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Height–diameter relationship of plantation-grown juvenile black locust trees is differentiated according to their growth rate, which is positively affected by spacing


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Figure 1

Mixed-effects height–diameter model estimated by plots
Mixed-effects height–diameter model estimated by plots

Figure 2

Generalised height–diameter model estimated by spacings
Generalised height–diameter model estimated by spacings

Description of the experimental data used to derive the height–diameter relationships for Robinia pseudoacacia L.

Sample plot Parental genotype Geographic region Plot size (m2) Growing space (m2) Age (years) Number of measured trees d (cm) h (m)
PP 1 southern 185.00 2.5 6 48 3.6–7.1 4.7–6.3
PP 2 southern 173.25 2.5 2 51 3.1–6.0 4.7–6.5
PP 3 southern 202.50 2.5 3 50 3.8–4.6 6.4–6.5
PP 4 southern 165.00 3.5 4 67 1.5–4.6 2.9–4.7
PP 5 Roszin Varga northern 304.00 4.5 5 64 2.3–6.7 2.8–7.7
PP 6 Karaisen northern 306.04 4.5 5 52 2.4–7.6 3.9–9.2
PP 7 Tsarevets northern 300.00 4.5 5 70 2.2–9.1 4.2–9.2

Comparison of the mixed-effects height–diameter models by Likelihood Ratio Test

Model Mixed-effects parameters df logLik Test Likelihood Ratio p-value
abbreviation localisation level
1 GR.PP.01 sample plot within geographic region b0, b1 9 –413.990
2 PP.01 sample plot b0, b1 6 –414.324 1 vs. 2 0.669 0.881
3 PP.0 sample plot b0 4 –419.808 2 vs. 3 10.967 0.004
4 GR.PP.0 sample plot within geographic region b0 5 –419.407 3 vs. 4 0.800 0.371
5 PP.1 sample plot b1 4 –430.327 4 vs. 5 21.839 <0.001
6 GR.PP.1 sample plot within geographic region b1 5 –430.130 5 vs. 6 0.393 0.531
7 GR.01 geographic region b0, b1 6 –438.471 6 vs. 7 16.682 <0.001
8 GR.0 geographic region b0 4 –440.748 7 vs. 8 4.553 0.103
9 GR.1 geographic region b1 4 –445.830
10 simple local no localisation 3 –453.059 9 vs 10 14.457 <0.001

Calibration of the random component of the mixed-effects model with 1-tree height–diameter measurement: accuracy estimates by plots

Plot u Relative errors MARE% Bias
Perc0 Perc25 Perc50 Perc75 Perc100
PP 1 –0.789 –0.719 –0.150 –0.077 –0.003 0.166 11.829 –0.363
PP 2 –0.561 –0.579 –0.133 –0.037 0.016 0.205 11.001 –0.233
PP 3 0.369 –0.100 –0.018 0.017 0.076 0.153 5.423 0.163
PP 4 –0.981 –0.350 –0.182 –0.067 0.063 0.391 14.612 –0.228
PP 5 –0.125 –0.405 –0.116 –0.011 0.086 0.198 10.536 –0.050
PP 6 1.118 –0.390 –0.047 0.086 0.167 0.242 13.004 0.506
PP 7 0.968 –0.673 –0.025 0.068 0.118 0.238 12.661 0.403

Regression estimates and goodness-of-fit statistics of the mixed-effects and the generalised deterministic height–diameter models

Mixed-effects model: h = 1.3 + (u + b0)eb1
ME 0.773 Model parameters Model variances
b0 b1 σu2 \sigma _u^2 σ2
MARE% 10.322 Estimate 8.302 –2.631 0.639 0.555
Bias 0.010 SE 0.395 0.146 0.363 0.042
Generalised deterministic model: h = 1.3 + (a0 + a1Spacing)eb1/d
ME 0.724 Variance function Model parameters
(θ+dη)2 a0 a1 b1
MARE% 11.634 Variance function parameters Estimate 7.322 0.422 –2.918
Bias 0.025 Θ H SE 0.417 0.087 0.123
37.243 1.701

Local height–diameter models and goodness-of-fit statistics

Model Mean Bias (m) Aggregated MSE (m)* 90th percentile of ARBi*
abbreviation formula
M1 h = 1.3 + a1d 0.1515 6.9068 0.2184
M2 h = 1.3 + a1d + a2d2 –0.0024 3.8496 0.1367
M3 h = a0da1 –0.0031 4.0965 0.1176
M4 h = 1.3 + exp[a0 + a1/(d + 1)] –0.0034 3.8616 0.1100
M5 h = 1.3 + a0 exp(a1/d) –0.0005 3.7790 0.1077
M6 h = 1.3 + a0da1 –0.0053 4.1714 0.1191
M7 h = 1.3 + a0d/(a1 + d) 0.1221 6.9214 0.2412
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Englisch
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Biologie, Botanik, Medizin, Veterinärmedizin