Changes in woody plant composition of three vegetation types exposed to a similar fire regime for over 46 years

The effect of regular burning of woodland vegetation in Africa over an extended period (46 years) was studied in the Murchison Falls National Park, Uganda. Areas identified as having different vegetation types in 1958 were revisited to analyze vegetation changes and to test the prediction that convergence would occur as a result of the regular fire. In each of the three vegetation cover types, a transect was analysed. Results show that the vegetation cover types have changed and there is evidence of vegetation convergence. A detrended correspondence analysis (DCA) and a Morisita similarity index analysis showed a good separation between the 1958 and 2004 transects for each of the vegetation cover types. The DCA also showed that the three 2004 transects were ompositionally closer to each other than the 1958 transects. The 2004 transects had also shifted away from the 1958 transects. Whereas in 1958 compositional similarity was highest between the Terminalia glaucescens conversion transect (T2) and the wooded grassland conversion transect (T3) (0.86), in 2004 it was most similar between the transects closest to Wairingo river (T1 and T2, correlation coefficient of 0.80). T1 was referred to as the Terminalia woodland transect. Comparing the 2004 transects to the 1958 transects, a low compositional similarity was observed. The highest was between T3-1958 and T3-2004 (0.62). Additionally, fewer indicator species (species specific for one transect) were identified in 2004 than in 1958 and, the transects shared more species in 2004 than in 1958. All the big trees (DBH _ 30 cm) that existed along T1 in 1958 died off. Clustering of individual woody plants, a protective mechanism used by plants in presence of fire, was identified in each of the plots analysed. To counterbalance the unifying effect of fire for the vegetation in the area and to maintain diverse vegetation, a variety of fire management regimes are needed.