Table 7.

Three-dimensional PCA pair-wise comparison of headspace volatile metabolites released from Tilia sp. wood blocks decayed by different wood decay fungi (Armillaria mellea, A. ostoyae, Ganoderma lucidum, Heterobasidion annosum, Inonotus dryadeus) relative to undecayed healthy (control) wood blocks.

Analyte 1 volatiles	Analyte 2 volatiles	Quality factor significance1
Undecayed healthy Tilia sp.	Tilia sp. decayed by A. mellea	13,527 ***
	Tilia sp. decayed by A. ostoyae	9,832 ***
	Tilia sp. decayed by G. lucidum	27,957 ****
	Tilia sp. decayed by H. annosum	51,873 ****
	Tilia sp. decayed by I. dryadeus	3,567 **

¹Statistical levels of difference between analyte aroma classes, indicated by quality factor significance according to 3-d PCA, are based on the following approximate scale of significant differences: * = P < 0.01, ** = P < 0.001, *** = P < 0.0001; **** = P < 0.00001, respectively. Quality factor (QF) is a numerical value that provides an absolute measurement of the discrimination (statistical difference) between two sample types, being compared using PCA, by indicating the distance between the centers of the data clusters being compared relative to the spread distribution of those two clusters. A quality factor of 2 or more is considered a significant discrimination at an approximately statistical significance level of P = 0.10.