Abstract ID: 316

Long-term potential for fires in estimates of the occurrence of savannas in the tropics

Potential vegetation models are important to represent large-scale biosphere-atmosphere interactions in environmental studies. The CPTEC Potential Vegetation Model (CPTEC-PVM), for example, is used for studying long-term equilibrium states between climate and vegetation. The model is able to reproduce most of contemporary natural (not considering land use) vegetation features globally, based on dominant climate and soil hydrology characteristics. Without considering fires, however, the model indicates that the potential vegetation in large regions in India and SE Asia is savannas while reference maps for current climate conditions indicate that the natural vegetation in those regions is dry forests. In order to improve the formulation and results of the CPTEC-PVM, we developed a new parameterization for long-term occurrence of fires in regions with potential for the establishment of savannas in the tropics. Fires are important to consider in this case because they may favor grasses and reduce tree coverage due to their fast biomass consumption and mortality relatively to slower carbon uptake and growth of the vegetation. To find relations between long-term potential for fires and other environmental factors, we have assumed that generally precipitation seasonality in savannas support both the presence of fuel and flammability. Thus, fire activity in these regions may be limited primarily by the presence of ignition sources. Following other studies indicating that lightning is the most important source of ignition for natural fires, we built the long-term fire parameterization for savannas based on large-scale potential for lightning activity during transitions between dry and wet seasons. The application of this new relation improved the formulation and the results of the CPTEC-PVM. In particular, important commission errors in allocating savannas instead of dry forests in India and SE Asia are now substantially lower than in previous studies.

Session:  Fire - Fire, drought, and changes in vegetation structure and composition

Presentation Type:  Oral