In virgin forest the biodiversity is maintained thanks to the natural disturbances that allow the coexistence of different succession stages. On this basis, the aim of this project is to study the effect of gap size on the initial vegetation dynamics, in mixded beech dominating forest. On this purpose, the different regeneration step, dispersal, germination and survival of tree species are studied in gaps, resulting from the December 1999 storms. Moreover the study of the relations between gap and the vegetation dynamic is approached. The sampling sits is in the forest of la Petite Pierre, in the North Vosges, in Alsace.