Early growth of different tree species on agricultural land along a latitudinal transect in Sweden

Fast-growing tree species will be an important tool in the future production of renewables and in substituting non-renewable fossil energy sources. Sweden, like other countries around the Baltic Sea, has large areas of abandoned farmland usable for biomass production, but knowledge of growth performance of tree species candidates is insufficient. An experiment was initiated where six potentially high-producing tree species were compared. The best available plant material for each species was used on five sites over latitudes 56–64°N in Sweden. Results from the first 8–9 years are reported. Short rotation coppice willow (Salix schwerinii Wolf × S. viminalis L., clone ‘Tora’) had the fastest initial growth and production in southern Sweden. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) and poplar (Populus spp., section Tacamahaca), grown as short rotation forest, grew well over all sites and showed the highest productivity at the two northern sites. Hybrid larch (Larix ×eurolepis Henry) displayed a high potential at the two most southerly sites, whilst silver birch (Betula pendula Roth) was a medium-producing species at all sites. Norway spruce (Picea abies (L.) Karst.) started slowly, and Siberian larch (L. sukaczewii Dylis) produced poorly at the two northern sites in the initial stage. All tree species followed existing height development curves for the respective species on a high site quality level. Currently, well-growing clones of Populus spp. indicated that a wider selection of tree species can be used at high latitudes under climate change. The study showed a high growth potential for most species on former agricultural lands. However, measures to reduce climate and biological damage must be included in future efforts.