Included here is Borneo (Kalimantan) and adjacent islands such the Bunguran (Natuna) Islands, Calamian Islands, Jolo Island, Laut Island, Palawan Island, Pangutaran Islands and the Tawitawi Islands.

Bornean Heath Forest

On the nutrient poor, acidic soils of Borneo a type of forest known as heath forest occurs (also known as Kerangas in Indonesia). The term ‘heath forest’ is slightly misleading since they are not particularly rich in heathland species, but are regarded as edaphic climax forest of poor soils where you would expect to find heathlands in other parts of the world. They have a low uniform single-layered canopy reaching no more than about 20 m in height, and are less species-rich than dipterocarp forests, but can extend well into the highlands where the trees become stunted and contorted. The tree species are dominated by members of the Casuarinaceae and Myrtaceae familes together with conifers such as Agathis, Dacrydium and Podocarpus, but dipterocarps may also be present especially in some of the less nutrient poor areas. Other, less favourable areas are dominated by species of Tristania (Myrtaceae). Some characteristic species, such as Casuarina nobilis, are able to fix nitrogen. Among the many endemic trees are Agathis borneensis (Araucariaceae), Castanopsis borneensis, Lithocarpus sericobalanus, Quercus kerangasensis (Fagaceae), Dactylocladus stenostachys (Crypteroniaceae), Hopea micrantha, Shorea coriacea, Vatica compressa (Dipterocarpaceae) and Horsfieldia carnosa (Myristicaceae). Shrubs such as the endemic Arthrophyllum crassum (Aristolochiaceae) and Diplycosia kalmiifolia (Ericaceae) may be present. The lack of available nutrients has fostered the developement of a rich assemblage of carnivorous plants including pitcher plants (Nepenthes), sundews (Drosera) and bladderworts (Utricularia), and these represent a characteristic feature of these forests. Some of the Nepenthes species are spectacular such N. veitchii with its red-streaked rims and N. reinwardtiana with its sensuous curvy shapes. The rich epiphytic flora is largely dominated by orchids, such as the endemic Bulbophyllum beccarii (Orchidaceae), and ferns like the endemic Selliguea setacea (Polypodiaceae). There are also many epiphytic shrubs, particularly of the Ericaceae such as the endemic Rhododendron nieuwenhuisii and Vaccinium monanthum, while among the endemic lianas and climbers are Bauhinia foraminifer (Caesalpiniaceae) and Costera cyclophylla (Ericaceae). The forest floor is typically dominated by bryophytes but may also include a number of herbaceous species such as the endemic ground orchid Entomophobia kinabaluensis (Orchidaceae) and the endemic sedge Tetraria borneensis (Cyperaceae). In other places, presumably because of low light levels and poor soil quality, the ground layer maybe completely devoid of species.

Bornean Peat Swamp Forest

Peat swamp forests are widespread occurring in the lowlands of Kalimantan and on the coastal plains of Brunei and Sarawak - the largest being on the Maludam Peninsula. Some of these are thought to have been established for many thousands of years and in places have developed a peat layer up to 20 m thick. The dominant trees vary from place to place, but in a number of peat swamps including those of the Maludam Peninsula, the endemic Shorea albida (Dipterocarpaceae) is dominant. Other trees may include Dyera costulata, Gonystylus bancanus and several endemic taxa such as Adenanthera malagana subsp andersonii, Albizia dolichadena (Fabaceae), Lophopetalum sessilifolium (Celastraceae), Prunus turfosa (Rosaceae), Xanthophyllum ramiflorum (Polygalaceae), and on the edges of peat swamps the endemic Shorea balangeran (Diperocarpaceae). Several of these trees have prominent aerial roots (pneumatophores) for obtaining oxygen in waterlogged conditions. Another feature of these low nutrient forests is the presence of many plants with supplementary means of nutrition such as the ant plants Hydnophyton and Myrmecodia and pitcher plants.

References

Bruenig, E. F. 1990. Oligotrophic forested wetlands in Borneo. In: Ecosystems of the World 15. Forested Wetlands. Eds. A. Lugo, M. Brinson and S. Brown. Elsevier.

MacKinnon, K., Hatta, G., Halim, H. & Mangalik, A. 1997. The Ecology of Kalimantan. Oxford University Press.

Phillips, V. D. 1998. Peatswamp ecology and sustainable development in Borneo. Biodiversity and Conservation, 7: 651-671.

Specht, R. L. & Womersley, J. S. 1979. Heathlands and related shrublands of Malesia (with particular reference to Borneo and New Guinea). In: Ecosystems of the World (9A) – heathlands and related shrublands: descriptive studies. Ed. R. L. Specht. Elsevier Science.

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.