. 2021 May 26;7(22):eabb7572. doi: 10.1126/sciadv.abb7572

Table 1. Differential effects of temperature and precipitation on tree ecophysiology based on slope aspect.

Summary of mixed-effects models showing the habitat-specific magnitude and direction of the effects of climate variables on (A) iWUE and (B) BAI. Higher temperatures make all trees more water use efficient but more so on south aspects. Less cold years favor growth of trees on north-facing aspects. More precipitation makes all trees less water use efficient but especially south aspect trees. More precipitation also increases growth on south aspects relative to north aspects. ICC, intraclass correlation coefficient.

(A)
	Temperature iWUE (mmol/mol)				Precipitation iWUE (mmol/mol)
Predictors	Estimates	SE	Statistic	P	Estimates	SE	Statistic	P
(Intercept)	48.0497	7.0356	6.8295	<0.001	94.1427	6.0395	15.5877	<0.001
Mean annual max. temp	1.5002	0.2864	5.2389	<0.001
Aspect [south]	−7.8136	3.95	−1.9781	0.0501	12.1106	2.9478	4.1083	0.0002
Tree size	0.0603	0.0737	0.8185	0.4441	0.0594	0.0737	0.8066	0.4504
Tree age	0.0154	0.0279	0.5509	0.6012	0.0161	0.0279	0.5792	0.5832
Mean annual max. temp * aspect [south]	0.6233	0.1628	3.8291	0.0001
Mean annual precipitation					−5.9019	2.1804	−2.7068	0.009
Mean annual precipitation * aspect [south]					−2.7747	1.0391	−2.6704	0.0079
Random effects
σ²		18.43				18.74
τ⁰⁰		21.77 CO2.mean				33.92 CO2.mean
		5.78 TreeID				5.76 TreeID
ICC		0.47 CO2.mean				0.58 CO2.mean
		0.13 TreeID				0.10 TreeID
Observations		460				460
Marginal R²/conditional R²		0.412/0.764				0.251/0.760
(B)
	Temperature BAI (cm²)				Precipitation BAI (cm²)
Predictors	Estimates	SE	Statistic	P	Estimates	SE	Statistic	P
(Intercept)	−9.5589	4.2518	−2.2482	0.0257	14.3815	3.7625	3.8223	0.0002
Mean annual max. temp	0.8741	0.1312	6.6635	<0.001
Aspect [south]	19.129	3.4773	5.5011	<0.001	−11.751	2.5519	−4.6046	<0.001
Tree size	0.8482	0.0498	17.031	<0.001	0.8482	0.0498	17.0354	<0.001
Tree age	−0.2925	0.0319	−9.1701	<0.001	−0.2928	0.0319	−9.1793	<0.001
Mean annual max. temp * aspect [south]	−1.0422	0.1478	−7.0535	<0.001
Mean annual precipitation					−2.1489	0.8818	−2.437	0.0166
Mean annual precipitation * aspect [south]					3.5814	0.9327	3.84	0.0001
Random effects
σ²		156.84				158.06
τ⁰⁰		37.63 TreeID				37.59 TreeID
		2.01 CO₂				2.79 CO₂
ICC		0.19 TreeID				0.19 TreeID
		0.01 CO₂				0.01 CO₂
Observations		4642				4642
Marginal R²/conditional R²		0.425/0.541				0.419/0.537