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Luostarinen, K. 2011. Density, Annual Growth and Proportions of Types of Wood of Planted Fast Grown Siberian Larch (Larix sibirica) Trees.  Baltic Forestry 17 (1): 58-67

Siberian larch (Larix sibirica Ledeb.) is widely cultivated in Finland as it thrives very well and grows rapidly on fertile sites in the country. As rapid growth affects the wood properties, particularly in softwoods, it is not clear that these fast growing trees would produce raw material of similar quality as trees grown in their native areas. Thus, in this study the proportion of wood types (juvenile wood, mature heartwood, and sapwood) was quantified at three different heights up the trunk (butt end, 4.5 and 9.0 m) in Siberian larch trees cultivated in Finland. Additionally, density and annual growth patterns were studied in the three wood types at the respective heights. The wood located at the butt differed in some respects from the wood located higher up the trunk, but particularly wood density and the proportion of latewood (LW%), important for the mechanical properties, stayed similar up to 4.5 m of height. Thus the lower part of the trunks, also containing the smallest proportion of juvenile wood, seems to be most suitable for structural use. The effect of extractive content on the density is emphasised, as many of the observed correlations were different in mature heartwood and sapwood. Radial density differences are larger in Siberian larch wood grown in Finland than in Siberia, which emphasises the poorer quality of juvenile wood of fast grown planted trees.

Key words: earlywood, juvenile wood, latewood, mature heartwood, proportion of latewood, ring width, sapwood