Impact of mechanized harvesting on compaction of sandy and clayey forest soils: results of a meta-analysis

Table 3 Correlation between the response ratio (or absolute bulk density increase) and bulk density before traffic, machine mass, machine mass per tyre, and number of machine passes, where n = number of substudies, τ = weighted Pearson product–moment correlation coefficient, * = significant value with α = 0.05 and ** = significant value with α = 0.01

Correlation	Texture	Depth class
		All depth classes			0–10 cm			10–20 cm			20–30 cm
		n	τ		n	τ		n	τ		n	τ
Absolute bulk density increase—bulk density before traffic	Alltext	288	−0.23	**	98	−0.14		102	−0.29	**	88	−0.39	**
	Clay	11	−0.77	**	4	−0.65		4	−0.75		3	/
	Sand	61	−0.05		20	−0.42		24	−0.29		17	−0.15
Response ratio—machine mass	Alltext	260	0.48	**	87	0.38	**	91	0.55	**	82	0.63	**
	Clay	11	0.19		4	0.77		4	0.77		3	/
	Sand	55	0.39	**	17	0.42		21	0.25		17	0.66	**
Response ratio—machine mass per tyre	Alltext	255	0.11		86	0.09		88	0.11		81	0.17
	Clay	11	−0.19		4	−0.10		4	−0.21		3	/
	Sand	44	0.57	**	14	0.04		16	0.17		14	0.18
Response ratio—number of machine passes	Alltext	275	0.06		92	0.07		96	0.13		87	−0.01
	Clay	11	0.35		4	0.93		4	0.26		3	−0.91
	Sand	55	−0.13		17	0.08		21	−0.13		17	0.05

ISSN: 1297-966X