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Douglas Fir Wood from Plantations in Germany – Some Selected Characteristics
42 year-old Douglas fir (Pseudotsuga menziesii) trees from four scientifically managed plantations in the south of Germany were analyzed by means of light microscopy and X-ray diffractometry (Silviscan-3®). An important feature for wood quality is the determination of the transition point from juvenile to adult heartwood. Juvenile wood is generally known to be of lower quality when compared with adult wood. Latewood percentage, tracheid wall thickness, microfibril angle and density were determined along radial profiles from pith to bark. Latest at the age of around 25 years, the trees initiate adult wood formation, whereby latewood percentage indicated the earliest transition at around an age of 18 years and density the latest transition at around 25 years. As Douglas fir wood is also used for outdoor applications, natural durability was tested against various basidiomycetes. As expected, juvenile wood showed a slightly lower durability than adult heartwood. According to the highest mass loss produced by one of the three test fungi (Poria placenta), adult heartwood was grouped in durability class (DC) 4 only, which means slightly durable. This is the same DC like Norway spruce and one class below Douglas fir wood from natural sites. Mechanical properties of adult heartwood of the plantation trees are only slightly inferior when compared with average values of European Douglas fir. This might be due to the involvement of some very fast grown trees in the tests.