Table 4 Summary statistics of the model [1] investigating the long-term trend in mean wood, earlywood and latewood density for the period 1901–2016. MWDI = mean wood density index, EWDI = earlywood density index, LWDI = latewood density index, YEAR = calendar year, TRW = tree-ring width, SPEI = Standardized Precipitation Evapotranspiration Index, cDBH = current DBH, LER = latewood to earlywood ratio, value = coefficient values, SE = standard error, significant (i.e., p-value < 0.05) parameter estimates are in bold

Beech

 Density type

Intercept

YEAR

TRW

SPEI

cDBH

LER

TRW*SPEI

cDBH*SPEI

LER*SPEI

 MWDI

value

467.25

0.13

14.69

-8.35

-1.44

15.05

0.20

-0.05

7.36

SE

324.95

0.17

2.22

6.33

0.51

2.47

1.70

0.18

2.54

p-value

0.151

0.432

 < 0.001

0.188

0.005

 < 0.001

0.904

0.788

0.004

 EWDI

value

946.15

-0.15

10.03

-5.63

-0.68

-12.03

-0.46

-0.05

7.08

SE

342.62

0.18

2.34

6.67

0.54

2.60

1.79

0.19

2.67

p-value

0.006

0.402

 < 0.001

0.399

0.210

 < 0.001

0.799

0.788

0.008

 LWDI

value

-99.48

0.51

24.24

-11.12

-2.36

-18.63

-0.26

0.13

3.78

SE

361.06

0.19

2.47

7.07

0.57

2.75

1.90

0.20

2.83

p-value

0.783

0.007

 < 0.001

0.116

 < 0.001

 < 0.001

0.892

0.524

0.183

Fir

 Density type

Intercept

YEAR

TRW

SPEI

cDBH

LER

TRW*SPEI

cDBH*SPEI

LER*SPEI

 MWDI

value

1567.20

-0.57

0.47

-1.62

1.82

83.60

0.42

-0.41

25.98

SE

206.70

0.11

1.22

4.99

0.26

4.15

0.94

0.09

3.25

p-value

 < 0.001

 < 0.001

0.702

0.745

 < 0.001

 < 0.001

0.651

 < 0.001

 < 0.001

 EWDI

value

73.85

0.14

4.05

0.28

0.63

30.02

-0.90

-0.14

13.53

SE

185.39

0.10

1.10

4.51

0.23

3.74

0.85

0.08

2.93

p-value

0.690

0.155

 < 0.001

0.951

0.007

 < 0.001

0.290

0.967

 < 0.001

 LWDI

value

3848.92

-1.53

23.31

16.13

2.19

-68.40

-2.43

-0.61

1.14

SE

351.80

0.19

2.08

8.54

0.44

7.09

1.60

0.16

5.56

p-value

 < 0.001

 < 0.001

 < 0.001

0.059

 < 0.001

 < 0.001

0.130

 < 0.001

0.837

Spruce

 Density type

Intercept

YEAR

TRW

SPEI

cDBH

LER

TRW*SPEI

cDBH*SPEI

LER*SPEI

 MWDI

value

1257.24

-0.38

-2.71

-0.60

1.00

71.29

0.26

-0.09

9.02

SE

218.45

0.12

1.14

5.09

0.29

4.44

1.01

0.10

4.05

p-value

 < 0.001

 < 0.001

0.018

0.907

 < 0.001

 < 0.001

0.801

0.349

0.026

 EWDI

value

366.44

0.04

-0.45

5.61

-0.10

18.30

0.05

-0.10

-0.38

SE

203.73

0.11

1.07

4.76

0.27

4.15

0.95

0.09

3.79

p-value

0.072

0.727

0.676

0.238

0.707

 < 0.001

0.962

0.256

0.921

 LWDI

value

3792.97

-1.49

15.85

-3.55

2.84

-77.49

-0.54

0.06

-10.89

SE

353.90

0.19

1.85

8.25

0.46

7.20

1.64

0.16

6.57

p-value

 < 0.001

 < 0.001

 < 0.001

0.667

 < 0.001

 < 0.001

0.744

0.713

0.097