Sugar maple trees were fertilized in June 1988 on an individual tree basis in an attempt to improve tree vigour. Fertilizers included K$ sb2$SO$ sb4$, a phosphate and base cations mix, and a commercial organic mix (Maplegro). No effect of fertilization was found on foliar nutrient concentrations and water status of trees during the 1990 growing season. This is possibly the result of dilution in tree biomass, the addition of non limiting nutrients or the experimental design. A positive effect of fertilization on growth was found for one site and, at another, fertilization was found to impair growth. Thus fertilization requirements of declining sugar maple are site specific. Soil Mg was higher around trees fertilized with Maplegro, and trees fertilized with K$ sb2$SO$ sb4$ had low leaf buffering capacities.

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Optimum nutritional levels for most commercial hardwoods of eastern Canada are unknown. This thesis dealt with the development of a method to determine nutritional standards using within site variation in tree growth and foliar chemistry. To this end, sugar maple (n = 87) and red maple (n = 39) trees were sampled in summer 2001 at the Station de biologie des Laurentides. Leaves were sampled for nutrients (N, P, K, Ca, Mg and Mn) and tree stems were measured for determination of basal area growth (BAG). Similar measurements for trees sampled annually during 1995--2001 were also used to measure the effect of annual variation on nutritional standards. A boundary line approach was used to assess tree growth response to nutrition using nutrient concentrations and Compositional Nutrient Diagnosis (CND) scores as predicting variables. A Basal Area Growth Index (BAGI) was computed using the live crown ratio to correct for the effect of stand density on BAG. An iterative and unbiased protocol was also developed to eliminate outliers. Optimum, critical and optimal range levels were derived from quadratic models significant at P < 0.15.

No description available.