Estimation of Pinus radiata D. Don tracheid morphological characteristics by near infrared spectroscopy

Eight Pinus radiata D. Don increment core samples were selected from a total of 32 cores for the development of calibrations for several tracheid morphological characteristics: coarseness, perimeter, radial and tangential diameter and wall thickness. Near infrared (NIR) spectra, obtained from the radiallongitudinal face of each core in 10-mm sections from pith to bark, were used to develop the calibrations. Calibrations for coarseness and wall thickness were excellent, with coefficients of determination (R-2) of 0.91 and 0.89, respectively. Calibrations for the remaining characteristics were weaker (R-2 ranged from 0.65 to 0.69). To test the predictive ability of the calibrations, two intact P. radiata increment cores (core A and B) were selected from the same set as the calibration samples. NIRpredicted tracheid coarseness and wall thickness were in strong agreement with measured (SilviScandetermined) values. Radial patterns of variation (NIRpredicted, measured) closely followed each other for both cores, but coarseness and wall thickness were underestimated for core B. Tracheid tangential perimeter was well predicted with R2 of 0.69 (core A) and 0.79 (core B). Relationships for the remaining characteristics were weak. Collection of NIR spectra in smaller increments, to capture more of the variation, may improve calibration.