Included here are forests of Sulawesi (Celebes) and its neighbouring islands. Unlike Borneo where the lowland forests are dominated by dipterocarps with in excess of 250 species, Sulawesi has only six species Anisoptera costata, Shorea assamica, Vatica rassak, V. flavovirens and the two endemics Hopea celebica and H. gregarica (Dipterocarpaceae). As a result neither dipterocarps nor any other family dominate these forests, although several families including the Annonaceae, Euphorbiaceae, Lauraceae, Myristicaceae, Rubiaceae and Sapotaceae are well represented. There is, however, considerable variation between sites in terms of the major species and families, but some of the species that are abundant at particular sites include Adina fagifolia, Ailanthus integrifolia, Canangium odoratum, Calophyllum soulattri, Dracontomelum dae, Duabanga molluccana, Elmerillia, ovalis, Garuga floribunda, Gonostylus macrophyllus, Gossampinus valetoni, Intsia amboinensis, Itoa stapfi, Kleinhovia hospita, Koordersiodendron pinnatum, Metrosideros vera, Mussaendopsis beccariana, Octomeles sumatrana, Palaquim obovatum, Planchonella firma, Planchonia valida, Pterocarpus indica, Strychno axillaria, Tetrameles nudiflora and the two endemics Homalium celebicum (Flacourtiaceae) and Manilkara celebica (Sapotaceae).  Adina fagifolia, for example, is very common in the hills west of Marisa, while Elmerrilia ovalis is frequently encountered in parts of Minahasa (eastern Bolaeng Mongondow). Ebonies (Diospyros) are also conspicuous in certain areas. They are represented by several species including the endemic Diospyros celebica (Ebenaceae), and of interest from an ecological point of view, they tend to form dense stands covering several hectares and may constitute up to 90% of all trees. Palms are also common and include, for example, the unusual black-spined Oncosperma horrida and the trunkless endemic Licuala celebensis (Arecaceae) but most common of all is the fan palm Livistonia rotundifolia, which can reach heights of 30 m. In one hectare of forest at Toraut 88 specimens were found.

In terms of their vertical structure, these forests, as exemplified by the stands at Toraut, typically have a three-tiered vertical structure with a canopy reaching heights of between 30-40 m. However, they are slightly unusual in the absence of large emergents and tend to have a more or less level canopy top. Also of an atypical nature is the presence of large numbers of trees with small, roundish crowns. Among the other endemic trees of these forests are Archidendron minahassae (Fabaceae), Arthrophyllum kjellbergii (Araliaceae), Chisocheton warburgii (Meliaceae), Elattostachys erythrocarpum (Sapindaceae), Euonymus impressus (Celastraceae), Gomphandra velutina (Icacinaceae), Gyrinops decipiens (Thymelaeaceae), Horsfieldia coriacea (Myristicaceae), Kalappia celebica (Caesalpiniaceae), Kjellbergiodendron celebicum (Myrtaceae), Knema matanensis (Myristicaceae), Leea smithii (Leeaceae), Macadamia hildebrandii (Proteaceae), Myristica kjellbergii (Myristicaceae), Osmoxylon masarangense (Araliaceae), Sarcotheca celebicus (Oxalidaceae), Stemonurus celebicus (Icacinaceae), Symplocos maliliensis (Symplocaceae), Terminalia celebica (Combretaceae) and Vaccinium aucupis (Ericaceae). The shrub layer is normally up to about 3 m tall with an often dense, impenetrable structure and typically includes many rattans (all species of Calamus or Daemonorops). Other shrubs include various endemics like Diplycosia haemantha, Rhododendron radians, Vaccinium centrocelebicum (Ericaceae) and Thottea celebica (Aristolochiaceae). There are also numbers of aerial parasitic or semi-parasitic shrubs, such as the endemic Amyema celebica, Decaisnina celebica (Loranthaceae) and Viscum exile (Viscaceae).  Climbers and lianas are frequent although boles tend to remain ‘clean’ of these species except for occasional specimens of Freycinetia or the superficially similar aroid Pothos hermaphrodita. The few endemic climbers include Tinospora celebica (Menispermaceae). Epiphytes, apart from occasional orchids and epiphytic shrubs like the endemic Diplycosia filipes and Vaccinium tomicipes (Ericaceae), are not common and boles are often free of bryophytes and filmy ferns. The forest floor, as is typical for lowland rainforests, has few herbaceous species.


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