The higher biomass export for 9-year-old shoots compared
to the export of 3-year-old shoots indicates that the total
nutrient export increased with rotation period (Table 1). Jug
et al. (1999) reported for short rotation plantations in Germany,
that during growth decreasing N concentrations in the plants
were compensated by increasing biomass stocks. However,
this trend will not continue indifferently if the trees continue
grow older. Although biomass export was still increasing with
age and therefore highest in conventional forestry, nutrient
exports were seen to be decreasing (Steiner, 2006). This points
out that with increasing age nutrient export is mainly affected
by decreasing nutrient concentrations within the biomass (e.g.
lower share of bark in the biomass yield) whereas the
increasing biomass export does not influence nutrient exports
significantly. This is why the nutrient exports from short
rotation plantations are almost always higher than those from