Production potential of 36 poplar clones grown at medium length rotation in Denmark

• 36 poplar clones were tested on two sandy former farmland sites in Denmark.
• Choice of parental species combination was very important for biomass production.
• Among the best was hybrids including Populus maximowiczii and Populus trichocarpa.
• The clone O.P. 42 (Hybrid 275, NE 42) P. maximowiczii x trichocarpa performed best.

The importance of choosing suitable clones for production of timber and biomass has long been recognized. The aims of this study were to describe the genetic variation and production potential among 36 poplar clones grown in a rotation of 5–13 years and evaluate the different species and hybrid group's potential for use in Northern Europe and comparable growth conditions. Based on two trials with randomized block designs, 36 clones from 4 species and 5 groups of species hybrids, measurements of height and diameter were used for estimating biomass production for rotation lengths of 5 and 13 years. The estimated mean annual increment of above ground biomass ranged from 1 to 9 Mg ha−1 yr−1 at age 13 years. A hybrid clone O.P. 42 (synonyms Hybrid 275, NE 42) Populus maximowiczii × trichocarpa, performed best, but also clones of the species Populus trichocarpa had a high biomass production. In general the hybrids using P. maximowiczii as a parent were well performing. Lowest production had pure species Populus nigra and Populus deltoides as well as their hybrids. The choice of species hybrid combination had a very strong impact on biomass production, but less influence on quality and health traits like dead shoot tips, leaf density and stem form.