Bioenergy 1 Biomass production 1 Climate adaptation 1 Climatic conditions 1 Climatic gradients 1 Cloning 1 Forestry 1 Growing conditions 1 Growing degree-days Growing season lengths 1 Higher latitudes 1 Late frost 1 Leaf phenology 1 Northern Europe 1 Phenological stage 1 Plants (botany) 1 Populus 1 Relative performance 1 Springs (components) 1