Recurrent fires in the dry season are a common feature of Africa’s Miombo region and shape the boundaries and extent of the forest-grassland mosaic. The current vegetation is thought to be well adapted to fire disturbances, as many C4-grasses, geoxylic suffrutices, and trees either tolerate low intensity fires or readily resprout after burning.

Although today fires are a frequent disturbance factor in these landscapes, the vast majority of fires are manmade and thus fire frequency, seasonal timing and fire return period are controlled by people. The timing of fires in the dry season, however, has a great impact on fire intensity since the biomass/fuel becomes drier and the ambient temperature hotter with progressing dry season. Until now it is poorly understood how the vegetation of Angola’s highly diverse natural suffrutex-grasslands reacts to different timing and return intervals of fire. Particularly the effects on vegetation structure, i.e. growth height and dominant life forms, and on species composition (via competition between early and late succession species) are assumed to be great.

To quantify the effect of different fire treatments on vegetation structure and species composition we established systematic fire experiments (Purgatories) at sites typical for suffrutex-grasslands in central Angola, related to the Biodiversity Observatories (Bicuar National Park, S75, and Cusseque, S74). Research is done in close cooperation with the team of Dr. Fernanda Lages from ISCED da Huíla in Lubango.

Each Purgatory comprises a hectare of grassland divided into a 15 m x 15 m grid with a 5 m fire break along the outer edges. We apply three different treatments following a random design: 12 plots are burned early in the dry season, 12 late in the dry season and 12 are not burned at all. A complete vegetation survey follows in the subsequent wet season, including measurements of selected traits of perennial grasses, suffrutices and tree species.