Ecological Archives E089-008-A1

Juan Alberti, Mauricio Escapa, Oscar Iribarne, Brian Silliman, and Mark Bertness. 2008. Crab herbivory regulates plant facilitative and competitive processes in Argentinian salt marshes. Ecology 89:155–164.

Appendix A. Statistical results for the effects of Sarcocornia perennis removal on herbivory and growth of two Spartina densiflora patch size classes.

Comparisons of herbivory on Spartina patches (as the percentage damaged leaves per stem) from Control (resampled from an original sample of 33 replicates) and Sarcocornia removal treatments in the four seasons. The column "Removal – Control" presents the average (10000 iterations) of the difference (for each iteration) between the mean values of the Removal group and the Control group. Asterisks in this column denote significant differences between treatments (P < 0.05). CL: Confidence limit.

Herbivory (percentage damaged leaves per Spartina stem)

Control patches vs. large patches with Sarcocornia removed

Season

n per group

Mean Removal

Mean Control

Removal – Control

Lower CL

Upper CL

Summer

4

15.43

6.57

8.86

-0.42

15.42

Fall

4

27.84

22.34

5.50

-17.71

20.42

Winter

4

49.00

46.67

2.33

-18.69

21.25

Spring

4

30.80

25.00

5.80

-9.20

19.72

Control patches vs. small patches with Sarcocornia removed

Summer

19

19.68

6.57

13.11 *

4.07

19.64

Fall

16

44.79

22.34

22.45 *

11.81

30.79

Winter

14

75.36

46.67

28.69 *

17.76

39.07

Spring

8

51.21

25.00

26.21 *

15.85

36.11

 

Comparisons of Spartina patch growth (as the percentage difference in the number of stems per day) from Control (resampled from an original sample of 33 replicates) and Sarcocornia Removal treatments in the four seasons. The column "Removal – Control" presents the average (10000 iterations) of the difference (for each iteration) between the mean values of the Removal group and the Control group. Asterisks in this column denote significant differences between treatments (P < 0.05). CL: Confidence limit.

Patch growth (percentage per day )

Control patches vs. large patches with Sarcocornia removed

Season

n per group

Mean removal

Mean control

Removal – Control

Lower CL

Upper CL

Summer

4

2.18

0.80

1.38 *

0.49

2.21

Fall

4

-0.09

-0.04

-0.05

-0.48

0.78

Winter

4

0.08

0.03

0.05

-0.49

0.88

Spring

4

0.42

0.06

0.36 *

0.01

1.00

Control patches vs. small patches with Sarcocornia removed

Summer

29

0.73

0.80

-0.07

-0.40

0.23

Fall

19

-0.98

-0.04

-0.94 *

-1.19

-0.60

Winter

16

-0.54

0.03

-0.57 *

-0.87

-0.19

Spring

14

0.12

0.06

0.06

-0.17

0.37



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