Dry heathlands and sandy open grasslands in a suburban environment in the south of Brussels (Belgium) : Assessment of the conservation status

The Brabant sablo-limoneux region is located in the south and near Brussels, in the phytogeographic district of Brabant (Atlantic domain). This region is characterized by a high diversity of local ecological conditions due to the alternance of important tertiary sand outcrops and quaternary silty layers. The agro-sylvo-pastoral activities, which were practiced on these sandy and sand-silty soils for centuries, caused the evolution of the climactic forest into semi-natural habitats such as dry heathland, sandy grassland and grassheath. The evolution of the heathland distribution from 1770 to the present has been studied on the scale of the Dyle hydrographic subbasin (43.000 ha). It is characterized by an important regression of this habitat in the study area (from 1460 ha in 1770 to 72 ha in 2006), mainly due to Pinus sylvestris orchards, and more recently, to urbanisation caused by the proximity of Brussels. A generalized ageing and an environmental closing characterize the evolution of heathland physiognomy since the middle of the 20th century. The phytosociology of heathlands, sandy grasslands and grassheaths has been characterized and 19 groups of vegetation have been differentiated. Among the 393 listed higher plant species, more than 30 are of great conservation interest in the regional context. A hierarchisation of restoration priorities has been established on the scale of the studied hydrographic subbasin and management measures have been proposed.