Plant Formations in the Sulawesian BioProvince Peter Martin Rhind Sulawesian Lowland Rainforest 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 in which they constitute up to 90% of all trees. Palms are also a common sight in these forests and include, for example, the unusual black-spined Oncosperma horrida and the trunkless endemic Licuala celebensis (Arecaceae) but most common of all in 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 Copyright © 2010 Peter Martin Rhind 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. Sulawesian Peatswamp Forest The only major area of peatswamp on Sulawesi is the Aopa Swamp 100 km west of Kenderi. In the undisturbed areas these rich forests reaching heights of up to 35 m. Strangling figs are common, while other trees include Artocarpus teysmannii, Baeckia frutescens, Calophyllum soulattri, Diospyros malabarica, Geunsia paloensis, Hopea gregaria, Premna foetida and Saccopetalum horsfieldii. There are also many palms including species of Arenga and Livistona and climbers are common. Epiphytes, on the other hand, are comparatively rare, but the undergrowth includes a varied assemblage of herbaceous species. Sulawesian Swamp Forest Fresh water swamps more or less devoid of peat and are mainly found on riverine alluvium or alluvium deposited by lakes such as Lake Lindo and Lake Poso. The tree species composition of these forest can vary considerable but may include Barringtonia racemosa, Elaeocarpus littoralis, Polyalthia lateriflora, Quassia indica and Terminalia copelandii, while in the swamps of Lake Ranu species like Calophyllum soulattri, Mimusops elengi and the endemic Haplolobus celebicus (Burseraceae) have been recorded. Other endemic species include trees such as Guioa hirsuta (Sapindaceae) and Terminalia kjellbergia (Combretaceae) and shrubs such as Diplycosia minutiflora (Ericaceae). A feature of these forests is the presence of large numbers of pitcher plant (Nepenthes) which are generally climbing of scrambling plants Sulawesian Eucalyptus Forest These forests, which are confined to the margins of rivers, are dominated by the distinctive Eucalytpus deglupta, which can reach heights of up to 60 m. It is also the only species of this huge genus (about 500 species) that is regularly found in rainforest. Other large trees include Duabanga moluccana, Dracontomelon dae, Emirilla ovalis, Octomelus sumatrana and Pometia pinnata. These riverine forests are subject to regular flooding and the deposition of new sediments, and an interesting adaptation of a number of trees, such as Sauravia oligolepis, is to produce inflorescences at the base of their trunks, which eventually push their fruit into the soil. This is phenomenon known as geocarpy and helps to prevent their seeds being swept away by river foods. Sulawesian Forest of Ultrabasic Soils Sulawesi has the most extensive area of ultrabasic soils in the World. Given the high concentration of heavy metals and low fertility of the these soils it is not surprising that certain areas support no more than low, scrubby vegetation, but in places, such as on Mount Konde west of Sovoaka, closed canopy forests have developed reaching heights of up to 35 m. Most of the tree species, which are often specially adapted to these conditions, usually belong to the family Sapotaceae or the genus Ficus, while other trees include Deplanchea bancana, Metrosideros petiolata and the endemic Hopea celebica (Dipterocarpaceae), Knema celebica (Myristicaeae) and Terminalia supitiana (Combretaceae). Included among the many epiphytes are species of the ferns Drynaria and Lecanopteris and the ant plants Hydnophyton and Mymecodia. These form symbiotic relationships with ants – the plants provide enlarged chambered stems for the ants, and plants benefit from the organic frass that is brought into these chambers by the ants. Copyright © 2010 Peter Martin Rhind These relationships seem to have been engendered by the plant’s requirements for nutrients in these low fertile areas. Other endemic species associated with these soils include trees such as Gymnacranthera maliliensis, Myristica devogelii, M. ultrabasica (Myristicaceae) and Horsfieldia lancifolia (Myristicaceae), shrubs such as Gardenia celebica (Rubiaceae), and ferns like Tectaria subtriloba (Tectariaceae). Sulawesian Lower Montane Forest Dominated by chestnut, such as Castanopsis acuminatissima, and oaks, such as the endemic Lithocarpus celebicum (Fagaceae), these forests range in altitude from about 1500 to 2400 m, and can be found on mountains such as Lompobatang, Roroka Timbu and Tambusisi. Their canopies reach heights of over 30 m and normally include a sub- canopy of smaller trees. Other broad leaf trees include Acer caesium and the endemic Macadamia hildebrandii (Proteaceae), and conifers such as Agathis dammara, Dacrycarpus steupi, Dacrydium nidulum, Phyllocladus hypophyllus and Podocarpus neriifolius. In the undergrowth rattans and tree ferns are well represented. In fact, tree ferns reach their peak of diversity in these forest with species such as Culcita villosa, Dicksonia blumei, Cyathea oosora, C. oinops and several endemics like Cyathea dimorpha (Mt Bohaa), C. inquinans (Mt Lompobatang), C. pallidipaleata (Mt Rantemario), C. saccata (Mt Topapu) and C. sarasinorum (Mt Sibaronga). Epiphytes including many orchids and ferns are common. Among the ferns, the endemic Lindsaea pulchella (Lindsaeaceae) is unusual in being exclusively associated with tree ferns. Sulawesi also appears to be the evolutionary centre for the epiphytic fern genus Lecanopteris with more species found here than anywhere else. Most of the endemic species like Lecanopteris balgooyi, L. carnosa, L. celebica,