## 3 Results
### Analyzing Productivity Simulations Under Wet Conditions
Simulated GPP by VBSall_NS model run driven by the observed near-surface soil water contents, \(\theta\), is compared vs. observed GPP derived from eddy covariance (EC) CO\({}_{2}\) exchange. DOY means day of year. such that \(\overline{\theta}\geq\overline{\theta}_{\text{FC}}\) and thereby soil air availability \(\text{f}_{\text{OR}}<1\) in Equation (9), while \(\text{f}_{\text{OA}}>1\) in Equation (11a), reflecting enhanced adaptations to wetland soil conditions. The combined effects of \(\text{f}_{\text{OR}}\) and \(\text{f}_{\text{OA}}\) in Equation (2a,b) resulted in similar, although slightly lower \(\text{f}_{\text{0}}\) in hollows compared to \(\text{f}_{\text{0}}\) in hummocks, where the higher \(\text{f}_{\text{OR}}\) in Equation (9) reflecting higher air availability was offset by the lower \(\text{f}_{\text{OA}}<1\) in Equation (11b) reflecting fewer adaptations (with higher air availability). As a result, simulated shrub GPP in hollows (Figure 13c) was only slightly lower than simulated hummock shrub GPP (Figure 13a), which is consistent with the conservative response of vascular GPP to different WT levels observed in previous studies [10; 41]. The \(\text{f}_{\text{0}}\) in Equation (3) increased with increased water availability \(\text{f}_{\text{0}}\) in Equation (8), resulting in higher moss GPP (Equation ((S2.1.1.2a)) in hollows (Figure 13d) than in hummocks (Figure 13b), consistent with field observations [39]. Figure 13: Hourly simulated GPP of hummock shrubs (**a**), hummock moss (**b**), hollow shrubs (**c**), and hollow moss (**d**) by VBall_WT model run driven by the observed depth to water table, \(\text{d}_{\text{WT}}\), applied to Mer Bleue bog during 2–15 August 2000. DOY means day of year. In VBall_NS, the high \(\theta\) of the near-surface peat matrix in hollows compared to that in hummocks (Figure 15f), both with 0.8 m\({}^{3}\) m\({}^{-3}\) macroporosity [26], resulted in pronounced reductions in hollow shrub GPP. The low soil air availability f\({}_{\text{RR}}\) in Equation (9) and relatively low f\({}_{\text{OA}}\) in Equation (11a,b) with d\({}_{\text{WT}}\) close to the hollow surface (reflecting the general difficulties for plants in near-saturated soils, in contrast to higher f\({}_{\text{OA}}\) with moderately deep WT below the soil surface) caused a decline in f\({}_{\text{0}}\) in Equation (2a,b). The reduced f\({}_{\text{0}}\) caused markedly lower shrub GPP during days with higher hollow near-surface \(\theta\), i.e., DOY 215-218 and DOY 221-227, compared to GPP on DOY 214, DOY 219, and DOY 220, with lower near-surface \(\theta\) (Figure 14c). The GPP of hummock shrub and moss and hollow moss in VBall_NS was similar to that in VBall_WT due to the mechanisms described above for VBall_WT. Overall, the contributions of hummock and hollow shrub and moss GPP resulted in the simulated ecosystem GPP closely following the observed GPP (Figure 11a). Figure 14: Hourly simulated GPP of hummock shrubs (**a**), hummock moss (**b**), hollow shrubs (**c**), and hollow moss (**d**) by VBall_NS model run driven by the observed near-surface soil water contents, \(\theta\), applied to Mer Bleue bog during 2–15 August 2000. DOY means day of year. Figure 15: Hourly observed incoming short-wave radiation, I\({}_{\text{SWR}}\) (**a**), air temperature, T\({}_{\text{a}}\) (**b**), relative humidity, RH (**e**), wind speed, v\({}_{\text{w}}\) (**d**), and daily observed depth to water table, d\({}_{\text{WIT}}\), in hummocks assumed to be 25 cm below hollows (negative values mean below soil surface) (**e**), and near-surface soil water contents, \(\theta\), at 10 cm depth in hummocks and 3 cm depth in hollows (**f**), at Mer Bleue bog during 2–15 August 2000. DOY means day of year.