P. David Jones

Estimation of Microfibril Angle and Stiffness by near infrared Spectroscopy using sample sets having Limited wood Density Variation

Near infrared (NIR) spectroscopy offers a rapid method for the estimation of microfibril angle (MFA) and SilviScan-estimated wood stiffness (EL(SS)). The success of these NIR calibrations may be related to airdry density, because density varies in wood simultaneously with MFA and stiffness. The importance of density variation was investigated by developing calibrations for MFA and EL(SS) using Pinus radiata D. Don (radiata pine) and Pinus taeda L. (loblolly pine) sample sets where the density range was small and the relationships between density and MFA and density and EL(SS) were poor. Excellent calibrations for MFA and EL(SS) were obtained, particularly when sets had densities greater than 500 kg/m3, can provide strong relationships for MFA and stiffness even when density variation is limited. Examination of loading plots from the MFA and EL(SS) calibrations indicates that variation in wood components such as cellulose, lignin and possibly hemicellulose is important.

Comparison of Pinus taeda L. wood property calibrations based on NIR spectra from the radial-longitudinal and radial-transverse faces of wooden strips

Abstract When a radial strip is cut from an increment core it can potentially be cut with two orientations: parallel to longitudinal tracheids, i.e., a radial-longitudinal (RL) strip (the orientation of SilviScan samples), or at an orientation of 90° to the tracheids, i.e., a radial-transverse (RT) strip. Both strips could be used for near-infrared (NIR) analysis, but it is unknown how calibrations based on RT-face NIR spectra compare with those based on RL-face NIR spectra. A total of 20 Pinus taeda L. (loblolly pine) RL strips were characterized in terms of air-dry density, microfibril angle (MFA), stiffness and several tracheid morphological characteristics. NIR spectra were collected in 10-mm increments from the RL and RT faces of matching strips and used to develop calibrations for each property. In general, RL-face NIR spectra gave calibrations that provided stronger relationships. Differences between the two sets of calibrations were small, indicating that either face could be used for NIR analysis.

Nondestructive estimation of tracheid length from sections of radial wood strips by near infrared spectroscopy

Abstract The use of calibrated near infrared (NIR) spectroscopy for predicting tracheid length of Pinus taeda L. (loblolly pine) wood samples is described. Ten-mm sections of 14 P. taeda radial strips were selected and NIR spectra obtained from the radial longitudinal face of each section. The fibers in these sections were characterized in terms of arithmetic and length-weighted mean tracheid length using a fiber quality analyzer, and calibrations with NIR spectra were developed for both measures of tracheid length. Relationships were good, with coefficients of determination (R 2) of 0.88 for arithmetic tracheid length and 0.96 for length-weighted tracheid length. The accuracy of NIR predicted length-weighted tracheid length was sufficient for ranking purposes.

High Resolution Scanning of Radial Strips cut from Increment Cores by Near Infrared Spectroscopy

Near infrared (NIR) spectroscopy provides a rapid method for the determination ofwood properties of radial strips. The spatial resolution of the NIR measurements has generally been limited to sections 10mm wide and as a consequence the estimation of wood properties of individual rings or within rings has not been possible. Many different NIR instruments can be used to collect NIR spectra from the surface of radial strips at relatively high spatial resolution and the purpose of this study was to compare wood property calibrations obtained using NIR spectra collected in 5 mm and 2 mm seetions with several different NIR instruments. We found that calibrations based on spectra collected in 5 mm seetions had good statistics, with those based on the Bruker Vector 22/N spectrometer the strongest. Of the three properties examined (density, microfibril angle and stiffness), density had the weakest statistics. When the spatial resolution was decreased to 2 mm, calibration and prediction statistics were weaker than those at 5 mm. RPDps were relatively low with the highest being 1.76 for predicted stiffness based on NIR spectra obtained using the ASD Field Spec Pro spectrometer. Based on the low RPDps, we conclude that none of the instruments examined were suitable for scanning radial strips at a spatial resolution of 2 mm.

Development of wood property calibrations using near infrared spectra having different spectral resolutions

A range of important wood properties can be predicted using calibrations obtained using SilviScan data and diffuse reflectance near infrared (NIR) spectra collected from wooden strips cut from increment cores. The ease of NIR measurements and the rapid provision of SilviScan data provides the opportunity to establish extremely large data sets, causing calibration problems. An option is to reduce the number of data points representing an individual NIR spectrum. NIR spectra were collected in 10 mm increments from the radial longitudinal face of 89 Pinus taeda L. (loblolly pine) breast height (1.30 m) wooden strips using a Foss NIRSystems 5000 [wavelength range 1100–2498 nm, spectral sampling interval (SSI) 2 nm]. Air-dry density, microfibril angle (MFA) and stiffness calibrations were obtained using SSIs ranging from 2 to 64 nm. Calibrations developed using NIR spectra having SSIs of 4 or 8 nm performed as well as those obtained at 2 nm. As resolution was decreased (SSI increased), the quality of the calibrations associated with the various wood properties was affected to different degrees. The MFA calibration was the most affected and air-dry density the least.

Success in using near infrared spectroscopy to estimate wood properties of Pinus taeda radial strips not due to autocorrelation

Near infrared (NIR) spectroscopy provides a rapid method for estimating several important wood properties of 10 mm sections of radial wooden strips. Successful calibrations have been obtained with NIR spectra collected from 3 to 16 consecutive 10 mm sections of the same wood core. The success of these calibrations might be due to an autocorrelation that exists between the adjacent sections of a core. In this study, we compared calibrations with spectra collected from consecutive 10 mm sections to calibrations obtained with spectra collected from unrelated 10 mm sections. Very similar calibration statistics were obtained with both sets of spectra, demonstrating that existing calibration success is not due to an autocorrelation.