## 3 Results and Discussion
### Interannual Variability in CO\({}_{2}\) Fluxes and ET during Dormant Seasons  
Half-hourly binned diurnal patterns of NEE for a selected pasture (P18), based on the availability of data for a longer period, were comparable from November to February for multiple years, with some larger discrepancies occurring in March (Figure 5a). The monthly average peak NEE during the daytime ranged from \(-\)2.2 umol m\({}^{-2}\) s\({}^{-1}\) in December to \(-\)3.0 umol m\({}^{-2}\) s\({}^{-1}\) in February. Half-hourly binned diurnal patterns of ET were also comparable from November to February, with the monthly average peak ET during the daytime ranging between 0.03 and 0.04 mm 30-min\({}^{-1}\) (Figure 5b). The peak daytime ET rates were substantially higher in March 2019 (0.11 mm 30-min\({}^{-1}\)) than in March 2018 (0.05 mm 30-min\({}^{-1}\)) because of greater ET rates after mid-March 2019 due to higher rainfall. Monthly rainfall was 9 mm in March 2018 and 58 mm in March 2019 (52 mm of rainfall from 13 to 30 March). Some discrepancies in diurnal patterns of NEE and ET over multiple years can also be attributed to different averaging periods to create mean monthly diurnal values as we used non-gap-filled half-hourly data to create diurnal means. Figure 5: \(Cont.\)  
As with diurnal patterns, daily ET and NEE patterns in P18 were similar for multiple dormant seasons (Figure 6). Average daily ET from November through February ranged from 0.41 \(\pm\) 0.21 (SD) to 0.54 \(\pm\) 0.27 mm d\({}^{-1}\) and daily NEE ranged from 0.34 \(\pm\) 0.45 to 0.53 \(\pm\) 0.52 g C m\({}^{-2}\) d\({}^{-1}\). Similarly, daily GPP ranged from 0.8 \(\pm\) 0.37 to 1.02 \(\pm\) 0.36 g C m\({}^{-2}\) d\({}^{-1}\). Daily rates of CO\({}_{2}\) fluxes were also similar in March, though ET rates differed among seasons. For example, average ET rates for DOY 74-90 in P18 were \(1.1\pm 0.4\) (SD) and 2.22 \(\pm\) 0.45 mm d\({}^{-1}\) in 2018 and 2019, respectively, due to higher rainfall for that period in 2019. However, NEE rates were 0.92 \(\pm\) 0.47 (SD) and 1.05 \(\pm\) 0.53 g C m\({}^{-2}\) d\({}^{-1}\) and GPP rates were 0.76 \(\pm\) 0.40 and 0.65 \(\pm\) 0.24 g C m\({}^{-2}\) d\({}^{-1}\) for DOY 74-90, 2018 and 2019, respectively. Evapotranspiration is composed of evaporation ((E) from wet soil, vegetation, and litter) and transpiration ((T) from plant tissues). Evapotranspiration can increase after rainfall due to increased E loss from wet canopies, litters, and soil surfaces, despite the lack of green vegetation to increase T. However, GPP may not increase much after rainfall during the dormant season, as the amounts of green vegetation involved in photosynthesis due to the presence of some C\({}_{3}\) grasses and forbs are small in prairie pastures. However, rainfall during the dormant season can have an effect on microbial activities and soil respiration [46]. Rainfall promotes microbial activities by increasing solute mobility and the supply of substrates to decomposers [47]. Studies have reported log-linear relationships between water potential (i.e., a measure of soil water available to microbes) and microbial activities [48; 49]. Rainfall events can induce pulses of soil respiration due to the enhanced  
Figure 5: Half-hourly binned diurnal patterns of net ecosystem CO\({}_{2}\) exchange (NEE) (**a**) and evapotranspiration (ET) (**b**) during non-growing seasons in P18. microbial activity and physical displacement of CO\({}_{2}\)-rich soil air by soil water after rainfall events [50]. Monthly NEE, GPP, and ET values were also similar in P18 during the dormant seasons of multiple years (Table 1). The monthly average ET ranged between 12 \(\pm\) 1 mm and 16 \(\pm\) 2 mm from November through February but increased to 39 \(\pm\) 13 (SD) mm in March. The monthly average NEE ranged from 1 g C m\({}^{-2}\) (\(\pm\)5 SD) in February to 28 g C m\({}^{-2}\) (\(\pm\)7 SD) in November.