Table III. Two-way ANOVA (proc general linear model) results testing the influence of the class variables species (A. platanoides, C. betulus, Q. robur, and T. cordata), root order class (≥3, 1 + 2 brown, and 1 + 2 white), diameter class (0–2 and ≥2 mm), and species × class effects on the dependent variables RR_DWT, RR_SA, and RR_VOL.

DF, Degree of freedom; SS I, sum of squares Type 1.

Source	DF	RRDWT			RRSA			RRVOL
		SS I	F	P	SS I	F	P	SS I	F	P
Species	3	863	8.56	<0.001	0.001	2.43	0.067	5.07	4.07	0.008
Root order class	2	11,800	175.63	<0.001	0.088	295.74	<0.001	17.16	20.65	<0.001
Diameter class	1	28	0.86	0.355	0.001	7.77	0.006	4.26	10.26	0.002
Species × root order class	6	99	0.49	0.814	0.007	8.10	<0.001	1.56	3.75	0.002
Species × diameter class	2	38	0.57	0.568	0.004	14.51	<0.001	2.42	2.91	0.057
Model	14	12,829	27.28	<0.001	0.102	48.87	<0.001	38.25	6.58	<0.001
Error	177	5,912			0.026			73.52