## 3 Results
### Mechanical Properties
#### 3.1.5. Brinell Hardness  
Descriptive statistics of HB are presented in Table 13. HB was strongly correlated with air-dry density in spruce (0.629) and pine (0.701). The correlations of HB with the MOE and MOR were moderate in spruce (0.465 and 0.476, respectively) but higher in pine (0.678 and 0.721, respectively). This was consistent with the more significant effects of density on the MOE and MOR in pine in the linear mixed model analysis than in spruce.  
Similar to other mechanical properties, density was the most significant factor for HB (Table 14). In pine, the radial position and the interaction between the radial position and density had some effects, similar to the MOE and MOR. In spruce, these factors were not significant. Instead, fire damage class proved significant (\(p<0.01\)). The RMSE value was slightly smaller in spruce than in pine. Most of the random variation in both species was residual (74.8% for spruce and 53.6% for pine). Density had a positive effect on HB in both spruce and pine (Table 15). In spruce, the sapwood position was a positive predictor of HB. Although the estimate for the dummy term of sapwood was negative in pine, because of the positive interaction between the dummy term or sapwood position and density, the higher density indicated a higher HB in pine sapwood. Similar to the MOR, density had a higher effect on hardness in pine sapwood than in pine heartwood. It was notable that fire damage positively affected HB in spruce.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline  & \multicolumn{3}{c}{**Norway Spruce**} & \multicolumn{3}{c}{**Scots Pine**} \\ \hline
**Wood Material** & **Butt Log** & **Middle Log** & **Top Log** & **Butt Log** & **Middle Log** & **Top Log** \\ \hline Sapwood, heavily burned side & 12.4 (1.9) & 12.0 (2.7) & 11.8 (2.0) & 15.3 (2.4) & 12.4 (1.0) & 12.6 (2.0) \\ Sapwood, slightly burned side & 11.9 (1.8) & 11.4 (1.6) & 10.1 (1.8) & 14.9 (2.6) & 12.3 (1.1) & 12.6 (0.7) \\ Heartwood, burned trees & 9.9 (1.8) & 9.6 (1.3) & – & 14.7 (2.2) & 12.5 (1.8) & – \\ Sapwood, reference trees & 11.4 (1.1) & 10.6 (2.1) & 10.2 (2.0) & 13.9 (4.3) & 12.2 (2.9) & 10.3 (2.1) \\ Heartwood, reference trees & 11.2 (2.1) & 11.2 (2.6) & – & 11.7 (2.1) & 10.7 (1.3) & 9.9 (2.2) \\ \hline \end{tabular}
\end{table}
Table 13. Brinell hardness (HB) by species, damage class, radial position, and log type (MPa). Values are presented as means, with the standard deviation in parentheses.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline  & \multicolumn{3}{c}{**Norway Spruce**} & \multicolumn{3}{c}{**Scots Pine**} \\ \hline
**Wood Material** & **Butt Log** & **Middle Log** & **Top Log** & **Butt Log** & **Middle Log** & **Top Log** \\ \hline
**S**apwood, heavily burned side & 1.47 (0.11) & 1.34 (0.11) & 1.29 (0.18) & 1.42 (0.19) & 1.39 (0.11) & 1.43 (0.08) \\ Sapwood, slightly burned side & 1.48 (0.15) & 1.28 (0.15) & 1.19 (0.32) & 1.52 (0.19) & 1.40 (0.11) & 1.47 (0.07) \\ Heartwood, burned trees & 1.53 (0.37) & 1.24 (0.32) & – & 1.37 (0.21) & 1.44 (0.09) & – \\ Sapwood, reference trees & 1.42 (0.18) & 1.31 (0.21) & 1.35 (0.14) & 1.59 (0.25) & 1.46 (0.13) & 1.60 (0.23) \\ Heartwood, reference trees & 1.23 (0.18) & 1.32 (0.16) & – & 1.47 (0.22) & 1.36 (0.21) & 1.46 (0.10) \\ \hline \end{tabular}
\end{table}
Table 12. Flexural strain at maximum force by species, damage class, radial position, and log type (%). Values are presented as means, with the standard deviation in percentage points in parentheses.