Included here is the island of Sumatra and surrounding islands such as Nias, Siberut, Bangka and Belitungare

Sumatran Riparian Forest

These forests, confined to riverbanks, undergo temporary flooding during heavy rain. They show considerable floristic diversity and vary according to location and flooding regime. On the west coast the enormous Canarium pseudodecumanum is often the dominant emergent species reaching heights of up to 50 m, while the main canopy trees, at heights of 25 m, include Antiaris toxicaria, Blumeodendron kursii, Dracontomelon dae, Pometia pinnata, Pterospermum javanicum, Santiria apiculata and the endemic Neoscortechinia sumatrensis (Euphorbiaceae).  In southern areas other species may dominate including Alstonia spathulata, Canthium dicoccum, Dillenia excelsa, Ficus retusa, Gluta renghas, Kayea ferruginea, Koompassia excelsa, Myristica elliptica, Neesia malayana and several endemic species like Mangifera gedeba (Anacardiaceae), Shorea sumatrana and Vatica venulosa (Dipterocardiaceae).

Sumatran Swamp Forest

These forests occur in areas that are periodically flooded for relatively long periods of up to four months or more, and their floristic composition varies according to factors such as frequency and duration of flooding. As a result they are much more varied than forests of well-drained ground. In east Sumatra the main canopy trees are Artocarpus kemando, Baccaurea bracteata, Blumeodendron tokbrai, Campnospermum auriculatum, Mangifera paludosa and Parartocarpus venenosus. These can reach heights of up the 25 m or so, but often towering above these are various emergents like Alstonia pneumatophora and several dipterocarps such as Dipterocarpus apterus and Shorea balangeran that can reach 50 m or more. Among the associated endemic trees are Casearia gigantifolia (Flacourtiaceae) and Vatica teysmanniana (Dipterocarpaceae).  In the undergrowth palms like Eleiodoxa conferta, Licuala spinosa, Oncosperma tigillarum are common as are various rattans such as Calamus caesius, Daemonorops geniculata and Korthalsia flagellaris. Shrubs may be present including the endemic Erycibe sumatrensis (Convolvulaceae).  Ferns are also characteristic and besides Stenochlaena palustris, a climbing species with edible shoots, there are species such as Mesophlebion chlamydophorum, Microsorum musifolium, Paragramma longifolia, Pyrrosia lanceolata, Vittaria elongata, and in more open areas tree ferns like Cyathea contaminan. At ground level, not surprisingly, members of the Cyperaceae are common and may include Thoracostachyum bancanum and the endemic Scleria sumatrensis.

Sumatran Peat Swamp Forest

Mainly confined to the east coast at the central and southern parts of the island, these forests are particularly abundant from the Musi delta to the Siak River. The peat deposits are usually about 50 cm deep but can be up to 20 m in places, and as a result of the low nutrient status and high acidity of these soils their floras are not as species-rich or as rich in endemics as other forests.  Their floristic composition varies from place to place, but in southern Sumatra the most representative canopy trees are Campnospermum coriaceum, Durio carinatus, Mezzettia leptopoda, Santiria laevigata, Tetramerista glabra and Xylopia fusca. These reach heights of 35 m, but exceeding these by a further 15 m or so are various emergents like Dyera lowii and Shorea teijsmanniana. Among the many smaller, sub-canopy trees are Blumeodendron tokbrai, Combretocarpus rotundatus, Parastemon urophyllus, Tetractomia obovata, the endemic Neoscortechinia sumatrensis (Euphorbiaceae) and numerous species of Diospyros. The few palms include the emergent Livistonia hasseltii and the bright-red sealing wax palm Cyrtostachys lakka. Shrubs in the undergrowth are mostly Antidesmus montanum, Dacryodes rostrata, Eugenia setosa, Goniothalamus malayanus, Ixora malayana and Memecylon oligoneura. However, the flora that is specific to peat swamps is very limited, but includes, for example, the endemic dipterocarp Vatica teijmanniana (Dipterocarpaceae). Some of these peat swamp forests are described as pole forests because of the dominance of long straight trees.

References

Bihari, M. & Lal, C. B. 1989. Species composition, density and basal cover of tropical rainforest of central Sumatra. Tropical Ecology, 30: 118-137.

Chapman, V. J. 1977. Wet coastal formations of Indio-Malesia and Papua New Guinea. In: Ecosystems of the World 1 - Wet Coastal Ecosystems. Ed. V. J. Chapman. Elsevier Scientific Publishing Company.

Laumonier, Y. 1997. The Vegetation and Physiography of Sumatra. Kluwer Academic Press.

Leith, H. & Werger, M. J. A. 1989. Ecosystems of the World 14B - Tropical Rain Forests. Elsevier Scientific Publishing Company.

Steenis, C. G. G. J. van. 1957. Outline of the vegetation types in Indonesia and some adjacent regions. Proceedings of the Pacific Scientific Congress, 8: 61-97.

Whitten, T., Damanik, S. J., Anwar, J. & Hisyam, N. 2000. The Ecology of Sumatra. Periplus.