Discoloration in poplar tree and production of sprouts after harvest

Abstract: Poplar is distributed widely throughout the world. There are about 30 natural species. Taxonomically poplars are divided into six groups. Poplar tree can be 200-300 years old. Normally two sets of 19 chromosomes are present in the nucleus of Poplar, while the size of genome is remarkably small. Poplar is a fast growing species. Poplar species are deciduous and semi evergreen and are distributed widely on the northern hemisphere. Poplars have various ecological habitats. They can grow in pure stands or mixed with other hardwood and conifer species. Poplars are also used in short rotation forestry for production of biomass for bio energy, fiber and environmental services. The short rotation forestry in Sweden is based on Salix but in this study the focus is on poplar. Discoloration occurs normally in the core wood for most poplar species. Present thesis is made in order to study the distribution of the discoloration for poplars. In the study 36 poplar trees from three provinces in Sweden (Lat. 56-60˚ N.) were measured. Discs were collected at different percentages of different stem height. The objective of work was to observe the relationship of discoloration with diameter and height of poplar tree. Besides these 36 sample trees, a clear felled poplar stand at Valsätra in Uppsala Municipality was studied. Diameter and discoloration on 110 stumps were measured. In the third part the measurements of shootings of poplar species in Valsätra are shown. The discoloration in stems was directly proportional with the height of the tree. The percentage of discoloration in a stem decreased with increasing tree height.