identify the potential limits of accuracy and precision. This paper reports the results of the first seven testing cycles. The NIR calibration was expanded from an initial sample set of 104 mixed eucalypt samples to over 720 samples covering more than 40 species from predominantly temperate sites across Australia. The performance of the final calibration using two independent and contrasting data sets showed that a multisite and multispecies calibration is feasible. The expected potential accuracy and precision that can be expected from NIR predictions is discussed.
Accurate measurement of sapwood depth (D S ) is essential for calculating volumetric water use of individual trees and stands. Various methods are available to measure D S but their accuracy is rarely cross-validated. We sampled 15 Eucalyptus and 1 Corymbia species along a gradient of aridity and obtained reference values of D S in fresh wood cores using light microscopy, which represents our reference method. We compared this method to the simpler and widely used macroscopic method: visual assessment of natural or induced colour change from sapwood to heartwood. In a third method, estimation of D S was based on species-specific models that rely on wood properties measured using near infrared spectroscopy (NIR). Microscopy allowed clear identification of D S based on the presence of blocked vessels. Measurement of D S using microscopic methods was possible for 78 of a total of 80 cores and ranged from 3.6 mm (E. loxophleba) to 43.8 mm (E. viminalis). Macroscopic assessment clearly differentiated sapwood and heartwood in 60 cores. Results from microscopic and macroscopic methods agreed closely (\10% deviation between estimates) in 35 of 78 cores. After elimination of clearly erroneous measurements ([50% deviation between estimates), macroscopic measurement across all species agreed well with microscopic assessment of D S (R 2 = 0.92). Models developed for differentiation between sapwood and heartwood using NIR spectroscopy were very robust (high coefficient of determination) for four species, but D S could only be predicted well for one (E. obliqua) of the four species. Even after elimination of apparent false estimates, prediction of D S by NIR across species was not as strong as for macroscopic assessment (R 2 = 0.88). D S can accurately be measured using microscopy if vessel occlusion is clearly visible. Although slightly overestimated, D S from macroscopic assessment was generally similar to that measured by microscopy. NIR spectroscopy was unable to predict D S with acceptable accuracy for the majority of species. Further improvements in the prediction of D S using NIR will require more intensive model calibration and validation, and may not be applicable to all species.
A fibre-optic accessory with a linear drive transport system has been coupled to a near infrared (NIR) instrument to enable solid samples, in this instance increment cores from standing trees, to be scanned at 1 mm increments along the length of the sample. This allows the NIR prediction of wood properties (oven-dry chemical composition and microfibril angle) to be undertaken so that the radial profile of chemistry or microfibril angle can be determined from the pith to the bark. Calibration models provided prediction errors for microfibril angle in Pinus radiata softwood of 4.1° while for Eucalyptus globulus the error is 3.9°. The errors for prediction of chemical composition in Pinus radiata are 0.2% (arabinose) 1.1% (galactose), 2.3% (glucose), 0.7% (mannose), 0.7% (xylose) and 1.6% (lignin).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.