Grant: Collaborative Research and Development Grants

Sandy soils are abundant in the boreal forest. On these soils, a high spatial and temporal variability of forest productivity is observed as closed-canopy productive stands as well as open canopy; slow growing ones that respond poorly to forest management are found. The observation of a recent increased abundance of open lichen woodland also indicates a dynamic nature of forest productivity and that, on a given site-type, some factors, or a combination of factors could lead to the creation of either a productive or an unproductive forest stand. Open canopy lichen woodland, once formed are thought to be relatively stable, therefore maintaining closed canopy productive forest is an important forest management objective. The project aims at providing a better understanding of the factors, both biotic and abiotic, that determine the maintenance of forest productivity on sandy sites. It has important implications for the management of the boreal forest as the northern limit to commercial forestry is define in large part by the abundance of unproductive open forest stands. Also, because forest managers have frequently observed reversion of productive to unproductive forests on sandy sites as well as poor responses to silvicultural treatments such as thinning, the project will provide knowledge that will help forest managers to select the best management options to maintain site productivity on this site type. The objectives of the project are to: 1) determine the influence of abiotic soil conditions (including soil organic matter content) as well as biotic factors (including stand density and composition of tree regeneration and understory plant composition and disturbance history) in explaining tree growth and tree growth patterns on sandy soils 2) determine what physiological factors limit tree growth and how these factors change with tree development and 3) determine the conditions for the responsiveness of tree growth to the opening of the canopy by thinning and possibly identify thresholds in environmental conditions that confer a productive state to these forests and finally 4) set up an experimental design to test the effect of mixed species plantation and plantation density on stand development.