# The Long-Term Consequences of Forest Fires on the Carbon Fluxes of a Tropical Forest in Africa
## 2 Materials and Methods
### Simulation Settings  
To analyze the effects of a fire event on forest dynamics, a forest area of nine hectares was simulated over a period of 500 years with a yearly time step. The fire model has four parameters: the mean fire frequency, the mean fire size, the mean fire intensity, and the fire tolerance of the individual species groups. To determine fire frequency in the study area, the satellite datasets \"MODIS Burned Area Product MCD4\" from 2000 to 2012 were analyzed. (In total 144 images were analyzed; see [[https://modis-fire.umd.edu/index.html](https://modis-fire.umd.edu/index.html)]([https://modis-fire.umd.edu/index.html](https://modis-fire.umd.edu/index.html)), accessed on 12 February 2021, for more information about MODIS Burned Area Product; for user manual and downloading see [[https://modis-fire.umd.edu/files/MODIS_Burned_Area_Collection51_User_Guide_3.1.0.pdf](https://modis-fire.umd.edu/files/MODIS_Burned_Area_Collection51_User_Guide_3.1.0.pdf)]([https://modis-fire.umd.edu/files/MODIS_Burned_Area_Collection51_User_Guide_3.1.0.pdf](https://modis-fire.umd.edu/files/MODIS_Burned_Area_Collection51_User_Guide_3.1.0.pdf)), accessed on 12 February 2021). These maps show the monthly burned area in an area through spectral variations and changes in vegetation (see, for example, [49]). In the savannah area of the Kilimanjaro region, almost every year a fire can be observed; in the tropical forests of this region, a fire can be observed somewhat less frequently [15]. The analysis of the available satellite data for the entire Kilimanjaro area (region investigated: 2\({}^{\circ}\)29-3\({}^{\circ}\)72 South and 37\({}^{\circ}\)12-37\({}^{\circ}\)57 East) showed that a large-scale fire occurs on average every three to four years and is between 1 and 16 pixels in size (pixel resolution 500 m) [50]. The larger fires were observed in 2001, 2004, 2007, and 2009, and they mostly occur in the dry seasons, which are characterized by the El Nino Southern Oscillation [20]. In the forested area at Mt. Kilimanjaro, the satellite data show that on average a fire is about 25 hectares in size (=1 image pixel, with the size of 500 \(\times\) 500 m). However, smaller fire areas cannot be detected due to the spatial resolution (i.e., 500 m) of the satellite product, and thus this mean size seems too high. Since the simulated forest area in the model has a size of 9 hectares, the mean fire area was set to 20% of the considered forest area--which corresponds to experiences from other areas [7; 40; 51]. Fire intensity indicates the difference between a light ground fire (fire intensity = 0.1) and a strong crown fire (fire intensity = 1.0). For this study, a mean value of 0.55 was set [43; 48]. All parameter values for the fire model ForFire can be found in Table 1.  
Figure 7: Probability of death of a tree in a fire event, after [43]. This probability depends on the fire tolerance of the tree species, the stem diameter in breast height (DBH), and the severity of the fire (f\({}_{\text{sev}}\)). (**a**) The probability of death in a weak fire (f\({}_{\text{sev}}\) = 0.2). (**b**) The probability of death in a stronger fire (f\({}_{\text{sev}}\) = 0.7). The mortality of a tree in a fire event is influenced by its fire tolerance. There are four groups of fire tolerance in the fire model: Species with fire tolerance group 1 burn in any fire, whereas fire tolerance group 4 is very resistant to fire. For each tree species in the study area, the fire tolerance was determined by the literature or expert knowledge (for a complete list, see Appendix A). The thickness of the bark is the most important factor [52]. The thicker a bark is, the less heat is generated in the cambium layer of the tree (responsible for the growth of the tree). In the study area, for example, the species _Agarstia salicidia_ and _Morella salicidia_ have particularly thick bark and are therefore considered to be fire tolerant [15; 53; 54]. The species _Alagium chinense_ is a deciduous species, which is also considered to be adapted to the occurrence of fire [53; 55].