Growth, wood chemistry, and fibre length of Norway spruce in a long-term nutrient optimization experiment

The study was performed as part of a nutrient optimization experiment at Asa in southern Sweden. The experiment was established 1987, in a Norway spruce (Picea abies (L.) Karst.) stand planted in 1975. In the nutrient optimization treatment (IL), all essential macro- and micronutrients were supplied, with irrigation water, every second day during the growing season. In October 2003, nine trees were harvested on both untreated control and IL plots. The IL treatment increased annual ring width during the first years of the experiment by ca. 30% and cumulative cross-sectional area 1.5-fold by the end of the experiment. Tracheid length was, however, not affected by the IL treatment. The nitrogen concentration of wood increased and starch concentration decreased as an effect of the IL treatment, suggesting that carbon was allocated to growth rather than storage. The IL treatment increased lignin concentration of wood by 3.4%. Chemical composition varied at different heights along the stem, but with no apparent trend.