## 3 Results
### GPP, Reco, and NEE Fluxes
#### 3.2.2 Ecosystem Respiration (Reco)  
As ecosystem respiration is one of the most important sources of carbon flux between terrestrial ecosystems and the atmosphere, it is crucial to determine its seasonal variation and the effect of applying a silicon-based antitranspirant. Figure 7 shows the daily Reco fluxes for individual plots in each cut. During the 2021 growing season, the lowest average daily Reco flux was observed in the first cut and equaled to 6.88 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for the HWL plot, 6.26 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL_Si, 6.41 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL, and 5.94 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL_Si. The highest daily Reco fluxes were recorded in the second cut for the plots with higher WTD and reached up to 22 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL and 20.63 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL_Si. For the plots with lower WTD, the maximum daily Reco fluxes occurred in the first cut for LWL (17.90 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\)) and in the third cut for LWL_Si (26.46 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\)). The increase in Reco and higher average fluxes in the second cut were caused mainly by the higher mean daily air temperatures of this period. The TA of the first cut was 9.0 \({}^{\circ}\)C, whereas in the second cut it was much higher, reaching 19.4\({}^{\circ}\)C (Table 1). Figure 6: Cumulative GPP values for individual plots in each cut in 2021–2022. The largest range of respiration rates can be observed in the first cut of 2022. Both the lowest (1.81 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for HWL, 1.64 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) on HWL_Si, 1.51 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) on LWL, and 1.17 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) on LWL_Si) and the highest daily CO\({}_{2}\) fluxes (16.56 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for HWL, 17.34 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for HWL_Si, 15.15 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for LWL, and 14.79 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for LWL_Si) were recorded in this cut for the entire growing season in 2022. The average daily Reco fluxes for the 2022 growing season were 8.47 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for HWL, 8.08 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for HWL_Si, 6.98 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for LWL and 7.33 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) for LWL_Si, respectively. In the previous year, the daily mean values of Reco fluxes were higher for all plots and reached 9.47 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) at HWL, 9.54 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) at HWL_Si, 8.92 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) at LWL, and 9.12 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\) at LWL_Si. A Wilcoxon matched-pairs test for daily Reco fluxes in individual plots in each cut showed that in most cases, daily plot emissions differed significantly; \(p<0.05\) (all pairs of plots in the first and second cut in 2021). For the third cut in 2021, the only pair that did not differ significantly was LWL_Si and HWL_Si (Figure 8). The same pair also showed no significant differences in the third cut in 2022. Furthermore, in the 2022 growing season in the first cut, the silicon antitranspirant application had no significant effect on daily Reco fluxes in the site with lower WTD. Moreover, there were significant differences in the daily  
Figure 7: Daily Reco fluxes for individual plots in each cut and growing season (a) in 2021; (b) in 2022. CO\({}_{2}\) fluxes in each cut between the plots with higher (HWL) and lower (LWL) groundwater levels.