Ecological Archives E088-065-A2

Jamie R. Crait and Merav Ben-David. 2007. Effects of river otter activity on terrestrial plants in trophically altered Yellowstone Lake. Ecology 88:1040–1052.

Appendix B. Tables showing (1) final logistic regression models used to predict occurrence of river otter latrine sites o Yellowstone Lake and tributary streams; and (2) intercept coefficients for regressions of δ15N (‰) vs. fecal deposition rate (estimate ± SE) for plants growing on otter latrine sites compared with δ15N (‰; mean ± SE) of plants growing on non-latrine sites.

TABLE B1. Logistic regression models used to predict occurrence of river otter latrine sites on Yellowstone Lake (A) and tributary streams (B), summer 2002 and 2003. Lake shoreline model correctly classified 92.3% of non-latrine (n = 53), 77.4% latrine (n = 31), and 86.7% overall. Stream model correctly classified 83.7% non-latrine (n = 49), 68.6% latrine (n = 35), and 77.4% overall.

Variable

Coefficient

SE

Significance

A)      

Shading

0.057

0.016

0.000

Alder

0.662

0.345

0.055

Grasses

0.830

0.294

0.005

Rock Formation

5.100

1.477

0.001

Lagoon

6.587

1.715

0.000

Tributary Stream

3.320

1.837

0.071

       
B)      

Shading

0.017

0.008

0.027

Other Understory

-0.508

0.209

0.015

Forbs

-0.641

0.219

0.003

Brush

-0.430

0.214

0.045

Sand Substrate

0.466

0.151

0.002

Large Rock Substrate

0.391

0.249

0.117

 

TABLE B2. Intercept coefficients for regressions of δ15N (‰) vs. fecal deposition rate (estimate ± SE) for plants growing on otter latrine sites compared with δ15N (‰; mean ± SE) of plants growing on non-latrine sites.

 

Latrine Y intercept

       

Non-latrine

   

Sample

n

δ15N

Lower 95% CI

Upper 95% CI

 

n

δ15N

Lower 95% CI

Upper 95% CI

P value

Spruce

23

-1.6 ± 0.9

-3.4

0.2

 

20

-2.2 ± 0.5

-3.2

-1.2

0.53

Whortleberry

11

0.1 ± 0.8

-1.8

1.9

 

7

-0.0 ± 1.0

-2.4

2.3

0.93




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