| The degradation of forest ecosystems has led to the development of new approaches to forest management, in which tree planting supplements natural regeneration. Not enough is known, however, about the ecology of planted trees or about the management of planted forests. This thesis is an analysis of the method of forest regeneration known as under-planting. The objective of under-planting is to enrich stands by using desirable species while conserving forest cover (shelterwood) and the structures and functions associated with it.; A literature review and a meta-analysis of under-planting trials throughout the world were carried out. Light thinning seems to be sufficient in the majority of situations to obtain maximum yields in growth and optimum survival rates during the establishment phase. This level of thinning maximizes the protective effects of forest cover and minimizes the effects of competition, while better conserving forest structures and functions.; Under-planting was tested over six years in young pioneer stands on abandoned agricultural land. Our study focused on the effects of a second thinning two years after planting. Red oak grew faster than black cherry, responding well to thinning while suffering no increase in deer predation. Black cherry probably would have needed earlier and heavier thinning to improve its growth.; The morphological plasticity of seedlings as a function of light climate under shelterwood management was studied. Results observed for both black cherry and sugar maple were the reverse of those predicted by shade tolerance models. These results are discussed in relation to present gaps in knowledge of the ecology and management of artificial regeneration.; The measurement of available light in the understory was an important methodological element of this study. Several methods were compared and a new technique free of the constraints of sky conditions was developed.; Keywords. Hardwood reforestation; enrichment planting; shelterwood; pioneer forests; restoration; available light; canopy cover; morphological plasticity; shade tolerance and successional status; meta-analysis.; Organisms. Acer saccharum; Prunus serotina, Quercus rubra. |
