English summary - Natuurherstel Korenburgerveen
Peatbog restoration programme of the Korenburgerveen
The Korenburgerveen (pSCI) nature area covers 510 hectares; it is located near the eastern border of the Netherlands close to Winterswijk in the province Gelderland. Ecologically the Korenburgerveen is a valuable peat area and is one of the few remaining areas in the Netherlands with peat bog life communities (habitat type 7120). Apart from peat bog, the nature area is also characterized by the presence of varying habitat types, such as low fen marsh bogs (priority habitat type 7210), wet moorlands, nutrient-poor grasslands (habitat type 6410) and peat forests (priority habitat type 91D0). Thanks to the presence of these different types of vegetation and the gradients among the different environments, the compounded species are particularly varied in comparison with other peat areas.
One of the threats to the peat area is dehydration. In the second half of the 19th Century the acrotelm, i.e. the top layer which consists of live peat moss with a large water absorption capacity, was dug off in large parts of the territory for fuel. As a result the peat now has lower water absorption and the water level fluctuations and surface water drainage have become greater. It is only in places where the peat was dug leaving deep pits that regenerative peat can be found. Due also to former drainage for the supply to the surrounding agricultural land the Korenburgerveen has become dehydrated. Due to dehydration the peat mass mineralizes and internal eutrophication occurs. Another threat is formed by external eutrophication by water which flows into the Korenburgerveen from the surrounding agricultural land. As a consequence of dehydration and eutrophication the typical species which depended on the peat bogs, have disappeared. Failing an improvement of the hydrological situation the former open landscape will rapidly be overgrown with thicket and forest. Acidification forms a threat locally, which particularly plays a role in the nutrient-poor grasslands which are home to many different species and in which many plants that are threatened with extinction, occur. The influence of calciferous ground water is of life importance.
To preserve the precious life communities and varied habitat types of the Korenburgerveen for the future, the “hydrological plan for the restoration of the Korgenburgerveen” (Hullenaar, Febr. 2000) has been drawn up. The restoration measures are specifically aimed at water conservation and curbing influences of eutrophication. Measures to curb the influx of nutrient agricultural water have already been implemented by assigning reservation grounds in the border zone and hydrological debarkation of agriculatural areas. Thus the pre-conditions for the implementation of hydrological measures in the peat bog area itself are met.
To avoid dehydration, the peat bog area is divided into a number of compartments by erecting wooden sheet piling, thus avoiding surface outflux of any precipitation surplus. In addition, the water level is raised in a number of water courses to reduce its draining effect. Thanks to the permanently wetter conditions a new acrotelm can develop out of the peat bogs which still remain. The new acrotelm will cover the area and overgrow the sheet piling. This new layer of peat moss (Spaghnum sp.) will retain water and reduce the water level fluctuations. This is favourable to the development of typical peat bog species. Wildshoots will be strongly reduced by the water conservation. In the low fen marshes it is important that ground water influences are maintained. The measures against dehydration and eutrophication will result here in a moderately nutrient environment which is under the influence of the ground water.
In the nutrient-poor grass lands the fluctuation in the water level will be tempered and the influence of calciferous seepage will be maintained. This will result in an improved situation for species as parnassia, orchids and heidekartelblad In view of the vulnerability of the species as well as the life communities in the Korenburgerveen, careful waterlevel management and monitoring the effects are important. This is why the water level is gradually raised so that it can be checked via the monitoring programme whether the system is developing in the desired directions or that adjustments are needed.
In order to obtain people’s support for the restoration provisions as well as the conservation of the Korenburgerveen it is essential that the area remains accessible by means of excursions for visitors and people living in the vicinity. The plan provides in the construction of a path of planking and a vantagepoint. The public will be informed on special gatherings, by distributing brochures and showing videos about the necessity of carrying out the restoration project.
The Korenburgerveen is owned by the municipality Winterswijk, the Marke Vragenderveen Foundation and Natuurmonumenten. A joint venture agreement for the peat bog restoration programme has been entered into by the land owners, whereby Natuurmonumenten will act as co-ordinator for the realization of the project.