Le paysage végétal de la Réserve Biologique des Hauteurs de la Solle en Forêt de Fontainebleau : un exemple de synassociation soustraite aux interventions de l’Homme

The biological reserve of « Les Hauteurs de la Solle » is but one of the geomorphological units of the Fontainebleau Forest characterized by numerous rocky and sandy forested slopes. However, the uniqueness of this reserve comes from the fact that it did not suffer during the past two centuries from any forest fire or anthropic disturbance. As a result the landscape is varied, and made up of four phytosociological units : 1, a species poor heath, a remnant of that existing three or four thousand years ago ; 2, some birch stands with an understorey of forest vegetation devoid of characteristic species ; 3, a beechwood with some old sessile oak trees, rich in holly, and belonging to a Leucobryum glaucum variant of Quercion roboripetreae ; 4, standstone screes harbouring a complex of permanent lichen associations, with patches of heath on thin organic soil ; these rocky areas are interspersed with sandy areas where trees and shrubs have taken root, forming open stands of Pinus silvestris and Juniperus communis on southern exposures, whereas hardwood species or holly are dominant on northern slopes and in shady areas. The determinants of the distribution of these phytosociological units are topography, substratum, and history of the site, as retraced through pollen analysis of the podzols. Pollen analysis has shown the importance of forest fires in promoting the seral stages from heathland to birch woodland and to beechwood on sandy slopes. The limits of the four units are presently stable, but changes are nevertheless taking place within each of them : a colonization of the heathland by Pteridium aquilimm and Molinia coerulea took place after the last forest fire, followed by a regression of Pteridium, a recent establishment of Quercus petraeae and Fagus under old birch stands, the occurrence of several windfalls within the beechwood, the partial afforestation of the scree beds by Pinus silvestris since the beginning of the XIXth century, the death of some birches and the destruction of part of the organic rock cover after the 1976 drought.Lemée Georges. Le paysage végétal de la Réserve Biologique des Hauteurs de la Solle en Forêt de Fontainebleau : un exemple de synassociation soustraite aux interventions de l’Homme. In: Revue d'Écologie (La Terre et La Vie), tome 47, n°4, 1992. pp. 351-366