Introduction
Materials and methods
Description of samples
Fourier transform infrared spectroscopy
No. | Sites | Site codes | Tree ID | Species | No. recorded spectra |
---|---|---|---|---|---|
1 | Artikutza | Ps-ART | Ps-ART-A |
P. sylvestris
| 15 |
2 | Artikutza | Ps-ART | Ps-ART-B |
P. sylvestris
| 15 |
3 | Linarejos (plot 1) | Pn-LIN01 | Pn-LIN01-A |
P. nigra
| 15 |
4 | Linarejos (plot 1) | Pn-LIN01 | Pn-LIN01-B |
P. nigra
| 15 |
5 | Linarejos (plot 3) | Pn-LIN03 | Pn-LIN03-A |
P. nigra
| 15 |
6 | Linarejos (plot 3) | Pn-LIN03 | Pn-LIN03-B |
P. nigra
| 15 |
7 | La Sagra | Pn-LSA | Pn-LSA-A |
P. nigra
| 15 |
8 | La Sagra | Pn-LSA | Pn-LSA-B |
P. nigra
| 15 |
Total | 120 |
Data analysis
No. | Bands (cm−1) | Band assignments (References) | PCA factora
|
---|---|---|---|
1 | 805 | Vibration of mannan in hemicellulose and CH out of plane bending in phenyl rings (Evans et al. 1992) | PC1 |
2 | 825 | CH out of plane bending in guaiacyl units (Faix 1991) | PC3 |
3 | 860 | PC3 | |
4 | 900 | PC1 | |
5 | 945 | O–H out of plane deformation in carboxylic acid (Shearer 1989) | PC2 |
6 | 960 | PC3 | |
7 | 985 | CO stretching in cellulose (Herrera et al. 2014) | PC1 |
8 | 1005 | C–O stretch in cellulose (Liang and Marchessault 1959) | PC1 |
9 | 1025 | C–O stretching in primary alcohols in cellulose (Popescu et al. 2007) | PC1 |
10 | 1055 | C–O stretching of secondary alcohols (Faix 1991) | PC1 |
11 | 1105 | PC1 | |
12 | 1155 | PC1 | |
13 | 1185 | C–O stretching in Cellulose (Zhou et al. 2015) | PC1 |
14 | 1225 | – | |
15 | 1265 | PC3 | |
16 | 1315 | PC1 | |
17 | 1335 | – | |
18 | 1360 | PC1 | |
19 | 1385 | C–O stretching in cellulose and hemicellulose (Labbé et al. 2006) | – |
20 | 1405 | C=O in carboxylic groups in carboxylic acid, ester (Zhang et al. 2010) | PC2 |
21 | 1425 | PC3 | |
22 | 1465 | PC3 | |
23 | 1510 | PC3 | |
24 | 1590 | PC3 | |
25 | 1610 | C=O stretching conjugated to the aromatic ring, and in carboxylic groups in lignin, carboxylic acid, ester compounds (Zhao et al. 2014) | – |
26 | 1635 | – | |
27 | 1655 | – | |
28 | 1690 | PC2 | |
29 | 1730 | PC1 |
Results and discussion
Absorbance and second derivative spectra
Discriminant analysis
Discrimination based on lignin and polysaccharide absorption bands separately
Stepwise discriminant analysis with all absorption bands
Interpretation of absorption bands that discriminate between species and locations
Bands (cm−1) | DF1T
| DF2Total
|
---|---|---|
860 | 2.33 | − 0.23 |
900 | − 1.56 | 1.44 |
1105 | 1.62 | 1.08 |
1225 | − 1.13 | − 0.94 |
1315 | − 1.83 | − 3.83 |
1335 | 1.70 | 5.15 |
1385 | 2.21 | 1.11 |
1405 | 2.10 | 1.55 |
1425 | − 3.44 | − 0.94 |
1610 | 1.09 | − 1.31 |
1635 | − 4.28 | 0.95 |
1655 | 3.52 | − 1.91 |