## 4 Discussion
### Subirigation and WTD Impacts on CO\({}_{2}\) Emissions  
One of the most complex issues in relation to grasslands is the area's water management and its direct impact on CO\({}_{2}\) emissions. Clear differences in daily, seasonal, and annual Reco rates between LWL and HWL plots have been demonstrated in this study. As indicated in Table 2, the annual cumulative Reco rates were higher at the HWL plot (depending on the year, they amounted to from 2092.23 to 2310.57 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\)) than at the LWL plot (from 1723.40 to 2175.86 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\)). These rates of Reco fluxes are similar to those estimated by [PERSON] et al. [51] for intensive grasslands in Germany (2490-2960 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\)), but they are half of those estimated by [PERSON] et al. [52] for a three-cut intensive meadow fertilized with biogas digestate on Mollic Gleysoil (4265 \(\pm\) 379 gC\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\)). The broad range of Reco fluxes from grasslands reported in the literature indicates differences in these ecosystems and makes any results comparison complicated, as complex factors, such as soil type and its moisture, plant species composition, fertilization, the intensity of meadow use, grazing, and meteorological conditions may impact the CO\({}_{2}\) emissions from grasslands [14; 51; 53; 54; 55]. Figure 14: Relationship between cumulative GPP fluxes in each cut and yield of aboveground biomass from HWL and LWL plots. Anyway, in the case of this study, the higher Reco rates at HWL than at LWL plots may lead to the conclusion that higher WTD and higher soil moisture are increasing CO\({}_{2}\) emissions from grasslands on organic soils. This finding might be in contradiction to other studies in which it is generally indicated that raising the WTD can have a beneficial effect on reducing CO\({}_{2}\) emissions from degraded peatlands and grasslands [7; 14; 56]. [PERSON] et al. [57] also indicated that too-high groundwater levels can reduce soil respiration (Rs) in grassland due to anaerobic conditions, which are unfavorable for the oxidation of soil organic matter, plant residue, and aerobic respiration. This condition may lead to a reduction of heterotrophic respiration (Rh) of soil microorganisms. On the other hand, Rs accounts for about 45-59% of ecosystem respiration in grasslands, and its contribution to Reco flux may vary from 46% in summer to 59% in winter [57; 58]. In the present study, Rs was not measured; hence, it is hard to estimate the amount of CO\({}_{2}\) emitted from soils and its contribution to Reco. But, due to the fact that a higher WTD leads to a higher yield of aboveground biomass and causes higher Reco, it can be speculated that higher CO\({}_{2}\) emissions from HWL plots are a result of higher autotrophic respiration (Ra) of aboveground biomass and may indicate that the Ra/Rh ratio might also be higher at plots with higher WTD. As indicated in Figure 3, cutting the grass reduces Reco fluxes due to the reduction of Ra [51], although this reduction seems to be smaller at LWL plots, where Rs might be higher due to less moisture and smaller plant biomass. Similarly to this study, [PERSON] et al. [59] did not show a positive effect of increasing WTD on the reduction of CO\({}_{2}\) emissions from peat meadow with a subsoil irrigation system (perforated pipes \(-\)70 cm from surface level with a spacing of 5-6 m) in the Netherlands, due to the fact that changes in the WTD occurred in the deeper soil layers (60-120 cm depth), which have little impact on organic matter oxidation in the upper layers contributing most to the overall CO\({}_{2}\) emissions. [PERSON] et al. [60] found that temporal variation in meteorological conditions, spatial variation in landscape seepage, and variation in dithwater level management decisions can explain the wide range in subsoil irrigation and drainage (SSI) effectivity that other researchers had previously reported.