Influence of Fire on Floristic Diversity and Herbaceous Production in the Ollombo Savannahs in the Republic of Congo

Abstract

The Loudetia simplex (Nees) C.E. Hubb. savanna and the Hyparrhenia diplandra (Hack.) Stapf savanna are the main savannas in the Ollombo area of the Republic of Congo. The functioning of these savannas is influenced by the different types of fire. The aim of this study is to assess the influence of fire on the floristic diversity and herbaceous production of the savannahs in the Ollombo area. The floristic inventory and phytomass measurements were carried out at the peak of vegetation before the fires and at 2 and 10 months after the fires. The floristic inventory was carried out using the aligned quadrat points method. The data from this inventory were used to calculate diversity indices, including the Shannon-Weaver index (H'). Above-ground herbaceous phytomass was assessed using the harvesting method. The results show that floristic diversity and herbaceous above-ground phytomass vary from one type of fire to another and from one type of savannah to another. In the Loudetia simplex (Nees) C.E. Hubb. savannah, seasonal fire (H'=2.69) and late fire (H'=2.43) appear to favour floristic diversity at 2 and 10 months after burning, respectively. In the Hyparrhenia diplandra (Hack.) Stapf savannah, on the other hand, only early fire seems to favour floristic diversity two months (H'=2.7) and 10 months (H'=2.4) after burning. In terms of herbaceous above-ground phytomass, seasonal fire (0.82 ±0.07 t DM/ha) and early fire (6.49 ±1.06 t DM/ha) appear to increase herbaceous production at 2 and 10 months after burning, respectively, in the Loudetia simplex Nees C.E. Hubb. savannah. On the other hand, late burning (0.88 ±0.07 t DM/ha) and early burning (6.98 ±1.01 t DM/ha) appear to increase herbaceous production at 2 and 10 months respectively in the savannah with Hyparrhenia diplandra (Hack.) Stapf. These results could serve as a scientific basis for the sustainable management of pastures by fire and as a benchmark for future studies.