Woodland Management Techniques

A major aim of habitat management in woodlands is to diversify their structure.

It aims to create greater age and size class diversity in an even age stand of trees by felling groups or lines of trees at different intervals. It may also involve planting or natural regeneration and encourage growth of understorey shrubs and enhance deadwood.

An opportunity for creating a range of habitats for species that need younger and older growth stages.

Thinning/Selective felling: Light

Assumes selection to favour native broadleaf trees with beneficial features e.g. in-tree deadwood etc.

Re-spacing, especially of post thicket or pole stage stands can effectively generate a broadly native mixed strata wood with canopy trees and understorey/coppice. As canopy trees develop, shade will reduce understorey.

Selective thinning to incrementally increase crowns

• Retain at least 75% canopy cover (to limit thicket regenerations)
• Select for larger crown potential
• Retain standing deadwood & trees with snags
• Retain potential replacement trees (c 10/ha where they occur)

Opens canopy enough to facilitate crown development and the low light levels restrict understory growth and aid the structure required by characteristic bird assemblages. Note such treatments can be damaging to lichen rich woodlands as they fail to let in enough light. To compensate for this, ensure some slow growing and twisted trees are maintained for lichens and create some small glades to allow more light penetration in areas close to these trees.

Note that this type of thinning is appropriate in some habitats such as upland oakwoods, or in some areas of a large wood, but heavier thinning is often more appropriate for conservation purposes.

Thinning/selective felling: Heavy

Assumes selection to favour native broadleaf trees with beneficial features e.g. in-tree deadwood etc.

Re-spacing, especially of post thicket or pole stage stands can effectively generate a broadly native mixed strata wood with canopy trees and dense understorey/coppice.

Selective thinning to a) increase crown growth, b) encourage understorey regeneration

• To achieve usually between 55% & 60% canopy cover
• Select for large crown potential
• Select for native species

Provides conditions for complex structures to develop with mature canopy trees, gaps, understorey, field layer and deadwood, providing habitat for a variety of birds and other species. Can also improve herb layer and increase nectar and pollen sources for bees and other insects. In many cases regeneration following thinning/selective felling will require grazing and browsing pressure to be low. Deer management plans and measures to control browsing pressure may be necessary.

In order to restore lichen rich woodlands from dense growth (following grazing reduction), creating frequent glades and highly uneven grazing pressure is needed. Ensure a lichen survey before removing any mature trees.

Small group felling

To regenerate woodland, create temporary open space

• Clear-fell small areas (size depends on woodland context, but >0.25ha)
• Encourage natural regeneration (see deer management; if possible time to catch mast years)
• Determine regeneration cycle e.g. 80-100 year in upland oak woods and devise rotation plan - exclude mature/veteran features
• Where woodlands contain few tree species and it is desirable to diversify species mix, these open spaces can be planted with desirable species, including understory plants. NB this will depend on the woodland type, some types such as upland oakwood may naturally contain few tree species and sparse understorey

Lets in light and warmth and creates niches for light-loving species. Encourages new generations of trees and regeneration of understorey, providing increased habitat diversity.

Can also be used to 'rescue' veteran trees in recent woodland or conifer plantations, although beware of sudden changes in conditions around such trees, and remember that bats may be using them. Threatened lichen rich veteran trees should only be treated in this way if re-shading from vigorous regrowth and ivy can be restrained - while removing trees from around them more gradually and retaining some nearby trees should prevent damage to the veteran and organisms it supports, and provide continuity of habitat for bats.

Halo thinning

Allows light and space for development of a selected tree, often selected for existing or potential biodiversity value, e.g. potential to develop a large leafy crown or old- growth features such as decaying branches, knot holes etc. Tree usually crowded by other (usually smaller) trees which are restricting light to, and development of, the selected tree. Might include release of supressed veteran trees within Plantations on Ancient Woodland Sites (PAWS).

• Remove a proportion of closely surrounding trees by selective felling (or other method, e.g. ring barking), prioritising those that are most obviously suppressing the selected tree
• Retain around 50 % of the surrounding trees in the first operation, to protect the tree and any occupying wildlife (e.g. bats) from sudden dramatic changes in microclimate and habitat
• Return in 1 to 5 years' time to assess the tree's development, and if necessary remove more surrounding trees. Signs of improved condition include a better developed canopy, new epicormic growth etc. - remove more trees if such signs are lacking
• Do not remove all surrounding trees unless they are in very close proximity - retain some surrounding canopy to prevent ill effects on the tree of sudden exposure, and to provide continuity of wildlife habitat. A gradual approach is particularly important when dealing with veteran trees in a PAWS restoration context

Allows development of mature trees with large leafy canopies, old growth features and in-tree decaying wood, which provide habitat and food sources for a variety of wildlife. Includes habitat for decaying wood invertebrates and fungi (some of these rare), as well as canopy invertebrates, which in turn provide food sources for bats, and birds such as lesser spotted woodpeckers. Old growth features and decaying wood can provide roosting habitat for bats and nesting opportunities for hole-nesting birds.

Detrimental effects on some wildlife are possible, particularly where a tree already contains in-tree decaying wood and old-growth features. Roosting bats, or potentially rare decaying wood invertebrates which require specific micro-climate conditions, may inhabit such trees and be particularly vulnerable. In such instances a gradual approach is essential and complete halo thinning should be avoided. All bats in the UK are European Protected Species, and bat surveys should be carried out where a selected tree (or nearby tree) contains potential roosting habitat.

Coppice short-medium rotation (<12 years)

Reinstate and maintain rotational coppice management

• Cut coupes/panels in rotation. Usually one or more per year - small sites may warrant cutting one larger panel every other year rather than very small panels annually
• Cut adjacent panels in succession to provide optimum extent of similar age-classes, and improves chances of colonisation by species with low mobility
• Provide access rides as needed for management and keep open (see 2-zone rides and 3-zone rides)
• Retain mature standards and non-crop species for ecological value, within 10 - 40 % canopy cover - e.g. elm suckers, thorn, elder etc.

Creates temporary open spaces repeatedly, with associated sheltered warm sunny microclimate for invertebrates, with pioneer plants; followed by thicket of coppice regeneration.

Most birds of coppice will utilise up to 10 years growth. They depend on density of thicket, hence mixed species stands are better than pure stands e.g. of hazel or ash. Invertebrates with low mobility are more likely to survive where adjacent coupes/panels are cut consecutively, providing continuous availability of habitat over time.

Coppice medium-long rotation (>>12 years)

As for short-medium coppice rotation:

• Cut coupes/panels in rotation. Usually one or more per year - small sites may warrant cutting one larger panel every other year rather than very small panels annually
• Cut adjacent panels in succession to provide optimum extent of similar age-classes, and improve chances of colonisation by species with low mobility
• Provide access rides as needed for management and keep open (see 2-zone rides and 3-zone rides)
• Retain mature standards and non-crop species for ecological value, within 10 - 40 % canopy cover - e.g. elm suckers, thorn, elder etc.

Creates temporary open space repeatedly, with associated sheltered warm sunny microclimate for invertebrates, with pioneer plants; followed by thicket and pole stage. Usually more suited to large sites. Some species utilise the later stages of coppice e.g. marsh tit, dormouse.

Manage standard trees/groups

To conserve mature and veteran trees within coppice

• Identify mature trees and retain where shading will not compromise coppice. Always aim to retain veteran trees.
• Identify potential replacements and exclude from coppice
• Retained canopy cover range varies by a) rare species interest, b) shade-cast by tree species; for vigorous coppice: no more than 40% canopy cover, ideally <25% for rare woodland butterflies: 10% - 15% maximum
• Retain ivy as foraging habitat and nest cover

Provides habitat and niches (including ivy) for those species which require mature trees.

Provides dappled shade which can suppress vigorous species e.g. bramble, and benefits species which require light shade.

Old coppice (or hazel which appears to be coppiced but is actually uncoppiced natural bushes) that has been colonised by lichen assemblages of conservation significance should ideally not be coppiced but converted to old growth woodland. This may need to be balanced with other species interest however, for example rare invertebrates or ground flora that require coppice/dappled shade.

Note this system is not a viable option for conserving rich epiphytic lichen assemblages, as conditions are too variable and ivy likely to wipe out most lichen diversity on the trunks.

• 'Continuous Cover' or 'Irregular' forestry is an approach to forest management which aims to achieve a varied structure without clearfelling. Thinning interventions, for example in small groups, create gaps which encourage regeneration, or allow for underplanting to renew the forest.
• Can help reduce the risks posed by future changes in the climate and biotic threats and can help protect the soil from erosion and disturbance, which in turn can reduce carbon emission.
• CCF encompasses a very diverse set of approaches to forestry management, producing a diverse set of outcomes in terms of habitat structure and condition.

For further information, see the Continuous Cover Forestry Group website: www.ccfg.org.uk/

The aim is to create more diverse forests both structurally and in terms of species composition. Some species are more likely to benefit from CCF approaches than others. For example, lowland broadleaved woodland birds could benefit from broadleaved CCF systems that provide sufficient canopy gaps and diversity of habitat structure.

In certain areas CCF could pose a threat to species that rely on larger areas of open space within a forest, such as forest nesting nightjar and woodlark, butterflies etc.

Restoring a native canopy from a non-native plantation e.g. a conifer plantation on an ancient woodland site (Plantation on Ancient Woodland Site, or PAWS). Not all such plantations are conifer, but can include e.g. beech plantations where beech is not native to the area.

Further information is available from the Woodland Trust's publication 'Ancient woodland restoration - an introductory guide to the principles of restoration management' and from the Forestry Commission's publication 'Choosing stand management methods for restoring planted ancient woodland sites'.

A wood does not have to be ancient in order to support threatened wildlife. Ancient woodland however contains some unique features which have developed over a very long period of time and cannot be found at younger sites. Ancient woodland soils contain unique communities of fungi, invertebrates and microbes. Woodland ground flora have evolved with these communities, and some depend upon them for survival. Some such plants, known as 'ancient woodland indicators' are only likely to be found in ancient woods, as they are very slow to spread to new sites. Some species of lichens, liverworts and mosses are also associated with ancient woodland, especially where old trees are present. Sites with numerous old and veteran trees, and high levels of decaying wood, are particularly valuable as these can support numerous species of fungi and invertebrates, some of which are extremely rare, as well as hole nesting species of birds and roosting bats.

Restoration of PAWS often focuses on removing plantation trees, while retaining and favouring remnant features of the ancient woodland, such as ground flora or remaining native trees. Restoration to a native canopy can provide these species with suitable conditions to thrive again. Depending on the length of time since plantation and the level of soil disturbance that has taken place, ancient soil communities might also recover. Remnant features can be damaged where a drastic approach is taken to restoration, such as clear felling the plantation trees. A more gradual approach is usually most appropriate.

Rides - 3 zone (preferred)

Provide/maintain network of rides to a) provide management access, b) provide internal edge habitat with thicket margins.

Create by

• Making width c1.5x height of adjacent trees to limit shading
• Providing range of aspects to increase sunlight
• Retaining some in-ride trees as features/habitat bridges
• Providing "pinch points" every 30m to 100m to limit wind funnelling and aid mobility of core woodland species e.g. dormouse
• Provide a scrub thicket/dense coppice edge
• Thin trees on ride edges to enhance the scrubby vegetation
• Create "scallops" in edges to provide extra sheltered conditions with some colonising scrub

Manage by

• Mowing centre/trackway annually
• Mid zone areas: mow every 2-3 years e.g. alternate sides in alternate years. Remove arisings to prevent mulching.
• Outer zone: coppice scrub edge on c 7-10 year rotation

Provides an internal edge with shelter, light, and warmth with diversity of structure and niches.

Potential conflict in management interest between species objectives if pinch points are not incorporated; butterflies vs. bats or dormice.

3 zone ride management will retain more overwintering sites for invertebrates than 2 zone ride management and will allow a greater variety of species to co-exist. Also provides more feeding and nesting habitat for birds.

If the scrub edge is Sallow allow some to mature and not coppice every 7-10 years, for willow tit, purple emperor, goat moth, lichens etc

Rides - 2 zone

Provide/maintain network of rides to a) provide management access, b) provide internal edge habitat

Create by

• Make width ideally c1.5x height of adjacent trees
• Provide range of aspects but especially E-W orientation
• Retain some in-ride trees as features/habitat bridges
• Provide "pinch points" every 30m to 100m to limit wind funnelling and aid mobility of core woodland species e.g. dormouse
• Create "scallops" in edges to provide extra sheltered conditions

Manage by

• Mowing centre/trackway annually
• Mow outer areas every 2-3 years to provide tussocky tall grass and herbs without scrub colonisation. Cut sections on alternate sides in alternate years to maintain continuity of structure. Remove arisings to prevent mulching.

Provides an internal edge with shelter, light, warmth, with some diversity of structure and niches.

Potential conflict between species objectives if pinch points are not incorporated; butterflies vs. bats or dormice.

Rides - veteran trees

Rides can act as linear glades and allow the conservation of lichen rich veteran trees on ride edges. These trees need to be set in the ride grassland zone, not in the shrub zones to avoid over shading and Ivy growth.

Manage by

• Mowing around trees annually

Provides stable and sheltered but well lit conditions for old growth dependant lichens on veteran trees. Potentially the only sustainable habitat for generally grazing dependant lichens within ungrazed woodlands.

Glades

• Maintain existing glades and create new ones if priority species require this niche
• Where possible use the 2 or 3 zone cutting technique as above

Provides light, warmth and a diversity of habitat and niches for many species, especially plants and invertebrates. Also provides edge habitats, bird feeding and nesting habitat, and flower rich sheltered areas - source of nectar and pollen.

Woodland edge - to agriculture

Buffers wood from agricultural operations and cooling drying winds.

Graduated edge: grass margin > scrub thicket > woodland with understorey.

• Create and manage similar to 3-zone ride
• Thin wood edge trees to increase light
• Retain lower branches on oaks in particular
• Develop tussocky grassy margin to edge, with scrub in intermediate zone
• Mow margins every 2-5 years. Manage scrub by coppice every 7-10 years

Buffering the interior of a wood can be important, particularly in heavily farmed areas. Developing a scrub edge also provides a wide range of habitats and niches, including feeding and nesting habitat for birds, while grassy margins with scattered scrub provide good invertebrate habitat. However, avoid destroying rich lichen assemblages on wood edge veteran trees by increasing shade on these trees, and be sure to preserve these trees when thinning woodland edges.

Creating scrub layer on edge of wood will probably require landowner to forfeit Basic Payment on that land if on a 7-10 year rotation, but will provide valuable habitat. Alternatively, thinning back trees from the edge will provide scrub within the existing woodland boundary, with additional value where this is adjoined by a tussocky grass margin.

Woodland edge - to open habitats

Manage to enable the wood to grade into adjacent open areas.

Mosaics of scrub, heath and grassland and of scrub and trees are of high value for many species. Management of trees/scrub may depend on relative values of woodland vs open habitats. Hawthorn and umbelifers are important plants for pollinating insects.

Deadwood: Fallen

Provide fallen deadwood in a range of niches; damp, dry, shade; partial shade, deep shade, sun

• Fell to waste during thinning and coppicing
• Leave in lengths to allow slow rot
• Distribute widely rather than in piles (although avoid excessive covering of sensitive ground flora). If piles are used then a few large piles provide more value for rare specie than many small ones
• Consider pushing/winching over trees to retain root plate for added ecological value (Live trees only, standing deadwood has own value)
• Large fallen trees propped off the ground on branches are a more valued habitat for rich lichen assemblages than trunks in full contact with the ground

Conserves and enhances deadwood habitat and niches for species which depend on fallen deadwood.

To increase habitat for saproxylic invertebrates (many rare species are associated with dead wood). Also provides insect food for birds, bats etc.

To increase habitat for fungi.

To increase soil moisture retention.

Deadwood: Standing

Provide standing deadwood in a range of situations

• Retain all existing where safe and practicable
• Increase by killing trees with low conservation or commercial value, where safe or where health and safety is not compromised
• Ring-barking is the easiest method, but can lead to low value deadwood (poor mobility of fungi through the stem). Stem injection is an alternative method
• Provide standing deadwood of a variety of sizes
• Standing deadwood can be provided by the "veteranisation" of young trees
• In otherwise closed canopy, maintain humidity by only killing small numbers of scattered trees.
• Well lit to partly shaded large diameter standing dead trees are most valuable for lichens

Conserves and enhances deadwood habitat and niches for species which depend on standing deadwood.

Standing deadwood is used for nesting by woodpeckers (but note lesser spotted woodpecker prefers dead branches on live trees) and starlings and is used by roosting bats. Willow tits excavate nests in small diameter standing deadwood (10-20 cm diameter), especially in damp woodland.

Deadwood: dead branches on live trees

Conserve by selecting and retaining live trees with dead branches

• Enhance by targeting small scale limb damage during felling operations

Conserves and enhances deadwood habitat and niches for species which depend on smaller scale standing deadwood, such as bats.

Preferred nesting habitat for lesser spotted woodpecker.

• Applies not only to wet woodland. There is evidence of significant local drying of woodland which may be implicated in the decline of some species.
• Aim to minimise water loss from the site. Damming drainage channels to hold water back is likely to be a key method; dam heights can be set to allow some drainage.
• NB - Environment Agency may need to be informed if major works are planned

Benefits species requiring specific wet or damp conditions, including many fungi and invertebrates. Willow tits and nightingales are associated with wet, scrubby woodland. Take care to prevent new ponds establishing in areas which were previously wet flushes, as these themselves are valuable habitats. Existing ponds potentially at risk of drying out/silting up so consider installing silt traps on feeder streams.

Provide stock fencing to (where needed) exclude livestock or regulate grazing

• To enable regeneration of understorey and replacement trees
• To release field layer from over-grazing
• Moderate stocking density to a) limit (not prevent) regeneration, b) maintain a varied low field layer structure.

Grazing can be important in preventing overgrowth of some species (particularly bramble), although overgrazing can be detrimental. Appropriate grazing levels can open up the field layer thereby promoting seedling growth, and can benefit some species e.g. pied flycatcher, redstart, wood warbler, blue ground beetle and over 100 old growth dependent lichen species, by providing an open understorey and well-structured field layer. This type of structure is appropriate in some kinds of woodlands, especially West Atlantic woods.

• Normally involves only safety measures and boundary infrastructure. Otherwise stands are left to successional processes.
• Virtually no British woodland is unaffected by human management so well structured native woodland is rare, hence minimal intervention is likely to need to follow some management to restore structure. No management at all can lead to canopy crowding, weak growth and excessive shade.
• Minimal intervention most likely to be beneficial in areas of established / mature woodland with existing variety of structure and relatively intact natural processes in operation. These conditions are most often found in wet woodlands, where a high water table accelerates decay processes and structural change. Some initial intervention might be necessary even in wet woodlands however, where sites have been previously managed and structure is more uniform, but ensure all dead and decaying wood is left in place. Larger sites can be managed with some areas (e.g. wetter areas) set aside for minimal intervention, while other sections of the woodland receive more active management.

Minimal intervention allows natural succession to take its course. This is particularly relevant to ancient woodlands which contain soils (and associated flora, fauna and fungi) which may have been undisturbed for centuries. Due however to the small size and management history of many British woodlands, some management is likely to be necessary to maintain appropriate woodland structure. Some bats for example prefer closed canopy woodland, but require a varied structure and understorey, which is unlikely to be present under full canopy shade, so occasional light thinning or small group felling may be appropriate.

Note this treatment is not suitable for lichen rich woodlands, unless significant grazing impacts are maintained. As natural grazing impacts on the wild wood were likely to be high, at least at times, and old growth lichen assemblages are grazing dependant, high grazing impact minimal intervention could be acceptable for lichen rich stands.

A large number of species (invertebrates, fungi and others), including rare species, are supported by wet woodlands where natural processes of succession and decay result in a varied structure and high decaying wood content.

• In clearfell forestry systems, whole, sometimes large compartments of trees are felled in one go (see Continuous Cover Forestry section for comparison). This can provide a patchwork of temporary open habitats which are useful for some wildlife species (see below).
• Clearfell systems are often found in conifer plantations, although can also be used in broadleaf areas. Such plantations often consist of one, or a limited number of tree species and may be lacking in useful diversity and structure for wildlife. This can be enhanced by sensitive management, particularly by creating open areas such as rides and glades, and encouraging scrubby vegetation along these and external edges.
• Leaving some areas un-felled to develop 'old growth' characteristics, large trees and high amounts of decaying wood can also add variety and wildlife value. Within clearfell areas, leaving occasional standing trees or small groups of trees can provide song posts for birds.

Clearfell systems can provide temporary open habitats with some low scrubby vegetation, suitable for species such as nightjar, woodlark, some woodland ground flora and butterflies. As these areas are encroached by bramble and regenerating trees they can provide habitat for various scrub-loving birds, and invertebrates including butterflies; while young, thicket stages of replanted conifer or birch regeneration can support redpolls and tree pipits.

Size and continuity of habitat can be an issue for many species of the earlier, more open stages of clearfell. Forest plans can be designed so that newly felled areas are located close to areas that are beginning to close over. For nightjar in particular, a continuity of clear-fells greater than 0.02 sq km in size is important, and where possible, creating a waved or scalloped edge to the coup will increase the length of foliage edge for feeding.

Try to minimise disturbance in clear felled areas, e.g. due to public access, particularly dogs, as this can be detrimental to ground nesting birds. Likewise try to time operations outside the bird nesting season (May to September for nightjar).