In order to test the effect
of different rotation periods on growth performance, the
experimental set-up included a 6-year-rotation where trees
were cut only once at the end of the experiment (see Fig. 1a).
At the Helmstedt study site yield estimateswere carried out by
harvesting annually eight trees representing the mean height
and diameter on a plot basis. Shoot biomass was weighed
immediately when harvesting the trees in the field using a
mechanical balance. Aliquots were sampled and dried in the
laboratory at 60 ◦C unless no further weight changes could be
detected