Nutrient status and growth of black spruce layers and planted seedlings in response to nutrient addition in the boreal forest of Quebec
The effect of nutrient addition (fertilization with N, P, and K at a rate of 448, 224, and 224 kg ·ha-1, respectively) on height growth, root biomass, leaf area, and foliar nutrient concentrations of slow-growing layers and newly planted seedlings of black spruce (Picea mariana (Mill.) BSP) was evaluated on an apparently productive mesic site in Quebec. Annual height growth increment of fertilized layers was greater than 20 cm ·year-1compared with 3-4 cm ·year-1for the other three treatments. Fine root biomass (< 2 mm in diameter) and leaf area growth were significantly higher for fertilized layers and seedlings compared with their respective controls. For both current and 1-year-old needles, foliar N concentration on a unit leaf area basis increased significantly for both layers and seedlings, and vector analysis showed that, in all cases, N was the most limiting nutrient. Five growing seasons after treatment, the only residual effect of fertilization on foliar nutrient concentrations was higher foliar N in fertilized seedlings. Thus, it appears that the slow growth of the unfertilized layers on this site was due to resource limitation rather than to the type of regeneration as such.