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Table 2 Relationships among variables of latitude, forest structural and functional attributes and biodiversity indices

From: Forest biodiversity, relationships to structural and functional attributes, and stability in New England forests

Relationships

Linear/non-linear

Equations

R 2

p

Latitude-tree height

Non-linear

H = 16.80–4.83/EXP(0.35 × (Lat–45.96)^2)

0.79

< 0.0001

Latitude-total biomass

Non-linear

BM = 109.23 + 91.28/EXP(0.31 × (Lat–42.83)^2)

0.72

< 0.0001

Latitude-species richness

Linear

S = 178.85–3.18 × Lat

0.35

0.0002

Latitude-species diversity

Linear

SppD = 139.15–2.66 × Lat

0.66

< 0.0001

Latitude-Simpson’s index of diversity

NA

NA

NA

NA

Age-tree height

Linear

H = 1.33 + 0.20 × Age

0.65

< 0.0001

Age-total biomass

Linear

BM = −136.65 + 0.37 × Age

0.81

< 0.0001

Age-species richness

Linear

S = −19.60 + 0.87 × Age

0.54

< 0.0001

Age-species diversity

Linear

SppD = −14.60 + 0.55 × Age

0.59

< 0.0001

Age-Simpson’s index of diversity

Non-linear

SID = 0.89 + 609.65 × EXP(1–0.16 × Age)

0.56

< 0.0001

Height-total live biomass

Linear

BM = −90.60 + 16.52 × H

0.74

< 0.0001

Height-species richness

Linear

S = −4.82 + 2.90 × H

0.39

< 0.0001

Height-species diversity

Linear

SppD = −12.29 + 2.30 × H

0.66

< 0.0001

Height-Simpson’s index of diversity

Linear

SID = 0.75 + 0.0084 × H

0.30

0.0006

Species richness-total biomass

Non-linear

BM = 237.7 6 + 330.66 × EXP(1–0.038 × S)

0.45

< 0.0001

Species diversity-total biomass

Non-linear

BM = 203.08 + 780.00 × EXP(1–0.14 × SppD))

0.61

< 0.0001

Simpson’s index of diversity-total biomass

Linear

BM = − 510.43 + 766.18 × SID

0.38

< 0.0001

  1. Note: p values from the F-test show that all regression models are statistically significant, given a significance level of 0.01. The values with bold fonts show the highest R2 coefficient of determination among the fitted regression curves in a group of the same independent variable