Fig. 6

Development of growing stock volume in four spruce stands growing on mesic site (MT) when fertilization is not allowed (thick light green line), one fertilization with 150 kg N ha^-1 is allowed (thick dark green line) and a maximum of three fertilizations with optimized N doses are allowed (thin dark green line). The percentages in parentheses are the relative improvements in NPV obtained with fertilization (the first percentage is the effect of fixed N dose and the second is the effect of optimized doses). The bottom right diagram is for the stand in which the absolute increase in NPV was the largest