INFLUENCE OF CAMBIAL AGE AND GROWTH-CONDITIONS ON MICROFIBRIL ANGLE IN YOUNG NORWAY SPRUCE (PICEA-ABIES [L.] KARST.)

Microfibril angle (MfA) of the tracheid cell wall of conifers influenc es the performance and properties of forest products. For instance a h igh MfA has been found detrimental for solid wood properties. Although it is assumed that there is a correlation between MfA and the growth conditions a tree experiences, there are few studies on how growth con ditions influence MfA. In this study mean MfA of the cell walls was de termined for 646 early wood samples, from pith and outwards, of Picea abies trees using automated double gaussian curve fitting of the 002 a rea generated by X-Ray diffraction and recorded using a area detector. The determinations of mean MfA were based on appr. 500-2000 tracheids per wood sample. It was indicated that a determination of mean MfA wo uld require less than 3 minutes, if the curve fitting program is inclu ded already at the time of data acquisition. In an attempt to model th e dependency of MfA on factors related to wood formation, the age effe ct was found most descriptive and a simple model based on 1/cambial ag e gave an r(2) = 0.69. Only a slightly higher correlation (r(2) = 0.73 ) was reached when additional variables significant at p less than or equal to 0.001 were used, although they, together with the age effect, supported the assumption that growth conditions affect MfA. The study suggests that to concentrate and minimize the volume of wood with hig h MfA, in an individual tree, juvenile growth suppression in combinati on with an extended rotation period should be used.