1

Fig. 1. Layout of the Block – Column -sample point design at the Jokioinen site (Blocks 1–3).

2

Fig. 2. Layout of the Block – Column – Sub-column -sample plot design at the Vihti site (Block 4 and 5).

Table 1. The main stand characteristics of the test sites.
    DBH Height Volume
Forest site Block   Mean, cm Mean, m m3 ha–1
Modelling data
Jokioinen 1       Pine 28.3 25.9 178
Spruce 27.6 24.8 185
Birch 8.4 7.4 17
Total 27.8 25.1 391
Jokioinen 2       Pine 20.2 16.8 37
Spruce 22.6 21.1 193
Birch 24.6 22.1 112
Total 23.6 21.6 351
Jokioinen 3     Pine 12.4 13.1 59
Spruce 11.4 12.7 49
Birch 10.8 13.1 86
Total 11.4 13.2 195
Test data
Vihti 4 Pine - - -
Spruce 12.7 14.5 262
Birch - - -
Total 12.7 14.5 262
Vihti 5 Pine - - -
Spruce 15.8 15.4 220
Birch 17.6 16.0 108
Total 17.0 15.8 328
Table 2. Mean (and standard deviation in parenthesis) of bulk density (BD), organic content (%), clay content (%) of the mineral soil samples and the thickness of humus layer (cm) in the modelling data set and test data set. N = Number of measurements.
Block Column BD
g cm–3		 Organic
content
% 		Clay
% 		Humus
layer
cm 		N
Modelling data
1 1.0 1.33
(0.07) 		3.5
(1.0) 		5.1
(1.6) 		4 4 
2.0 1.18
(0.09) 		4.3
(0.8) 		6.5
(1.8) 		4 4 
2 3.0 0.97
(0.08) 		9.5
(1.3) 		34.6
(3.1) 		2 4 
4.0 0.91
(0.24) 		11.9
(2.8) 		37.0
(8.3) 		3 4 
3 5.0 1.14
(0.20) 		7.9
(1.8) 		52.4
(5.5) 		8 4 
6.0 1.32
(0.20) 		5.7
(2.0) 		43.4
(14.9) 		12 4 
All 1.14
(0.22) 		7.1
(3.4) 		29.8
(19.4) 		5.6
(4.1) 		24
Test data
4 1.0 0.92
(0.13) 		9.7
(1.2) 		50.6
(3.8) 		4 12 
2.0 0.88
(0.18) 		9.4
(1.2) 		51.3
(2.4) 		3 12 
3.0 0.99
(0.07) 		8.5
(0.8) 		44.1
(2.6) 		4 12 
5 4.0 1.13
(0.11) 		8.3
(2.0) 		22.5
(9.2) 		5 12 
5.0 1.26
(0.15) 		8.0
(3.1) 		40.5
(13.1) 		11 12 
All 1.03
(0.2) 		8.4
(2.4) 		40.4
(15.3) 		5.2
(3.5) 		84
Table 3. Mean, standard deviation, minimum and maximum values for PR010ms, PR015ms and VWC by block in the Jokioinen data.
Block   PR010ms MPa PR015ms MPa VWC %
1 Mean 0.848 0.956 22.8
Std. Deviation 0.262 0.299 5.7
Minimum 0.470 0.542 14.6
Maximum 1.542 1.640 40.0
2 Mean 1.153 1.616 31.6
Std. Deviation 0.525 0.789 8.6
Minimum 0.324 0.381 18.5
Maximum 2.891 4.190 49.8
3 Mean 1.536 1.746 36.9
Std. Deviation 0.593 0.617 7.5
Minimum 0.536 0.733 19.2
Maximum 3.491 3.294 50.9
Total Mean 1.179 1.439 30.4
3

Fig. 3. Box-plot illustration of the VWC by day of the year (DOY). The bottom and top of the box are upper and lower quartiles, and the bolded black line indicates the median, lowest and highest point of the vector minimum and maximum values.

Table 4. Mean, standard deviation, minimum and maximum values for PR010, PR015 and VWC by block in the Vihti data.
Block   PR015
MPa 		PR020
MPa 		VWC %
4 Mean 1.072 1.249 33.6
Std. Deviation 0.365 0.436 8.0
Minimum 0.572 0.670 18.4
Maximum 2.296 2.588 45.3
5 Mean 0.875 1.138 39.6
Std. Deviation 0.153 0.212 6.6
Minimum 0.677 0.786 26.3
Maximum 1.150 1.523 51.4
Total Mean 1.028 1.224 34.9
Sampling was not possible in block 5 on the last testing occasion (December)
Table 5. Mixed regression models predicting PR of the first 10 cm (InvPR = Inverse of PR) of the inorganic soil.
Model Model 1 Model 2 Model 3 Model 4
Dependent variable InvPR010ms InvPR010ms InvPR010ms InvPR010ms
Parameter Estimate
(SE) 		Sig. Estimate
(SE) 		Sig. Estimate
(SE) 		Sig. Estimate
(SE) 		Sig.
Fixed
  Intercept 0.165
(0.368) 		.668 0.670
(0.282) 		.022 –0.314
(0.288) 		.434 –0.290
(0.135) 		.034
  VWC 0.0336
(0.00289) 		.000 0.0325
(0.00292) 		.000 0.0340
(0.00289) 		.000 0.0333
(0.00292) 		.000
  BD –0.446
(0.272) 		.114 –0.912
(0.249) 		.001 - -
Three clay classes
  Clay class 1 (<10%) 0.885
(0.173) 		.250 0.971
(0.122) 		.000 0.795
(0.465) 		.335 0.786
(0.142) 		.000
  Clay class 2 (10–30%) 0.340
(0.180) 		.074 0.506
(0.198) 		.019 0.179
(0.161) 		.281 0.175
(0.235) 		.464
  Clay class 3 (>30%) 0 0 0 0
ui 0.0080
(0.125) 		.522 - 0.138 (0.203) .678 -
vij 0.0279
(0.0136) 		.041 0.0417
(0.0184) 		.023 0.0335
(0.0149) 		.024 0.0850
(0.0309) 		.006
σ2meas 0.0908
(0.0105) 		.000 0.0924
(0.0108) 		.000 0.0897
(0.0103) 		.000 0.0900
(0.0104) 		.000
ρmeas 0.0267
(0.101) 		.791 0.0378
(0.102) 		.711 0.0211
(0.100) 		.833 0.0280
(0.102) 		.784
AIC 139.1 143.3 140.7 151.6
Table 6. Mixed regression models predicting PR of the first 15 cm (InvPR = Inverse of PR) of the inorganic soil.
Model Model 5 Model 6 Model 7 Model 8
Dependent variable InvPR015ms InvPR015ms InvPR015 InvPR015
Parameter Estimate
(SE) 		Sig. Estimate
(SE) 		Sig. Estimate
(SE) 		Sig. Estimate
(SE) 		Sig.
Fixed
  Intercept 0.276
(0.270) 		.331 0.457
(0.259) 		.052 –0.242
(0.178) 		.323 –0.220
(0.106) 		.040
  VWC 0.0263
(0.00238) 		.000 0.0259
(0.00237) 		.000 0.0267
(0.00238) 		.000 0.0261
(0.00239) 		.000
  BD –0.483
(0.228) 		.049 –0.643
(0.198) 		003 - -
Three clay classes
  Clay class 1 (<10%) 0.852
(0.167) 		.134 0.881
(0.0975) 		.000 0.754
(0.270) 		.213 0.746
(0.106) 		.000
  Clay class 2 (10–30%) 0.303
(0.160) 		.072 0.360
(0.158) 		.033 0.128
(0.146) 		.392 0.126
(0.174) 		.480
  Clay class 3 (>30%) 0 0 0 0
ui 0.0122
(0.0268) 		.648 - 0.0431 (0.0678) .636 -
vij 0.0237
(0.0110) 		.031 0.0253
(0.0115) 		.028 0.0287
(0.0123) 		.019 0.0443
(0.0171) 		.010
σ2meas 0.0594
(0.00716) 		.000 0.0597
(0.0724) 		.000 0.0588
(0.00705) 		.000 0.0591
(0.00716) 		.000
ρmeas 0.0929
(0.103) 		.371 0.0971
(0.104) 		.352 0.0902
(0.104) 		.383 0.0978
(0.105) 		.350
AIC 58.7 57.4 61.0 64.2
4

Fig. 4. The PR of the soil for the first 15 cm below the surface of the inorganic soil (model 5 from Table 6) by VWC and clay content (BD constant 0.9 g cm–3).

5

Fig. 5. The PR of the soil for the first 15 cm below the surface of the inorganic soil (model 5 from Table 6) by VWC and BD (Clay class 3).

Table 7. Accuracy of the PR models in terms of bias and mean absolute error (MAE). Error is a result of the predicted value subtracted with the measured value.
Variable Models utilized Predictors Bias 95% confidence
interval for Bias 		MAE
kPa % kPa kPa %
PR0est15 Model 1 and Model 9 Clay class (2 or 3), VWC and BD –59 –5.9 –130 11 191 19.1
PRest015 Model 3 and Model 5 Clay class (2 or 3) and VWC –0.1 –0.01 –88 88 220 22.0
PRest020 Model 5 and Model 10 Clay class (2 or 3), VWC and BD 11 1.0 –70 93 225 18.8
PRest020 Model 7 and Model 10 Clay class (2 or 3) and VWC 115 9.6 –2 232 286 23.9
6

Fig. 6. Residuals of the predictions of the PR of first 20 cm above the ground surface constructed with models 5 and 10. Error is a result of the predicted value subtracted with the measured value.