. 2014 Oct 17;5:562. doi: 10.3389/fpls.2014.00562

Table 2.

Categorical and regression moderators examined for the three^* summary effects showing significant true heterogeneity among effect sizes.

	Shoot K⁺/Na⁺ ratio					Root K⁺/Na⁺ ratio					Root proline
Categorical Moderator	Qm	n	p_hetero	df	I²	*Q_m*	n	p_hetero	df	I²	*Q_m*	n	p_hetero	df	I²
A
% NaCl in salt stress^***	11.4	249	0.003	2	82.4	6.7	95	0.009	2	85.1
Stress severity	6.8	158	0.009	1	85.2	1.0	56	0.326	1	0.0	0.0	90	0.913	1	0.0
AM taxa^**	43.7	242	<0.001	6	86.3	9.0	88	0.061	4	55.7	28.7	111	<0.001	3	89.5
Host water status^***	<0.01	23	0.952	1	0.0	0.0	23	0.952	1	0.0
Host type	23.7	249	<0.001	2	91.6	1.1	95	0.591	2	0.0	4.9	123	0.086	2	59.2
Woodiness	0.2	249	0.697	1	0.0	3.1	95	0.077	1	68.0	3.5	123	0.060	1	71.7
Shoot size	21.8	248	<0.001	2	90.8	4.7	74	0.095	2	57.5	0.9	116	0.636	2	0.0
Regression Moderator	n	intercept	slope	p_hetero	I²	n	intercept	slope	p_hetero	I²	n	intercept	slope	p_hetero	I²
B
Time of exposure	234	0.691	−0.004	0.070	14.0	88	0.964	−0.010	0.002	18.6	123	−0.196	0.005	0.015	15.8
Root colonization	225	0.222	0.006	0.009	17.3	85	0.113	0.005	0.172	25.2	118	0.153	−0.002	0.413	16.0

Q_m = between study heterogeneity; n = sample size; p_hetero = probability that all observed (total) heterogeneity is due to sampling error (expected variation); df = degrees of freedom, levels within a moderator; I² = percentage of total heterogeneity due to true differences in summary effects among levels of a moderator. The levels of of each categorical moderator with their summary effect sizes, CIs, number of studies and significance values are given in Figures 2–4.

Total amino acid concentration of shoots also showed significant heterogeneity but there were not enough studies within moderator levels to perform moderator analysis for this summary effect.

^**

A single species was included as a level in the AM taxa moderator if at least 8 studies from >1 paper reported data for it. Those species with data from <8 studies or just 1 paper were grouped into “other species.”

^***

% NaCl in salt stress and Host water status are blank for root proline because of insufficient articles providing these data.