Upland mixed ashwoods

These woodlands occur in western and northern Britain on thin soils usually over limestone. The support important bird communities as well as rare assemblages of flora, especially mosses and lichens, and invertebrates.

Upland Ash Woods can be created on sites with moist base rich soils.

Choose which trees to plant and in what relative proportions based on:

The woodland types that would regenerate naturally on a site, based on local conditions such as soil pH, nutrient levels, hydrology, and climate.
The appropriate frequencies of species in a given community.
Availability of appropriate management both during establishment and subsequently, which would aid community development.

The Forestry Commission can advise on these factors locally (see contact pages for more details).

Large, new woods should include areas of open ground as this aids structural diversity and encourages high biodiversity.

Size and proximity to other woodlands are important:

Larger woodlands (ideally > 5 ha) support and retain more woodland wildlife.
Small woodland blocks can be enhanced by scrub established around the perimeters to reduce wind penetration to the interior.

Adding to existing woods or creating new blocks close by will increase the potential for species colonisation. Edges should be designed to avoid a simple interface eg hard edge between woodland and open ground, and managed to maintain it.

Woodland creation is not appropriate where existing valuable habitats occur, or where there is the potential to restore high priority open habitats, or where it will create barriers for wildlife movement between existing habitats.

Establishment techniques

Several methods can be used. When deciding on which to use, assess available resources, the local landscape and the site objectives.

Natural colonisation

Natural colonisation will suit sites adjacent to existing upland mixed ash woodland.

Preparation of a rough seedbed will often enhance germination and take of new trees. Only use a (low fertility) thin topsoil where exposed beds are excessively impoverished or do not offer rooting opportunities. Compaction and waterlogging can severely affect tree growth. These factors can be improved, for example by subsoiling.

Pioneer species, such as downy birch can develop a dense scrub cover relatively quickly (over 10 years). Thereafter natural succession will see the balance gradually change as new species colonise. This can take a very long time, but as this is a natural process, the value for wildlife will remain.

Benefits of natural colonisation are:

Low cost – although rabbit fencing and deer control may be needed.
Natural composition – of species adapted to the conditions found on the site.
Natural distribution of trees – natural look to the landscape as opposed to planting in rows.
Promotes conservation of local biodiversity.

Disadvantages:

Slow to develop full assemblage of species (but valuable in the meantime)
Can look untidy during establishment

Tree and shrub planting

This would be appropriate where the natural colonisation is unlikely, eg is far from existing woodland, or establishment is required especially quickly.

Whatever the planting method used it is important to ensure that:

Trees and shrubs are planted in loose friable soil to ensure adequate water storage.
Rootstock is always protected from desiccation.
Competing rank grass and other plants are managed for 4-5 years (see below).

When preparing the soils, redress any compaction where necessary by ripping.

Do not improve soil fertility - if soil fertility is extremely low then consider other habitats such as heathland or use natural colonisation over a long time period. Most woodland soils are infertile, especially in phosphorus. Tree establishment depends on root penetration and low competition. Poorer soils help to reduce competition from grasses and herbaceous vegetation, and develop a diverse ground flora.

Planting patterns and spacing

The planting scheme used at the outset will be a major influence on resulting woodland structure.

Plant naturalistically, not in straight lines - this leads to wind tunnelling and a simplified structure of limited value for wildlife.
Sparse planting leads to the development of more natural woodlands than the dense planting traditional in commercial silviculture.Wider spacing involves fewer trees, lower planting and lower maintenance costs. It produces bushy trees and a slower closing canopy, as well as reducing weeding during establishment, and delaying thinning for several decades.
» at an average spacing of 3.6 m, 722 trees are required per ha.Closer spacing, results in taller trees, earlier canopy closure and requires earlier thinning, otherwise a simple structure develops lacking many of the features needed by birds and other wildlife. Closer spacing than 2m should not be considered.
» at an average spacing of 2 m, 2,500 trees are required per ha.

Planting mixes should include shrubs appropriate to the conditions. Upland ash wood shrubs include hazel, rowan and holly. Planting design will include shrubs planted randomly, some in tight clusters forming thickets, others more widely spaced, in single and mixed species clusters, depending on soils and topography.

Downy birch occurs commonly in upland ash woods and being quick growing can work as a nurse for other species, helping soil formation, and adding shelter and warmth without casting heavy shade.

Where nursery-grown trees are used, whips (small, bare-rooted stock) generally out-perform standards. They are usually more cost effective as prices range from £0.50 to £1.00 per unit, depending on species.

Planting should be undertaken during the dormancy period – November to February – avoiding frosty weather. Roots must not dry out. Heel unplanted stock in until it can be planted out. One person can plant 800-1,500 whips a day by hand.

Where they occur, protection from deer and rabbits is essential. Tree shelters are costly but increase survival rates, aid early growth and reduce the need for weed control. Fencing costs are high: ca £5 m-1 for rabbit fencing, ca £10 m-1 for deer fencing, but reusable types are available. Any fencing in black grouse areas will need to be appropriately marked with high visibility markers to prevent collisions. Remove tree guards and fencing once the crop is well established (5+ years).

Weed control is usually needed for the first 4-5 years to limit competition. This need not be rigorous as occasional losses will create useful gaps. Options include: biodegradable mats fitted around base of tree; wood chip or bark mulch application; glyphosate application once or twice a year; mowing or tillage. Where tree shelters are used, grazing works to control grass.

Ground flora establishment

A woodland ground flora will colonise very slowly. Introduction is only required where colonising is unlikely.

Woodland topsoil will include seeds and root material as well as fungal spores and mycelia, and can therefore be an effective means of introducing ground flora. Where available, this can be applied in clumps from which vegetation will spread over time. Permission will be required from Natural England where the donor site is an SSSI.

Alternatively, seeds can be collected and sown. Otherwise, once trees and shrubs have developed, a surrogate woodland flora will develop as taller grasses and plants are suppressed by shade. This will continue to develop. Light grazing will also help to promote ground flora.

Long-term management

Long-term management can involve various measures at various stages, including:

Removal of nurse species.
Thinning and coppicing to develop a complex structure.
Filling in gaps where plantings have failed. However, consider the value of keeping gaps open.
Maintaining rides to retain open ground and edge for wildlife such as butterflies.
Retaining both standing and fallen deadwood where it occurs. This is important for a range of invertebrates and hole nesting birds (e.g. woodpeckers).
Management of deer and grazing. Deer numbers must be kept low to ensure regeneration and structure are maintained. Low intensity grazing can be beneficial particularly to ground flora.
Encouraging a diffuse edge to other e.g. open habitats, will add considerable wildlife interest.

Relevant case study

We currently have no case studies for this habitat type. If you know of one and would like it to feature on the site contact us.

The information set out within this advisory sheet in no way constitutes legal or regulatory advice and is based on circumstances and facts as they existed at the time Nature After Minerals compiled this document. Should there be a change in circumstances or facts, then this may adversely affect any recommendations, opinions or findings contained within this document