Table 4.
Relative level of non-terpenic VOCs from red pine needles analyzed by HS-SPME-GC/MS

Chemical Class	Compounds	Intact	Senescent	Litter
Alkane	1-Hexanol	16.6 ± 23.71	14.6 ± 18.2	4.0 ± 2.6
	2-Hexanol	n. d2	2.9 ± 0.4	0.8 ± 0.1
	4-Methyl-2-pentanol	n. d	1.8 ± 0.7	1.6 ± 1.6
	4-Methyl-2-pentanone	n. d	1.2 ± 1.2	2.8 ± 2.6
	2-Methyl-3-pentanone	n. d	0.9 ± 0.7	1.6 ± 1.0
	Cyclohexanol	1.0 ± 1.9	0.9 ± 0.8	1.1 ± 0.9
	2-Butoxy-ethanol	n. d	2.4 ± 0.4	1.5 ± 1.1
	Methyl hexanoate	1.7 ± 1.6	4.4 ± 4.9	4.6 ± 4.9
Alkene	1-Penten-3-ol	12.5 ± 5.0	0.8 ± 0.5	0.6 ± 0.4
	2,4-Hexadienal	1.8 ± 1.3	0.6 ± 0.7	n. d
	2-Methyl-2-butenoate	n. d	0.5 ± 0.4	1.2 ± 0.6
	2-Heptenal	1.2 ± 0.7	1.9 ± 0.4	0.2 ± 0.1
	(E)-2-Hexenal	203.8 ± 108.8	2.6 ± 0.5	n. d
	(Z)-2-Penten-1-ol	8.2 ± 4.4	0.3 ± 0.1	n. d
	Isoprenol	0.3 ± 0.2	2.0 ± 2.1	3.3 ± 3.3
	Sulcatone	0.6 ± 0.1	2.0 ± 0.6	3.0 ± 0.7
	Cyclohexene oxide	4.6 ± 0.5	0.6 ± 0.1	0.8 ± 0.1
	(Z)-3-Hexen-1-ol	25.5 ± 20.0	17.9 ± 19.8	1.9 ± 2.1
Heterocyclics
Furan	2-Ethyl-furan	3.7 ± 2.5	0.4 ± 0.3	0.2 ± 0.1
Aromatic	Benzaldehyde	2.6 ± 1.8	21.1 ± 21.1	23.3 ± 12.7
	Methyl benzoate	7.8 ± 6.1	25.2 ± 11.5	19.2 ± 16.6

Compound amount was estimated based on the percent ratio of peak area of identified compound to internal standard peak area. Each amount was calculated based on extracted ion chromatograms from scanning data.
n. d: not detected