## Results
### CenW Performances to Simulate Carbon Dioxide and Water Fluxes of Mown and Grazed Grasslands
#### 3.1.2 Soil Water Content and Evapotranspiration  
Evapotranspiration (ET) measurements were also used for the parameterization and validation of the CenW model for both grassland sites. Soil water content observations were only available for the mowed paddock and were not used for the calibration of the model. Figure 4 shows the time series of daily observed and modeled soil water content (SWC) of the mowed paddock for three depths averaged over the entire soil profile. Over the entire study period, the soil water content measured and modeled at different depth agree quite well (Figure 4a-c), confirming the correct set up of the soil water flows procedure in CenW. Averaged soil water content was generally well modeled, with an EF of 0.83. On average, over the study period and over the entire soil profile, modeled and measured SWC were 22.4% and 21.9%, respectively. There was no systematic over- or underestimates of soil water content. Lower modeled SWC were found in spring 2006 and during summers of 2008 and 2010 (Figure 4) and were most likely due to higher CenW modeled water losses in spring and early summer than actual field conditions. Conversely, measured SWC was sometimes lower than modeled values. In 2007, observed soil water drawdown was faster than model simulation, but Figure 6d shows no discrepancies in ET, and so the problem seems to be linked to water drawdown. It could be that CenW extracted too much water from deeper layers and preserved it in the top layers. This situation was encountered following a water-limited period and could be due to cracks in the soil, causing preferential water flows not accounted for in the model or to the incomplete capture of vegetation dynamic in response to droughts. Overall agreement for SWC is good, and remaining discrepancies could be due to measurement errors like the heavy rainfall in 2006 either not measured correctly, or not all water infiltrating but running off. Others could be due to shortcomings of the model, like not having soil cracks represented, or because of some measurement uncertainties reducing the model/data agreement. Because SWC and ET are tightly linked, achieving to get a good agreement between observed and modeled soil moisture is consistent with the good results reported for the modeling of daily and weekly evapotranspiration rates (Figure 5a and Table 1). The CenW model explained more than 80% of the variation in daily ET for the two grassland sites. There was a close agreement between modeled and observed daily ET across the monitoring period (Figure 5), with R\({}^{2}\) of 0.82 and 0.81 and EF of 0.82 and 0.80 for moved and grazed paddocks, respectively. The coefficients of the linear regression lines (Figure 5) show a tendency of the model to slightly underestimate low ET (positive intercepts) and overestimate high evapotranspiration rates (slopes lower than 1), however slopes and intercepts are very close to their optimal values, showing that there is no systematic differences between modeled and observed evapotranspiration rates. Overall, very good agreements between the CenW modeled and observed daily CO\({}_{2}\) and water fluxes were achieved for both management practices (i.e., moving and grazing). This indicated that the response of the model to climatic conditions and management practices were well captured in the simulations and that most of the processes encountered in the fields were properly implemented in  
Figure 4: Time series of daily-modeled (black line) and observed (red symbols) soil water content at (**a**) 10 cm, (**b**) 30 cm, (**c**) 90 cm belowground, and (**d**) averaged over the whole soil profile (0–100 cm) for the moved grassland. Figure 5: Scatter plots of observed vs. modeled evapotranspiration rates for the mown (**a**) and grazed (**b**) paddocks. CenW. Student's \(t\)-tests were used to statistically test if slopes of linear regressions were significantly different from 1 and intercepts different than 0.