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 r ate of 448, 224, and 224 kg.ha(-1), respectively) on height growth, ro ot biomass, leaf area, and foliar nutrient concentrations of slow-grow ing layers and newly planted seedlings of black spruce (Picea mariana (Mill.) BSP) was evaluated on an apparently productive mesic site in Q uebec. Annual height growth increment of fertilized layers was greater than 20 cm.year(-1) compared with 3-4 cm.year(-1) for the other three treatments. Fine root biomass (<2 mm in diameter) and leaf area growt h were significantly higher for fertilized layers and seedlings compar ed with their respective controls. For both current and 1-year-old nee dles, foliar N concentration on a unit leaf area basis increased signi ficantly for both layers and seedlings, and vector analysis showed tha t, in all cases, N was the most limiting nutrient. Five growing season s 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 th is site was due to resource limitation rather than to the type of rege neration as such.