# The Long-Term Consequences of Forest Fires on the Carbon Fluxes of a Tropical Forest in Africa
## 3 Results  
### The Consequences of a Fire Event on the Carbon Fluxes in a Tropical Forest  
In order to understand the effects of a large-scale fire on tropical forest dynamics, a single fire was simulated with the forest model FORMIND (simulation area 9 ha, fire size 60%, fire severity 0.67; see Figure 8). After the simulated fire event, the total aboveground biomass was reduced by 46% (Figure 9). Overall, it takes up to 150 years after the fire event for the forest biomass to reach the level of an undisturbed forest and to stabilize--which is much longer than the natural succession (100 years, cf. Figure 9). Compared with the succession in the undisturbed forest, this is mainly due to the climax species, which need up to 2 times longer to reach the biomass level of the undisturbed forest. \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Description** & **Parameter Value for This Study** \\ \hline Fire frequency F & mean time between two fire events & 4 years \\  & average size of a fire (here: 2 ha) in & \\ Fire size S & relation to the total size of the & 20\% \\  & simulated forest (here: 9 ha) & \\  & indicator (0–1) for the strength and & \\ Fire severity f\({}_{\text{sev}}\) & type of fire (light ground fire or & 0.55 \\  & strong crown fire) & \\ \hline \end{tabular}
\end{table} 
Table 1: Parameter of the fire model ForFire and parameter values for the study region for the scenario where repeated fire events are simulated. For the scenario with only one fire event, the parameters are S = 60% and f\({}_{\text{sev}}\) = 0.67). \begin{table}
\begin{tabular}{c c c c} \hline
**PFT** & **Maximum Height [m]** & **Shade Tolerance** & **Exemplary Tree Species** & **Fire Tolerance** \\ \hline
1 & \textgreater{}33 & shade tolerant & _Strombosa scheffleri_ & 2 \\
2 & 16–33 & shade tolerant & _Heinsen diervilleoides_ & 1 \\
3 & 16–33 & medium shade tolerant & _Ficus sur_ & 1 \\
4 & 16–33 & shade intolerant (pioneer) & _Polyscias albersiana_ & 4 \\
5 & \textless{}16 & shade tolerant & _Leptonychia usambarensis_ & 2 \\
6 & \textless{}16 & shade intolerant (pioneer) & _Cyathe manniana_ & 2 \\ \hline \end{tabular}
\end{table} 
Table 2: Species grouping with fire tolerance at Mt. Kilimanjaro region. Grouping of all tree species in the study area into six species groups according to maximum height and shade tolerance (for full species list, see Appendix A). This species grouping into plant functional types (PFT) was already investigated in former studies [32; 33]. In this study, only a fire tolerance was assigned to each species group. Due to the different fire tolerances, but also due to the different tree size distributions of the individual tree species, the fire affects the species groups differently (Figure 9a). The biomass of the dominant climax species was reduced by 46%; the biomass of the pioneer species was reduced by about 53%. However, since the forest was dominated by climax species before the forest fire, this led to the largest absolute biomass losses (\(-158\) t/ha) compared with the other species groups. After the fire, secondary succession starts at the burnt areas. First, the pioneer species colonize these areas. The previously absent fire-tolerant and shade-intolerant tree species dominate the forest in this regeneration phase. After about 50 years, the biomass of trees with high shade tolerance then also increases again. Forest productivity two years after the fire is up to 4 times larger than before the fire (up to 92 t\({}_{\text{C}}\)/(ha yr), Figure 9b). The higher productivity is mainly caused by growing pioneer species on the burnt area. The respiration of the living vegetation increases 5-fold after the forest fire. However, the resulting net primary production remains rather stable after the fire at the value of about 3-4 t\({}_{\text{C}}\)/(ha yr). Both productivity and respiration do not return to pre-fire levels until more than 100 years after the fire (Figure 9b).