# The Long-Term Consequences of Forest Fires on the Carbon Fluxes of a Tropical Forest in Africa
## 1 Introduction  
Tropical forests are important for the climate of the Earth because they represent a relevant carbon sink [1, 2, 3]. Tropical forests account for about 50% of the total carbon stored in global vegetation [4, 5]. However, these forests are threatened by various environmental and anthropogenic hazards such as logging and fire [6, 7, 8, 9]. Between 2000 and 2012, tropical rainforests accounted for 32% of global forest area loss [10]. Extreme weather events and agricultural practices have already intensified forest fire regimes, which have led to accelerated losses of tropical forest [11, 12]. Global fire carbon emissions were 2.0 Gt C per year (=10\({}^{9}\) t of carbon), with the majority of carbon emissions occurring in savannas and tropical forests [13]. Annual carbon emissions from tropical deforestation and degradation were on average 0.5 Gt C, whereby it is debated whether these carbon emissions from fires may not be compensated by forest regrowth after the fire [13]. It is also assumed that the number of fires in tropical forests will continue to increase in the future [14]. Almost 70% of all global forest fires are found in Africa [15, 16]. These fires are rarely caused by natural processes such as lightning strikes; instead, human actions are often the cause [17]. This can happen through conversion to agricultural land but also through poachers or gatherers [17, 18]. Forest fires can have an impact on the species composition, the living biomass, and the carbon balance of tropical forests [19]. These fires are also an influential ecological factor in the forests around Mt. Kilimanjaro in Africa [15, 18, 20]. In the last century, the impact of fire on the vegetation has increased due to climatic changes as well as the consequences of the growing population in the Kilimanjaro area. The upper tree line has already decreased by up to 800 m in altitude [15]. Consequently, about 15% of the forest area at the Kilimanjaro region has been destroyed in the last 40 years [15], with negative consequences for the water supply of lowland farmland. However, the long-term consequences of fires on tropical forest dynamics are difficult to assess, as forest fires create heterogeneous landscapes with long-lasting impacts. A fire regime can be described by characteristics such as frequency, size, and severity. All these factors and also their interactions form a complex dynamic system. The long tradition in fire ecology has produced a broad understanding of these processes. Numerous models have been developed to simulate damages caused by fires in forests. These fire models are mainly developed as extensions of vegetation models [21; 22; 23]. Many fire models simulate the spread of fire as a function of topographic features. They were mainly developed for geoinformation systems and work on a scale of several kilometers [24]. Dynamic Global Vegetation Models (DGVM) have also been extended to include fire models [9; 21]. Since these types of models mostly operate at a coarse scale of several kilometers, they use a top-down approach. Instead, high-resolution forest models operate at a much finer spatial resolution of up to 10-20 m [25; 26]. In order to understand the effects of fire events on forest structure and dynamics, it is therefore necessary to develop an adapted fire model for this fine scale. For the analysis of the effects of fire events on the dynamics of tropical forests at Mt. Kilimanjaro, the forest model FORMIND [27; 28] was extended by a fire model. Specifically, the following question was answered: **How strong is the influence of forest fires on the aboveground biomass, productivity, and carbon balance of sub-montane tropical forests at Mt. Kilimanjaro? **  
To answer this question, the forest model FORMIND was used to simulate typical fire patterns for this region and to look at long-term forest dynamics. For this purpose, first the forest dynamics after a fire event were investigated, i.e., the long-term regeneration of forest attributes such as biomass after the fire.