Ecological Archives A025-076-A3

Jared J. Beck, Daniel L. Hernández, Jae R. Pasari, and Erika S. Zavaleta. 2015. Grazing maintains native plant diversity and promotes community stability in an annual grassland. Ecological Applications 25:1259–1270. http://dx.doi.org/10.1890/14-1093.1

Appendix C. ANCOVA results for the association between quantitative measures of grazing intensity and community composition.

Table C1. ANCOVA results describing the relationship between average annual grazing intensity (Cow bites 12.5 m-2 yr-1), fertilization treatment, and both community composition (mean cover or diversity) as well as directional changes in plant communities (LRRs). Cow bites and species richness were log-transformed. The R² for the full model as well as the F-statistic (F1,6 unless otherwise noted) and P value for each parameter are provided.

Community metric

Experiment 1

 

Experiment 2

Parameter

R²

F

P

 

R²

F

P

Mean total grass cover

 

 

 

 

 

 

 

Cow bites

0.22

0.001

0.992

 

0.16

0.979

0.361

Fertilization

 

0.791

0.408

 

 

0.087

0.778

Cow bites × Fertilization

 

0.946

0.368

 

 

0.101

0.762

Mean native forb cover

 

 

 

 

 

 

 

Cow bites

0.043

0.270

0.622

 

0.10

0.671

0.444

Fertilization

 

0.002

0.966

 

 

0.006

0.939

Cow bites × Fertilization

 

<0.001

0.986

 

 

0.005

0.948

Mean native plant diversity (H')

 

 

 

 

 

 

 

Cow bites

0.10

0.182

0.685

 

0.29

0.011

0.920

Fertilization

 

0.345

0.578

 

 

0.031

0.866

Cow bites × Fertilization

 

0.119

0.742

 

 

2.459

0.168

Mean native plant richness

 

 

 

 

 

 

 

Cow bites

0.29

0.136

0.725

 

0.12

0.179

0.687

Fertilization

 

0.943

0.369

 

 

0.021

0.890

Cow bites × Fertilization

 

1.336

0.292

 

 

0.634

0.456

∆ Total grass cover

 

 

 

 

 

 

 

Cow bites

0.09

0.404

0.549

 

0.16

0.211

0.662

Fertilization

 

0.038

0.853

 

 

0.018

0.898

Cow bites × Fertilization

 

0.125

0.736

 

 

0.883

0.384

∆ Native forb cover

 

 

 

 

 

 

 

Cow bites

0.13

0.163

0.701

 

0.23

1.743

0.235

Fertilization

 

0.263

0.627

 

 

0.006

0.941

Cow bites × Fertilization

 

0.466

0.520

 

 

0.081

0.785

∆ Native plant diversity (H')

 

 

 

 

 

 

 

Cow bites

0.54a

2.667

0.178

 

0.26

0.841

0.395

Fertilization

 

1.032

0.367

 

 

0.034

0.859

Cow bites × Fertilization

 

0.948

0.385

 

 

1.279

0.301

∆ Native plant richness

 

 

 

 

 

 

 

Cow bites

0.53b

2.480

0.190

 

0.56c

1.500

0.275

Fertilization

 

1.649

0.268

 

 

1.776

0.240

Cow bites × Fertilization

 

0.340

0.591

 

 

3.081

0.140

a Model excluded two influential outliers (F1,4), cow bites was significant (P<0.05) with outliers

b Model excluded two influential outliers (F1,4), cow bites was marginally significant (P<0.10) with outliers

c Model excluded one influential outlier (F1,5), cow bites was marginally significant (P<0.10) with outlier

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