SUPPLEMENTARY MATERIAL FOR ONLINE PUBLICATION ONLY
Laughlin and others. Environmental Filtering and Positive Plant Litter Feedback
Simultaneously Explain Correlations Between Leaf Traits and Soil Fertility
Supplementary Material, Figure A1. Map of distribution of permanent forest plots
throughout New Zealand.
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Supplementary Material, Figure A2. Organic P comprises the majority of total P in the
majority of the indigenous temperate rain forest plots. (a) Scatterplot of total phosphorus (P)
and organic P in the 241 forest plots, and the 1:1 line. (b) The distribution of the ratio of
organic P:total P among the forest plots.
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Supplementary Material, Table A1. Results of the Principal Components Analysis of the
Correlation Matrix Derived from the 3 Soil Properties (pH, C:N ratio, organic P) Measured
on 241 Forest Plots
Eigenvalues
Proportion of variance
Cumulative proportion
PC1
1.95
0.65
0.65
PC2
0.79
0.26
0.91
PC3
0.26
0.09
1.00
Eigenvectors
Soil pH
0.63
-0.36
0.69
Soil C:N ratio
-0.65
0.24
0.72
Soil organic P
0.43
0.90
0.08
For each axis, the eigenvalues and proportion of variance explained are provided.
Eigenvectors for each of the axes are listed below. The first axis explains 65% of the total
variation in the three soil properties, and the second and third axes of variation are less
important because their eigenvalues were < 1.
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Supplementary Material, Table A2. Results of the SEM Model that Included the Basal
Area of Beech (Nothofagaceae) Trees as an Exogenous Factor, Including Unstandardized
Parameter Estimates and Associated Standard Errors, Z Scores (that is, Estimate Divided by
Standard Error), and P-values
Model parameters (path coefficients)
Unstandardized
estimate
Standard
error
Z score
P-value
Pathways related to the effect of
beech trees
Beech BA  Soil fertility
Beech BA  Wood density
Beech BA  LDMC
Beech BA  Litter N
-0.029
-0.005
0.002
0.003
0.010
0.002
0.001
0.003
-2.943
-2.132
2.084
0.760
0.003
0.033
0.037
0.447
Pathways related to environmental
filtering (i)
Soil fertility  Wood density
Soil fertility  LDMC
Soil fertility  Litter N
-0.168
-0.082
0.285
0.028
0.013
0.043
-5.942
-6.114
6.665
<0.001
<0.001
<0.001
Pathways related to erosion and soil
physical processes (ii)
Topography  Soil fertility
Particle size  Soil fertility
0.053
-0.014
0.013
0.005
3.986
-2.641
<0.001
0.008
Pathways related to plant litter
feedback (iii)
Wood density  Soil fertility
LDMC  Soil fertility
Litter N  Soil fertility
-0.585
-1.524
1.568
0.294
0.562
0.256
-1.991
-2.712
6.117
0.046
0.007
<0.001
Pathways defining the latent variable
‘Soil fertility’
Soil fertility  pH
Soil fertility  C:N ratio
Soil fertility  organic P
pH  C:N ratio
1.000
-0.265
0.364
-0.028
0.019
0.058
0.004
-13.605
6.292
-6.131
<0.001
<0.001
<0.001
* Units and transformations: Basal area (BA; square-root m2 ha-1); LDMC (g g-1); Leaf litter
N (log10 %N by dry weight); wood density (mg mm-3); pH (standard pH units); soil C:N ratio
(log10 dimensionless ratio); soil organic P (log10 mg kg-1); topography (horizon index from
McNab (1993) divided by 10 to reduce variance); psize (ordinal value 1 through 5)
Soil pH sets the scale for the latent variable. Units and transformation are given below*. The
model fit the data (χ2 = 18.4, df = 17, P = 0.37, CFI = 0.998, RMSEA = 0.018), but was not a
superior model to the one illustrated in the main text (Figure 3, Table 2) because the
covariance matrix of latent variables was not positive definite, an indication that the model
structure is incorrect.
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