Our results indicate that Populus spp. is not sufficiently
adapted to the nutrient–poor sandy substrates and the low
precipitation regime at the Lusatian study site. At Helmstedt
conditions seemed to be more favourable for Populus
spp. because after 3 years biomass increments were much
higher than at the Lusatian study site after the first 3 years.
These findings emphasise that high biomass increments for
poplar can only be achieved on loamy sites or through soil
amelioration. However, yields fall still below the threshold of
5tha−1 a−1 (shown above). The positive influence of fertiliser
and compost amendments on biomass production at the
Helmstedt study site, therefore, reflects the limitations of
nutrient and water supply possibly existing at the reference
site in Lusatia.
Based on our results and studies of Bungart and Huettl
(2002) S. viminalis is not adapted to such site conditions at all,
and, therefore, should not be considered furthermore.
Annual yields of R. pseudoacacia matched or even exceeded
the yields reported in the literature. Because of differences
in site conditions and planting densities results of different
sites cannot simply be compared. However, present
results clearly show that R. pseudoacacia is well adapted to
nutrient–poor sandy substrates and the low precipitation
regime.