Impact of Invasive Alien Species- Acacia nilotica on the Remnant Dry Deciduous Forest of Palu Valley, Central Sulawesi, Indonesia

Abstract

Aims: The study was carried out to assess the species composition, vegetation structure, regeneration and possible direction of vegetation development due to Acacia nilotica invasion. Study Design: The study applied the vegetation analysis and remote sensing technique in the deciduous forest of the Palu Valley in Central Sulawesi. Place and Duration of Study: The study was conducted in Biromuli District, Sigi Regency, Central Sulawesi Province of Indonesia in February 2019. Methodology: Species composition, vegetation structure and regeneration were studied using the split plot method, while the specific population and distribution of A. nilotica were studied using drone photos in an area of 10.24 ha. Results: Individuals >2cm in diameter are 24 species, 22 genera and 14 families. The main species are Tabernaemontana pandacaqui, A. nilotica and Jatropha gossypiifolia. The ground vegetation (diameter<2cm) contained 21 species, 21 genera and 17 families, dominated by Digitaria ciliaris and A. nilotica. The species diversity index is 2.3880 (moderate), while the species evenness index is 0.75 (unstable). Density of 1.069 individual’s per ha and total basal area 2.48 m2 per ha. The dominance of individuals with a diameter of 2.0-4.9 cm (62.9%), followed by diameter of 5.0-9.9 cm (32.4%),  and diameter of 10 cm up (4.67%). The canopy layer consists of only one main layer at a height of 4-7m. Canopy analysis using drone photos showed that 27% of the total forest canopy area and 32.9% of the total individuals were controlled by A. nilotica. Conclusion: The dry forest in Sigi is the remnant deciduous forest located specifically in the Palu Valley which is still in the process of development. The invasion of A. nilotica needs to be controlled in a sustainable way so that the rest of the forest does not turn into a stretch of A. nilotica.