5. Conclusion
By growing poplar SRC on degraded lands and with a minimum
of energy input (e.g. use of chemicals, irrigation and
fertilization), environmental challenges and competition with
food crops can be minimized [8]. From this study, we learnt
that the SRC systems on degraded lands can payback the energy
invested in their production. Carefully selected plant
material and adjusted plantation maintenance may even
further increase the energy ratio of poplar SRC on degraded
lands. Particularly pure P. nigra and P. trichocarpa clones
appeared to be most suitable for growth under suboptimal
conditions, i.e. being planted on degraded land and coping
with several harvest cycles and with diseases as leaf rust. The
initially highly promising D T and T D hybrids hardly
survived the fourth rotation. Therefore, more long-term
research is needed to reveal significant shifts in clonal
ranking over the entire lifetime of a poplar SRC and to identify
most appropriate clones.
Acknowledgements