## 3 Results
### CO\({}_{2}\) Fluxes
In the April-July period, the forest generally acted as a CO\({}_{2}\) sink, as the GPP increased faster than the TER could reach the maximum CO\({}_{2}\) uptake rates in June (up to NEE = 7 gC\(\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\) and GPP = 22 gC\(\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\)). From August to mid-November, \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **2016** & **2017** & **2018** & **2019** & **2020** \\ \hline
**NEE (gC\(\cdot\)m\({}^{-2}\))** & \(196\pm 29\) & \(51\pm 37\) & \(-67\pm 34\) & \(107\pm 32\) & \(160\pm 34\) \\
**NEE\({}_{\text{g}}\). (gC\(\cdot\)m\({}^{-2}\))** & \(121\pm 55\) & \(-76\pm 76\) & \(-158\pm 64\) & \(-24\pm 65\) & \(21\pm 71\) \\
**GPP (gC\(\cdot\)m\({}^{-2}\))** & \(1264\pm 130\) & \(1566\pm 45\) & \(1748\pm 165\) & \(1558\pm 43\) & \(1466\pm 62\) \\
**GPP\({}_{\text{g}}\). (gC\(\cdot\)m\({}^{-2}\))** & \(1220\pm 252\) & \(1458\pm 78\) & \(1653\pm 281\) & \(1461\pm 78\) & \(1336\pm 101\) \\
**TER (gC\(\cdot\)m\({}^{-2}\))** & \(1459\pm 121\) & \(1618\pm 45\) & \(1192\pm 165\) & \(1664\pm 43\) & \(1627\pm 62\) \\
**TER\({}_{\text{g}}\). (gC\(\cdot\)m\({}^{-2}\))** & \(1342\pm 252\) & \(1382\pm 76\) & \(1015\pm 301\) & \(1437\pm 76\) & \(1358\pm 125\) \\
**GPP\({}_{\text{TER}}\)** & 0.87 & 0.97 & 1.47 & 0.94 & 0.90 \\
**GPP/TER (g.s)** & 0.91 & 1.06 & 1.63 & 1.02 & 0.98 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Annual and growing season (g.s.) sums of the net ecosystem exchange (NEE), gross primary production (GPP), and total ecosystem respiration (TER) with the uncertainty estimates associated with random error in the measured fluxes: u\({}^{\bullet}\)—threshold estimation, gap-filling, and flux partitioning procedures (\(\pm\)SD) as well as GPP/TER ratio in 2016–2020. Growing season sums were calculated for the long-term average growing season: 12 April–11 October in the 1991–2020 period. the forest was usually a strong CO\({}_{2}\) source, as the TER decreased slower than the GPP (NEE reached 6 gC-m\({}^{-2}\).d\({}^{-1}\)). The interannual variations in the environmental conditions led to the changes in the typical TER, GPP, and, consequently, NEE courses. To show the relative differences in CO\({}_{2}\) fluxes within the period of study, we calculated the anomalies in the monthly TER and GPP as the difference between the sum of GPP or TER for the month and its mean value in the 2015-2020 period expressed in % relative to the mean sum of the TER or GPP for each month, respectively (Figure 4), as well as absolute anomalies of NEE. The relative anomalies of TER and GPP, as well as the NEE anomalies, were positive or negative depending on the weather conditions and varied over the months and years. For example, in the growing season of 2017, under the low Rg, air temperature, and high precipitation, \begin{table}
\begin{tabular}{l c c c c c} \hline  & **2015/2016** & **2016/2017** & **2017/2018** & **2018/2019** & **2019/2020** \\ \hline
**NEE (gC-m\({}^{-2}\))** & 64 \(\pm\) 26 & 82 \(\pm\) 25 & 65 \(\pm\) 37 & 94 \(\pm\) 28 & 95 \(\pm\) 28 \\
**GPP (gC-m\({}^{-2}\))** & 22 \(\pm\) 26 & 52 \(\pm\) 25 & 62 \(\pm\) 37 & 52 \(\pm\) 30 & 74 \(\pm\) 28 \\
**TER (gC-m\({}^{-2}\))** & 85 \(\pm\) 28 & 134 \(\pm\) 25 & 145 \(\pm\) 37 & 135 \(\pm\) 33 & 169 \(\pm\) 29 \\
**GPP/TER** & 0.25 & 0.39 & 0.43 & 0.39 & 0.44 \\ \hline \end{tabular}
\end{table} 
Table 4: Winter (1 November–31 March) sums of net ecosystem exchange (NEE), gross primary production (GPP), and total ecosystem respiration (TER) with uncertainty estimates associated with random error in the measured fluxes. u\({}^{\bullet}\)—threshold estimation, gap-filling, and flux partitioning procedures (\(\pm\)SD), as well as GPP/TER ratio at the memorose spruce forest in the 2015–2020 period. Figure 3: Seasonal courses of the daily sums of CO\({}_{2}\) fluxes in the memorose spruce forest in the 2015–2020 period: (**a**) net ecosystem exchange (NEE), (**b**) total ecosystem respiration (TER), and (**c**) gross primary production (GPP).