Le suivi des programmes d'études préuniversitaires au ministère de l'Education

Bibliogr.Webographie

Harmonisation des programmes d'études préuniversitaires

Update Aug. 2009Titre de l'écran-titre (visionné le 3 décembre 2009)Première éd. en 2004Traduction de: Harmonisation des programmes d'études préuniversitaire

Harmonisation des programmes d'études préuniversitaires

Mise à jour août 2009Titre de l'écran-titre (visionné le 3 décembre 2009)Première éd. en 200

Harmonisation des programmes d'études préuniversitaires

Titre de l'écran-titre (visionné le 14 août 2008)Version électronique d'un document imprimé publié en 2004Traduction de: Harmonisation des programmes d'études préuniversitaire

Anthropogenic N – A global issue examined at regional scale from soils, to fungi, roots and tree rings

Globally increasing anthropogenic airborne emissions of reactive nitrogen (N) generate several environmental issues that require investigating how N accumulation modifies the N cycle. Tree-ring δ15N series may help understanding past and current perturbations in the forest N cycle. Although several studies have addressed this issue, most of them were of local scale or based on short δ15N series. The development of this environmental indicator however would benefit from examining, at the regional scale, the relationships of long tree-ring series with soil N biogeochemical processes. Here we explore these links for tree stands of the oil-sands region in northern Alberta, and the coal-fired power plants region in central Alberta, Canada. We characterize the tree-ring δ15N trends, the N modification rates and bacterial and fungal communities of soil samples collected in the immediate surrounding of the characterized trees. The dataset suggests that specific soil pH, and N-cycling bacterial and fungal communities influence tree-ring δ15N responses to anthropogenic emissions, correlating either directly or inversely. Overall, tree-ring δ15N series may record changes in the forest-N cycle, but their interpretation requires understanding key soil biogeochemical processes. «In nature nothing exists alone», Rachel Carson

La réussite au coeur-- du collégial

Titre de l'écran-titre (visionné le 15 août. 2013