Role of Asian Elephant (Elephus Maximus) in Dispersing Mallotus Phillipinensis in Bardia National Park, Nepal

Abstract

Mallotus phillipinensis is one of the most preferred food tree species of Asian elephant. This herbivorous interaction can largely influence the evolution of plant life histories. The Asian elephant is currently recolonizing in BNP in lowland Nepal, concurrently the density of this most preferred Mallotus phillipinensis is increasing and that of hardly utilized Shorea robusta is decreasing. Pradhan et al. thus speculated that rapidly growing elephant population might be playing role in dispersing Mallotus phillipinensis and thus modifying the forest composition by increasing its preferred food species. This study was thus carried out to test this speculation with major objectives of testing the elephant’s role in dispersing Mallotus phillipinensis seeds through defecation and fostering regeneration of Mallotus phillipinensis either by dispersing seeds or by helping aerial buds to regenerate through coppicing in damaged trees. Experiments of the study were carried out from the month of September 2008 to June 2009. For seed dispersal through defecation, 37 and 40 dung piles were collected and sown into the soil respectively for two consecutive seed ripening seasons and observed for the germination of seedlings. One single separate control plot was also set in each season by directly sowing seeds of Mallotus phillipinensis in the same environmental conditions as for dung piles. For regeneration of Mallotus phillipinensis in sal forest juveniles of Mallotus phillipinensis in 100 circular plots of 15 m radius were observed in 10 systematic parallel transects and 100 such plots in 10 elephant tracks randomly selected in same block of forest. A total area of 14.3 Km

was observed in the whole block. Student’s ‘t’ test was applied for analyzing the data for regeneration. Among all 37 and 40 dung piles sown in the soil in two seasons there were not found any seedlings germinated but more than 90% of Mallotus phillipinensis seeds in control plot were germinated. Among the 100 circular plots in 10 elephant tracks and 100 such plots in 10 systematic parallel transects no significant difference was found in Mallotus phillipinensis regeneration. Among all circular plots very few damaged trees with few average coppiced aerial buds were found. No germination of any Mallotus phillipinensis seeds in elephant dung piles, no significant difference found in the regeneration of Mallotus phillipinensis in elephant tracks and systematic parallel transects and very few trees of Mallotus phillipinensis damaged by elephants, with few coppiced aerial buds, indicate that the recolonizing elephant population in BNP could not be playing any role in the shifting forest composition. The actual reason behind such shift in forest is speculated to be increased flooding and ecological succession. Further research is recommended to find the actual cause of such shift.

Key words- Asian elephant, ecological succession, Mallotus phillipinensis, regeneration, seed dispersal