Included here is the Malay Peninsula roughly south of the line between the Kedah River near Alor Setar on the west coast and Songkhlia on the east coast. The northern boundary therefore roughly crosses the border between Malaysia and Thailand.

Malayan Limestone Forests

The enormous variation in Malayan limestone vegetation makes it difficult to summarize. At the base of hills a fairly tall, closed canopy forest can be found comprising trees such as Dendrocnide stimulans, Diospyros cauliflora Gmelina asiatica, Mallotus philippensis, Melanolepis multiglandulosa, Pisonia umbellifera and the endemic Orophea hirsuta (Annonaceae). The undergrowth is equally varied, but in the wetter areas where water drips down from the rocky slopes and overhanging cliffs, a distinct herbaceous ground layer including Alocasia lowii, Epithema saxatile, Monophyllaea horsfieldii the endemic Chirita caliginosa (Gesneraceae), and a luxuriant assemblage of bryophytes is often encountered. Moving on to the talus slopes the dominant trees are more likely to include Cleidion javanicum, Morinda elliptica, Strebulus ilicifolius, Trivalvaria macrophylla and the endemic Atalantia roxburghiana (Rutaceae). The herbs include Heterogonium pinnatum and a number of Impatiens species such as the endemic Impatiens mirabilis (Balsaminaceae). Where the slopes comprise boulder outcrops other endemic trees such as the rare Diospyros adenophora (Ebenaceae) and Polyalthia brunneifolia (Annonaceae) may become more conspicuous. Here the ground flora is usually sparse but may include several species in sheltered niches such as the endemic Gymnostachyum decurrens (Celastraceae). In the more sheltered gullies and valleys the typical trees and shrubs include Agrostistachys gaudichaudii, Canthium didymum, Randia densiflora, Sauropus suberosus, Sterculia rubiginosa and the endemic Fagraea curtisii (Loganiaceae). These locations also include several endemic palms such as Arenga westerhoutii and Iguanura polymorpha (Arecaceae).

On the summits the vegetation is usually more scruby (2-7m tall), but the canopy typically remains closed and there may be several emergent trees such as the endemic Madhuca ridleyi (Sapotaceae). Other trees and shrubs usually include Cleistanthus gracilis, Decaspermum fruticosum, Eriobotrya bengalensis, Erythroxylum cuneatum, Garcinia minutiflora, Mallotus brevipetiolatus, Murraya paniculata, Neolitsea zeylanica, Sycopsis dunnii and several endemics such as Buxus malayana (Euphorbiaceae), Dehaasia curtsii (Lauraceae), Eugenia pendens (Myrtaceae), Glycosmis calcicola (Rutaceae), Pandanus irregularis (Pandanaceae) and Pistacia malayana (Anacardiaceae). Despite the shady conditions caused by the canopy there is comparatively rich ground flora with many bryophytes and ferns. The flowering plants may include Adenia nicobarica, species of Amorphophallus and the two endemic species Arisaema fimbriatum (Araceae) and Dichanthium mucronulatum (Poaceae).

References

Chin, S. C. 1977. The limestone hill flora of Malaya I. Gardens’ Bulletin Singapore, 30: 165-219.

Chin, S. C. 1977. The limestone hill flora of Malaya II. Gardens’ Bulletin Singapore, 32: 64-203.

Crowther, J. 1982. Ecological observations in a tropical karst terrain, West Malaysia. I. Variations in topography, soils and vegetation. Journal of Biogeography, 9: 65-78.

Henderson, M. R. 1939. The flora of the limestone hills of the Malay Peninsula. Journal of the Malay Branch of the Royal Asiatic Society, 17: 13-87.

Latiff, A., Faridah Hanum, I., Zainudin Ibrahim, A., Goh, M. W. K., Loo, A. H. B. & Tan, H. T. W. 1999. On the vegetation and flora of Pulau Tioman, peninsular Malaysia. The Raffles Bulletin of Zoology, supplement No. 6: 11-72.

Ridley, H. N. 1967. The flora of the Malay Peninsula. Volumes 1-5. L. Reeve & Co Ltd. London.

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.

Whitmore, T. C. 1978. The forests ecosystems of Malaysia, Singapore and Brunei: description, functioning and research needs. In: Tropical forest ecosystems. Natural Resources Research Vol. XIV. UNESCO.

Wong, K. M., Saw, L. G. & Kochummen, K. M. 1987. A survey of the forests of the Endau-Rompin area, Peninsular Malaysia: principle forest types and floristic notes. Malayan Nature Journal, 41: 125-144.