Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

For over sixty years research has been carried out on the ecology, management and control of bracken . Much of this has been aimed at discovering the best methods of control where it has invaded communities of higher conservation value, such as heathland and unimproved grassland. More recent research has focussed on the damage it may do to archaeology. Conflicts between different environmental interests can arise where bracken is present. Where they do it is important that any decisions on management are made in the light of the best information available and that the proposals are sustainable. This note identifies some of the issues and suggests priorities in a number of conflict situations. Further information is available in SIN011 Bracken and the TIN048 Bracken management and control.

Bracken and Biodiversity Action Plan late summer when other grasslands have (BAP) priority habitats become scorched and less palatable. Grassland Heathland Bracken grows best on deep well drained soils. Both lowland and upland heath are considered It will invade grassland on acid and neutral soils. of international importance and recognised as It is less likely to be a problem on calcareous BAP priority habitats. They both may be invaded grasslands. Where it grows on acid grassland by bracken. In areas of established and healthy around moorland edges, it is of particular heath, bracken may only increase slowly. concern because of its negative impacts on However, in fragmented heath bracken densities valuable grassland communities. In these can increase rapidly. moorland edge habitats, enclosed areas containing acid grassland are recognised by the On heath, and particularly in the case of upland UK Biodiversity Action Plan as the priority heath, fire is commonly used as a management habitat Lowland Acid Grassland. tool. This can lead to the spread of bracken as it is well placed to survive fire due to its deep In more productive grassland bracken tends to system that is likely to remain largely be controlled by heavy stock grazing or cyclical unaffected by heath fires. Following a heath fire cultivation and re-seeding. In the uplands sprout vigorously and can be the first bracken will most readily invade U4 bent-fescue green to show through the ashes. In addition late grasslands. summer and autumn fires offer ideal At certain levels of grazing grassland can be opportunities for colonisation by bracken from maintained beneath bracken without a significant . build up of bracken litter. These grasslands can be of value to agricultural stock, particularly in

First edition 16 October 2008

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Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

Woodland Black grouse is a UK Red List and UK BAP Bracken spores preserved in peat have shown species and has a minor association with its early native occurrences to be as a minor bracken as part of a wider habitat mosaic. They element in the woodland flora. In woodland it may use small patches as refuge from survives in glades and ride edges. When light predators, particularly during moult. Whilst there intensity drops below 25% of full sunlight is no evidence of black grouse feeding from bracken cover may be as low as 5%. However, bracken, birds will utilise a good herb rich in managed woodland with an open canopy, or ground layer where this is present. Control of where grazing has denuded the understorey, bracken is usually advised for black grouse bracken can dominate the shrub layer. where there is perception that bracken encroachment will be detrimental to other more Bracken stands are found commonly in a valuable habitats. number of woodland types, in particular oak/birch woodland, and beech woodland. Bluebell is a UK BAP plant species with between Bracken may be present, and even frequent, in a quarter and a half of the world population in other woodland types, but cover is likely to be Britain. It is often found under bracken stands, low. Old woodlands are likely to have the least where it flowers before the bracken canopy bracken. closes in the summer. This species is intolerant of trampling, heavy grazing, deep shade and Bracken and UK BAP species competition from vigorous grasses, therefore the Two UK BAP fritillary butterflies: high brown and conditions below many bracken stands are pearl-bordered fritillary, are closely associated suitable. with stands of bracken that have violet species growing profusely through a thin layer of litter. Other species associated with bracken Heath fritillary is also a UK BAP priority species Mammals and its caterpillars feed on cow-wheat, often A number of mammals use bracken as shelter where it is growing under a bracken canopy. and cover, in addition a small number will occasionally eat it. Smaller mammals may use These bracken habitats are now considered bracken stands that have a well developed litter crucial for many populations of high brown and layer throughout the year. Larger mammals find pearl-bordered fritillary. The meta-population little or no winter shelter or cover in bracken, survival strategy means colonies may react to although some deer may use them to provide changes in habitat conditions and to pest cover for giving birth, particularly where sited species by becoming extinct at one site and near a woodland edge. The effects of deer moving on to another site. The maintenance of a grazing in bracken stands may benefit fritillary number of sites in suitable condition within the butterfly colonies. Rabbits may occasionally eat meta-population range is essential to the bracken, but are generally thought to encourage survival of the species. Thus, a bracken stand it by eating competitor . within a meta-population range and with the correct attributes for breeding fritillary butterflies Birds may be of high importance even if the species is No bird species are completely dependent upon not present. bracken, the ones most commonly associated with it are and stonechat. Both are Nightjar is the only UK BAP bird species with known to nest and feed within the stands. Other close associations with bracken. It may use birds known to nest in, or beneath, bracken bracken as its preferred habitat, and birds may include (it will also use bracken to lay their eggs on bare ground under bracken. construct its nest), tree pipit, yellowhammer, ring Skylark, another UK BAP species, often nests in ouzel, woodcock and twite. habitats that contain bracken and will use bracken for cover. Meadow pipit, tree pipit, yellowhammer and wren all use bracken for cover and foraging.

Page 2 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

Mistle thrushes have been spotted foraging in the wild . It is confined in Britain to the bracken patches on open moorland in June and New Forest and always found beneath a canopy July. of bracken. Climbing corydalis and chickweed wintergreen also seem to benefit from the Where twite are present the RSPB advise that conditions found under bracken stands. small patches of bracken are retained on steep slopes for twite to nest under. If management is Other necessary, it should be done as late as possible A range of ferns thrive on acid heaths and (ideally August). Note, twite is a colonial nester uplands, including: so destruction of core sites and the availability of suitable sites can be a limiting factor to  Lady Athyrium filix-femina expansion.  Hard fern Blechnum spicante Moonwort Botrychium lunaria Reptiles and amphibians  Parsley fern Cryptogamma crispa In the spring adders may be found basking on  dead bracken where their camouflage conceals  Mountain male fern Dryopteris oreades them well. It may be that they take advantage of  Scaly male fern Dryopteris affinis the higher temperatures on the surface of  Broad buckler-fern Dryopteris dilitata bracken litter compared to surrounding  Wilson’s filmy-fern Hymenophyllum wilsonii vegetation.  Lemon-scented fern Oreopteris limbosperma

Invertebrates Any of the above might be found growing in There are a number of invertebrates that feed on close association with bracken. However, the bracken. For instance, the sawfly likelihood of this will be far greater where Strongylogaster lineatus, a plant hopper bracken is less dense or at the edge of bracken Dytroptis pteridis and the caterpillar of the moth stands. All ferns are susceptible to damage from map-winged swift Hepialus fusconebulosa. In herbicides used to control bracken and most are the UK it is thought that between 27 and 40 severely affected. different insects feed on bracken, including nine moth species. Of these, the larvae of map- Lower plants winged swift and brown silver-line Petrophora Bracken canopies generally retain relatively chlorosata and the species Paltodora cytisella higher humidity levels than those found in open are thought to be confined to bracken. grassland. This favours mosses, which are often found under bracken. A number of moss species The number and frequency of insects feeding on even grow under vigorous, dense bracken bracken increases as the season progresses, canopy, including, bryum species, Campylopus possibly as a result of decreasing levels of toxins flexuosus, , Polytrichum in the bracken. Also young bracken fronds commune, Pseudoscelopodium purum and produce extrafloral nectaries sited in the axils of Rhytidiadelphus squarrosus. the pinnae and pinnules. These are only active in early spring and provide food for ants that in Fungi turn may provide the bracken with some There are a number of fungi that can be found protection from invertebrate herbivores. growing beneath the bracken canopy. Many, such as the yellowleg bonnet Mycena There is evidence that bracken is a good habitat epipterygia, are woodland fungi. At least one, for orb-web spiders and provides good wind- Camarographium stephensii, is host specific to shelter for flying insects. dead stems of bracken.

Higher Plants Bracken and archaeology The higher plants associated with bracken are Bracken has two major impacts on mainly those of woodland or the woodland edge. archaeological sites. Firstly, it destroys and Among the more notable of the higher plants is Page 3 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities reduces the significance of sub-surface Bracken in the landscape archaeological evidence, including the ability to Bracken has existed as a component in the reconstruct past environments. Secondly, it landscape for millennia. The form that bracken obscures sites. Each summer until mid-winter a stands take in the landscape are varied, but may large part of our rural archaeological heritage be said to fall into two categories: continuous, disappears under the cloaking effect of bracken. relatively uniform stands, and discontinuous, Not only does this reduce the accessibility to, relatively patchy distribution. The visibility of the and visibility of sites, it also makes them more stands depend on their position in the landscape vulnerable to inadvertent damage, for instance which may be on open hillsides or in more from agricultural or forestry operations. confined situations, perhaps adjacent to woodland, where stands may less visible. The bracken canopy hides low level upstanding archaeological features and field marks in Continuous stands will be constrained by grassland and unrecorded sites are unlikely to elevation and exposure, by ground-water and by be found, recorded, studied or protected. A the interaction with other vegetation complete canopy of bracken indicates a communities such as heathland or woodland. On substantial rhizome system and the high low open hillsides bracken may completely cloak probability of ongoing damage to an the landscape. On hills and moorland that rise to archaeology. greater elevations an elevational limit defines the limit of the vegetation. The shape of the upper Research work on archaeological sites in limit may be defined by topography and Scotland and on Dartmoor has shown that the exposure. The shape of the lower limit may be rhizome system develops as a dense mat defined by the enclosed and more intensively between up to 20 cm and 40 cm below ground managed land or by woodland. surface. Beneath this there is a thinner riddling effect between 40 cm and 90 cm. This indicates Discontinuous stands on open hillsides may that all deposits near the surface may be form a mosaic of lesser or greater intensity. completely destroyed, while the palaeo- They may rise up along valleys and stream- environmental integrity and content of the sides or be confined to the lower areas of the underlying deposits will increasingly be hillsides and remain fragmented due to intensity compromised. of grazing or other management.

Bracken may also discourage grazing stock, Where bracken control or management is to be particularly as it dominates grass and herb implemented the boundaries of treatment areas species which in turn can lead to scrub invasion. need careful consideration, particularly in Whether scrub is the lesser of two evils as relation to the impact they could have in the concerns damage to archaeology is another landscape. matter. Dense stands of bracken can prevent infestation by rabbits and it may not be advisable Principles for integrating management to control bracken where rabbits pose a threat to The main objective of any management should a site. be the protection and maintenance of the environmental feature or features of the highest From purely historic environment interests the value. In some cases the enhancement of high best control on archaeological sites where there value features will be at the expense of features are upstanding remains (either earthworks or of lesser value even where those may be in stone structures) is by spraying with an better condition. appropriate chemical. However, chemical spraying to control and eradicate bracken from The general principle is that international extensive areas of archaeological landscape designations will take precedence over national could have potentially serious implications for designations. National designations will take the carbon load in, and the quality of, water. precedence over regional designations with

Page 4 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities regional designations having a higher priority While the finest of archaeological sites may over local designations or importance. cover may hectares of land it is often the case that bracken affecting isolated features can be Two issues that may cause concern in setting controlled without damaging ecological interest. priorities are: Indeed, it may be possible, and it is always desirable, to carry out control and management  Where two or more feature on a site are with integrated objectives. similarly designated.  Where management for the feature of highest Case studies priority will severely damage or destroy a An example of integrated management is feature of high, but not as high, value. Spitchwick Common on Dartmoor where an attempt is being made to control bracken on and Bracken is unlikely to be a feature of high value around archaeological features that coincide in its own right. As has been shown above, it is with fritillary butterfly interest. The bracken mainly the conditions created by bracken that control aims to protect the archaeological sites are important. A number of the species from any further damage while creating grazing associated with bracken are of high conservation lawns. The fresh grass should encourage stock value. Management of bracken at a greater or into the butterfly habitat keeping it in favourable lesser degree would normally continue to condition. provide suitable conditions for these species. However, bracken is highly damaging to Another case of integrated management can be archaeology. found on Ugborough Common, also on Dartmoor, where the agricultural and To resolve a conflict between management of environmental objectives are integrated. Here bracken for associated values and control of the commoners are managing bracken on the bracken to protect archaeological features lower parts of the common in order to produce consideration must be given to the scale of the more sweet grazing for stock. The stock will be archaeological feature or features and the form shepherded towards this new grazing away from that they take. It may be necessary to take higher value Upland Heath. informed opinion as to the value of the archaeological feature to assess its value Prioritising management between relative to other features. In some cases conflicting archaeological and ecological archaeology will be designated. Very few interests archaeological sites have international Where conflicts between different environmental designations. There are a great many that are features arise the following methodology can be designated as Scheduled Monuments of national used to help determine the most appropriate importance and numerous features are listed on management for a given site. This methodology the County Sites and Monuments Register. is based on What are the management options Only Scheduled Monuments receive legal in Bracken Control?: a Guide to Best Practice protection in this country. However, where land produced by The Southern Uplands Partnership, is under an agri-environment Scheme Galasheils, March 2001. agreement all features of archaeological or In table 1 overleaf there are four management historic value or interest must be protected from options: any damage, destruction or removal. Hence, on agri-environment land, where a conflict is  no control, perceived, protection of archaeological features will take precedence.  maintenance or conservation management,  limited control and Where archaeological and ecological interests  eradication. coincide it is often possible to tailor control and management to the benefit of both interests. Page 5 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

A decision on the approach or approaches in Further information any given situation will depend on the This document has been developed from comparative values of the features on that site. guidance written by the Rural Development Service for Environmentally Sensitive Areas Table 2, overleaf, sets out the comparative Project Officers in the South West Region. values of a range of features. Where conflicts may arise there is normally a need to decide on Natural England Information Notes are available a course of action. to download from the Natural England website: www.naturalengland.org.uk. In particular Table 3, on page 8, sets out the relative priority SIN011 and TIN048: for management where conflict between two features arises. Where a balance of  Bracken management is called for it may be possible,  Bracken management and control within a site, to control bracken on features where it is desired while managing the bracken For information on other Natural England away from those features, preventing invasion publications contact the Natural England Enquiry yet maintaining conditions suitable for the other Service on 0845 600 3078 or e-mail interest feature. [email protected].

Table 1

Management Situation

options

No control On steep slopes, heavily grazed areas or where regeneration of other habitats to replace bracken is difficult and where wildlife considerations are important

Conservation Where it is desirable to maintain low intensity or patchy cover for supporting management species and habitats for conservation importance, any control is likely to be limited and selective

Limited control Where the aim is to reduce the area or severely limit vigour and spread but not eliminate

Eradication Where bracken is to be replaced with other vegetation

Page 6 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

Table 2 Interest features associated with bracken and their relative importance

International National Regional Local Landscape Historic Parks and Gardens Archaeology World Heritage Scheduled County Register Unregistered Sites Monuments, sites, Unregistered Features Unregistered Features Features UK BAP Upland heath, Prioirty Lowland Habitats Heath, Lowland Acid Grassland, Lowland pastures, Upland Oakwood UK BAP Nightjar, species skylark, , pearl-bordered fritillary, heath fritillary, Vigurs eyebright, bluebell Other Twite, Yellowhammer, Brown Silver-line, Wren, Whinchat, Species Ring Ouzel, Tree Map-winged Swift, Mistle Thrush, Gold Pipit, Meadow Pipit, , a Swift, Buff Ermine, Stonechat, gall-midge Broom Moth, Angle Woodcock, Willow Dasyneura filicina, Shades, Small Angle warbler, Adder, Wild Climbing Corydalis, Shades, a micro- Gladiolus, Moonwort, Chickweed moth Paltodora Parsley Fern, Wilsons Wintergreen, cytisella, Lady Fern, Filmy Fern Mountain Male Hard Fern, Scaly Fern, Lemon Male Fern, Broad Scented Fern Buckler Fern

Page 7 Natural England Technical Information Note TIN047 Bracken management: ecological, archaeological and landscape issues and priorities

Table 3

Site Designation UK BAP nationally notable regionally notable locally

species species species notable

species

World Heritage balance balance control bracken control Site management management bracken

Historic Park or balance balance control bracken control Garden management management bracken

Scheduled balance balance control bracken control monument management management bracken

SMR balance balance control bracken control management management bracken

UK BAP Habitat balance control bracken control bracken control management bracken

Nationally manage for UK balance control bracken control Important Habitat BAP sp management bracken

UK BAP species x manage for UK manage for UK BAP manage for UK BAP sp sp BAP sp

Nationally notable x x manage for Nat sp species manage for Nat sp

Regionally notable x x x manage for species Regional sp

Locally notable x x x x species

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