Abstract
ABSTRACTFour stands of 28-year-old radiata pine (Pinus radiata D. Don) grown in the eighth region (Biobio) of Chile were sampled to determine the effect of tree spacing on the microfibril angle. The samples were taken at two different stem levels of the tree, 2.5 m and 7.5 m, with increment strip taken in the Nothern direction. The four experimental stands were characterized by the following spacing 2x2, 2x3, 3x4 and 4x4. The microfibril angle was measured by X-ray diffraction with the SilviScan technology at the FP-Innovation-Paprican Division in Vancouver, Canada. The results showed a significant effect of tree spacing on the microfibril angle in both juvenile wood and mature wood as well as at the two stem levels considered. The minimum (9.42º) was reached in 2x2 stand at 7.5 m in mature wood, while maximum microfibril angle (24.54º) was obtained in 2x3 stand at 2.5 m in juvenile wood. Regarding the effect of tree spacing, 4x4 stand had the lowest microfibril angle,except in mature wood at 7.5 m where 4x4 had the highest microfibril angle (11°) of the four stands.
Highlights
It was noticed that tree height and diameter at breast height (DBH) had two different trends regarding the effect of tree spacing
While DBH increased linearly with increasing spacing, tree height presented an irregular trend marked by a low 3x4 average tree height
The DBH variable showed high variations between plantations ranging from 23.9 cm for 2x2 to 38.3 cm for 4x4 stand
Summary
Radiata pine is grown in plantations and has become over the last decades so important that it could have an impact, in the long term, on other Chilean native forests (BUSTAMANTE; SIMONETTI, 2005) This species covers about 1,7 million hectares and is mainly grown under intensive forest management with treatments like soil preparation, fertilization, pruning, thinning in order to increase the yield per hectare (TORO; GESSEL, 1999). The growing use of radiata pine in the pulp and paper industry or construction has been a driver of research on its wood characteristics, especially for stiffness This last property has been shown to be dependent of the initial tree spacing in young trees (LASSERRE et al, 2004) which presented high stiffness in high density stands. Researches suggested that stand management operations such initial tree spacing and rotation age, had a direct impact on wood volume yield along with wood quality (KENNEDY, 1995; ZOBEL, 1981) and on the end use product
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