Included here is the island of Sumatra.

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.

Sumatran Rhododendron-Vaccinium Alpine Scrub

Above an altitude of about 3000 m most trees give way to a dense ericaceous scrub characterized by Rhododendron retusum and the endemic Vaccinium miquelii (Ericaceae).  There are also many other endemic ericoids including Diplycosia atjehensis, D. glauciflora, D. sumatrensis, Gaultheria acroleia, G. atjehensis, G. kemiriense, Rhododendron adinophyllum, R. aequabile and R. sumatranum, while other endemic shrubs or small trees include Lithocarpus atjehensis (Fagaceae) and Symplocos sumatrana (Symplocaceae). One of the last trees to peter out is Myrica javanica but at these altidudes it grows no more than about 8 m high. The ground layer consists of tussocky species like Carex hypsophyla and Gahnia javanica and occasional herbs such as Anaphalis javanica and the two endemic species Pyrola sumatranum (Pyrolaceae) and Senecio sumatrana (Asteraceae). Ferns, such as Dicranopteris pubigera, Gleichenia volubilis and Hypolepis punctata, are also present.

References

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

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

Ohsawa, M., Nainggolan, P. H. J., Tanaka, N. & Anwar, C. 1985. Altitudinal zonation of forest vegetation on Mount Kerinci, Sumatra: with comparisons to zonation in temperate regions of East Asia. Journal of Tropical Ecology, 1: 193-216.

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.