# The Carbon Dynamics of Dry Tropical Afromontane Forest Ecosystems in the Amhara Region of Ethiopia
## 4 Results  
### Evaluation of Biome-BGC for Ethiopian Afronontane Forests  
Observed vegetation carbon stocks, soil carbon and NPP differed markedly among the four study areas. Gelawdiiwas, the study area highest in elevation showed the highest productivity and carbon storage, whereas Mahibereselassie, located in the dry lowlands showed the lowest productivity and carbon storage. Taragedam with the second lowest precipitation also showed the second lowest productivity and carbon storage.  
Biome-BGC simulations followed this general pattern. Note that the assumed management with 5% extraction annually was identical for the performed simulations in the four study areas. Figure 4 shows the median, the 25 th and 75 th percentile values of predicted versus observed vegetation and soil carbon. The observed vegetation carbon of the four study locations ranged from 1 t C ha\({}^{-1}\) to 187 t C ha\({}^{-1}\). The corresponding Biome-BGC predictions of the carbon content of the vegetation carbon for nine combinations of soil depth and nitrogen deposition levels ranged from 11 t C ha\({}^{-1}\) to 67 t C ha\({}^{-1}\). The observed soil carbon ranged from 14 t C ha\({}^{-1}\) to 253 t C ha\({}^{-1}\) and the modeled numbers ranged between 16 t C ha\({}^{-1}\) to 242 t C ha\({}^{-1}\).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & \multicolumn{3}{c}{**Grid Data**} & \multicolumn{3}{c}{**Transect Data**} \\ \cline{2-9}
**Study Area** & & & \multicolumn{3}{c}{**Forest Soil**} & \multicolumn{3}{c}{**Agricultural Soil**} \\ \cline{2-9}  & \(N\) & \begin{tabular}{c} **Carbon** \\ **(t ha\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Nitrogen** \\ **(t ha\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Sand/Silt/Clay (\%)** \\ \end{tabular} & \(N\) & \
\begin{tabular}{c} **Carbon** \\ **(t ha\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Nitrogen** \\ **(t ha\({}^{-1}\))** \\ \end{tabular} \\ \hline Gelawdiiwas & 7 & 207.4 \(\pm\) 24.0 & 19.0 \(\pm\) 2.2 & 8 /40/52 & 10 & 116.5 \(\pm\) 22.4 & 9.3 \(\pm\) 1.9 \\ Katassi & 14 & 204.5 \(\pm\) 31.8 & 17.6 \(\pm\) 2.7 & 15/40/45 & 10 & 31.0 \(\pm\) 9.6 & 5.1 \(\pm\) 1.3 \\ Mahabereselessie & 15 & 607.7 \(\pm\) 38.5 & 5.5 \(\pm\) 3.5 & 55/23/22 & 10 & 77.1 \(\pm\) 29.9 & 5.5 \(\pm\) 2.5 \\ Targedam & 7 & 173.1 \(\pm\) 28.4 & 14.9 \(\pm\) 2.4 & 13/40/47 & 10 & 102.8 \(\pm\) 34.8 & 9.0 \(\pm\) 2.6 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of the available soil data; The grid data refer to the soil carbon, nitrogen and Sand/Silt/Clay information collected on parts of the forest inventory grid points; The transect data are based on [32] and refer to transects with 10 samples taken every 50–100 m, placed in the agricultural area of our study areas.  
NPP derived from the recorded data, ranged between 4 g C m\({}^{-2}\) year\({}^{-1}\) to 1567 g C m\({}^{-2}\) year\({}^{-1}\) (Figure 4). Corresponding Biome-BGC predictions were within a range of 186 g C m\({}^{2}\) year\({}^{1}\) to 1095 g C m\({}^{-2}\) year\({}^{-1}\). Except for Mahibereselassie, predicted NPP was in the range of observed NPP.