Table 2.

Results of the best linear mixed-effects models assessing the impact of the experimental treatments on Bromus tectorum and Pseudoroegneria spicata proportion of the total pot biomass (prop. biomass) and relative yield total (RYT) for both experiments

Fixed effects							Random effects
Response	Predictor	Est.	SE	df	t value	P (>)	Variance
							Trial	Residual
Experiment 1
Prop. biomass	Intercept	− 2.18	0.60	1.09	− 3.61	0.155	0.68 ± 0.83	0.49 ± 0.70
	Water (−)	0.40	0.15	80.00	2.68	0.009
	Temp (+)	0.28	0.15	80.01	1.83	0.071
	NPK (+)	0.46	0.15	80.01	3.02	0.003
	P. spicata	− 10.23	0.72	80.12	− 14.30	<0.001
Relative yield total (RYT)	Intercept	0.51	0.02	2.89	22.24	<0.001	<0.001 ± 0.02	0.007 ± 0.08
	Water (−)	− 0.04	0.02	79.00	− 2.21	0.030
	Temp (+)	0.03	0.02	79.20	1.74	0.086
	NPK (+)	0.04	0.02	79.08	2.26	0.027
	P. spicata	0.96	0.08	80.00	11.43	<0.001
	P. spicata 2	0.46	0.08	79.61	5.59	<0.001
Experiment 2
Prop. biomass	Intercept	− 1.23	0.32	1.46	− 3.87	0.098	0.15 ± 0.39	1.15 ± 1.07
	CO2 (+)	− 1.66	0.19	131.00	− 8.82	<0.001
	Water (−)	− 0.15	0.18	131.00	− 0.80	0.428
	P. spicata	− 11.29	1.74	131.61	− 6.50	<0.001
	P. spicata 2	5.69	1.84	131.06	− 3.10	0.002
	P. spicata × CO2	3.81	2.42	131.33	1.57	0.118
	P. spicata 2 × CO2	− 6.89	2.38	131.12	− 2.89	0.004
Relative yield total (RYT)	Intercept	0.68	0.05	1.19	13.58	0.030	0.004 ± 0.07	0.01 ± 0.12
	CO2 (+)	− 0.02	0.02	134.00	− 1.13	0.259
	Water (−)	− 0.01	0.02	134.00	− 0.57	0.571
	P. spicata	0.98	0.12	134.14	7.94	<0.001

The experimental treatments assessed for experiment one: P. spicata pot density, decreased water availability, water (−), increased temperature, temp. (+), and increased nutrient availability, NPK (+). The experimental treatments assessed for experiment two: P. spicata pot density, decreased water availability, water (−), and elevated atmospheric CO₂ concentration, CO₂ (+). The random effects are the mean trial and residual variance and the associated standard deviation