Ecological Archives M076-014-A3

Jennifer M. Withington, Peter B. Reich, Jacek Oleksyn, and David M. Eissenstat. 2006. Comparisons of structure and life span in roots and leaves among temperate trees. Ecological Monographs 76:381–397.

Appendix C. The effects of diameter, soil depth and number of days until a white root turned brown (pigmentation) on the risk of fine root mortality calculated using Cox proportional hazard regression.

TABLE C1. The effects of diameter, soil depth, and number of days until a white root turned brown (pigmentation) on the risk of fine root mortality calculated using Cox proportional hazard regression. The value of the hazard ratio (HR) is less than one when the parameter estimate (β) is negative. This indicates an inverse relationship between the variable (e.g., diameter) and the risk of death. When the Chi-Square test is significant, then the description of the risk is indicated in the Risk column. SE is the standard error of the parameter estimate, β P is the level of significance for the χ2 test with degrees of freedom = 1.

 

β

SE

χ2

P

HR

Risk

Diameter

           

   A. platanoides

-1.85

1.38

1.79

0.181

0.157

---

   A. pseudoplatanus

-1.97

1.73

1.30

0.254

0.139

---

   F. sylvatica

-2.06

1.08

3.64

0.057

0.128

Thin>Coarse

   Q. robur

-2.39

1.01

5.51

0.019

0.092

Thin>Coarse

   T. cordata

-0.60

0.94

0.41

0.523

0.548

---

   A. alba

-6.73

2.16

9.69

0.002

0.001

Thin>Coarse

   L. decidua

  1.95

2.00

0.96

0.328

7.057

---

   P. abies

-2.57

1.25

4.22

0.040

0.076

Thin>Coarse

   P. nigra

-0.75

0.88

0.73

0.393

0.470

---

   P. sylvestris

-0.41

1.24

0.11

0.742

0.665

---

   P. menziesii

-1.69

1.41

1.43

0.231

0.184

---

             

Soil Depth

           

   A. platanoides

-0.03

0.01

27.73

<0.0001

0.969

Shallow>Deep

   A. pseudoplatanus

-0.03

0.01

11.44

0.0007

0.975

Shallow>Deep

   F. sylvatica

-0.01

0.01

4.74

0.0295

0.988

Shallow>Deep

   Q. robur

-0.02

 0.004

24.83

<0.0001

0.976

Shallow>Deep

   T. cordata

-0.01

 0.004

11.04

0.0009

0.986

Shallow>Deep

   A. alba

 0.01

0.01

0.93

0.335

1.01

---

   L. decidua

-0.01

0.01

2.51

0.113

0.985

---

   P. abies

-0.03

0.01

18.93

<0.0001

0.973

Shallow>Deep

   P. nigra

-0.02

 0.004

18.70

<0.0001

0.981

Shallow>Deep

   P. sylvestris

-0.01

0.01

4.51

0.0336

0.989

Shallow>Deep

   P. menziesii

-0.03

0.01

12.20

0.0005

0.972

Shallow>Deep

             

Pigmentation

           

   A. platanoides

-0.01

 0.004

13.00

  0.0003

0.987

Fast>Slow

   A. pseudoplatanus

-0.01

 0.002

4.18

0.041

0.995

Fast>Slow

   F. sylvatica

-0.01

 0.002

8.71

0.003

0.994

Fast>Slow

   Q. robur

 -0.003

 0.001

11.22

0.001

0.997

Fast>Slow

   T. cordata

  0.001

 0.002

0.59

0.444

1.001

---

   A. alba

 -0.004

0.01

0.61

0.435

0.996

---

   L. decidua

-0.03

0.01

3.75

0.052

0.975

Fast>Slow

   P. abies

 -0.002

 0.001

5.42

0.020

0.998

Fast>Slow

   P. nigra

-0.01

 0.002

11.02

0.001

0.994

Fast>Slow

   P. sylvestris

-0.01

 0.002

7.10

0.008

0.995

Fast>Slow

   P. menziesii

 -0.001

 0.002

0.17

0.682

0.999

---

Example calculation with HR: in A. platanoides, for every day a root remained white, its risk of death in the next sampling interval decreased an estimated 1.3% (=100*(0.987-1)), holding diameter and depth in soil constant.



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