Understanding tree diversity in ultrabasic forests of Sulawesi, Indonesia for restoration and conservation planning

Abstract

Abstract. Nasri, Nursaputra M, Hamzah AS, Larekeng SH, Arif AR, Ardiansyah A. 2026. Understanding tree diversity in ultrabasic forests of Sulawesi, Indonesia for restoration and conservation planning. Asian J For 10: r100102. https://doi.org/10.13057/asianjfor/r100102. Ultrabasic (or ultramafic) forests in Sulawesi, Indonesia, support high endemism but remain understudied, especially in disturbed and reclaimed areas. This study assessed tree diversity and composition across five forest cover types: High-Density Forest (HDF), Moderate-Density Forest (MDF), Low-Density Forest (LDF), Reclaimed Forest (RF), and Shrub (S), within an ultrabasic mining landscape in East Luwu. A total of 143 adult-tree species were recorded, including 17 endemic species to Sulawesi and 6 endangered species. HDF exhibited the highest species richness (30 species/cluster) and basal area (17.79 m²/ha), while RF and S had the lowest. Diversity was significantly different among forest types (p<0.05), with HDF and MDF also showing the highest community similarity (Morisita Similarity Index=0.60). In contrast, RF and S showed distinct species compositions, dominated by pioneer or generalist species. The presence of threatened endemic species, such as Diospyros celebica, Hopea celebica, and Vatica flavovirens, was mostly confined to undisturbed forests. Cluster analysis based on plant families revealed a close taxonomic relationship between MDF and LDF. These findings underscore the importance of intact ultrabasic forests as biodiversity reservoirs for endemic and threatened species. While reclaimed areas support vegetation recovery, they require enhanced efforts to increase native species richness, functional diversity, and taxonomic representation. Protecting high-diversity forests is essential to sustain source populations for conservation and support more ecologically meaningful restoration outcomes.

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