Ecological Archives M078-011-A1

Katharine N. Suding, Isabel W. Ashton, Heather Bechtold, William D. Bowman, Megan L. Mobley, and Ryan Winkleman. 2008. Plant and microbe contribution to community resilience in a directionally changing environment. Ecological Monographs 78:313–329.

Appendix A. Statistical results for the effects of nutrients and species-removal manipulations on soil and community characteristics in 2006.

TABLE A1. Results of mixed-model GLM examining the effects of effects of nutrient amendment (fixed; 3 levels: carbon addition, ambient, nitrogen addition) and species removal (fixed; 3 levels: Geum removal, Deschapsia removal, no removal) and their interaction on soil and ANPP measures (a) and community measures (b). The random factors, site (7 levels) and, for the soil measures, plot (3 levels), were also included in the model, but effects are not shown. Manipulations were initiated in 2001, these results are from measures taken six years after manipulations began, in 2006. See the text for specific pairwise comparisons. P values < 0.05 appear in boldface type. Abbreviations: N, nitrogen; ANPP, aboveground primary productivity (biomass); df, degrees of freedom for term and error that accounts for the random effects; SS, sum of squares; F, F ratio.

a) Soil and ANPP Measures

                       
 
 Nutrient
 
Removal
 
 Nutrient × Removal
 
df
SS
F
P
 
df
SS
F
P
 
df
SS
F
P

Resin N

2,47

143.711

89.89

<.0001

 

2,47

1.638

1.02

0.3668

 

4,47

0.970

0.33

0.8577

Inorganic N

2,48

181.163

326.90

<.0001

 

2,48

0.718

1.30

0.2830

 

4,48

0.404

0.36

0.8324

DON

2,48

269.320

90.18

<.0001

 

2,48

0.860

0.29

0.7510

 

4,48

0.981

0.16

0.9555

Microbial N

2,48

15.560

14.00

<.0001

 

2,48

0.758

0.68

0.5103

 

4,48

1.151

0.52

0.7230

Productivity

2,48

15.593

16.40

<.0001

 

2,48

12.945

13.62

<.0001

 

4,48

3.178

1.67

0.1721

Soil moisture

2,48

0.022

0.32

0.7257

 

2,48

0.100

1.51

0.2313

 

4,48

0.093

0.71

0.5877

pH

2,48

0.054

9.95

0.0002

 

2,48

0.006

1.15

0.3252

 

4,48

0.004

0.32

0.8625

                             

b) Community Measures

                         
 
 Nutrient
 
Removal
 
 Nutrient × Removal
 
df
SS
F
P
 
df
SS
F
P
 
df
SS
F
P

Geum 

2,30

9.210

14.52

<.0001

 

1,30

5.970

18.83

0.0001

 

2,30

2.665

4.20

0.0246

Deschampsia

2,30

0.091

0.25

0.7824

 

1,30

3.869

20.96

0.0001

 

2,30

0.280

0.76

0.4778

Forbs

2,48

0.773

2.32

0.1091

 

2,48

2.732

8.20

0.0009

 

4,48

0.686

1.03

0.4015

Graminoids

2,48

10.661

6.82

0.0025

 

2,48

10.876

6.96

0.0022

 

4,48

0.816

0.26

0.9015

Species richness

2,48

0.150

2.73

0.0750

 

2,48

0.009

0.17

0.8418

 

4,48

0.128

1.16

0.3387

Evenness

2,48

0.011

1.01

0.3719

 

2,48

0.207

19.59

<.0001

 

4,48

0.028

1.34

0.2682

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