Table 2. r² values in multiple regression analyses of soil carbon, nitrogen, phosphorus and their ratios.

Model	SOC	TN	TP	AN	AP	TC:N	TC:P	TN:P	AN:P
Aridity (A)	0.567***	0.520***	0.331***	0.184***	0.001 ns	0.194***	0.324***	0.326***	0.100**
Temperature (T)	0.761***	0.742***	0.306***	0.161***	0.040 ns	0.353***	0.555***	0.568***	0.133**
Rainfall (R)	0.419***	0.370***	0.275***	0.136**	0.008 ns	0.116**	0.224***	0.212***	0.063*
Soil type (ST)	0.336***	0.282**	0.092 ns	0.073 ns	0.034 ns	0.124 ns	0.270**	0.218**	0.003 ns
Soil pH (pH)	0.620***	0.642***	0.154***	0.308***	0.098*	0.372***	0.542***	0.567***	0.268***
Plant cover (PC)	0.088*	0.079*	0.073*	0.005 ns	0.016 ns	0.020 ns	0.030 ns	0.033 ns	0.009 ns
T + R	0.765***	0.747***	0.336***	0.161**	0.041 ns	0.359***	0.558***	0.576***	0.119**
T + R + ST	0.779***	0.785***	0.419***	0.244***	0.010 ns	0.371***	0.592***	0.572***	0.125*
T + R + ST + pH	0.802***	0.827***	0.426***	0.321***	0.112 ns	0.460***	0.663***	0.665***	0.268**
Overall	0.810***	0.831**	0.427***	0.289**	0.097 ns	0.458***	0.670***	0.667***	0.239*
stepAIC	−213	−181	−225	−205	−189	−260	−221	−177	−136
TotalAIC	−211	−170	−214	−200	−180	−252	−210	−170	−126

ns (not significant, P > 0.05), *(P < 0.05), **(P < 0.01), ***(P < 0.001). The ‘+’ includes the relevant predictors and their interactions. The models labelled ‘Overall’ includes temperature, rainfall, soil pH and plant cover as explanatory variables. StepAIC: AIC value of model selected by the stepwise procedure. TotalAIC: AIC value of model with all parameters. AIC is the Akaike Information Criterion.