## 3 Results
### Identification of Specific Periods during Wood Growth  
In order to determine the individual dendrometric phases, the stem increment for both studied years was followed. In order to distinguish growth processes from reversible water-related processes and to avoid the disturbing effects of rapid freezing-induced changes in stem diameter during winter, the starting point for annual radial growth of the stem was set as the previous year's culmination [47]. The point of the maximum winter contraction (MWC) occurred at a similar time in both years (21 April 2019 and 23 April 2020) (Figure 6a). From that moment, rapid relaxation began and DBH increased simultaneously. However, in order to quantify the actual increase, the biomass growth was estimated from the beginning of seasonal growth after rehydration--i.e., 1 May and 2 May for 2019 and 2020, respectively, until the end of the growing period when DBH stopped increasing. In early October 2019, the end of the seasonal increase in biomass was recorded (tree circumferential growth), while the DBH growth continued in 2020 until mid-October (Figure 6a). Thus, the total period of actual wood growth (B) was 14 days longer in the second year. During winter, the change in DBH was caused by reversible trunk variations. The beginning of the seasonal biomass growth was then assessed from the cessation of growth in the previous year (P0 point). By applying the methodology described in the Materials and Methods section (Figure 4) and recognizing B period range for the average tree, NPP was calculated for both years. (Figure 6b).  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**YEAR** & **P (mm)** & **Tair (°C)** & **VPD (kPa)** & **R\({}_{\text{g}}\) (Wm\({}^{-2}\))** & **SWC (\%)** & **GPP (gCm\({}^{-2}\))** & **R\({}_{\text{eco}}\)** & **ET (mm)** \\ \hline
2019 & 509 & 9.87 & 0.37 & 127.7 & 6.7 & 1724 & 1284 & 479 \\
2020 & 624 & 9.73 & 0.33 & 127.2 & 8.6 & 1727 & 1316 & 493 \\ \hline Spring 2019 & 116 & 9.32 & 0.49 & 165.3 & 7.7 & 536 & 301 & 129 \\ Spring 2020 & 98 & 7.97 & 0.39 & 191.4 & 9.9 & 511 & 259 & 140 \\ \hline Summer 2019 & 70 & 18.48 & 0.76 & 238.4 & 5.1 & 776 & 527 & 168 \\ Summer 2020 & 232 & 17.45 & 0.58 & 209.7 & 5.5 & 765 & 575 & 181 \\ \hline Autumn{2}{c}{191} & 191 & 9.64 & 0.12 & 71.8 & 7.1 & 314 & 330 & 112 \\ Autumn{2}{c}{2019} & 132 & 10.32 & 0.25 & 75.8 & 7.0 & 317 & 352 & 100 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Annual and seasonal (spring: March–May, summer: June–August, and autumn: September–November) precipitation totals (P), mean vapor pressure deficit (VPD), mean global radiation (R\({}_{\text{g}}\)), mean soil water content (SWC), and totals of gross primary productivity (GPP), ecosystem respiration (R\({}_{\text{eco}}\)) and evapotranspiration (ET) during the period 2019–2020 at the ME site.  
Differences in the course of DBH growth between the years are visible, especially in summer--August in particular--when dry conditions prevailed in 2019 year (Figure 6a). According to the theory of zero growth during periods of stem shrinkage, the increase in biomass was significantly limited in the most optimal period in terms of productivity [40], since any potential growth-induced expansion is associated with the time after tree water deficit-induced reversible stem shrinkage has completely ceased. In 2019, the increase in DBH was on average 0.14 mm per tree, while in 2020 it was 0.16 mm, so the difference was over two hundredths of a millimeter. Nevertheless, considering there is over 4200 trees per hectare in our study area, even a small change in DBH increment over a year can translate into an increase in carbon accumulation in the biomass by as much as 0.6 tons per hectare (Figure 6; Table 3).