## 2 Materials and Methods
### DIMONA Platform and Model
#### 2.1.2. DIMONA Process-Based (PB) Model
Equation (2a) represents \(f_{\rm{0}}\) in wet soil, i.e., when the average ambient water content of the unsaturated soil, \(\overline{\theta}\), is above the field capacity, while Equation (2b) represents \(f_{\rm{0}}\) in dry soil, i.e., when \(\overline{\theta}\) is \(\leq\)the field capacity. For vascular species that do not develop adaptations to wetland soils, \(f_{\rm{0A}}=0\) (Equation (S4.2.1.1c,d)). The products of \(f_{\rm{0R}}\) and \(f_{\rm{0W}}\), as well as \(f_{\rm{0A}}\) and \(f_{\rm{0W}}\), in Equation (2a,b) reflect the combined effects of water and air availability on GPP (Equations (S2.1.1.1) and (S2.1.1.2)) and plant growth through constraining \(f_{\rm{0}}\) for the extreme conditions of water saturation and severe droughts. With soil drying, \(f_{\rm{0W}}\) declines such that with severe droughts, \(f_{\rm{0W}}\) approaches zero (d. Soil Water and Air Availability to Plants); hence, \(f_{\rm{0}}\), and thereby GPP, approach zero and simulated plants can eventually die. With waterlogging, \(f_{\rm{0R}}\) approaches zero (d. Soil Water and Air Availability to Plants) and the ability of simulated plant species to survive is reflected by \(f_{\rm{0A}}\) (e. The Effect of Air Availability on Plants from Adaptations to Wetland Soil Conditions), such that if \(f_{\rm{0A}}\) is large enough, i.e., with adaptations to wetland soil conditions, plants sustain productivity and growth in the model. Respectively, if \(f_{\rm{0A}}\) is too small or zero, i.e., with insufficient or no adaptations to wetland soil conditions, then \(f_{\rm{0}}\) and thereby GPP approach zero and simulated plants eventually die. The exponent terms in Equations (1a,b) and (2a,b) are determined for the Mer Blue bog by trial and error and may differ for other plant species and sites, reflecting the specifics of growth for each plant species under different hydrological conditions. For many bryophyte species, including _Sphagnum_, most of their living parts are above the soil and their rhizoids occupy the near-surface soil layers [23]. Hence, the modifier \(f_{\rm{0}}\) considers only the effect of soil water availability on bryophyte growth and is not considered limited by soil air. Thus  
\[f_{\rm{0}}=f_{\rm{0W}} \tag{3}\]  
reflecting the primary importance of water for bryophyte physiological processes. The Effect of Air Availability on Root/Rhizoid Respiration and Nutrient Uptake  
The modifier for the effect of soil air availability and air availability due to adaptations (if any) to wetland soils on vascular root respiration, \(\mathrm{f_{R}}\) (Equation (S4.3.1.1)), is formulated as follows:  
\[\mathrm{f_{R}}=\frac{\mathrm{f_{OR}}+\mathrm{f_{0A}}}{1+\mathrm{f_{0A}}} \tag{4}\]  
where \(\mathrm{f_{OR}}\) and \(\mathrm{f_{0A}}\) are as defined above. For many bryophytes, \(\mathrm{f_{R}}\) (Equation (S4.3.1.2)) is formulated as  
\[\mathrm{f_{R}}=\mathrm{f_{0R}} \tag{5}\]  
With waterlogging, \(\mathrm{f_{0R}}\) approaches zero and the ability of simulated plant species to survive is reflected by \(\mathrm{f_{0A}}\). If \(\mathrm{f_{0A}}\) is large enough, i.e., with adaptations to wetland soil conditions, then \(\mathrm{f_{R}}\) is sufficiently large to sustain \(\mathrm{R_{r}}\) (Equation (S2.1.2.5)) and hence the biomass (Equation (S2.4.6.1)) and ambient area of roots/rhizoids (Equation (S2.4.6.2)), and thereby GPP (Equations (S2.1.1.1), (S2.1.1.2) via (S3.1.1.1), (S3.1.1.2) (S3.2.1.1), and (S3.3.1.1), (S3.3.1.2) and (S3.3.1.3)). Respectively, if \(\mathrm{f_{0A}}\) is too small or zero, then \(\mathrm{f_{R}}\) and thereby GPP are too small or zero, and the simulated plants eventually die.