Table 4.

Root (>3 mm diameter) attributes correlated with trunk bending stress^{^z} during tree pulling tests on 28 trees from four planting treatments combined.

	Trunk bending stress when trunk pulled to
	10 degrees from vertical	Maximum^{^y} trunk bending stress
Root attributes	Pearson’s correlation coefficient^{^x}
Root CSA (windward 1/2)^{^w}	0.68	0.31
Total root CSA	0.64	0.31
Root CSA (0–13 cm soil depth)	0.61	0.31
Root CSA (windward 1/2, 0–13 cm soil depth)^{^w}	0.60	0.31
Root CSA (14–25 cm soil depth)	0.59	NS
Diameter of largest root (windward 1/6)^{^v}	0.59	0.32
Root CSA (windward 1/6)^{^v}	0.58	0.31
Root CSA (windward 1/2, 14–25 cm soil depth)^{^w}	0.58	NS
Total root diameter	0.57	0.48
Diameter of largest root (windward 1/6, 0–13 cm soil depth)^{^v}	0.57	0.43
Mean root diameter (windward 1/2)^{^w}	NS	0.53
Number of roots (windward 1/2)^{^w}	0.51	NS
Largest root diameter (windward 1/6, 14–25 cm soil depth)^{^v}	0.46	NS
Largest root diameter (leeward 1/6, 14–25 cm soil depth)^{^u}	NS	0.46
Total root CSA area (leeward 1/6, 14–25 cm soil depth)^{^u}	NS	0.45
Total number of roots	0.45	NS
Number of roots (windward 1/6)^{^v}	0.45	NS
Root number (windward 1/2)^{^w}	0.45	NS
Root CSA (windward 1/6)^{^v}	0.45	0.31
Number of roots (14–25 cm soil depth)	0.44	NS
Number of roots (0–13 cm soil depth)	0.39	NS
Number of roots (leeward 1/2)^{^t}	0.36	NS
Root diameter (windward 1/6)^{^v}	0.33	0.53

↵^zTrunk bending stress = (pulling force × length × trunk radius) ÷ (0.25π × trunk radius⁴).
↵^yMaximum trunk bending stress encountered as trees were pulled to 25 degrees trunk tilt in five degree increments.
↵^xSignificantly correlated at P < 0.01; NS indicates not significant at P < 0.01.
↵^wRoots in the 180 degree section opposite pulling winch.
↵^vRoots in the 60 degree section opposite pulling winch.
↵^uRoots in the 60 degree section toward pulling winch.
↵^tRoots in the 180 degree section toward pulling winch.