United Kingdom: England: Re-creating Heathland and Acid Grassland at Minsmere RSPB Nature Reserve

Project Stage:
Completed

Start Date:
1990-04-01

End Date:
2003-12-31

Primary Causes of Degradation

Degradation Description

Lowland heathland, confined mostly to Western Europe, is a priority for nature conservation because it is a rare and threatened habitat. In England it has declined by over 80% since 1800 due to losses to agriculture, forestry, urbanisation and infrastructure development. Much of what remains is fragmented and in poor condition. The UK holds about 20% of the international total of this habitat. As the heathland habitat declined, so did the populations of associated species, especially birds such as the stone curlew and woodlark.

Loss of heathland to arable farmland not only physically changes the habitat through vegetation removal but also causes changes in the soil chemistry and pH (decreases in pH and increases in soil nutrients) as the result of the addition of fertiliser and lime.

Reference Ecosystem Description

The project area was commercially managed arable farmland, cropped under licence by a local farmer, using a rotation of spring barley, winter barley, rye and linseed depending on the stage of rotation of a much larger cropping regime in the area. There was regular use of inorganic fertilisers and herbicides/pesticides and the overall biodiversity value of the area was low.

The project area is surrounded by extensive lowland heathland and acid grassland supporting a high diversity of characteristic flora and fauna including regionally or nationally important populations of several species including woodlark Lullula arborea, nightjar Caprimulgus europeus, Dartford warbler Sylvia undata, natterjack toad Epidalea calamita, ant-lion Euroleon nostras, silver-studded blue butterfly Plebejus argus and red-tipped cudweed Filago lutescens. Stone curlew Burhinus oedicnemus bred until 1969.

Project Goals

The objective of the project is the reversion of 186 ha of arable to Sandlings-type heath by re-creating a semi-natural habitat comprising 80% acid grassland and 20% heather/gorse, primarily to encourage re-colonisation by the nationally rare stone curlew and provide breeding and wintering habitat for woodlark. The work described here was the trial stage before large scale habitat re-creation was initiated.

Lowland heath and many of its associated species are recognised as conservation priorities in the UK and it was considered that habitat restoration and subsequent re-colonisation by key species at Minsmere would make a significant contribution to achieving the conservation goals set both by the RSPB and local and national conservation bodies.

It was also envisaged that the pioneering work at Minsmere would provide a template for similar habitat restoration/ creation projects elsewhere.

Monitoring

The project does not have a monitoring plan.

Stakeholders

The whole area is owned by the Royal Society for the Protection of Birds (RSPB) having been purchased in 1989 with the intention of re-creating heathland and acid grassland. As the largest re-creation project of its kind in the UK, the project was of interest to a wide range of nature conservation organisations, both locally and nationally. As much of the re-creation work was of a pioneering nature, initial small scale trials were developed and implemented with the University of Liverpool Botanic Gardens (1990 to 1998) and the Institute of Terrestrial Ecology (1998 to 2002). The overall planning of the work was by a Steering Committee composed of RSPB staff and academic advisers, with day to day operations carried out by reserve staff based on the reserve’s management plan.

Description of Project Activities:
The project area consisted of five fields in the northern part of the larger re-creation area. 1) Nutrient stripping - In an attempt to reduce soil nutrient levels, particularly extractable phosphorus and exchangeable calcium the whole area was cropped under licence between 1990 and 1996, with a combination of rye, barley and linseed. Minimal fertiliser application was allowed. 2) Soil acidification and vegetation establishment - five techniques were trialled depending on whether a heather dominated or acid grassland dominated vegetation community was desired. 2i) Heather heath (8 ha) - this field was ploughed to a depth of 15 cm in April 1996, then topped prior to the addition of elemental sulphur at a rate of 0.65 tonnes/ha in October 1996. It was then sprayed with glyphosphate and MCPA in September 1999 to remove ruderal weeds. A further 3 tonnes/ha of sulphur was applied in November 2000, principally around the margins of the field closest to the public rights of way. Heather and bell heather seed and clippings were spread on the sulphured areas in April 2002 and March 2003. 2ii) Acid grassland 1 (5.1 ha) - this field was ploughed to a depth of 15 cm in April 1996, then topped prior to the addition of elemental sulphur at a rate of 2.58 tonnes/ha in October 1996. It was then sprayed with glyphosphate and MCPA in September 1999 to remove ruderal weeds and with Roundup Bi-active in August 2000 to remove all re-colonising vegetation. An acid grassland mix (83% sheep's-fescue Festuca ovina, 10% common bent Agrostis capillaris and 7% fine-leaved sheep's-fescue Festuca filiformis by weight) was then sown at a rate of 20 kg/ha in September 2000. 2iii) Acid grassland 2 (6.1 ha) - this field was sprayed with Gramoxane in April 1996 then ploughed to a depth of 15 cm and pressed with a tractor-drawn roller before the addition of a 2.5 cm deep layer of bracken litter and 3.28 tonnes/ha of sulphur. Five to ten trailer loads of heather clippings and litter were spread over the field in April 1998 and May 1999. 2iv) Acid grassland 4 (33.5 ha) - as these fields appeared to be closer to the surrounding heathland in character, re-creation was attempted using a combination of sheep grazing and natural regeneration. The majority of the area was grazed by Speckled-faced Beulahs year round from January 1999 at an overall annual grazing intensity of 0.09 to 0.10 livestock units/ha. Sheep were excluded from areas with a high infestation of ragwort Senecio jacobaea using temporary electric fencing until the ragwort had been controlled by mowing and/or herbicide treatment.

Ecological Outcomes Achieved

Eliminate existing threats to the ecosystem:
All of the techniques applied at the field-scale have resulted in the creation of short, open grassland, despite the moderate levels of residual soil nutrients from agriculture remaining in the soil, and treatments involving the addition of elemental sulphur successfully lowered the pH of the soil to levels suitable for the establishment of acid grassland. Addition of sulphur and bracken litter reduced the soil pH from 7 at the start of the project to 4.5 in 2000. Addition of sulphur and re-seeding resulted in the highest cover of acid grassland plants. Addition of sulphur, bracken litter and heather cuttings was successful in creating a mixture of acid grassland and heathland. Natural regeneration on sandier soils has resulted in the establishment of the most botanically-rich acid grassland, containing a number of scarce annuals, including clustered clover Trifolium glomeratum, spring vetch Vicia lathyroides and smooth hawk's-beard Hypochaeris glabra. The sandier and more open parts of the reversion area have also been colonised by a number of rare ground beetles, including the Cockney, Polystichus connexus, the first recorded in Suffolk since 1828. Breeding stone curlews re-colonised the acid grassland in 2003. The re-created acid grassland is also used by as a feeding area by woodlarks, which nest on adjacent areas of heathland.

Factors limiting recovery of the ecosystem:
None.

Socio-Economic & Community Outcomes Achieved

Economic vitality and local livelihoods:
Not applicable.

Key Lessons Learned

Establishment of heathland and acid grassland and re-colonisation of the site by breeding stone curlews, silver-studded blue butterflies and a range of scarce ground beetles and plants are all indicators of the success of the project. The larger acid grassland re-creation project has contributed 28% of the UK Government’s National Biodiversity Action Plan target for lowland acid grassland creation.

The results clearly demonstrate that it is possible to establish heathland vegetation on ex-arable land by adding sulphur and heather litter. Acidification was undoubtedly necessary to provide suitable conditions for the establishment of heathland. Although the soil pH of non-acidified areas did decline significantly during the ten years following cessation of cropping, from 7.2 to 6.7 in one field and from 6.7 to 6.4 the other, it still remained higher than that suitable for the development of heathland vegetation. The quantities of sulphur required to reduce soil pH to a suitable level (typically pH 3.5 – 4.0) for the re-creation of heathland vary between soil types, and can be difficult to predict.

The rate of heathland establishment in acidified areas is variable, with a range of factors, including soil conditions, grazing levels and conditions during germination and establishment, contributing to this variability. The results show that it may often be necessary to continue adding litter in successive years until heathland plants have established and started setting seed.

Despite the success of the heathland creation at Minsmere, research and experience during this and other projects has demonstrated the considerable effort required to re-create heathland on ex-arable land, because of its usually unsuitable soil conditions and lack of a heathland seed bank. A far easier and more cost-effective option for re-creating this habitat is by removing conifers from afforested heathland, whose soils and seedbank are more similar to those of heathland. The re-creation of acid grassland is a more easily achievable objective on ex-arable land.

The results suggest that natural regeneration is the best method for developing species-rich, acid grassland on suitably nutrient-poor, sandy, ex-arable fields. Natural regeneration on the sandiest field at Minsmere resulted in a flora rich in annuals and scarce Ground Beetles. It was also the cheapest and generally easiest option, although it did require substantial control of Common Ragwort. In the end, concentrations of phosphorus do not appear to have limited the establishment of acid grassland plant species on this field or on either of the two acidified fields. By 2005 concentrations of Olsen extractable phosphorus in the sandiest field were 4.6 mg per litre, while concentrations in the two acidified fields were between 11.5-11.9 mg per litre, compared to 9.0 mg per litre on the adjacent, existing acid grassland. The higher concentrations of plant-available phosphorus in the soil of the acidified fields were probably caused by the process of soil acidification .

Where conditions are less suitable, i.e. on less sandy soils with a higher pH and higher concentrations of nutrients, the results show that addition of sulphur and the seeds and spores of acid grassland plants can be used to establish acid grassland. Even though it is possible to acidify these soils and establish the dominant acid grasses, these (re)-created grasslands are likely to lack the array of drought-prone annuals and invertebrates characteristic of sandy soils. Acidification will also have the potentially negative effect of reducing the biomass of earthworms available to feeding stone curlews. This having been said, re-creation of a relatively species-poor, acid grassland on otherwise unsuitable soils through acidification, is still likely to provide conservation benefits.

Finally, the results show that adding bracken or other suitable litter and cuttings from adjacent acid grasslands is a useful method for introducing seeds and spores of desirable plant species. Providing soil conditions and subsequent management are suitable, it is probably only necessary to introduce a relatively small quantity of litter. This could be applied on its own, or used to introduce additional desirable species to areas otherwise sown with a more species-poor, commercial mix of acid grassland species.

Long-Term Management

Long term management of the whole area is low intensity grazing, principally by sheep but also by rabbits which are present naturally. Rabbit grazing is important in providing suitable conditions for stone curlews and other acid grassland plants and invertebrates. An innovative and very successful technique for increasing rabbit numbers has been to leave piles of brash on the acid grassland, to provide shelter while the rabbits burrow to establish warrens. Small plots throughout the area are also being regularly rotovated, ploughed and sprayed with herbicide to provide disturbed conditions for nesting stone curlews.

Monitoring work consists of:
Development of acid grassland in random quadrats, every 2 years.
Habitat suitability for stone curlews – sward height, rabbit dropping density and amount of bare ground – on a 50 x 50 m grid annually since 2003.
Ground beetle assemblages using random pitfall traps in 1997 and 2004.
Breeding numbers and productivity of key bird species annually.

Sources and Amounts of Funding

RSPB
Countryside Stewardship and Higher Level Scheme
Heritage Lottery Fund’s “˜Tomorrow’s Heathland Heritage’ Sandlings Project
Suffolk Environmental Trust
SITA (landfill tax)

Primary Contact

Organizational Contact