Ecological Characteristics of Tropical Montane Forest in Lore Lindu National Park Central Sulawesi

Abstract

Tropical montane forest ecosystem making up 21 percent of the total area of the world’s tropical forest. This ecosystem has high level of species diversity, constributes positively to the water catchment, and provides an essential habitat for many endemic and threatened plant and animal species. The objectives of this research were 1) to determine plant species diversity, 2) to study composition of vegetation community and tropical montane forest structures. This study was conducted at three primary forest sites were located in Lore Lindu National Park, Central Sulawesi. The first site was located in Watukilo at 900 m asl, the second site was in Torongkilo at 1 500 m asl, and the third site was in Torenali at 2 300 m asl around 1.5 km to peak of Mount Rorekatimbu. All sites are submontane forest, lower montane forest, and upper montane forest respectively. Plot-based plant inventory and identification were carried out in the period of July 2011 to July 2012. Plot size was 40 m x 60 m (0.24 ha) devided up into a 10 m x 10 m grid. All trees of diameter at breast height (dbh) ≥10 cm (at 1.3 m). Within each of the 10 m x 10 m, one 5 m x 5 m-sized subplot was surveyed (0.06 ha per plot) to study saplings (2 cm ≤ dbh < 10 cm), and one 2 m x 2 m-sized subplot (0.024 ha) to additionaly study understorey vegetation in each of the 5 m x 5 m subplot. We recorded a total 310 plant species belonging to 129 genera and 106 families in all forest types. Lower montane forest has the highest species richness (61 tree species, 51 sapling species, 57 seedling species, and 56 understorey plant species), followed by submontane forest and upper montane forest. Shannon diversity index showed that all forest types in this study has moderate to high in species diversity (2 < H' < 4), and has low similarity in species composition with the similarity <10% (Sørensen index). Among the species recorded, only one species that found in all three forest types, i.e. Lithocarpus celebicus (Fagaceae). In submontane forest, the most dominant tree species were Castanopsis buruana (Fagaceae), Gironniera subaequalis (Cannabaceae) and Santiria apiculata (Burseraceae), while the most dominant saplings were C. buruana, S. apiculata and Praravinia mindanaensis (Rubiaceae). For seedlings and understorey, the most dominant species were Antidesma riparium subsp. riparum (Phyllanthaceae) and Calamus sp.1 (Arecaceae), respectively. In lower montane forest, the most dominant tree species were Platea excelsa var. borneensis (Icacinaceae), Elaeocarpus sp.1 (Elaeocarpaceae) and Magnolia carsonii var. carsonii (Magnoliaceae), while the most dominant saplings were Lophopetalum beccarianum (Celastraceae), Ardisia forbesii (Primulaceae) and Cyathea contaminans (Cyatheaceae). For seedlings and understorey, the most dominant species were Calophyllum soualattri (Calophyllaceae) and Calamus sp.5, respectively. In upper montane forest, the most dominant tree species were Phyllocladus hypophylla (Podocarpaceae), Dacrycarpus steupii (Podocarpaceae) and Lithocarpus havilandii (Fagaceae), while the most dominant saplings were Trimenia papuana (Trimeniaceae), Tasmannia piperita (Winteraceae) and Myrsine minutifolia (Primulaceae). For seedlings and understorey, the most dominant species were Myrsine minutifolia (Primulaceae) and Sonerilla pumila (Melastomataceae), respectively. There was major differences of community composition at the family level among all three forest types. Trees and saplings in submontane was dominated by Fagaceae. Seedlings and understorey plants were dominated by Lauraceae and Arecaceae. Trees, sapling, seedlings, and understorey plants in lower montane forest were dominated by Icacinaceae, Lauraceae, Calophyllaceae and Arecaceae respectively, while upper montane forest Podocarpaceae was the most dominant family, whereas saplings, seedlings, and understorey dominated by Trimeniaceae, Primulaceae and Melastomataceae respectively. Lauraceae has highest number of species (18 species), followed by Myrtaceae (16 species), and Fagaceae (11 species). Tree density increased with increasing elevation. Upper montane forest had highest tree density, followed by lower montane and submontane forest. The difference was found in the average tree height, escpecially in upper montane that had lowest tree height (15 m), however submontane and lower montane forest had similar average tree height (20 m). Trees with smaller stem diameter had higher density than trees with larger stem diameter, especially in submontane and upper montane forest. Moreover, there were no trees more than 70 cm stem diameter in upper montane forest than two others forest types. The highest basal area of stem found in submontane (46.76 m2/ha), followed by lower montane forest (44.42 m2/ha), and upper montane forest (38.28 m2/ha).