## Results
### Seasonal and Interannual Variabilities of Modeled and Observed Carbon Dioxide and Water Fluxes
#### 3.2.1 Day-to-Day and Seasonal CO\({}_{2}\) and Water Fluxes Variability
Their corresponding Pearson (linear) correlation coefficients are listed in the upper triangle (above the diagonal in gray). For example, the relationships between NEE and precipitation is shown in the pink circled scatter plot below the matrix diagonal and corresponding correlation coefficients for the different categories are given in the symmetric panel above the matrix diagonal (pink-circled). Important relationships are circled in blue on the upper panels. harvested/grazed and N fertilizer applications) but with marked differences across the two managed grassland sites. For the moved paddock, observed, and modeled amounts of carbon harvested are highly correlated with air temperature (OM: \(-0.78\) and MM: \(-0.93\)), precipitation (OM and MM: 0.82), and N fertilizer (OM: 0.93 and MM: 0.99). On the contrary, correlations for the grazed paddock were lowest with N fertilizer (OG: 0.57 and MG: 0.60) and weak with climate ([OG] and [MG] <0.50). The analysis also showed that, for the moved paddock, the modeled and observed NEE were highly correlated with climate and management practices, but that for the grazed paddock NEE values were only weekly correlated with other variables. In this section and like for all this study, negative NEE represent a net gain, and a positive NEE is a net loss of CO\({}_{2}\) for the ecosystem. It is interesting that for the grazed paddock, modeled, and observed summer half-year NEE responded differently to the amount of vegetation grazed (i.e., CenW giving a positive moderate correlation of NEE with the amount of vegetation grazed while observations were giving a week negative correlation). This is due to the differences between modeled and observation-derived ER rates during grazing events and CenW simulating higher ER rates during grazing events: the more vegetation is eaten the more NEE increased (reduction of the sink strength of the pasture). There were also high correlations between ET, climate and management practices for both grasslands, with a general upward trend of ET as precipitation, amounts of N fertilizer and C mowed/grazed increased and a downward trend with the increase of air temperature. More water vapor is returned to the atmosphere when there was more rainfall compared to dryer and hotter spring and summer periods. The modeled and observed annual (full year average/sum) carbon and water balances for the mowed and grazed paddocks are shown in Figure 11. For the mowed paddock, observed annual GPP values ranged between 16 and 20.5 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 18.2 tC ha\({}^{-1}\) yr\({}^{-1}\)) and modeled GPP values ranged between 15.3 and 22.7 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 19.2 tC ha\({}^{-1}\) yr\({}^{-1}\)). For the grazed paddock, observed annual GPP values ranged between 15.9 and 20.3 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 18.1 tC ha\({}^{-1}\) yr\({}^{-1}\)) and modeled GPP values ranged between 14.9 and 20.2 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 18.2 tC ha\({}^{-1}\) yr\({}^{-1}\)). Figure 11: Bar plot showing modeled and observed annual CO\({}_{2}\) and water balances for the mowed ((**a**) and (**c**)) and grazed ((**b**) and (**d**)) paddocks. Carbon fluxes (NEE, GPP, ER, and C harvested are given in tC ha\({}^{-1}\) and precipitation and ET are given in mm yr\({}^{-1}\)). On all years but 2006, CenW-modeled ER for the moved paddock were lower than annual sums of EC-derived ER (Figure 11) with annual modeled ER values between 12.7 and 16.1 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 14.9 tC ha\({}^{-1}\) yr\({}^{-1}\)), while observation-based ER values varied from 11.6 to 15.7 tC ha\({}^{-1}\) yr\({}^{-1}\) (five-year average: 14.1 tC ha\({}^{-1}\) yr\({}^{-1}\)).