Appendix H. Comparisons between alternative statistical models for the proportion of the aboveground biomass contributed by each species.
TABLE H1. Comparisons between alternative statistical models for the proportion of the aboveground biomass contributed by each species. M1 = model including all main effects, M2 = model including all main effects and interactions (full model), and M3 = model including all main effects and significant interactions, as revealed by MANOVA/ANOVA analyses (see Appendix F for full ANOVA results). P values below 0.05 are in bold, and indicate that the addition of interactions (present in models M2 and M3) significantly increases the amount of variation explained by the model. All the analyses were conducted using S-Plus for Windows version 6.0 (Insightful Co, Seattle, Washington, USA). All the models assume a Gaussian distribution of errors.
Species |
Comparison |
Change in deviance |
Change in df |
F |
P |
Plantago lanceolata† |
M1 vs. M2 |
0.05 |
11 |
0.89 |
0.550 |
M1 vs. M3 |
-‡ |
- |
- |
- |
|
Lolium perenne† |
M1 vs. M2 |
0.15 |
11 |
1.70 |
0.080 |
M1 vs. M3 |
0.098 |
1 |
10.39 |
0.002 |
|
Trifolium repens† |
M1 vs. M2 |
0.01 |
11 |
1.14 |
0.338 |
M1 vs. M3 |
-‡ |
- |
- |
- |
|
Anthoxanthum odoratum |
M1 vs. M2 |
1336.15 |
11 |
0.98 |
0.466 |
M1 vs. M3 |
561.27 |
1 |
4.54 |
0.035 |
|
Holcus lanatus |
M1 vs. M2 |
2165.32 |
11 |
1.57 |
0.115 |
M1 vs. M3 |
-‡ |
- |
- |
- |
† Results are shown for arcsine-transformed data.
‡ No significant interactions were found for this species.