The hypotheses that retranslocation is controlled by soil nutrient availability or plant nutrient reserves were tested under field conditions for one growing season using nutrient‐loaded and non‐loaded (conventional) black spruce [ Picea mariana (Mill.) BSP] seedlings planted on a poor, medium, and rich fertility soil created by equivalent applications of 0, 200, and 400 kg N ha −1 , respectively. Growth and nutrient uptake increased with N supply, and was consistently higher in loaded than conventional seedlings, demonstrating the advantage of nutrient loading practices to accelerate seedling growth across the range of soil N tested. Compared to the poor soil, new shoot biomass of loaded seedlings increased by 34 and 134% on the medium and rich soils, suggesting loaded seedlings may be more efficiently transplanted on more fertile sites. Net retranslocation of N, P, and K increased by 569, 185, and 102% by nutrient loading in the nursery, supporting the hypothesis of translocation driven by the magnitude of plant nutrient reserves. However, net N retranslocation diminished with time due to root system expansion that promoted uptake and reduced the need for N redistribution. Net retranslocation of N (the most limiting nutrient) declined with soil N supply, but that of P and K were relatively independent of soil fertility. Increased N availability in the soil enhanced N accumulation in the plants but lowered N retranslocation. We conclude that higher net retranslocation of N on poor soils is a phenotypic adjustment by P. mariana seedlings to maximize N use at low availability.
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Salifu et al. (2001) studied this question.