Table 5 Results of the mixed-effects model using Eq. (7): Effect of tree species on growth response indices to drought depending on soil texture (see hypothesis 4)

Drought 2003/04

Rt

Rc

Rs

Soil texture

Fixed effects

Estimate

P value

Estimate

P value

Estimate

P value

 Clay

a₀ (Intercept)

0.934

< 0.001

1.488

< 0.001

1.379

< 0.001

b₅ (Norway spruce)^a

−0.121

0.014

−0.232

0.022

−0.390

< 0.001

 Silt

a₀ (Intercept)

1.039

< 0.001

1.101

< 0.001

1.126

< 0.001

b₅ (Norway spruce)^a

−0.172

0.011

0.027

0.842

−0.136

0.270

Random effects

Variance

Variance

Variance

 α_s

< 0.001

< 0.001

< 0.001

 ε_st

0.033

0.140

0.112

Drought 2018

Rt

Rc

Rs

Soil texture

Fixed effects

Estimate

P value

Estimate

P value

Estimate

P value

 Clay

a₀ (Intercept)

0.726

< 0.001

1.260

< 0.001

0.893

< 0.001

b₅ (Norway spruce)^a

−0.191

< 0.001

0.561

< 0.001

0.056

0.325

 Silt

a₀ (Intercept)

0.511

< 0.001

1.406

< 0.001

0.718

< 0.001

b₅ (Norway spruce)^a

0.070

0.154

0.162

0.239

0.162

0.041

Random effects

Variance

Variance

Variance

 α_s

< 0.001

< 0.001

< 0.001

 ε_st

0.018

0.139

0.046