## 3 Experimental Results  
### Physical Properties of Subfossil Oak in Comparation with Aged Oak from Construction and Recent Oak  
#### 3.1.1 Wood Density  
The oven-dry and basic densities of all the seven assortments from the three types of oak wood material (SO, AO, NO) are summarized in Table 1 and graphically illustrated by the box plots in Figure 3.  
It can be observed that average values of oven-dry density, \(\rho_{0}\), for the SO assortments varied between 609 \(\pm\) 28 kg/m\({}^{3}\) (SO_S1) and 752 \(\pm\) 47 kg/m\({}^{3}\) (SO_S2b). For the two AO assortments, the average values were 685 \(\pm\) 39 kg/m\({}^{3}\) (AO_C3) and 733 \(\pm\) 47 kg/m\({}^{3}\) (AO_C1_C2). All these values were slightly lower than the experimental average value 755 \(\pm\) 63 kg/m\({}^{3}\) for NO. The obtained results are supported by the literature data. According to [38], the oven-dry density of _Quercus Robur_ and _Petraea_ (NO) can vary between 390 and 930 kg/m\({}^{3}\) with an average of 650 kg/m\({}^{3}\), while values of about 618-696 kg/m\({}^{3}\) were reported by [2]. The reported values for SO varied in the range of about 526-734 kg/m\({}^{3}\)[3]. Also, lower density values for SO compared to NO were previously reported in the literature, e.g., [14; 22]. Statistical analysis of our experimental data showed that there were no statistically significant differences between the SO_S2a and SO_S3 assortments and between NO and SO_S2b and AO_C1-C2 assortments in terms of oven-dry density. On the other hand, there was a statistically significant difference in oven-dry density of about 93 kg/m\({}^{3}\) between SO_S2a and SO_S2b samples originating from the same log but from different positions on the trunk length (base and 6m from the base), with a 14% higher density in the upper position. This higher value was statistically similar to that determined for NO. Usually, wood in the trunks of oak (ring-porous) trees shows a maximum density at the base of the trunk, then decreases to remain constant over a relatively large height, and then increases again under the crown. Also, the density of ring-porous wood material is correlated positively with the width of the annual rings respective to the higher proportion \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Wood** & **NOR** & \(\rho_{0}\)**, & \(\rho_{c}\) \\
**Material** & & **kg/m\({}^{3}\)** & **kg/m\({}^{3}\)** \\ \hline
**SO\_S1** & 15 & 609 \(\pm\) 28 & 504 \(\pm\) 19 \\ \hline
**SO\_S2a** & 13 & 658 \(\pm\) 48 & 508 \(\pm\) 36 \\ \hline
**SO\_S2b** & 12 & 752 \(\pm\) 47 & 568 \(\pm\) 32 \\ \hline
**SO\_S3** & 10 & 690 \(\pm\) 29 & 558 \(\pm\) 19 \\ \hline
**AO\_C1\_C2** & 25 & 733 \(\pm\) 47 & 623 \(\pm\) 34 \\ \hline
**AO\_C3** & 20 & 685 \(\pm\) 39 & 585 \(\pm\) 32 \\ \hline
**NO** & 27 & 755 \(\pm\) 63 & 629 \(\pm\) 49 \\ \hline \hline \end{tabular} Notes: NOR = Number of replicates.  
\end{table} 
Table 1: Oven-dry density (\(\rho_{0}\)) and basic density (\(\rho_{c}\)) of subfossil oak (SO) from different sources compared to aged oak recovered from constructions (AO_C) and recent oak (NO)—average values and standard deviations. of latewood [31; 39]. Our results showed, however, an axial increase in oven-dry density for SO_S2 over the value at the base at approximately 2/3 height of the 9 m trunk. Presence of tension wood might be an explanation. In terms of basic density (\(\rho_{c}\)), it can be observed that the average value for NO was the highest (629 \(\pm\) 49 kg/m\({}^{3}\)), followed by the average values of AO (585-623 kg/m\({}^{3}\)) and lower average values for the SO assortments (504-568 kg/m\({}^{3}\)). Similar values for basic densities of SO were previously reported: 521.7 kg/m\({}^{3}\)[22] and 530 kg/m\({}^{3}\)[23].