Ecological Archives E089-011-A2

**Eric G. Lamb. 2008. Direct and indirect control of grassland community structure by litter, resources, and biomass. Ecology 89:216–225.**

Appendix B. Full model results including direct and indirect effects and unstandardized path coefficients.

TABLE B1. Unstandardized and standardized path coefficients, the standard error of the unstandardized coefficients and t test results from the structural equation model of species richness. The paths were from the variables in lower case to the variable in bold at the top of each section in the table.

	Unstand. path coefficients	Std Error	t value	P value	Standard. coefficients
Litter
Initial litter	1.187	0.338	3.507	<0.001	0.29
Nitrogen	0.467	0.072	6.514	0	0.384
Water	0.293	0.061	4.827	0	0.228
Shade	0.615	0.089	6.949	0	0.478
Shoot biomass	0.441	0.18	2.453	0.015	0.293

Shoot Biomass
Nitrogen	0.03	0.057	0.528	0.598	0.037
Water	0.156	0.043	3.618	<0.001	0.182
Shade	-0.446	0.051	-8.745	<0.001	-0.522

Root Biomass
Nitrogen	0.014	0.068	0.2	0.842	0.016
Water	-0.255	0.073	-3.511	0.001	-0.28
Shade	-0.486	0.084	-5.798	<0.001	-0.533

Light Interception
Shoot biomass	0.064	0.049	1.301	0.196	0.093
Litter biomass	0.053	0.027	1.946	0.054	0.115
Shade	0.533	0.042	12.792	<0.001	0.909
Water	0.108	0.035	3.098	0.002	0.183
Nitrogen	0.097	0.024	4.126	<0.001	0.175

Species Richness
Shoot biomass	0.148	0.1	1.478	0.142	0.139
Root biomass	0.02	0.114	0.173	0.863	0.02
Litter	-0.166	0.067	-2.489	0.014	-0.236
Initial species richness	0.255	0.097	2.636	0.009	0.2
Light interception	0.032	0.223	0.142	0.887	0.021
Nitrogen	-0.125	0.053	-2.356	0.020	-0.147
Water	0.043	0.071	0.601	0.549	0.047
Shade	-0.345	0.165	-2.09	0.039	-0.381

Shoot Biomass- Root Biomass Covariance	0.039	0.011	3.442	<0.001	0.226

TABLE B2. Total direct and indirect effects in the species richness model. These effects were calculated using standardized path coefficients. Nonsignificant effects are indicated by "ns", while a dash indicates a path that was not included in the model.

Litter Cover	Direct	Indirect	Total
Initial litter cover	0.290	-	0.290
Nitrogen	0.384	ns	0.384
Water	0.228	0.053	0.281
Shade	0.478	-0.153	0.325
Shoot biomass	0.293	-	0.293

Shoot Biomass	Direct	Indirect	Total
Nitrogen	ns	-	ns
Water	0.182	-	0.182
Shade	-0.522	-	-0.522

Root Biomass	Direct	Indirect	Total
Nitrogen	ns	-	ns
Water	-0.280	-	-0.280
Shade	-0.533	-	-0.533

Light Interception	Direct	Indirect	Total
Shoot biomass	ns	0.034	0.034
Litter cover	0.115	-	0.115
Shade	0.909	0.037	0.946
Water	0.183	0.032	0.215
Nitrogen	0.175	0.044	0.219

Species Richness	Direct	Indirect	Total
Shoot biomass	ns	-0.069	-0.069
Root biomass	ns	-	ns
Litter cover	-0.236	ns	-0.236
Initial richness	0.200	-	0.200
Light interception	ns	-	ns
Nitrogen	-0.147	-0.091	-0.238
Water	ns	-0.054	-0.054
Shade	-0.381	-0.113	-0.494
Initial litter	-	-0.068	-0.068

TABLE B3. Unstandardized and standardized path coefficients, the standard error of the unstandardized coefficients and t test results from the structural equation model of species evenness. The paths were from the variables in lower case to the variable in bold at the top of each section in the table.

	Unstand. path coefficients	Std Error	t value	P value	Standard. coefficients
Litter
Initial litter	1.187	0.338	3.507	<0.001	0.29
Nitrogen	0.467	0.072	6.514	<0.001	0.384
Water	0.293	0.061	4.827	<0.001	0.228
Shade	0.615	0.089	6.949	<0.001	0.478
Shoot biomass	0.441	0.18	2.453	0.015	0.293

Shoot Biomass
Nitrogen	0.03	0.057	0.528	0.598	0.037
Water	0.156	0.043	3.618	<0.001	0.182
Shade	-0.446	0.051	-8.745	<0.001	-0.522

Root Biomass
Nitrogen	0.014	0.068	0.2	0.842	0.016
Water	-0.255	0.073	-3.511	<0.001	-0.28
Shade	-0.486	0.084	-5.798	<0.001	-0.533

Light Interception
Shoot biomass	0.064	0.049	1.301	0.196	0.093
Litter biomass	0.053	0.027	1.946	0.054	0.115
Shade	0.533	0.042	12.792	<0.001	0.909
Water	0.108	0.035	3.098	0.002	0.183
Nitrogen	0.097	0.024	4.126	<0.001	0.175

Species Evenness
Shoot biomass	0.028	0.048	0.582	0.562	0.083
Root biomass	-0.008	0.026	-0.311	0.756	-0.025
Litter	-0.066	0.016	-4.079	<0.001	-0.294
Initial species evenness	0.151	0.059	2.58	0.011	0.136
Light interception	-0.137	0.079	-1.73	0.086	-0.28
Nitrogen	0.069	0.026	2.649	0.009	0.254
Water	0.004	0.025	0.175	0.861	0.015
Shade	0.039	0.066	0.59	0.556	0.135

Shoot Biomass- Root Biomass Covariance	0.039	0.011	3.442	<0.001	0.226

TABLE B4. Total direct and indirect effects in the evenness model. These effects were calculated using standardized path coefficients. Nonsignificant effects are indicated by "ns", while a dash indicates a path that was not included in the model.

Litter Cover	Direct	Indirect	Total
Initial litter cover	0.290	-	0.290
Nitrogen	0.384	ns	0.384
Water	0.228	0.053	0.281
Shade	0.478	-0.153	0.325
Shoot biomass	0.293	-	0.293

Shoot Biomass	Direct	Indirect	Total
Nitrogen	ns	-	ns
Water	0.182	-	0.182
Shade	-0.522	-	-0.522

Root Biomass	Direct	Indirect	Total
Nitrogen	ns	-	ns
Water	-0.280	-	-0.280
Shade	-0.533	-	-0.533

Light Interception	Direct	Indirect	Total
Shoot biomass	ns	0.034	0.034
Litter cover	0.115	-	0.115
Shade	0.909	0.037	0.946
Water	0.183	0.032	0.215
Nitrogen	0.175	0.044	0.219

Species Evenness	Direct	Indirect	Total
Shoot biomass	ns	-0.095	-0.095
Root biomass	ns	-	ns
Litter cover	-0.294	-0.032	-0.326
Initial evenness	0.136	-	0.136
Light interception	-0.28	-	-0.28
Nitrogen	0.254	-0.162	0.092
Water	ns	-0.134	-0.134
Shade	ns	-0.350	-0.350
Initial litter	-	-0.085	-0.085

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