## 3 Results
### Moisture Gradient  
The moisture content at different distances from the log surface is illustrated for the burned wood and the wood of the reference trees of spruce and pine by log type in Figure 5. A clear trend of decreasing moisture content from the surface to the pitu was observed in all cases. The highest moisture content was observed in the surface layer of the reference trees for all log types (140-160%), and the lowest moisture content was observed in the core of the butt logs and middle logs of the burned and reference trees (30-40%). Due to the smaller diameter of the top logs, no samples were obtained there at 12-14 cm from the log surface.  
Because the logs had varying thicknesses and the moisture content was expected to vary by distance from the log surface, the fixed effect of the radial position in the linear mixed models was divided into two classes. The specimen at 0-2 cm from the log surface represented the tree surface (outer sapwood), and the specimen at the farthest distance from the log surface represented the core (inner heartwood).  
The fixed effects are illustrated in Table 16. In spruce, height class was highly significant for the moisture gradient (\(p<0.001\)); other significant factors included fire damage class and the interaction between fire damage class and the radial position. In pine, the radial position and the interaction between the radial position and basic density were highly significant factors (\(p<0.001\)), and basic density and height class were significant (\(p<0.01\)). Most of the random variation was residual in spruce (53.5%) and pine (50.0%). The RMSE values were lower for pine than for spruce. For both spruce and pine, the moisture content was the lowest in the butt logs and the highest in the top logs (Table 17). In  
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Norway Spruce**} & \multicolumn{4}{c}{**Scots Pine**} \\ \hline
**Variable** & **Estimate** & **Std. Error** & **95\% CI** & **Estimate** & **Std. Error** & **95\% CI** \\ \hline  & & & **Lower** & **Upper** & & & **Lower** & **Upper** \\ \hline Intercept & 0.163 & 2.357 & –4.505 & 4.830 & 7.452 & 2.2330 & 3.030 & 11.873 \\ Fire damage class (ref: no damage) & & & & & & & & \\ More damaged side & 1.509 & 0.519 & 0.483 & 2.536 & –1.568 & 0.7980 & –3.148 & 0.012 \\ Less damaged side & 0.659 & 0.525 & –0.380 & 1.699 & –1.832 & 0.7973 & –3.411 & –0.254 \\ Height class (ref: top log) & & & & & & & & \\ Butt log & 0.697 & 0.392 & –0.080 & 1.474 & 0.879 & 0.5381 & –0.187 & 1.944 \\ Middle log & 0.364 & 0.389 & –0.407 & 1.134 & 0.139 & 0.5398 & –0.929 & 1.208 \\ Radial position (ref: heartwood) & & & & & & & & \\ Sapwood & 0.568 & 2.958 & –5.288 & 6.424 & –4.992 & 2.3406 & –9.626 & –0.357 \\ Air-dry density & 0.023 & 0.006 & 0.012 & 0.034 & 0.001 & 0.010 & 0.0039 & 0.002 \\ Interaction of radial position with air-dry density (ref: heartwood * density) & & & & & & & \\ Sapwood * density & –0.002 & 0.006 & –0.015 & 0.011 & 0.012 & 0.0048 & 0.002 & 0.021 \\ \hline \hline \end{tabular}  
* refers to interaction.  
\end{table}
Table 15: Fixed coefficients in the linear mixed model (Equation (9)) for Brinell hardness.  
spruce, the burned wood had a lower moisture gradient than the wood from the reference trees because the forest fire decreased the moisture content in sapwood. The moisture content was higher in sapwood than in heartwood in pine and spruce. In pine, the fixed coefficient for basic density was positive, but due to the interaction between the radial position and basic density, the higher the basic density, the lower the moisture content in sapwood.  
Figure 5: The moisture content of wood at different distances from the log surface in the butt, middle, and top logs.