Table 1.

Results of linear mixed effects models on the influence of soil depth and root diameter as fixed continuous variables on eight wood anatomical variables in roots of European beech (Fagus sylvatica) (n = 197), and the interaction of both factors.

	Soil depth			Root diameter			Soil depth:root diameter			VCintra	VCinter	VCintra	VCinter
Variable	Δi	LR	P	Δi	LR	P	Δi	LR	P	Root diameter class		Soil depth class
Age	0.27	2.27	0.13	96.86	98.86	<0.001	1.82	0.18	0.67	31.40	68.60	96.08	3.92
Axylem	1.18	0.82	0.37	406.85	408.85	<0.001	0.57	2.57	0.11	5.27	94.73	99.53	0.47
Alumen:Axylem	1.24	3.24	0.07	6.40	8.40	0.004	2.22	4.22	0.04	98.46	1.54	91.10	8.90
VD	1.55	0.45	0.50	64.95	66.95	<0.001	1.70	0.30	0.58	51.38	48.62	97.52	2.48
D	1.97	0.03	0.86	53.44	55.44	<0.001	1.92	0.08	0.78	50.35	49.65	96.13	3.87
Dmax	0.13	1.87	0.17	77.39	79.39	<0.001	1.68	0.32	0.57	45.04	54.96	97.43	2.57
Dh	1.35	0.65	0.42	36.46	38.46	<0.001	1.98	0.02	0.90	62.92	37.08	98.24	1.76
Kp	0.61	2.61	0.11	27.59	29.59	<0.001	0.53	1.47	0.23	74.95	25.05	95.88	4.12

Studied traits are root age (years), cross-sectional xylem area (A_xylem, mm²), relative vessel lumen area (A_lumen: A_xylem, %), vessel density (VD, n mm^-2), vessel diameter (D, μm), maximal vessel diameter (D_max, μm), hydraulically weighted vessel diameter (D_h, μm) and potential hydraulic conductivity (K_p, kg m^-1 MPa^-1 s^-1). Also expressed is the variation of the traits (variance component, VC in %) within (VC_intra) and between (VC_inter) different root diameter classes (n = 9) and soil depth classes (n = 7). Given are the delta Akaike information criterion (Δi), the likelihood ratio (LR) and probability of error (P-value). Significant correlations (p < 0.05) are shown in bold.