Acacia nilotica was introduced to Baluran National Park (BNP) in 1969 to serve as firebreaks. It quickly invaded the Bekol Savanna in BNP, where it inhibited the growth of native grasses that are important food for wildlife, such as the endangered banteng (Bos javanicus). To determine the effect of A. nilotica invasion on plant species assemblages and diversity and to evaluate how well the management technique is preventing further invasion and restoring the native ecosystem, we laid out 25 plots (10 m × 10 m) in a belt transect in each of three vegetation types: uninvaded area (UIA), invaded area (IA), and managed area (MA) where the slash and burn method has been attempting. In each vegetation type, we counted the number of individuals of each plant species and calculated the species richness and diversity indices. The results showed that the savanna changed dramatically after the introduction of A. nilotica. Seven of the nine species detected in UIA were absent from IA, and the relative dominance of surviving plants also decreased. Consequently, the diversity of the savanna was degraded by A. nilotica invasion, causing a reduction of food resources for herbivores. In MA, however, five of the seven species absent from IA had recovered after the slash-and-burn removal of A. nilotica. Several forest species had newly invaded MA owing to both the decreased allelopathic influence and the perch effects of remnant A. nilotica. Thus, the slash-and-burn method could contribute to the recovery of native species, although additional efforts are required to remove remnant A. nilotica.
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