Variation in wood density, grain orientation and anisotropic shrinkage of plantation grown Azadirachta indica.

Abstract

This paper examines the effects of within tree variation on wood density, grain orientation and anisotropic shrinkage of plantation grown Azadirachta indica. Five 15-year old Azadirachta indica were randomly selected from a plantation within University of Maiduguri, in the north-eastern part of Nigeria. Wood samples were prepared from the three height levels, bottom, middle and top, at the sapwood and heartwood positions of the stem according to BS 373 standard. The wood is dense, dimensionally stable and has moderate interlocking grain. The average density and grain orientation was found to be 679.48 kg.m -3 and 12.28 o respectively while the average tangential-radial shrinkage ratio and volumetric shrinkage was 1:1.71 and 12.78% respectively. Among tree variation had a marked effect on wood density and anisotropic shrinkage of the wood (p 0.05). A strong negative correlation was established between density and shrinkage properties. But, the relationship between grain orientation and anisotropic shrinkage was positive. Thus, it may be possible to use density and grain orientation biometry to predict anisotropic shrinkage of the wood and its dimensional stability.