# Assessment of Carbon Flux and Soil Moisture in Wetlands Applying Sentinel-1 Data
## 3 Results
### Soil Moisture  
In-situ soil moisture (SM) values (ranged from 10% to 100% volumetric.) from the test site have been related to the backscattering coefficient (\(\sigma^{\circ}\)) calculated from Sentinel-1 IW VV and VH data, applying various regression models. The best results have been found applying VH polarization and a linear model performed for particular vegetation habitat types separately (Figure 2). These results are presented in Table 4. The relationships between SM and \(\sigma^{\circ}\) at the 95% confidence level is statistically significant (\(p<0.05\)). The highest correlation belongs to \(\sigma^{\circ}\) calculated from Sentinel-1 IW VH data for sedge-moss and sedges, the most typical wetland habitats. Slightly better results have been found applying an exponential model. Derived equations (Table 4) were used to map soil moisture distribution over the Biebrza Wetland. Figures 3 and 4 present two maps composed using Sentinel-1 VH data acquired on 11 June 2015 and 10 July 2015, respectively, as an example. It can be noted that much lower SM value in July compared to June was caused due to severe drought, which started in May. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Platform** & **Habitat** & **R\({}^{2}\)** & **St. Error** & **Number of** & \(p\)**-Value** & **Equation** \\
**Sensor** & **Habitat** & **R\({}^{2}\)** & **of Est.** & **Data** & & \(p\)**-Value** & **Equation** \\ \hline \multirow{4}{*}{Sentinel-1 IW VH} & Reeds & 0.71 & 14.35 & 29 & 0.0000 & SM = 233.791 + 9.805 \(\times\)\(\sigma^{\circ}\) \\  & Sedge-moss & 0.76 & 11.23 & 30 & 0.0000 & SM = 278.537 + 11.898 \(\times\)\(\sigma^{\circ}\) \\ \cline{1-1}  & Sedges & 0.76 & 11.15 & 41 & 0.0000 & SM = 218.194 + 8.586 \(\times\)\(\sigma^{\circ}\) \\ \cline{1-1}  & Grass-herbs & 0.70 & 7.01 & 33 & 0.0000 & SM = 130.341 + 5.271 \(\times\)\(\sigma^{\circ}\) \\ \cline{1-1}  & Grass & 0.75 & 6.14 & 49 & 0.0000 & SM = 136.539 + 5.253 \(\times\)\(\sigma^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of relationships at a 95% confidence level between measured soil moisture (SM) and \(\sigma^{\circ}\) calculated from Sentinel-1A VH data. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Classified Data** & **Water** & **Coniferous Forest** & **Deciduous Forest** & **Sedge-Moss** & **Sedges** & **Grass-Herbs** & **Grass** & **Reeds** \\ \hline Water & 99.67 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ Coniferous forest & 0 & 99.28 & 0 & 0.28 & 0 & 0 & 0 & 0 \\ deciduous forest & 0 & 0 & 99.51 & 0 & 0 & 0 & 0 & 0 \\ Sedge-moss & 0.33 & 0.5 & 0.3 & 92.13 & 8.23 & 0.63 & 0 & 3.58 \\ Sedges & 0 & 0 & 0.08 & 5.2 & 91.06 & 0 & 0 & 0.63 \\ Grass-herbs & 0 & 0.03 & 0.05 & 0.98 & 0.08 & 98.68 & 0 & 0 \\ Grass & 0 & 0 & 0.06 & 0.35 & 0.03 & 0.4 & 100 & 0 \\ Reeds & 0 & 0.19 & 0 & 1.05 & 0.6 & 0.29 & 0 & 96.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Error matrix for classified data in %. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Class Name** & **Reference** & **Classified** & **Number** & **Producers** & **Users** \\
**Totals** & **Totals** & **Correct** & **Accuracy (\%)** & **Accuracy (\%)** \\ \hline Water & 6 & 6 & 6 & 100 & 100 \\ Coniferous forest & 16 & 17 & 16 & 100 & 94.12 \\ Deciduous forest & 31 & 26 & 26 & 83.87 & 100 \\ Sedge-moss & 21 & 31 & 21 & 100 & 67.74 \\ Sedges & 12 & 8 & 8 & 66.67 & 100 \\ Grass-herbs & 14 & 15 & 12 & 85.71 & 80 \\ Grass & 10 & 9 & 9 & 90 & 100 \\ Reeds & 5 & 3 & 3 & 60 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Accuracy totals for each class. Figure 4: Map of soil moisture based on Sentinel-1 VH data acquired on 10 July 2015. Figure 3: Map of soil moisture based on Sentinel-1 VH data acquired on 11 June 2015. Figures 5 and 6 present relationships between soil moisture measured in-situ and calculated from Sentinel-1 IW VV and VH data (respectively) applying a statistically derived algorithm (Table 5). The analyses were performed for all wetland habitats (for a representative sample).