## 3 Results
### GPP, Reco, and NEE Fluxes
#### 3.2.2 Ecosystem Respiration (Reco)
A significant effect of the silicon antitranspirant application on ecosystem respiration was seen in both sites, with higher and lower groundwater levels. The exception is the first cut in 2022, when the AT did not significantly differentiate the daily Reco fluxes in the site with a lower WTD. Therefore, it can be concluded that AT application has a stronger effect in the sites with a higher WTD than for those with a lower WTD. The highest cumulative Reco fluxes were recorded in the third cut of 2021 (Figure 9). This is most likely because the WTD was low during this period. The average WTD at the HWL site was 0.79 mbfl and as deep as 0.98 mbfl at the LWL site. Previous studies show that lowering WTD increases soil respiration [43]. Therefore, meadow treatments that contribute to this process should be avoided [44]. Analyzing the individual plots, it can be seen that in the third cut of 2021, the maximum emission was recorded in the LWL_Si plot and amounted to 1096.78 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\), while in the plot without silicon application, it was the lowest (996.11 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\)). Also, for the site with a higher WTD in the third cut of 2021, a similar pattern was observed. The silicon application resulted in increased emissions (1056.87 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\)) compared to the plot without silicon treatment (942.24 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\)). However, it should be noted that this was the only period when this pattern was observed. In the remaining periods, the application of antitranspirant at the site with a higher WTD reduced Reco fluxes, apart from the second cut in 2022, when the fluxes were similar to each other (HWL 734.49 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\), HWL_Si: 738.22 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)cut\({}^{-1}\)). AT application in site with higher WTD contributed to the reduction of Reco fluxes by 9% and 2.7% in the first cut of 2021 and 2022, respectively. In the second cut, the reduction of Reco fluxes was even higher, and reached 6% and as much as 11.4% in 2021 and 2022, respectively. At the site with a lower WTD, the antitranspirant application reduced Reco fluxes in the first and second cuts of 2021 by 7.4% and 4.1%, respectively, as well as in the first cut of 2022 by only 0.8%. In other periods, the Reco flux rates from plots with antitranspirant application were higher than those without silicon application (in the third cut in 2021 by 10.1%, in the second cut in 2022 by 6%, and in the third cut in 2022 by 9.6%). Therefore, it can be concluded that silicon is more effective in reducing CO\({}_{2}\) emissions in areas with a higher WTD. Figure 8: Comparison of daily Reco fluxes for individual plots (HWL, HWL_Si, LWL, LWL_Si) using Wilcoxon matched-pairs test in each cut in 2021 and 2022. \(p<0.05\) means that the pairs are significantly different from each other. When comparing plots with different WTD, it can be seen that in all cuts of 2022 and in the first and second cuts of 2021, the HWL plot emitted more CO\({}_{2}\) than the LWL plot. The exception is the third cut in 2021, when the Reco flux from the HWL (942.24 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)cut\({}^{-1}\)) plot was 53.87 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)cut\({}^{-1}\) smaller than that from the LWL plot. Looking at the individual cuts, it can be observed that the lowest cumulative Reco values occurred in the first cut of 2021. This was also the period when the soil moisture at both HWL and LWL sites was the highest, and reached up to 56% and 50%, respectively. Analyzing the annual patterns of ecosystem respiration, a clear peak in CO\({}_{2}\) flux is observed during periods with high precipitation (Figure 3b).