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Intra-increment lignin content of five western Canadian coniferous woods Wu, Yeng-tsu


Lignin contents of extractive-free wood meals prepared from three adjacent rings of mature wood, sampled at breast height, of amabilis fir, Douglas fir, western red cedar, Sitka spruce, and western hemlock were determined according to the micro-method of Johnson, Moore and Zank. Each of three rings within each species was divided into six positions from earlywood to latewood. Wood meals of 40-80 mesh size were extracted successively with ethyl ether, absolute ethyl alcohol and hot-water, and then solubilized with acetyl bromide and absorbence was calibrated against Klason lignin values. Wood methoxyl content of these same samples had been studied previously. Lignin contents were found to be highly significantly different within positions of growth increments for amabilis fir, Douglas fir, western red cedar and Sitka spruce, but no significant difference was found for western hemlock. Highly significant difference was found between growth rings for western red cedar and similarly significant difference was found for Douglas fir. No significant differences were obtained between growth rings for the other three species, although a slight but definite increase in lignin content with age was observed. Highly significant differences were also found between species and for total averages of each position for the five species. Earlywoods were higher in lignin content than latewood in each species by: Douglas fir, 2.27%; amabilis fir, 2.06%; western red cedar, 1.28%; Sitka spruce, 1.08%; and western hemlock, 0.46%. Lignin contents for individual species were in the order of: western hemlock, 32.85% (32.36-34.04%); western red cedar, 31.23% (29.69-32.68%); amabilis fir, 27.51% (26.17-28.24%); Douglas fir, 26.48% (24.08-28.66%); and Sitka spruce, 25.81% (24.91-26.98%). The correlation coefficient testing association between lignin and wood methoxyl was highly significant for amabilis fir (0.971), Douglas fir (O.913) and western red cedar (0.684). Non-significant correlation occurred with Sitka spruce (0.467) and western hemlock (0.340). The relationship between lignin and wood methoxyl appeared independent of species. The non-lignin methoxyl contents for the five species were estimated and the results showed that these were also independent of species.

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