Table 4. Ratios of syringyl (S), guaiacyl (G), and hydroxyphenyl (H) lignin units in suberin samples from Quercus variabilis and Quercus suber, analyzed via Py-GC/MS

	Q. variabilis		Q. suber
	Republic of Korea	China	Portugal	Italy
Lignin moieties	4.22	3.51	4.74	2.98
H	2.58	2.22	3.22	1.37
G	1.34	0.98	1.40	1.45
S	0.30	0.31	0.12	0.16
S/G	0.23	0.32	0.09	0.11
H:G:S	1:0.5:0.1	1:0.4:0.1	1:0.4:0.04	1:1.1:0.1

The S/G and H:G:S ratios reflect regional and species-specific variation in lignin structure and suberin composition.
Py-GC/MS: pyrolysis–gas chromatography/mass spectrometry.