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NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark, G. Peter and T. Shupe
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Page 1: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

NIR spectroscopy for the rapid measurement

of wood properties

L. Schimleck, C.-L. So, D. Jones, L. Groom

R. Daniels, A. Clark, G. Peter and T. Shupe

Page 2: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Overview

• Description of NIR spectroscopy

• Application of NIR to whole-trees

• Application of NIR to lumber

• Application of NIR to short clears

• Application of NIR to cores

Page 3: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

NIR spectrum of a typical wood sample

1100 1300 1500 1700 1900 2100 2300 2500

Log

(1/R

efle

ctan

ce)

0

0.1

0.2

0.3

0.4

0.5

0.6

Wavelength (nm)

Bands arise from rotations, vibrations of bonds in molecules

O-HN-H

S-H

N-H

O-H N-H

C-H vibration throughout spectrum

Page 4: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Methodology

• Estimation of a parameter involves the following steps:

• Collect spectra of calibration samples

• Develop a calibration (regression)(y = B0 + X1*B1 + X2*B2 + ………..+ XN*BN)

• Collect NIR spectra of test (or unknown) samples

• Estimate parameter of interest for test set samples using the calibration

Page 5: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Partial least squares regression

CALIBRATION MODEL

Measured CuO retention (pcf)-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2

Pred

icte

d C

uO re

tent

ion

(pcf

)

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Calibration SetValidation Set

Wavelength (nm)1000 1200 1400 1600 1800 2000 2200 2400

Rel

ativ

e In

tens

ity

-300

-200

-100

0

100

200

300

400

MOE

REGRESSION COEFF.

DECOMPOSEMATRICES

TEST SET

Wavelength (nm)

Abs

orba

nce

PREDICTED PROPERTIES

MOEMOR MFASG

MC

n x pmatrix

CALIBRATION SET

Wavelength (nm)

Abs

orba

nce

nsa

mpl

es

p variables

n x qmatrix

MEASURED PROPERTIES

MOEMOR MFASG

MC

nsam

ples

q variables

Page 6: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Laboratory determined pulp yield (%)

NIR

fitte

d pu

lp y

ield

(%)

45

50

55

60

45 50 55 60

n = 1334 factorsR2 = 0.88SEC = 0.84

Pulp yield range= 45.6 to 57.1 %

Pulp yield calibration for Tasmania

Page 7: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Within-tree property variation

MicrofibrilAngle

Page 8: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Within-tree property variation

Extractives Lignin

Hemicellulose Cellulose

Page 9: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Application of NIR to whole-trees

• Many studies, since late 1980’s

• Pulp yield, cellulose, lignin, extractives

• Based on whole-tree composite chips

• Examination of within-tree variation of PY

• Studies have shown that breast height cores provide similar calibration statistics to composite chips for whole-tree properties

• = nondestructive estimation of whole-tree properties

Page 10: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Within-tree variation of pulp yield

• Little is known about the within-tree variation of

pulp yield. NIR predictions of pulp yield can be

used to obtain maps that show the variation

47 50 53 56 59 62

Page 11: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Whole-tree chip versus core calibrations

•Core and whole-tree calibrations were similar for basic density, pentosans, specific cons and total lignin

• Core calibrations could be used to rank trees

• 1.30 m identified as the most suitable sampling height

0

0.2

0.4

0.6

0.8

1.0

BasicDensity

SodaCharge

Pulpyield

Totallignin

SpecificCons.

Pento-sans

R2

Wood property calibrations Whole-tree

0.65 m core

1.30 m core

Schimleck et al. (2005). Estimation of whole-tree wood quality traits using near infrared spectra collected from increment cores. Appita J. (in press)

Page 12: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Application of NIR to lumber

• Meder et al. (2003)

• 185 P. radiata cant centers scanned by NIR in mill scale trial

• Aim to ID corewood stiff enough to be graded as MGP 8 (lowest structural grade)

• MGP 8 worth $80/m3 more than non-structural

• Data from 409 boards available for regression

• Calibration R2 = 0.54 (big logs)

• Calibration R2 = 0.57 (small logs)

• Sufficient for economic segregation of cants

Page 13: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Bruker Matrix-F scanning a cant

Scanning speed approx. 2 m/s

Picture courtesy A. Thumm and R. Meder, Forest Research, New Zealand

Page 14: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Application of NIR to lumber

• Meder et al. (2003) cont.

• Based on stiffness, 50% of central boards could be upgraded to MGP 8

• Further calibration expected to increase percentage of upgraded boards

• Many upgraded boards were unstable

• Both stiffness and stability (twist) must be predicted for NIR to be useful for segregating radiata pine structural timber

• Calibration for twist investigated (R2 = 0.26)

Page 15: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Application of NIR to short-clears

• Several studies reported, different species and approaches

• Hoffmeyer and Pedersen (1995) P. abies

• Gindl et al. (2001) L. decidua

• Thumm and Meder (2001) P. radiata

• Schimleck et al. (2001) E. delegatensis, Schimleck et al. (2001) P. radiata

• Via et al. (2003) P. palustris

• Kelley et al. (2004) 6 softwood species

• Density, MOE and MOR examined

Page 16: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Measuring Mechanical Properties

IncrementCore

(SilviScan)

BendingSpecimen(Instron)

NIRNIR

Page 17: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Stiffness (Bending Specimens)

Calibration (313 spectra)

Calibration (313 spectra)

Prediction (156 spectra)

Prediction (156 spectra)

NIR

-MO

EN

IR-M

OE

Instron-MOEInstron-MOE

0 1e+6 2e+6 3e+6 4e+60

1e+6

2e+6

3e+6

4e+6

0 1e+6 2e+6 3e+6 4e+6 5e+60

1e+6

2e+6

3e+6

4e+6

5e+6

8 factorsR2=0.82SEC=0.4 Mpsi

R2=0.79SEP=0.4 Mpsi

Page 18: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Strength (Bending Specimens)N

IR-M

OR

NIR

-MO

R

0 10000 20000 30000 400000

10000

20000

30000

40000

0 10000 20000 30000 400000

10000

20000

30000

40000

Instron-MORInstron-MOR

8 factorsR2=0.80SEC=4 Kpsi

R2=0.75SEP=4 Kpsi

Calibration (313 spectra)

Calibration (313 spectra)

Prediction (156 spectra)

Prediction (156 spectra)

Page 19: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Application of NIR to cores

Radial strips cut from cores used but core surface OK for

NIR spectroscopy

Properties examined :

Tracheid length (FQA)

Cellulose, sugars, lignin (wet chemistry)

Air-dry density, MFA, stiffness, tracheid properties (SilviScan)

Page 20: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Georgia-wide calibrations

• P. taeda grown in 3 regions in Georgia

• Three sites selected as being

representative of each region

• Selection based on site index

• Ten trees selected per site representing a

range of breast height diameters

• Pith-bark breast height samples obtained

Page 21: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Georgia-wide calibrations

• Strong calibrations for density, MFA, stiffness and tracheid coarseness, length and wall thickness

• These calibrations performed well on the separate test set

• Strong calibrations for cellulose, lignin, glucan, arabinan, mannan and xylan

• Moderate prediction accuracy - possibly due to the small number of samples

Page 22: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

MFA – 729 MSC treated spectra

5

15

25

35

45

5 15 25 35 45

Fitted MFA (degrees)

Mea

sure

d M

FA (d

egre

es)

Factors = 8R2 = 0.90SEC = 2.33SECV = 2.38RPD = 3.11

Page 23: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Predicted MFA (225 spectra)

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50

Predicted MFA (degrees)

Mea

sure

d M

FA (d

egre

es)

Factors=8R2= 0.84SEP= 3.12RPD= 2.34

Page 24: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

What resolution??

• Increasing resolution = decrease in

calibration accuracy

• Management of spectra becomes

difficult owing to large number of

spectra

• Fiber optic probes with a small spot

size provides options

Page 25: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

2 mm MFA calibration (4156 spectra)

8 FactorsR2 = 0.75

SEC = 4.05SECV = 4.10RPD = 1.48

0

10

20

30

40

50

60

0 10 20 30 40 50 60

Fitted MFA (degrees)

Mea

sure

d M

FA (d

egre

es)

Page 26: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

2 mm MFA prediction

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

Distance from pith (mm)

MFA

(deg

)

Page 27: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

2 mm MFA prediction

05

1015202530354045

0 10 20 30 40 50 60 70 80 90

Distance from pith (mm)

MFA

(deg

)

Page 28: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Wood property calibrations – green versus dry wood

0.10

0.15

0.20

0.25

0.30

0.35

1100 1300 1500 1700 1900 2100 2300 2500

T - greenRL - green T - dryRL - dry

Wavelength (nm)Wavelength (nm)

Log

(1/R

)Lo

g (1

/R)

Page 29: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Stiffness (green wood spectra)

0

5

10

15

20

25

30

0 5 10 15 20 25 300

5

10

15

20

25

30

0 5 10 15 20 25 30

CalibrationCalibration PredictionPrediction

SS2-

stiff

ness

SS2-

stiff

ness

NIR-stiffnessNIR-stiffness

5 factorsR2=0.88

SEC=1.8 GPaR2=0.81

SEP=3.0 GPa

Page 30: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Stiffness (dry wood spectra)

0

5

10

15

20

25

30

0 5 10 15 20 25 300

5

10

15

20

25

30

0 5 10 15 20 25 30

CalibrationCalibration PredictionPrediction

SS2-

stiff

ness

SS2-

stiff

ness

NIR-stiffnessNIR-stiffness

6 factorsR2=0.95

SEC=1.1 GPaR2=0.92

SEP=1.9 GPa

Page 31: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

NIRVANA – Near Infrared Visual & Automated Numerical Analysis

• Automated spectra collection

• High resolution video camera

• Real time property predictions

• Ideal for process monitoring &

QC applications

Page 32: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

MOE VariationM

OE

(GPa

)M

OE

(GPa

)

Core Length (mm)Core Length (mm)

0.E+00

1.E+06

2.E+06

3.E+06

4.E+06

5.E+06

6.E+06

7.E+06

8.E+06

9.E+06

-250 -200 -150 -100 -50 0 50 100 150 200 250

Page 33: NIR spectroscopy for the rapid measurement of wood …NIR spectroscopy for the rapid measurement of wood properties L. Schimleck, C.-L. So, D. Jones, L. Groom R. Daniels, A. Clark,

Conclusions – NIR spectroscopy

• Determination of within-tree variation

• Estimation of whole-tree properties

• Applicable to milled wood, short-clears, increment cores

• Automatic scanning of cores possible

• Important to improve resolution

• Green wood can be examined


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