| This study assessed the magnitude of genetic variation in nutrient uptake and utilization efficiency among open pollinated tamarack (Larix laricina (Du Roi) K. Koch) families and characterized the individual families according to their adaptability to various nutrient regimes. Two separate experiments were conducted in a greenhouse. The first experiment investigated the response of 20 families from five populations to three nitrogen fertilizer levels for 20 weeks. The second experiment was concerned with the response of ten families to three soil types and three phosphorus fertilizer levels for 26 weeks. Characters assessed included height, root collar diameter, dry weights, nutrient (N, P, K, Ca and Mg) concentrations and accumulations, and nitrogen and phosphorus utilization efficiency. Estimates of variance components, heritabilities, genetic and phenotypic correlations and stability parameters were made.;The family x soil interaction was not significant for all traits. The family x nitrogen interaction was significant for growth traits and nitrogen uptake. Some families, however, were found to be stable over all nitrogen fertilizer levels. The family x phosphorus interaction was significant in some cases, but the magnitude of variation attributed to this interaction was relatively small in comparison to variation among families.;Variance components and individual-tree heritabilities showed that most of the traits studied were under moderately strong genetic control. This suggests that genetic gains can be made through mass selection. Positive genetic correlations existed between growth traits and nutrient uptake and utilization efficiency. This relationship implies that selection is likely to improve both groups of traits simultaneously.;Soil types, nitrogen and phosphorus fertilizer levels had a stronger influence on the development of the seedlings than families. Variation among populations and the population x nitrogen interaction were not significant for all traits studied. Variation due to soils, nitrogen, phosphorus and families was significant for all traits. Some families performed well at specific fertilizer levels, while others performed well at all levels. Generally the individual families that absorbed and utilized nutrients most efficiently at a given fertilizer level also grew best at that particular level. |
