In irregular stands (continuous cover forestry), understorey trees are submitted to successions of light and shading episodes during their recruitment. Whereas much work has been devoted to light reactivity, quite little is known on the effects of shade, especially for deciduous species. The main objective of this project is to study the reactivity of two deciduous species of contrasting shade tolerance (Fagus sylvatica L. and Quercus petraea Liebl.) to a range of shade conditions, as influenced by total height (range 1.5 – 4.0 m), crown ratio and competitive status. Reactivity will be assessed in terms of growth (diameter, height), form, and mortality. In addition, the dynamics of gap closure will be investigated, using a chronosequence approach.