A thorough experiment
The excavation of land for the restoration of heathland has been done before, but rarely on such a large scale as in Noordenveld. The national knowledge network for nature conservation and development (OBN) saw this as an opportunity for a thorough experiment. Researchers will try a number of methods on a section of excavated land to accelerate the development of heathland in the excavated soils. The fact that an area consisted of ¿¿heathland before it was turned into farmland (such as the Noordenveld) does not mean that the heathland automatically returns when the farmer leaves. Excavating the top layer is an important first step: this removes the nutrients derived from fertilizer. This is necessary because heathland requires soil that is lacking in nutrients. However, this process does not guarantee a fast return of heathland. If it holds off, the other plants are liable to take possession of the soils. And in unlucky cases, they will not be willing to relinquish their position.
Sometimes managers want to accelerate the development of heath by spreading mown heathland elsewhere. This contains seeds that advance the establishment of heather plants. Another possibility is to use ‘plagsel’ (the removed topsoil with vegetation), which apart from seeds also contains a rich soil life (insects, fungi, micro-organisms). Another important factor that is often attempted to influence is the acidity of the soil. Heathlands are naturally acidic, and most types of heather feel right at home there. Some rare heathers types appear in less acidic sites.
All possible combinations
The question for practical research in the Noordenveld is: what actually works best? Is ‘plagsel’ more effective than heather shavings? Does it help to acidify the soil or is it better to lime it? And do these methods accelerate the intended development, or might you as well, or even better, watch and let nature take its course? All possible combinations of these measures (including doing nothing) are tried out in the Noordenveld, both on dry and wet surfaces in sections of at least 25 by 25 meters. In total, there are 54 of those squares. The material (shavings and ‘plagsel’) comes from the immediate area.
For the future
The trial will start in October and will run for at least five years. The results are especially important for future projects elsewhere. For the Dwingelderveld itself, they will only come in handy for some redirection here and there. Heather shavings have been spread on the excavated soils in order to promote the restoration of the heathland.