Ecological Archives A016-055-A2

Alejandro C. Costamagna and Douglas A. Landis. 2006. Predators exert top-down control of soybean aphid across a gradient of agricultural management systems. Ecological Applications 16:1619–1628.

Appendix B. A table showing ANOVA results for (a) fixed and (b) random effects and (c) slicing tests results of the effect of agricultural management system and predator manipulation treatments on Aphis glycines within large field cages at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, 2003.

a) Full model with fixed effects


 

df

F

P


Agricultural treatment

2, 10

5.56

0.0237

Predator treatment

2, 27

94.63

< 0.0001

Agricultural treat. × predator treat.

4, 27

2.50

0.0661

Date

1, 42

644.46

< 0.0001

Agricultural treat × date

2, 42

0.55

0.5827

Predator treat × date

2, 42

1.47

0.2424

Agricultural treat. × predator treat. × date

4, 42

0.65

0.6278


 

b) Random effects


 

Estimate

Z

P


Block

0.090 ± 0.071

1.25

0.1053

Agricultural treat × block

0.006 ± 0.033

0.19

0.4248

Agricultural treat × predator treat × block

0.094 ± 0.048

1.97

0.0427

Residual

0.143 ± 0.031

   

† Graphical exploration of the significant 3-way interaction revealed consistently higher number of aphids on the exclusion cages in comparison with open and sham cages within each agronomic treatment and block.  Therefore, predator manipulation effects were not affected by the 3-way interaction.  However, the number of aphids obtained in the exclusion cages for each agronomic treatment varied in different blocks, showing an inconsistent effect of agronomic treatment in this experiment.

 

c) Slicing tests for significant interaction terms of fixed effects


Agricultural treat. × predator treat.

df

F

P


Conventional

2, 27

49.07

< 0.0001

No-till

2, 27

36.20

< 0.0001

Zero-chemical input

2, 27

17.03

< 0.0001

Predator exclusion

2, 27

1.43

0.2572

Sham

2, 27

8.28

0.0016

Open

2, 27

2.03

0.1508




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