De Levende Natuur nummer 5 van 2005 (English summary)


Herstel van de heide


DLN 2005-5

Heathland relics in the sandy region of Flanders: prospects for a bright future?

Piessens, K., H.A.I. Stieperaere, T.E.V, de Beelde & M.A. Hermy

Heathland relics in the sandy region of Flanders have always been neglected compared to the heaths in the Campine region. Nevertheless, important heathland relics containing a unique vegetation can be found here. Compared to the heathlands in the Campine region however patches in this region are often very small and strongly fragmented. This high degree of fragmentation has severe consequences for the heathland plant community in this area. Especially negative effects of low connectivity between the patches could be observed. Nevertheless, recent research has shown large opportunities for heathland restoration in the area. Since restoration of large areas only seems to be feasible in a small number of cases, the best option is a combination of these large patches with a network of smaller patches scattered in the forests surrounding them, e.g. on clearcut areas or along forest paths. Assuring suitable light conditions and preventing the build up of litter is very important. However, the severe fragmentation of these heathlands, the large amounts of atmospheric deposition present in the region, the threat of exotic species and the incompatibility with present forestry practices, can possibly cast a shadow on these bright prospects.

The misunderstanding on biodiversity conservation in heathlands by means of nature target types

Smidt, J.T. de

Nature target types are a strong instrument to chose the best strategy for developing new nature that connects isolated nature reserves by means of an ecological network. This new nature development is done on arable land that often lies between existing nature. The targets chosen in a particular case are based on the landscape ecological information of the location itself and on the vegetation ecological knowledge that is found in the relevant literature. Together they form the best available knowledge to chose the target that closest meets the aim to restore ecological spatial structure and function on that location. Unfortunately nature target types are also used in existing nature, as a management effectivity test. For that reason managers must focus on the species and factors that are mentioned in the manual, because the budget put at their disposal depends on reaching the target. Species and communities that do not fit in the description of the type, can easily be left out of focus. As a consequence important tributes to biodiversity can easily get lost, in particular when they depend on the complexity on landscape scale.

Serra da Estrela as a reference area for the restoration of heath landscapes in the Lowlands

Jansen, J.

The key to success of heathland-based farming in the conservation of semi-natural biotopes and biodiversity is the maintenance of low nutrient levels in the landscape, in combination with small-scaled repeated land-use practices. Traditional farmers have been safeguarding a number of EU-directives. For restoration projects in former heathland areas in the Lowlands, Serra da Estrela (Portugal) can be used as a reference area. In this area a range of applications can be observed, which can be of use to modern Dutch nature and environmental management. The present paper indicates that heathland-based farming in combination with new modern land-use options may constitute a sustainable basis for maintaining a scenic landscape, conserving its biodiversity, genetic crops and breeds and other cultural values.

Effects og changes in composition of the atmospheric nitrogen deposition on Dutch heathlands

Berg, L.J.L. & J.G.M. Roelofs

One of the main threats on heathlands in The Netherlands in recent decades is the increased atmospheric deposition of nitrogen. The increase in nitrogen deposition was suggested to be a strong determining factor in vegetation composition. However from recent experiments it became clear that the form of nitrogen deposited (reduced or oxidised) is of higher importance and that mainly the reduced form (NHx) causes the decline of characteristic herbaceous species in heathlands and species-rich grasslands. Mechanisms for the effects of reduced nitrogen in the soil are discussed and related to the decline of sensitive species and the increase of more general species (mainly grasses).

National Park Dwingelerveld: External hydrological measures are required for a sustainable development of this large wet heathland reserve

Everts, F.H., G.J. Baaijens, A.P. Grootjans, N.P.J. de Vries & A. Verschoor

The Dwingelerveld is an important heathland reserve in the northern part of the Netherlands. It consists of a mixture of forest, heathland, bogs and sand drifts. The area of wet heathland is among the largest in Europe. Hydrological restoration measures in the Dwingelerveld have led to a certain recovery of the characteristic features of the area. Internal measures have proven to be relatively easy to implement, because most of the area is owned by state or private nature conservation organizations. Hydrological measures to increase water levels in the surrounding river valleys are still being opposed by private farmers. The internal hydrological measures have resulted in successful restoration of many small bogs, but other areas still suffer from low water levels during the summer. Additional rewetting, in particular in the central and surrounding agricultural areas are being considered, but it will take much time to really implement such measures. Recently, three new farms were built in the valley of the Dwingelerstroom. In the future the present boundaries of the National Park will have to be re-considered, since much of the hydrological infiltration areas that supply the reserve with groundwater lay outside the present reserve boundaries.

Restoration of degraded dry and wet heaths and acidic grasslands in The Netherlands

Dorland, E., R. Bobbink & E. Brouwer

Most of the bottlenecks in the restoration of dry and wet heaths have been solved. A combination of restoration measures is generally necessary and most successful. In eutrophicated and acidified dry and wet heaths small-scale turf cutting and liming is advised, while in wet heaths desiccation should be tackled as well. Reintroduction of plant species should seriously be considered when seeds of target species are lacking in the seed bank and refuge populations are not present. A prerequisite is that the abiotic soil conditions have been successfully restored. Catchment liming is a relative new and potential successful measure to restore acidified heath systems on a larger scale. Soil conditions and moorland pool vegetation are improved, but restoration of the former species-rich wet heath vegetation may require more time. The sustainability of restoration measures is increasing. Their positive effects can still be found 10-15 years after. The reduced atmospheric deposition of acidifying compounds, as a result of lower emissions, is the major cause of this increase in sustainability.

Conditions and risks of reintroduction

Vergeer, P. & N.J. Ouborg

In The Netherlands, heathlands and species-rich grassland are strongly reduced in both area and habitat quality mainly due to fragmentation, eutrophication and acidification. As a result, many plant and animal species have become (locally) extinct, or are threatened by extinction as they are forced into small and isolated habitat patches. In this paper we describe several genetic reasons for the loss and threatening of these plant species. We investigated the possibility to use reintroduction as a management measure in order to preserve these small and isolated populations from extinction. Moreover we discussed several reintroduction strategies by using plant material from the local population and from non-local large, non-local small and several non-local populations.

The application of hay: recipe for rapid establishment of new plant communities?

Bekker, R.M., L.J.L. van den Berg, R.J. Strykstra & R. Verhagen

In this study we evaluated the application of hay to accelerate restoration of low-productive plant communities on former agricultural land after removal of the top soil. Characteristic target communities in these sites are heathlands and species-rich grasslands. However, the success of these restoration and development measures is in general low and sites develop into ruderal plant communities. Our analysis demonstrates that the addition of litter and/or hay from species-rich grasslands and heathlands can accelerate the development of characteristic target communities on former agricultural fields significantly. Both in numbers of established target species and in the reduction of the percentage cover of non-target plant species.

Large grazers as large seeders in heathlands

Mouissie, A.M.

Large grazers play an important role in the dispersal of plant seeds in heathlands. Many viable seeds germinate in cattle dung, horse dung and deer dung and many species are capable of surviving the digestive tract. Dispersal distances of seeds carried by large grazers are much higher than via wind dispersal. This was concluded from model simulations using measured seed retention data in the herbivore guts and furs. Hence, large grazers can connect distant plant populations and introduce seeds in ecological restoration sites. Unfortunately more seeds are dispersed from nutrient-rich soils to nutrient-poor soils than vice versa. Therefore, many unwanted species may be introduced in ecological restoration sites and large herbivores may even pose a threat to the conservation of heathlands. It is advised to take these results into consideration when creating ecological restoration sites and introducing large grazers into heterogeneous nature reserves with heathlands and nutrient-rich grasslands.

Do grazing on moist heathland and the rare butterfly Maculinea alcon go together?

Ketelaar, R. & M.F. Wallis de Vries

Grazing in general, but in moist heathland systems in particular is a controversial nature management practice. Much of this controversy is related to high expectations in theory, on the one hand, and sometimes disappointing results in practice on the other hand. In this article we describe recent insights in the role of grazing in the conservation and management of the endangered butterfly Maculinea alcon in The Netherlands as an example of a fauna species of moist heathland. A comparison of 127 heathlands revealed that grazing can contribute to a more diverse vegetation structure which is essential for the survival of M. alcon. In three nature reserves (Lankheet, Kampina and Plateaux/Hageven) the population of M. alcon recently recovered under a grazing regime. We conclude that these successes originate in the development and implementation of a specific set of measures, based on local conditions. Grazing is always one of the measures taken, in combination with small-scale measures like mowing and sod-cutting. We conclude that grazing is a valuable nature management tool in moist heathlands, but can only be regarded as the right choice when a number of conditions apply. Most important are a minimum size of the grazed compartment (50 ha), a minimum size of vulnerable moist heathland (1 ha) and a good knowledge and monitoring of relict populations of threatened and/or characteristic species. In the end, the local conditions drive the possibilities for nature management; an overall recipe cannot be applied to all locations.

Attention for reptiles in heathland management practice

Stumpel, A.H.P.

Reptiles are a threatened group of animals in The Netherlands and their habitats are affected continuously. As heathlands form their most important habitat, an optimal nature management is needed. Traditional management measures do generally not take into account the needs of reptiles. Heathland management should aim at old mature heather of at least 30 years old. Current measures such as mowing, burning and grazing destroy the required structure of plants or prevent its development. Managers should treat the heath as a scrub vegetation, and intervene only if too much shadow urges to cut some trees. The necessity is advocated of selecting the best habitats of reptiles and practicing an optimal management at least there.

Recovery of the lichens in heathlands

Aptroot, A. & C.M. van Herk

Terricolous lichens are a characteristic element of Atlantic heathlands. The abundance of species with a predominantly boreo-alpine distribution in Dutch heathlands indicates the affinity with more boreal vegetation types. The lichen diversity is generally highest in small, often accidented sandy enclaves. Attempts to recover the lichen diversity in heathlands which have become depauperate are evaluated. Stripping of the top soil often has good results. Grazing has either no effects (on the recovery of lichens) or a negative effect, especially when cattle densities are high and the area consist of a mosaic of vulnerable, nutrient-poor vegetations and eutrophicated areas.

How to protect the Saddle-backed bush-cricket?

Reemer, M., R.F.M. Krekels & P.H. van Hoof

The Dutch populations of the Saddle-backed bush-cricket (Ephippiger ephippiger) mark the northern limit of its distribution. Elsewhere in Northwestern Europe the species is extremely rare. The Dutch populations have suffered from a serious decline in the past decades. There are 11 populations left, of which 10 are situated in the province of Gelderland, especially in the Veluwe area. It seems necessary to take measures on a very short term to avoid disappearance of the species from The Netherlands. The main causes of the decline are the decrease of heathland area and the degradation in quality of the remaining area of this habitat. Management on population level is discussed and the necessity of defragmentating heathland areas is underlined. For the development of a succesful defragmentation policy, it will be necessary to adapt national and provincial forest legislation.

Changes are needed in the management of heathlands

Tooren, B.F. van, R. Bobbink, R.M. Bekker, L.J.L. van den Berg, I.C. Knevel & H.L. Schimmel - ten Kate

Heathlands are semi-natural ecosystems and should be maintained as such. Despite incorporation of many heathlands into nature reserves and successful application of restoration measures such as sod-cutting and grazing to reduce grass encroachment and a shift towards monotonous grasslands, heathlands have drastically decreased both in area as in biodiversity. Until now, much of the attention in research, conservation and restoration in heathlands was focused on the vegetation. It became clear that restoration aimed and developed for characteristic plant species, is not always succesful for characteristic animal species. Restoration measures for plant and animal species require different approaches on different scales. Where plant species can be maintained by adequately restoring the abiotic conditions and the restrictions in dispersal (reintroduction) for the vegetation, fauna needs many different (small and large) habitats (foraging, nesting etc). Restoration for both plant and animal communities, should therefore focus on creating many small-scale projects which include a variety of landscape elements, ecosystems and habitats. Special attention should be paid to raise awareness for small-scale human activities and disturbances which can create heterogeinity in heathlands and hence, increase biodiversity. These activities may also have a historical, cultural value as they were once part of this landscape. In order to apply existing restoration measures with more success, and for both flora and fauna, intensive research and monitoring is needed on the effects of restoration measures on characteristic heathland fauna. This applies also for the effects of grazing in heathlands. On the landscape level, restoration and conservation should focus integrating different landscape elements for the conservation of heathlands and their surrounding ecosystems as a whole. This will involve increasing connectivity between landscape elements and controlling drainage of large areas of the landscape.