The estate is part of the Lembeek woods, a so-called historic forest already visible on the Ferraris Map (circa 1770). It once formed part of a large forested complex including the Sonian Forest and the ‘Hallerbos’, of which it now constitutes, in a sense, the western extension. The forest covers an area of approximately 100 hectares. Three small streams, fed by local springs, traverse the forest, contributing to its remarkable ecological character.x alimentés par des sources locales, qui contribuent à son caractère écologique remarquable.

The construction of the château by Victor Brien at the end of the 1930s required only limited clearing. Except for a landscaped area stretching from the northern entrance to the château, most of the estate was entirely preserved by its owner. His wish was for the forest to be used by ULB for scientific and educational purposes, which has indeed been carried out.
Maintained and protected since Victor Brien’s death by the Victor Brien Fund and ULB, the Lembeek Forest exhibits impressive natural richness and is recognized for its biodiversity. It forms part of the Natura 2000 site “BE2400009 – Hallerbos en nabije boscomplexen met brongebieden en heiden”.
The forest’s substrate is primarily composed of Brusselian sand, which outcrops on the hilltops. On the slopes and in the valley bottoms, the substrate becomes enriched with finer elements (silt and clay).
Three main forest types are present :

  • An acidophilous Atlantic beech-oak forest (Natura 2000 Habitat: 9120), occupying the sandy, dry, acidic soils of the hilltops. Plant species typical of slowly decomposing humus (mor and moder) are observed here, including rowan (Sorbus aucuparia), silver birch (Betula pendula), wood sage (Teucrium scorodonia), carex pilulifera, and common veronica (Veronica officinalis). Very locally, at the forest edges, there are fragments of heathland with Common Heather (Calluna vulgaris).
  • A beech-oak forest with wood hyacinth and one-flowered melic grass (Natura 2000 Habitat: 9130) is found mainly on the slopes, on siltier, less acidic, and cooler soils. Plants indicative of moder humus are present, including common millet (Milium effusum), wood anemone (Anemone nemorosa), yellow dead-nettle (Lamium galeobdolon), wood spurge (Euphorbia amygdaloides), and daffodil (Narcissus spp.).
  • An alluvial forest with black alder and ash (Natura 2000 Habitat: 91E0) develops in valley bottoms, on wetter, nutrient-rich soils. Plants indicative of rapidly decomposing humus (active mull) include wild garlic (Allium ursinum) and lesser celandine (Ficaria verna). Drooping sedge (Carex pendula) colonizes the wettest areas, particularly near seepage zones.

Within the black alder alluvial forest, near slightly calcareous water sources at the base of the Brusselian sands, a particularly interesting vegetation community develops, dominated by bittercress (Cardamine amara) and opposite-leaved golden saxifrage (Chrysosplenium oppositifolium) (Natura 2000 Habitat: 7220).

Various exotic species have been progressively introduced to counter diseases and climate warming, including Corsican pine (Pinus nigra subsp. laricio) and sweet chestnut (Castanea sativa). Current site management promotes the conservation of dead wood, both standing and on the ground. Certain biological zones are being established, and forestry activities will be halted. Special attention is given to protecting wetlands in valley bottoms, along streams, and around ponds.

From a zoological perspective, the site hosts a significant population of roe deer and a rich diversity of forest animals. Lucky naturalists may observe the tawny owl, the black woodpecker, or the fire salamander.

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Updated on June 15, 2026