Biomass production on agricultural sites using aspen-varieties in short rotation plantations

To utilise agricultural sites for the production of woody biomass with last-growing trees in short rotation plantations, new varieties of aspen were bred and tested. Selected trees of European (Populus tremula L.) and American aspen (P. tremuloides Michx.) were cross pollinated. Six progenies of these crosses were planted in 1983 in different spacings and rotation periods. In the rows the trees were planted at distances of 0.6, 0.9, and 1.2 m with an equal distance of 2.0 m between the rows. The trees of the closest spacing were harvested after two consecutive live-year rotations, whereas the trees of the other two spaces were harvested only once after ten years. Altogether the plantation has developed well, although the establishment was difficult due to drought in the first year and weed competition poor growth and an average mortality rate of 8% after the second year. The first five years the site was fenced against deer and the weeds were cut in the first year.