Table 2.

Summary statistics for correlations of all measured variables and iWUE

Group	iWUE predictor	Effect size	Adjusted R2	Significance
Soil development	Clay	−4.7	0.08	<0.0001
	Fed	−4.1	0.06	<0.0001
	Eped	−5.6	0.12	<0.0001
	SWS	−3.9	0.06	<0.0001
Productivity	LAI	−6.5	0.16	<0.0001
	NDVI	−3.3	0.04	0.0003
	VPD maximum	−5.9	0.13	<0.0001
Soil and litter quality	C:N litter	0.50	0	0.56
	%N litter	0.40	0	0.65
	%N soil	−0.10	0	0.91
	%C soil	−0.40	0	0.65
	Feo	0.05	0	0.95
Seasonality	Temperature	−5.5	0.11	<0.0001
	Precipitation	1.7	0.01	0.05
	cvPPT	−0.97	0	0.27
	RUN	4.0	0.06	<0.0001
	RCH	−1.4	0	0.11
	SD NDVI	1.1	0	0.21
Other	Elevation	5.8	0.12	<0.0001
	SLA	−7.2	0.19	<0.0001
Categorical	Species		0.24	<0.0001
	Parent material		0.02	0.01
	Climate zone		0.13	<0.0001

The relationships are separated into major categories that are expected to effect iWUE. All variables were standardized to a mean of 0 and SD of 1 before analysis and related to untransformed iWUE values.