The effects of nitrogen stress on the stable carbon isotope composition, productivity and water use efficiency of white spruce (Picea glauca (Moench) Voss) seedlings

abonos nitrogenados azote biomasa biomass biomasse crecimiento croissance efficiency eficacia gas exchange genetic variation genotype environment interaction growth intercambio de gases irrigation measurement mesure nitrogen nitrogen fertilizers nutrition des plantes photosynthese photosynthesis picea picea glauca plant nutrition plant water relations plantule productividad productivity relaciones planta agua relation plante eau riego seedlings uso del agua utilisation de l'eau water use