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The wetlands and the areas of pastureland at the bottom of the valley are natural areas resulting from traditional agro-pastoral practices. In order to maintain the open nature of these areas and avoid too much expansion, they need to be managed. There are three possible ways of going about this:
- Clearing of the area every 5 to 10 years. The aim of clearing is merely to limit the expansion of young trees and shrubs in open areas. It is carried out manually and allows the person performing the activity to be highly selective when required. For example, maintaining a small number of shrubs that will rapidly form a dense copse offering a different micro-climate to that of the open area and that is conducive to the development of several insects which in turn will serve to feed birds, reptiles and others.
The clearing is carried out approximately every 5 to 10 years, depending on the speed at which the trees and shrubs are growing. This technique has the advantage of allowing the open areas to develop over time: heathland that is dotted with very scattered copses after the cutter has moved through, progressively moving towards a shrubbier heath, before the next management cycle takes place. When several sites are managed in this way in the same region, and as long as the clearing has been carried out by alternating between sites, the region offers a range of different areas of heathland (or pastureland) at various stages of recolonisation and therefore satisfying the ecological needs of a larger number of species than a more homogenous way of managing all of the sites.
- Late mowing managed by a farmer.
- Extensive grazing managed by a farmer.
D1. Preparations for grazing infrastructure
Compared to mowing, grazing lends a certain heterogeneity to the area. At the end of the grazing season, there is a clear contrast in the height of vegetation or in the density of small scrubs between the areas containing a wealth of crops that are popular with livestock and areas that contain fewer. Furthermore, the livestock moving repeatedly over the same places leaves bare patches of earth which promotes the germination of plant species requiring a great deal of light and/or little competition between species.
It may be necessary to delineate refuge areas here too, but not for the same reasons as for mowing. In fact, the animals alternate their browsing areas from day to day and over the course of the season. Smaller wildlife is therefore able to move around quite freely in order to avoid being trampled upon or devoured. On the other hand, as the grazing season generally lasts for several months, the flowering and seed formation of certain plants will inevitably take place during this season. Whenever the pastureland supports a population of rare or endangered plants, this population could be partitioned off and made inaccessible to livestock or at least during the most sensitive period in the plant's life cycle.
Additionally, cattle stocking rates (number of animals per hectare) are very low in order to safeguard the refusal zones, simultaneously offering refuge to small wildlife.
Highland cattle grazing the Fagne de Wiaupont (Domaine Provincial de Mirwart).
D2. Preparation for management by mowing
Mowing may be manual or mechanical. The first scenario requires hard labour, even for very small areas of land. Manual mowing is generally carried out by groups of volunteers involved in the site management.
Usually, however, mechanical mowing is carried out with the help of an agricultural tractor. This technique is very effective for managing the clearing of a site. But not all sites lend themselves well to this form of management which requires easy access for the machine, solid ground that is free of stones and a microrelief of the flat surface. Where it is possible, the hay is preferably removed from the area so as not to enrich it with decomposing organic matter. The groups of plant species we wish to preserve are often dependent on soil that is poor in nutrients.
Late mowing, typically after 15 July, gives the plants time to produce their seeds and therefore to multiply before being cut down. The fauna also benefits from late mowing: for example, ground-breeding birds will have the time to raise their brood, butterfly larvae will have time to hatch, etc.
The mower's movements are very sudden for the small wildlife. To avoid causing any damage to the insect and reptile population, among others, large refuge areas are preserved and are not mown. The location of the refuge areas in a given area of heath- or pastureland may remain the same for several years or may change from one year to the next.