TABLE 3.

Mixed effect modeling of the relationships between nutrients expressed on a tissue volume basis (Θ_v) and water content (Φ).

Θv (mol/m3) vs. Water content Φ (m3/m3)
Nutrient	[Ca]v	[K]v	[Mg]v	[N]v	[Na]v	[P]v
Fixed effects
Intercept (γ00)	1.59	1.89	1.42	2.44	0.70	0.97
Slope (γ10)	0.71	1.34	0.98	0.66	0.67	0.84
P	0.102	<0.001	0.008	0.012	0.175	0.014
$R_{\text{M}}^2$	0.01	0.13	0.04	0.04	0.00	0.02
$R_{\text{C}}^2$	0.71	0.68	0.61	0.74	0.91	0.76
Random effects
Species (σs2)	0.061	0.023	0.052	0.017	0.133	0.015
Plot (σp2)	0.059	0.009	0.006	0.021	0.502	0.107
Residual (σr2)	0.050	0.020	0.038	0.014	0.063	0.041

Subscript “v” indicates that concentrations are on a volume basis.

All parameters were estimated using restricted maximum likelihood (REML).

σ² represents the variance of each term.

$R_M^2$, marginal R² that represents the variation explained by the fixed effects; $R_{\text{C}}^2$, conditional R² that represents the variation of the whole model (including the random effects).

Significant relationships (P < 0.05) are in bold.

Random effects present the variance of the random intercepts (Equation 6).