suitability WETNESS (ALC grade) 2 suitable high ALC suitability WETNESS (ALC grade) 3a limited high ALC suitability WETNESS (ALC grade) 3b limited high ALC suitability WETNESS (ALC grade) 4 unsuitable high ALC suitability WETNESS (ALC grade) 5 unsuitable high Non-ALC biophysical suitability Winter Air Frost Hardly any frost suitable high Non-ALC biophysical suitability Winter Air Frost Weak, short-term frosts suitable high Non-ALC biophysical suitability Winter Air Frost Moderate severity and duration frosts suitable high Non-ALC biophysical suitability Winter Air Frost Strong frosts suitable high Non-ALC biophysical suitability Winter Air Frost Frequent strong frosts lasting many days suitable high Non-ALC biophysical suitability Late (Spring)Air Frost Hardly any frost suitable high Non-ALC biophysical suitability Late (Spring)Air Frost Weak, short-term frosts suitable high Non-ALC biophysical suitability Late (Spring)Air Frost Moderate severity and duration frosts limited high Non-ALC biophysical suitability Late (Spring)Air Frost Strong frosts unsuitable high Non-ALC biophysical suitability Late (Spring)Air Frost Frequent strong frosts lasting many days unsuitable high Non-ALC biophysical suitability Winter Ground Frost Hardly any frost suitable high Non-ALC biophysical suitability Winter Ground Frost Weak, short-term frosts suitable high Non-ALC biophysical suitability Winter Ground Frost Moderate severity and duration frosts suitable high Non-ALC biophysical suitability Winter Ground Frost Strong frosts suitable high Non-ALC biophysical suitability Winter Ground Frost Frequent strong frosts lasting many days suitable high Non-ALC biophysical suitability Late (Spring) Ground Frost Hardly any frost suitable high Non-ALC biophysical suitability Late (Spring) Ground Frost Weak, short-term frosts limited high Non-ALC biophysical suitability Late (Spring) Ground Frost Moderate severity and duration frosts unsuitable high Non-ALC biophysical suitability Late (Spring) Ground Frost Strong frosts unsuitable high Non-ALC biophysical suitability Late (Spring) Ground Frost Frequent strong frosts lasting many days unsuitable high Non-ALC biophysical suitability Salt spray Area where salt might affect crops unsuitable high Non-ALC biophysical suitability Salt spray Area where salt does not affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) -spring Areas with wind strength that might affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) -spring Areas where wind strength is unlikely to affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - summer Areas with wind strength that might affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - summer Areas where wind strength is unlikely to affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - autumn Areas with wind strength that might affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - autumn Areas where wind strength is unlikely to affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - winter Areas with wind strength that might affect crops suitable high Non-ALC biophysical suitability Wind exposure (Gusts) - winter Areas where wind strength is unlikely to affect crops suitable high Non-ALC biophysical suitability Aspect S & SW suitable high Non-ALC biophysical suitability Aspect Other aspects (not S or SW) suitable high Management consideration Fluvial/Pluvial Flooding frequency 1 in 10 yr event limited high Non-ALC biophysical suitability Fluvial/Pluvial Flooding frequency 1 in 30 yr event suitable high Non-ALC biophysical suitability Fluvial/Pluvial Flooding frequency 1 in 100 yr event suitable high Non-ALC biophysical suitability Fluvial/Pluvial Flooding frequency 1 in 1000 yr event suitable high Management consideration Fluvial/ Pluvial Flood duration Short suitable high Non-ALC biophysical suitability Fluvial/ Pluvial Flood duration Short - moderate limited high Non-ALC biophysical suitability Fluvial/ Pluvial Flood duration Moderate unsuitable high Non-ALC biophysical suitability Fluvial/ Pluvial Flood duration Moderate - long unsuitable high Non-ALC biophysical suitability Fluvial/ Pluvial Flood duration Long unsuitable high Management consideration Tidal Flooding frequency 1 in 10 yr event limited high Non-ALC biophysical suitability Tidal Flooding frequency 1 in 30 yr event suitable high Non-ALC biophysical suitability Tidal Flooding frequency 1 in 200 yr event suitable high Non-ALC biophysical suitability Tidal Flooding frequency 1 in 1000 yr event suitable high Management consideration Tidal Flooding duration Short suitable high Non-ALC biophysical suitability Tidal Flooding duration Short - moderate limited high Non-ALC biophysical suitability Tidal Flooding duration Moderate unsuitable high Non-ALC biophysical suitability Tidal Flooding duration Moderate - long unsuitable high Non-ALC biophysical suitability Tidal Flooding duration Long unsuitable high Welsh Government 49 Habitat Suitability Modelling Scoping Study Project no. 1021091
APPENDIX 2 – GLOSSARY
ALC – Agricultural Land Classification Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. AP – crop available water capacity AT0 – Accumulated temperature Brown earths, often referred to as brown forest soils or brown soils, are well drained with brownish subsoils where iron oxides created through weathering processes are bonded to silicate clays. CG1 - NVC community CG1 (Festuca ovina - Carlina vulgaris grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. It is one of three short-sward communities associated with heavy grazing, within the lowland calcicolous grassland group, and is regarded as the south-west coastal counterpart of "typical" chalk grassland (community CG2). CG2 - NVC community CG2 (Festuca ovina - Avenula pratensis grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. It is one of three short-sward communities associated with heavy grazing, within the lowland calcicolous grassland group, and is regarded as "typical" chalk grassland. CG3 - NVC community CG3 (Bromus erectus grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. It is one of four communities of rank, tussocky grassland associated with low levels of grazing, within the lowland calcicolous grassland group. CG6 - NVC community CG6 (Avenula pubescens grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. It is one of four communities of rank, tussocky grassland associated with low levels of grazing, within the lowland calcicolous grassland group. CG7 - NVC community CG7 (Festuca ovina - Hieracium pilosella - Thymus praecox/pulegioides grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. It is one of three short-sward communities associated with heavy grazing, within the lowland calcicolous grassland group, and is regarded as the eastern counterpart of "typical" chalk grassland (community CG2). CG10 - NVC community CG10 (Festuca ovina - Agrostis capillaris - Thymus praecox grassland) is one of the calcicolous grassland communities in the British National Vegetation Classification system. Of the upland group of calcicolous grasslands, it is the only one with a short sward associated with heavy grazing. CG12 - localised NVC calcicolous grassland community characterised by the presence of Alpine Lady's-mantle (Alchemilla alpina). CG14 - localised NVC calcicolous grassland community characterised by the presence of Mountain Avens (Dryas octopetala). Ellenberg scores - The Ellenberg's indicator values are based on a simple ordinal classification of plants according to the position of their realized ecological niche along an environmental gradient. FCD – Field Capacity Days
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Ffridd - unenclosed land, or enclosed land within a large field with a wall or fence surrounding it, close to the mountain wall. Gleying is essentially the process of waterlogging and reduction in soils. H4 - NVC community H4 (Ulex gallii - Agrostis curtisii heath) is one of the heath communities in the British National Vegetation Classification system. It is one of three communities which are considered transitional between the lowland dry heaths and the wetter communities classified in the NVC as mires. H8 – NVC community H8 (Calluna vulgaris - Ulex gallii heath) is one of the heath communities in the British National Vegetation Classification system. H9 – NVC community H9 (Calluna vulgaris - Deschampsia flexuosa heath) is one of the heath communities in the British National Vegetation Classification system. H10 – NVC community H10 (Calluna vulgaris - Erica cinerea heath) is one of the heath communities in the British National Vegetation Classification system. H12 - NVC community H12 (Calluna vulgaris - Vaccinium myrtillus heath) is one of the heath communities in the British National Vegetation Classification system. H18 - NVC community H18 (Vaccinium myrtillus - Deschampsia flexuosa heath) is one of the heath communities in the British National Vegetation Classification system. H21 - NVC community H21 (Calluna vulgaris - Vaccinium myrtillus - Sphagnum capillifolium heath) is one of the heath communities in the British National Vegetation Classification system. Humic substances are organic compounds that are important components of humus, the major organic fraction of soil and peat. M1 - NVC community M1 (Sphagnum auriculatum bog pool community) is one of the mire communities in the British National Vegetation Classification system. M2 - NVC community M2 (Sphagnum cuspidatum/recurvum bog pool community) is one of the mire communities in the British National Vegetation Classification system. M3 - NVC community M3 (Eriophorum angustifolium bog pool community) is one of the mire communities in the British National Vegetation Classification system. M15 – NVC Community M15 (Scirpus cespitosus - Erica tetralix wet heath) is one of the 38 mire communities in the British National Vegetation Classification system. M16 - NVC Community M16 (Erica tetralix - Sphagnum compactum wet heath) is one of the 38 mire communities in the British National Vegetation Classification system. M17 - NVC Community M17 (Scirpus cespitosus - Eriophorum vaginatum blanket mire) is one of the 38 mire communities in the British National Vegetation Classification system. M18 - NVC Community M18 (Erica tetralix - Sphagnum papillosum raised and blanket mire) is one of the 38 mire communities in the British National Vegetation Classification system. M19 - NVC Community M19 (Calluna vulgaris - Eriophorum vaginatum blanket mire) is one of the 38 mire communities in the British National Vegetation Classification system. M20 - NVC Community M20 (Eriophorum vaginatum raised and blanket mire) is one of the 38 mire communities in the British National Vegetation Classification system. M22 – The Juncus subnodulosus–Cirsium palustre fen-meadow is a plant association characteristically found on damp ground in portions of western Europe. This type of fen-
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meadow appears to have co-evolved with human agriculture in Europe since the earlier Holocene. M23 - NVC community M23 (Juncus effusus'/acutiflorus - Galium palustre rush-pasture) is one of the mire communities in the British National Vegetation Classification system. M24 - NVC community M24 (Molinia caerulea - Cirsium dissectum fen-meadow) is one of the 38 mire communities in the British National Vegetation Classification system. M25 - NVC Community M25 (Molinia caerulea - Potentilla erecta mire) is one of the 38 mire communities in the British National Vegetation Classification system. M26 - NVC Community M26 (Molinia caerulea - Crepis paludosa mire) is one of the 38 mire communities in the British National Vegetation Classification system. MB – Moisture Balance MD – Moisture Deficit MG4 - British NVC community MG4 (Alopecurus pratensis - Sanguisorba officinalis grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of four such communities associated with well-drained permanent pastures and meadows. MG5 - British NVC community MG5 (Cynosurus cristatus - Centaurea nigra grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of four such communities associated with well-drained permanent pastures and meadows. MG6 - British NVC community MG6 (Lolium perenne - Cynosurus cristatus grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of four such communities associated with well-drained permanent pastures and meadows. This community is a virtually ubiquitous community of the British lowlands. There are three subcommunities, one of which is divided into a number of variants. MG7 – Perennial rye grass grassland, associated with intensive agricultural grassland. MG8 - British NVC community MG8 (Cynosurus cristatus - Caltha palustris grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of three communities associated with poorly drained permanent pastures. MG9 - British NVC community MG9 (Holcus lanatus - Deschampsia cespitosa grasslands) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of three communities associated with poorly drained permanent pastures. MG11 - British NVC community MG11 (Festuca rubra - Agrostis stolonifera - Potentilla anserina grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of three types of mesotrophic grassland classified as grass-dominated inundation communities. MG12 - British NVC community MG12 (Festuca arundinacea grassland) is one of the mesotrophic grassland communities in the British National Vegetation Classification system. It is one of three types of mesotrophic grassland classified as grass-dominated inundation communities. MG13 - British NVC community MG13 (Agrostis stolonifera - Alopecurus geniculatus grassland) is one of the mesotrophic grassland communities in the British National
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Vegetation Classification system. It is one of three types of mesotrophic grassland classified as grass-dominated inundation communities. NRW – Natural Resources Wales NVC – National Vegetation Classification PH – Priority Habitat Podzolic soils are strongly acid soils that usually have a bleached horizon immediately beneath the topsoil. This horizon is the source of aluminium and iron oxides that have accumulated, in association with organic matter, in an underlying dark or reddish coloured horizon. Rankers are soils developed over non-calcareous material, usually rock. They are regarded in some soil classifications as lithomorphic soils, a group which also includes rendzinas, similar soils over calcareous material. Rendzinas are humus-rich shallow soils that are usually formed from carbonate- or occasionally sulphate-rich parent material. U1 – ‘sheep’s fescue – common bent – sheep’s sorrel grassland’ is one of the species-rich acid grassland communities in the British National Vegetation Classification system. U2 – ‘wavy hair-grass grassland’ is one of the species-rich acid grassland communities in the British National Vegetation Classification system. U3 – ‘bristle bent grassland’ is one of the species-rich acid grassland communities in the British National Vegetation Classification system. U4 – ‘sheep’s fescue – common bent – heath bedstraw grassland’ is one of the species-rich acid grassland communities in the British National Vegetation Classification system. W7 - NVC community W7 (Alnus glutinosa - Fraxinus excelsior - Lysimachia nemorum woodland) is one of the woodland communities in the British National Vegetation Classification system. W8 - NVC community W8 (Fraxinus excelsior - Acer campestre - Mercurialis perennis woodland) is one of the woodland communities in the British National Vegetation Classification system. It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. W9 - NVC community W9 (Fraxinus excelsior - Sorbus aucuparia - Mercurialis perennis woodland) is one of the woodland communities in the British National Vegetation Classification system. It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. W10 - NVC community W10 (Quercus robur - Pteridium aquilinum - Rubus fruticosus woodland) is one of the woodland communities in the British National Vegetation Classification system. It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. W11 - NVC community W11 (Quercus petraea - Betula pubescens - Oxalis acetosella woodland) is one of the woodland communities in the British National Vegetation Classification system. It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. W16 - NVC community W16 (Quercus spp. - Betula spp. - Deschampsia flexuosa woodland) is one of the woodland communities in the British National Vegetation Classification system.
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It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. W17 - NVC community W17 (Quercus petraea - Betula pubescens - Dicranum majus woodland) is one of the woodland communities in the British National Vegetation Classification system. It is one of the six communities falling in the "mixed deciduous and oak/birch woodlands" group. WG – Welsh Government
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