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Predicting the vessel lumen area tree-ring parameter of Quercus robur with linear and nonlinear machine learning algorithms

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Fig. 1

A) Locations of the research sites (circles) and the meteorological stations (triangles), B) location of Slovenia in Europe and climagraphs of C) Ljubljana and D) Maribor. The lines of climagraphs represent mean monthly temperature and the blocks represent monthly amounts of precipitation.
A) Locations of the research sites (circles) and the meteorological stations (triangles), B) location of Slovenia in Europe and climagraphs of C) Ljubljana and D) Maribor. The lines of climagraphs represent mean monthly temperature and the blocks represent monthly amounts of precipitation.

Fig. 2

Individual sample lengths. The shaded area represents the analysed period used for model comparison for QURO-1 and QURO-2.
Individual sample lengths. The shaded area represents the analysed period used for model comparison for QURO-1 and QURO-2.

Fig. 3

An example of a workflow of earlywood vessel analysis with ImageJ and macro EWVA: A) original image, B) image converted to a black and white mask for segmentation of the original image, vessels below the threshold were excluded from the analysis, C) recognised groups of earlywood vessels belonging to different years overlaid over the original image and D) measured earlywood vessels.
An example of a workflow of earlywood vessel analysis with ImageJ and macro EWVA: A) original image, B) image converted to a black and white mask for segmentation of the original image, vessels below the threshold were excluded from the analysis, C) recognised groups of earlywood vessels belonging to different years overlaid over the original image and D) measured earlywood vessels.

Fig. 4

Chronologies of vessel lumen area (VLA) for QURO-1 and QURO-2 with 95% confidence interval of the mean.
Chronologies of vessel lumen area (VLA) for QURO-1 and QURO-2 with 95% confidence interval of the mean.

Fig. 5

Examples of the Model Tree (MT) for A) QURO-1 and B) QURO-2 sites.
Examples of the Model Tree (MT) for A) QURO-1 and B) QURO-2 sites.

Fig. 6

Histograms of mean bias, calculated as the difference between observed and estimated mean responses for validation data.
Histograms of mean bias, calculated as the difference between observed and estimated mean responses for validation data.

Description of predictors of the VLA for QURO-1 and QURO-2.

PredictorDescription
QURO-1T_Jul_SepAverage temperature from July to September, previous growing season
T_MARAverage March temperature, current growing season
T_APRAverage April temperature, current growing season
T_MAYAverage May temperature, current growing season
T_JUNAverage June temperature, current growing season
P_JAN-MARSum of precipitation from January to March, current growing season
QURO-2T_Jul-NovAverage temperature from July to November, previous growing season
T_JANAverage January temperature, current growing season
T_APRAverage April temperature, current growing season
T_MAYAverage May temperature, current growing season
T_JUNAverage June temperature, current growing season

Pearson correlation coefficients between vessel lumen area (VLA) and climate data: mean monthly temperatures (TEMP) and sum of monthly precipitation (PREC) for QURO-1 and QURO-2. Months with capital letters refer to the current growing season, while months with lowercase letters refer to the year of the previous growing season. Only correlation coefficients with p ≤ 0.01 are shown.

MonthQURO-1QURO-2
TEMPPRECTEMPPREC
Previous growing seasonJul0.450.53
Aug0.490.46
Sep0.370.38
Oct0.35
Nov0.37
Dec
Jul–Sep0.57
Jul–Nov0.71
Current growing seasonJAN–0.410.44
FEB
MAR0.38–0.33
APR0.600.63
MAY0.320.47
JUN0.470.50
JAN–MAR–0.43

General description of the analysed sites.

Location / Site denotationYear of samplingLatitudeLongitudeElevation (m)BedrockForest soil typeMeteorological stationAverage age of measured tree
Mlace/ QURO-12012N46°18′21′′E15°30′35′′280–315MarlEutric brown soilMaribor150
Sorsko Plain / QURO-22015N46°11′23′′E14°25′26′′360–365Alluvial loams and claysDystric brown soilLjubljana90

Characteristics of site chronologies: number of samples (N), chronology span, mean and standard deviation (Std) of vessel areas, minimum and maximum range of vessel areas (Min – Max), rbar (r̄) and autocorrelation with lag 1, 2 and 3 (AC).

Mean ± StdMin – Max
SiteNChronology span(μm2 104)(μm2 104)AC_1AC_2AC_3
QURO-162012–19616.259 ± 0.6035.133–7.7430.440.420.400.31
QURO-282015–19614.691 ± 0.3954.072–5.7560.320.610.520.46

Comparison of the performance of five predictive modelling methods for A) QURO.1 and B) QURO.2 sites. Methods were evaluated by 3-fold cross-validation repeated 100 times. The five predictive modelling methods were Multiple Linear Regression (MLR), Artificial Neural Networks (ANN), Model Trees (MT), Bagging of Model Trees (BMT) and Random Forests of Regression Trees (RF). The performance measures were the correlation coefficient (r), root relative squared error (RRSE), root mean squared error (RMSE), index of agreement (d), reduction of error (RE), coefficient of efficiency (CE) and detrended efficiency (DE), calculated on the training (train) and testing (test) data of cross-validation splits. Across the 100 runs of cross-validation, we present the mean, standard deviations (Std), mean rank and share of rank 1 for each performance measure. The best values of each performance measure on the test set are highlighted in bold.

MLRANNMTBMTRF
meanstdmeanstdmeanstdmeanstdmeanstd
(A) QURO-1
rtrain0.7970.0370.8150.0430.7890.0590.8100.0300.8980.018
rtest0.6940.1030.7260.0950.6330.1340.6920.1120.6890.097
RMSEtrain0.3560.0270.3430.0420.3590.0470.3600.0250.3020.022
RMSEtest0.4530.0630.4280.0660.4880.0790.4470.0650.4530.066
RRSEtrain0.6010.0480.5800.0770.6060.0800.6080.0410.5100.035
RRSEtest0.7860.1340.7410.1230.8450.1480.7710.1060.7780.083
dtrain0.8770.0260.8780.0590.8710.0420.8510.0300.8980.019
dtest0.7940.0660.8080.0730.7530.0810.7570.0670.7230.069
REtest0.4050.2270.4730.1840.3120.2570.4350.1580.4290.110
CEtest0.3640.2370.4360.2020.2650.2730.3940.1740.3870.132
DEtest0.3170.2490.3940.2150.2100.2890.3480.1880.3390.155
rankrank1rankrank1rankrank1rankrank1rankrank1
rtrain3.920.002.670.024.160.032.950.001.050.95
rtest2.910.111.850.503.930.062.930.153.120.20
RMSEtrain3.450.002.330.053.930.073.900.001.130.88
RMSEtest2.950.141.890.493.860.062.820.123.220.21
RRSEtrain3.450.002.330.053.930.073.900.001.130.88
RRSEtest2.950.141.890.493.860.062.820.123.220.21
dtrain2.640.072.520.133.390.134.710.001.490.68
dtest2.180.241.500.653.320.093.450.024.290.03
REtest2.960.141.890.493.860.062.820.123.220.21
CEtest2.960.141.890.493.860.062.820.123.220.21
DEtest2.950.141.890.493.860.062.820.123.220.21
Overalltrain3.370.022.460.063.850.083.860.001.200.85
Overalltest2.750.161.790.533.740.073.000.113.460.16
(B) QURO-2
rtrain0.7960.0440.8430.0350.8000.0390.8390.0280.9070.020
rtest0.7170.0930.7810.0840.6870.1040.7400.0870.7470.094
RMSEtrain0.2320.0190.2090.0270.2320.0190.2160.0150.1800.013
RMSEtest0.2930.0410.2570.0420.2970.0400.2780.0400.2740.043
RRSEtrain0.6010.0580.5410.0800.6020.0520.5600.0440.4650.044
RRSEtest0.7920.1640.6940.1500.8010.1470.7450.1260.7330.107
dtrain0.8740.0320.8990.0590.8660.0300.8830.0240.9210.018
dtest0.7930.0570.8390.0770.7650.0680.7890.0520.7820.058
REtest0.4100.2530.5460.2020.4010.2340.4830.1890.5030.142
CEtest0.3460.2990.4960.2480.3370.2830.4280.2300.4510.179
DEtest0.2970.3560.4570.2950.2860.3590.3840.3000.4090.236
rankrank1rankrank1rankrank1rankrank1rankrank1
rtrain4.540.002.440.004.300.002.720.001.001.00
rtest3.610.061.700.614.210.042.820.072.650.22
RMSEtrain4.420.002.220.014.260.003.080.001.010.99
RMSEtest3.700.031.750.644.050.032.780.112.720.20
RRSEtrain4.420.002.220.014.260.003.080.001.010.99
RRSEtest3.700.031.750.644.050.032.780.112.720.20
dtrain4.050.001.990.114.340.003.490.001.130.89
dtest3.090.031.300.854.020.033.150.043.440.05
REtest3.700.031.750.644.050.032.780.112.720.20
CEtest3.700.031.750.644.050.032.780.112.720.20
DEtest3.700.031.750.644.050.032.780.112.720.20
Overalltrain4.360.002.220.034.290.003.090.001.040.97
Overalltest3.530.041.620.684.080.032.880.082.880.17

Multiple linear regression summary statistics for QURO-1 and QURO-2.

VariableCoefficientst valuep value
QURO-1Intercept0.4961640.4180.67767
T_Jul–Sep0.1654912.6170.01196
T_MAR0.0424911.4370.15744
T_APR0.1595523.4740.00113
T_JUN0.0649031.4220.16164
P_JAN–MAR–0.00598–2.2940.02639
R2Adj R2
0.63040.5903
QURO-2Intercept1.083241.7920.07914
T_Jul–Nov0.128122.5700.01319
T_JAN0.037922.5010.01569
T_APR0.082732.8790.00586
T_ JUN0.046691.8000.07782
R2Adj R2
0.62410.5941
eISSN:
1897-1695
Langue:
Anglais
Périodicité:
Volume Open
Sujets de la revue:
Geosciences, other