Information and Advisory Note Number 44 Back to menu
1.1 Developments such as the construction and widening of paths, hill tracks and
roads, pipeline installation and building work can all result in the loss of
moorland habitat The general principle should be to restore appropriate native
1.2 This note is principally concerned with the re-establishment of heather (Calluna vulgaris), for which there is now a reasonable body of experience. Heather, with or without a grass nurse component, provides a good starting point from which a diverse dwarf-shrub community may develop.
1.3 There are three principal scenarios for heather restoration:
1.4 There are five methods of restoring heather cover.
1.5 Removal and replacement of turf is usually the best option for new schemes.
This method permits restoration of a near full range of plant community species
and possibly elements of the invertebrate fauna. It may also produce more rapid
results as it largely involves vegetative regrowth of established plants All the
other methods rely on seedling germination and establishment.
1.6 Topsoil" use and large scale re-turfing are normally options only if the site is yet to be excavated or if there is a potential donor site which would otherwise be destroyed However, in exceptional circumstances, where re-turfing is likely to be the only way of restoring vegetation cover, it might be possible to take turfs from a donor site where revegetation by other methods is a realistic option If the turf area required is small, individual turfs may be lifted from within the surrounding heather matrix.
1.7 All other methods depend on the collection of seed and the provision of suitable seedbed conditions. Heather seed is very small and can be produced in great abundance A dense, vigorously flowering, ungrazed stand of heather can produce up to 1 million seeds m"2 and a similarly sized viable seedbank can accumulate in the top 3 - 4 cm of the soil beneath such a stand Seed production may be only 10% of this where the heather is less vigorous, patchy, or grazed.
1.8 Heather seed does not ripen until about October and most is shed from the seed capsules by late January Both dates vary from year to year Germination requires light, warmth and moisture, but waterlogging is inimical In the uplands most germination usually occurs in the second half of the summer If conditions are unsuitable, seed will remain dormant and can persist in the seedbank for decades although viability varies greatly according to site conditions.
1.9 Seedlings are highly susceptible to uprooting by surface erosion, due to water, wind, or frost heave, and to grazing and trampling They are also vulnerable to desiccation due to drought or drying winds.
110 The ideal seedbed for heather is-
1.11 The condition of the seedbed is central to any restoration and its
stability is usually the most problematic aspect.
112 Direct seeding and planting-out are possible remedial treatments for both new sites and sites of incorrect or failed restoration. The presence of topsoil, although desirable, is not absolutely essential provided the substrate can be stabilised Unless the substrate is correctly consolidated and protected from even small-scale surface erosion due to ram, wind or frost-heave, there is a high risk of failure. A grass nurse is usually regarded as essential to reduce erosion and ameliorate the microclimate.
1.13 Planting is relatively costly but reduces the risk of failure by removing the highly vulnerable seedling stage, though frost heave may still lift entire plugs. Erosion limitation measures may be required. Especially on slopes and at higher altitudes, heather should be planted into an established grass nurse.
1.14 All restored areas benefit from some protection from grazing animals until they are well established and they may fail if this cannot be provided.
1.15 Despite numerous studies and schemes there remain many uncertainties in technique, especially for steep or high altitude sites. It is therefore wise to resist development proposals involving soil disturbance or denudation in the latter areas.
2 1 Where there is existing heather cover, the ideal is to remove it with some
of the soil, store and replace. Traditional practice when cutting peats is to
remove the surface vegetation as turfs about 10 cm thick and place these,
roughly butted together, on to the bed of the cut area Usually rooting takes
place readily. This minimises the risk of erosion of the peat bank and loss of
grazing. Stress to the plants is reduced by the immediate transfer on to a moist
peat substrate. The situation is different where contractors are working on a
site because it is rarely possible to remove and replace the turf in an almost
2 2 To minimise evapotranspiration stress, where there is building or mature heather cover it should be burned or cut following normal good practice relative to its age and condition. Ideally it should be given one season for regrowth before stripping.
2 3 Turf transfer is likely to be more successful if earned out in spring or autumn rather than June to August when desiccation is more likely.
2 4 Sufficient turf depth is important to minimise root disturbance and the risk of desiccation in storage The area of each turf is important' large turfs minimise the amount of edge at which roots are severed and the soil is exposed to drying. However, there are practical limits imposed by size and weight Typically, the aim should be to remove turfs about 1 m x 1 m and 20 - 30 cm thick. Special equipment has been developed for use on lowland heaths in England and may be available. Otherwise, stripping will be by modified excavator bucket, with turfs loaded onto pallets which should be plastic sheeted to aid in sliding the turfs on and off.
2.5 The storage site will require preparation While this is best located off heather (to avoid additional damage to the habitat), moving turfs long distances will cause them to break apart and adds significantly to cost. If stored on heathland, existing heather should be cut or burned and sheeted with Geotextiles so that the turfs can be deposited and lifted with minimal impact. If working in a construction corridor, the best approach is simply to lower turfs onto pallets alongside the trench. Similarly, excavated soil should be stored as a low mound along the corridor, being placed on mats, sand or Terram to protect the vegetation underneath it.
2.6 Turfs cannot be stacked. In dry weather, desiccation may occur rapidly so provision should be made to cover them or to water if required Consider setting up an irrigation system As these measures are likely to be neglected without close supervision, it is essential to plan to replace turfs as soon as possible. With linear schemes, it is best to work in short sections.
2.7 Prior to replacement, subsoil must be replaced, levelled and firmed to the correct density to minimise the risk of uneven settlement Turfs are replaced, butted close, and firmed to ensure that voids do not remain Any unavoidable gaps should be filled with topsoil Large patches of bare ground should be seeded or planted to prevent erosion.
3.1 Where excavation is involved and the site carries heather (and turf removal
and restoration is not an option), the existing surface should be stripped and
stored for reuse. It is important to distinguish between the heather litter
layer plus the upper 2 cm of the humic layer which contains the bulk of seed,
the rest of the humic layer which is the medium for seedling establishment, and
the underlying peat or mineral soil. The seedbank may be tested by taking
samples of litter and soil for germination trials (see 4 8-49) With more than
300 seedlings m"2, or preferably more than 500 seedlings m"2, an adequate
seedbank exists. If the abundance is less, supplementary seeding may be required.
3.2 If the site is grassy and relatively fertile, reuse of the topsoil may result in dense or tall grass growth This may either prevent heather seed from germinating or out-compete the heather seedlings Deschampsia flexuosa does not form a seed bank but both Agrostis capillaris and Molinia caerulea do. The latter is undesirable in restorations because of its competitive nature If grass growth is excessive application of a selective graminicide may be beneficial On the other hand, short open growth may provide a valuable nurse, stabilising the soil and giving wind-shelter.
3.3 Prior to litter and soil stripping, existing above-ground vegetation should be cleared by burning, flailing or, if the site is sufficiently level, by cutting with a forage harvester. The latter, if done in winter, may take a seed crop for use in re-seeding the site.
3.4 Soil stripping requires removing a thin layer of topsoil. As this is difficult to do accurately supervision at this stage is important Care should also be exercised in wet or frost conditions when soil structure can be seriously damaged by handling.
3.5 The soil should be stored in mounds not more than 1.5 m high for as short a time as possible. Deterioration affecting soil structure and nutrient levels takes place in the first 1-3 months of storage so the ideal is to transfer soil from the area being stripped to an adjacent receptor site in one operation or at most within two weeks. If soil is stored on polythene or similar sheeting this facilitates subsequent removal.
3.6 Soil compaction, producing impeded drainage, may have occurred if vehicles have been running over the restoration site Sub-soiling may be necessary. Subsoils and topsoil should be replaced in sequence. The surface needs to be firm in order to aid germination, reduce water loss and reduce susceptibility to frost heave it may be firmed down by light rolling when dry to approximately its original condition. Over-consolidation must be avoided.
3 7 Small depressions offer better conditions of moisture and humidity for seedling regeneration than flat surfaces Trampling and vehicle tyres, or the use of a ridge (Cambridge) roller, can produce these microhabitats but any deliberate use of these methods must take careful account of soil conditions as compaction on wet substrates can be damaging.
3.8 When soil is replaced, particular attention must be given to stabilising the surface, especially on slopes. In all cases, it is important to divert any lines of surface drainage flow away from the reseed, taking care not to initiate new lines of erosion There are a number of stabilisation options, which may be combined
3 9 Liquid stabilising agents should not be used as they seem to inhibit plant establishment
4.1 This requires relatively even ground with easy access and heather in the
building or mature phase. To ensure the maximum amount of ripe seed still in
capsules harvesting should take place between early October and mid January,
though there is sometimes ample seed in capsules as late as April Cut shoots
should be about 15 cm long. If taken wet and stored there is a risk of
overheating affecting seed viability. Dry, frosty conditions are ideal but if
there is frost rime on the plants they should not be harvested as the rime will
make them very wet in store.
4 2 The cut material is spread thinly so that the soil surface is not obscured but adequate seed is available Recommended application rates are 600 -1200 g m"2 with the size of the area to be cut depending on the density and productivity of the heather. Reported examples of coverage range from less than the size of the donor site up to three times larger. It is claimed that the stem material helps to stabilise small scale soil movement and improves humidity at the soil surface but an alternative view is that the litter becomes mobile in wind and can damage or bury
seedlings Brashings may be used to reduce this risk (see 3.8)
4 3 Using a garden vacuum with a two-stroke
engine or an industrial vacuum cleaner with a
generator it is possible to collect 75 - 250 kg
of litter plus seed per day The ideal is to bum
the donor site following normal good practice in the preceding autumn, so making
access to the litter easy. Heat treatment of the seed also improves germination
rates The seed-litter material may be collected in winter and stored or sown at
once Alternatively, it may be collected in early summer when, being vernalised,
a proportion of the seed will germinate as soon as it is sown provided seedbed
and germination conditions are suitable (see 18-110) If collected when dry the
material can be safely stored in dry, airy conditions without need of further
4 4 The decision on application rates depends on seed abundance in the litter Reported examples are in the range 10-120 g m"2. An application rate near the upper end of this range would be advisable
4 5 The Heather Trust has developed a capsule harvester consisting of a rotary
brush and collecting box which is towed by a tractor. This removes only small
amounts of leaf and stem material On a good seed-producing stand it is possible
to collect, sift, bulk and bag enough material in one day to treat 10 ha. There
are also commercially available rotary brushes, hydraulically driven and
attachable to the front loader of a tractor, which have been used successfully
to collect heather seed e.g. the RSPB have used a Suton Sweeper Bucket Brush to
collect up to 500 kg of seed capsules per day at a site in North Wales. If large
amounts of woody litter are present, they can be removed by sieving through a 1
cm (or half inch) mesh.
4.6 As the volumes of collected material are relatively small, seed capsules can be collected wet and dried by spreading thinly under cover in an airy place The material should be less than 15 cm deep but it can be slightly more if it is turned occasionally.
4 7 If bulked with equal amounts of dry sawdust before bagging this will minimise the risk of it overheating. Bulking can also facilitate sowing. Large quantities can be mixed in a cement mixer. When sowing application rates should be increased to take account of the more dilute seed content.
4.8 For storage bags, use paper, jute or woven polypropylene which allow air circulation.
4.9 Most germination occurs in the second
half of summer when soils are moist and
warm. Seed and capsules may be spread as
soon as they are gathered in autumn and will
germinate after vernalisation and wetting and
drying in the following summer. The earlier
germination occurs the better as this ensures
maximum growth and rooting before winter
and reduces the risk of displacement by frost
4 10 Heather seed together with capsules and fine litter should be spread at 100
-150 g m"2 on a 1:1 mix of lime-free potting compost and coarse sand, gently
firmed into paper or fibre pots To test topsoil for its seedbank, the soil
should be thinly spread on the same compost and sand mix.
4 11 Ideally, propagation should be in a heated greenhouse kept at 18-25°C with mist sprayers to maintain moist but never waterlogged conditions. This should give 90% germination within 4 weeks Temperature fluctuation between 18 and 25°C can aid germination.
4.12 The seedlings should be thinned so that they can be planted with a plug of rooting medium, not bare-rooted. They can be hardened off at 22 weeks and planted out at 24 weeks. If a greenhouse is not available a warm, well-lit shed or polytube will do, though germination may be delayed.
4.13 Heather can also be propagated very effectively using cuttings Cuttings should be taken in June then grown on in peat plugs (or comparable alternative medium) in a mist unit, ready for planting out in late summer. Alternatively, cuttings can be rooted later and overwintered in the nursery before planting in the following year.
4 14 Timing of planting out is important. An early start gives plants the maximum time to develop the root system before winter
However, May is often dry and there is a consequent risk of plants dying Late June may be the optimum.
4 15 Planting density should be considered Nine plants m'2 is about the minimum to achieve reasonable coverage in less than five years: 100% cover is not required and if 60% cover is achieved after 7 years this should be regarded a success. For large sites it may be difficult to obtain sufficient material to plant at these densities over the whole area If this is the case consider planting in patches within a grass matrix.
5.1 Grass has several potential values It will trap wind-blown soil particles,
bind the soil while heather becomes established, and provide wind shelter In
many situations, grasses form part of the surrounding vegetation cover and are
therefore an appropriate component. Where heather cannot be established
initially, such as at high altitudes or if insufficient heather seeds or plants
are available, it may be possible to achieve or encourage a grass sward while
waiting for natural colonisation by heather over the long term.
5.2 However, a potential problem on moorland is that such newly established grass is likely to be much more palatable to herbivores than the surrounding vegetation. Unless the restored area is fenced this will attract high densities of animals which may hinder vegetation recovery or create a relatively green, fertile sward out of ecological and landscape character with the surrounding moorland. On road cutting sites high livestock numbers may also present a traffic hazard.
5.3 Agrostis capillaris, Anthoxanthum odoratum and Festuca ovina are appropriate grass nurse species. Agrostis castellena is another species which has been used successfully. It is a non-native species but said to be not very persistent. The Heather Trust has also used Holcus lanatus As the aim is an open sward with bare ground between plants, sowing rates should be around 1.5 - 3 g m"2 and could combine two grasses.
5 4 Seed should be sown as soon as possible after snow melt. A tested mix is, by weight, 45% Festuca rubra rubra, 25% Phleum bertolonii (cultivar S50), 15% Agrostis capillaris and 15% Poa pratensis. These grasses are non-competitive and wilt not spread into native moorland vegetation. Rather, mosses, heather and other plants will establish in time and ultimately displace them. The Phleum bertolonii is not a native upland species but is important in the mix as the cultivar specified makes quick initial growth Cultivars of the other species are not critical.
5 5 Sow at rates of at least 9 g m"2 and up to 15 g m'2 on steeper slopes and where topsoil is absent. The high rates are required to offset high mortality and slow establishment. Where there is topsoil, rake in to a depth of 1 cm.
5.6 On small sites, it may be possible to apply turfs cut from upland grassland or grass heath (see also 21 - 2.7) These turfs should be at least 5 cm thick and about 30 cm square. Fertiliser is not necessary Ensure that the edges of the turfed patch are level with the surrounding ground so that they are not exposed to wind. On sloping sites, turfs will need to be securely pegged or netted in place until established. After the following winter any turfs displaced by frost heave or wind should be replaced and secured.
6.1 Both correct pH and nutrient status are important. Germination of heather
seeds will occur over a range of pH from 3.2 to 6.6 but for long term survival
of heather plants a pH <5 is required The pH is not usually a problem if the
soil to be used has previously carried heather. If a grass nurse is to be used
then a pH>3 is required. This can be achieved by incorporating limestone dust,
at 100 g m-2, into the upper 5 cm of the soil.
6.2 The decision on whether to use fertiliser is more difficult as it will favour competing vegetation at the expense of the heather The consensus is that where heather seed is applied with a grass nurse, application of 3N:9P:9K fertiliser at 20 - 30 g m2 (50% slow release, 50% fast release) induces better growth of the nurse and better performance of the heather. It may be advisable to carry out growth trials on site to establish the optimum fertiliser rate.
6.3 At high altitude and other very v unproductive situations higher rates of application may be required. Ground limestone at 250 g m"2 and compound fertiliser (20N:20P:20K) at 30 - 40 g rrf2, plus additional ground mineral phosphate at 100 gm-2, should be applied and raked into the surface. If the first seeding fails and it is necessary to reseed the following year, only the compound fertiliser will need to be re-applied.
All restorations should be fenced against livestock, and hares and rabbits where present, for at least the first three years.
Bayfield, N.G & Aitken, R. (1992). Managing the impacts of recreation on
vegetation and soils: a review of techniques. Institute of Terrestrial Ecology,
EAMCTVol.4No.2(1996). Heathland Recreation. English Nature. (Articles describing practical experience of habitat restoration including techniques and costs.)
Environmental Advisory Unit, University of Liverpool (1988). Heathland Restoration: A Handbook of Techniques. British Gas, Southampton (Comprehensive and authoritative).
The Heather Trust Annual Reports The Heather Trust, The Cross, Kippen, Stirlingshire FK8 3DS (Frequently contains short articles about heather restoration trials in upland areas.)
Comments were kindly provided by Dr Philip Putwain (University of Liverpool), David Newborn (Game Conservancy), Sheila Rapson & Alan Ryder (RSK Environment), John Phillips, Pamela Todd & Isabel Guthrie (Heather Trust), Dr Helen Armstrong (SNH) and Dr Des Thompson (SNH).
Andrews Ward Associates
17 West Perry ,
Cambs PE18 0BX
Uplands and Peatlands Branch
Scottish Natural Heritage
2 Anderson Place, EDINBURGH EH6 5NP
Tel: 0131-447 4784
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