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Discolored stems of 12-63-year-old European aspen (Populus tremula L.).

Johansson, Tord


European aspen (Populus tremula L.) is an inherent species in Sweden and other Nordic countries. Products from aspen are timber, pulp wood, biofuel and veneer for furniture and matches. Aspen is damaged by fungi, insects and wild habitat. Two main forms of rot are root rot (Armillaria mellea (Vahl.) Quel.) and stem rot or white heartwood rot (Phellinus tremulae (Bondartsev) Bondartsev & P.N. Borisov). But discolored wood is the most frequent form of changes in the aspen wood. In the report an overview of the factors causing discolored wood as well as the industrial use and quality of the end products is presented. The study was made at eight locations in Sweden (Lat. 65° N. Long 20° E.; Lat. 64° N. Long 19° E.; Lat. 62° N. Long 15° E.; Lat. 60° N. Long 16° E.; Lat. 60° N. Long 17° E.; Lat. 58° N. Long 14° E.; Lat. 58° N. Long 12° E.; Lat. 57° N. Long 13° E. At each of the locations five stands were evaluated. In the stand ten aspens were sampled, totally 400 aspens. Stand parameters such as stem number, diameter at breast height, height, age, forest type and soil type was registered. The age, height and diameter at breast height of the felled stem was measured. The stem was cut in sections of 1 meter. Age and diameter of the sections was registered. The stem area was examined and the diameter of discolored wood or rot was registered. The mean total age was 33±10 range 12-63 years, the mean height was 16.0±3.3 range 8.2-25.2 meter and the mean diameter at breast height was 172±28 range 81-340 mm. Most of the stands were growing on light clay till or sandy till. Among the studied 400 aspens 91 % of the stems were discolored. At 1% of stem height 91 % was discolored and 56 % at 75 % of stem height. Part of the stem, 28 %, had a discolored radius of 21 range 5-51 mm at 25 % of stem height (≈ 4 meters). The discolored volume increased with increasing breast height diameter; 10.3 % at 153 mm and 19.1 % at 350 mm. Equations describing discolored volume, %, by total stem volume were constructed. A table was also presented. These might be helpful for estimating the percentage of fresh wood in a stem.

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Rapport (Institutionen för energi och teknik, SLU)
2013, nummer: 057
Utgivare: Department of Energy and Technology, Swedish University of Agricultural Sciences

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