One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites.

We examined the effects of a long-term nutrient-optimization treatment on the acquisition and allocation of biomass, carbon (C), and nitrogen (N) in young Norway spruce (Picea abies (L.) Karst.) growing in northern Sweden. After 12 years of fertilization the absolute biomass of stem, needles, living branches, and stump and coarse roots was more than doubled by nutrient optimization (irrigation – liquid fertilization treatment, IL), but the standing biomass of fine and small roots was unaffected compared with that of control trees. Biomass allocation among aboveground organs was not plastic to nutrient optimization and only the relative proportion of dead branches was reduced by nutrient optimization. Within the crown, biomass allocation to living branches was shifted towards the apex in IL trees. The N content in IL trees was substantially higher than in control trees. Most of the total N was allocated to needles and most of the needle N was found in the middle stratum of the living crown in both treatments, although the N concentration of current-year and older needles increased towards the apex in IL trees but not in control trees. The C concentration in the biomass components was not affected by the optimized fertilization. The results clearly show that there is a large potential to increase biomass production of Norway spruce (C sequestration) in the Nordic countries. This would secure the supply of raw material for the forest industry at the same time as the demand for biofuel from forest biomass is increasing.