Homogeneity in cellulose crystallinity between samples of Pinus radiata wood

Wood was sampled from 22 locations in 3 Pinus radiata trees and characterized by solid-state 13 C NMR spectroscopy. Values of a cellulose crystallinity index were confined to the range 0.486 to 0.541 despite inclusion of earlywood and latewood, compression wood and opposite wood, juvenile wood and mature wood. The mean value was 0.515 and the standard deviation was 0.015. Highest crystallinity was associated with relatively slow radial growth, with a correlation coefficient of R =−0.79 for a linear least-squares fit against ring width. The NMR results were consistent with published studies based on X-ray peak widths. Crystallinity indices based on X-ray peak heights or areas have shown wider ranges of variation, attributed to differences in cellulose content rather than cellulose crystallinity.