Effect of elephant browsing on selected species of Acacia along the great Ruaha River in Ruaha National Park, Tanzania

Abstract

Elephant damage was assessed in 1,007 Acacia trees and responses between Acacia tortilis and A. kirkii in Ruaha National park were compared in 30 transects randomly placed in 38.8 km² on the northern bank of Great Ruaha River (GRR) basing on six browsing categories and four debarking classes. There was no significant difference in browsing (F_{1, 10} = 0.6, p>0.05) and debarking (F_{1, 6} = 0.16, p > 0.05) between A. kirkii and A. tortilis. Trees were classified into three height and twelve diameter classes. About 3613 trees <1 m in height represented response in addition to coppices. The difference between the two species was observed only in regeneration potential (F_1,58 = 41.4, p < 0.05). In addition, low regeneration potential, severely browsed trees and restricted distribution made A. kirkii more vulnerable to elephant feeding compared to A. tortilis. The high A. tortilis regeneration potential suggests that the study area could become an Acacia bushland or woodland if fire is controlled. Further studies need to investigate, the suppressed regeneration of Acacia trees at Msembe, variations in vegetation utilization along the GRR and effects of fire and small browsers on Acacia species including monitoring of vegetation and animal trends.

Key words: Elephants, Acacia, Tree damage, Regeneration, Ruaha River