Effects of fire frequency on plant species diversity and composition in Queen Elizabeth National Park, Southern Uganda

Abstract

In savanna grasslands worldwide, periodic fires are important forces affecting plant species composition, richness, diversity and cover (Govender et al., 2006). It is not clear, however, how variations in fire frequency have affected these parameters in the Queen Elizabeth National Park (QENP) over time. This study investigated the effects of fire frequency on plant species diversity and composition in the QENP. Fire frequency data was derived from a burn scar map of QENP produced by the Woods Hole Research Centre. A field visit was conducted to categorize the vegetation of the study area after which the study sites were selected based on similarity in the burning frequency and nature of vegetation. The modified-Whittaker nested vegetation sampling method was then used to sample the vegetation in the study sites.

Data analysis was done using Genstat 5 Release 3.22.

Results showed that species richness of all vegetation varied quadratically with fire frequency (y = 0.254x2 – 4.2843x + 26.456; R2= 0.9666). Similarly, species diversity of all vegetation changed quadratically with fire frequency (y = 0.0917x2 – 1.3671x + 9.5838; R2= 0.7464). Percentage cover of all vegetation also varied quadratically with (y = -0.9784x2 + 14.102x + 42.037; R2= 0.9858) Plant species richness and vegetation cover were strongly correlated with fire frequency (R2 > 0.9)

Fire frequency produced a change in plant species composition with herbaceous plants dominating in all the study sites. The number of shrubs and trees recorded generally decreased with fire frequency. The study among others recommended continuous monitoring of the effects of the current controlled burning program on vegetation in QENP and the need to expand the study by combining the effects of fire with those of other factors such as grazing, soils, rainfall regime and topography.