Nitrogen uptake and utilization by slow- and fast-growing families of interior spruce under contrasting fertility regimes

Six full-sib families of interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) of contrasting growth rates (three fast-growing, three slow-growing families) were grown from seed in a greenhouse under three fertility regimes (25, 75, and 125 mg nitrogen/seedling over 175 days). The use of vector analysis showed that the lowest fertility regime was nitrogen-limited while the highest indicated luxury consumption. After 175 days, fast-growing families were larger than slow-growing at all fertility levels. At the lowest fertility level, fast-growing families exhibited greater nitrogen productivity and utilization of internal nitrogen. At higher fertility levels, fast-growing families took up nitrogen more quickly and efficiently thus accumulating greater nitrogen reserves. Fast-growing families also exhibited a greater plasticity in dry mass allocation between shoots and roots with different fertility levels.