Comparison of Methods for Estimating Mechanical Properties of Wood by NIR Spectroscopy

Table 1

Summary of publications that have utilized near-infrared (NIR) spectroscopy to estimate physical mechanical properties of short, clear samples. Information includes species examined, wood surface utilized, size of the short, clear sample tested, method for collecting NIR spectra, number of spectra collected, and size of the NIR beam. NA denotes that the information was not available in the publication. R = radial surface; T = tangential surface; X = transverse (or cross section) surface; GR = growth rings.

Authors	Species	Wood surface	Test specimen size (R × T × L, mm)	NIR method (number of spectra)	Window size
Hoffmeyer and Pedersen (1995) [5]	Picea abies	X	45, 95, 1800	Direct (NA)	NA
Gindl et al. (2001) [6]	Larix decidua	R	18, 18, 250	Probe (3)	4 mm diam.
Thumm and Meder (2001) [7]	Pinus radiata	R and T	20, 20, 300	Direct, sample moving (1)	20 mm
					Schimleck et al. (2001) [8]	Eucalyptus delegatensis	R	20, 20, 300	Direct (1)	5 × 20 mm
Schimleck et al. (2002) [9]	Pinus radiata	R	20, 20, 300	Direct (1)	5 × 20 mm
Via et al. (2003) [10]	Pinus palustris	R	3GR, 12.7, 304.8	Direct (2)	NA
Kelley et al. (2004) [11]	Pinus taeda	R	3GR 20–35, 15, 300	Probe (4)	20 mm^2
Kelley et al. (2004) [12]	6 softwood species	R	3GR 20–35, 15, 300 or 20, 15, 200	Probe (4)	20 mm^2
Schimleck et al. (2005) [13]	Pinus taeda	R, X	25.4, 25.4, 406	Direct (2)	5 × 12.5 mm
Via et al. (2005) [14]	Pinus palustris	R	3GR, 12.7, 304.8	Direct (2)	8 mm
				Probe (2)	5 mm
Andre et al. (2006) [15]	Populus	R	50, 50, 1000	Probe (4)	20 mm diam.
Haartveit and Flæte (2006) [16]	Picea abies	X	20, 20, 340	Direct (NA)	10 mm diam.
Fujimoto et al. (2007) [17]	Hybrid larch	R	20, 20, 320	Probe (2)	NA
Fujimoto et al. (2008) [18]	Hybrid larch	R and T	20, 20, 320	Probe (2)	NA
Lestander et al. (2008) [19]	Pinus sylvestris	X	3GR, 6.3, 120.5	Probe (NA)	4 mm diam.
Zhao et al. (2009) [20]	Eucalyptus pellita	R and T	NA	Probe (NA)	NA
Kothiyal and Raturi (2011) [21]	Eucalyptus tereticornis	R and T	20, 20, 300	Direct (10)	NA
Schimleck et al. (2011) [22]	Caesalpinia echinata	X	20, 20, 300	Direct (4,2,1)	5 × 5, 5 × 10, 15 × 15
				Probe (1)	15 × 15 mm
Kothiyal et al. (2014) [23]	Eucalyptus tereticornis	R and T	20, 20, 300	Direct (4)	15 mm
				Probe (4)	10 mm

Instruments from the following companies were utilized in the publications listed: ASD Field Spec [11, 12, 14, 15, 20, 22], Bran and Luebbe [17], Bruker [6, 18, 21, 23], FOSS [7–9, 13, 19, 22], LT industries [5], Perkin Elmer [16], and Thermo Nicolet [10, 14].