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Dipterocarpus lamellatus Hook. F.
by Yap Myo I
Newsletter
Dipterocarpus lamellatus Hook. F.
by Yap Myo I

The island of Borneo nurtures the highest diversity of Dipterocarpaceae species in the world. Of the 267 species that occur naturally in Borneo, 183 of them can be found in Sabah. While some dipterocarps are very common and widespread within the state, a number of them are very rare and highly restricted in their natural distribution. Dipterocarpus lamellatus belongs to the latter group and is one of the rarest and most endangered of all dipterocarps (Ashton, 2004).

Named by the British botanist Sir Joseph Dalton Hooker, D. lamellatus is a tall emergent tree that can grow up to 55 m in height and 1.2 m in diameter, with a golden crown when viewed from below. The leaves are boat-shaped and concave with elliptic blades, 13‒16 x 6‒9 cm, and have a chartaceous texture that resembles paper. Inflorescences are axillary and hardly branched, growing up to 8 cm long, while the flowers are yet to be described. The winged fruits consist of five revolute calyx lobes: two major ones that grow up to 14 x 2.5 cm while the other three are ovate and grow up to 1.4 x 0.7 cm.

Keruing jarang is the preferred vernacular name in Sabah for D. lamellatus, which literally means “the rare dipterocarp”, suggesting the scarcity of the species naturally. In fact, the species is endemic to Borneo Island and was known from only three confirmed collecting localities: Ladan Hills in Brunei Darussalam, and Labuan Island and Beaufort Hills in Sabah, Malaysia (Maycock et al., 2012). The species is found in mixed dipterocarp forest on hills with yellow sandy soil, at altitudes below 200 m and within 50 km of the coast. Ashton (2004) had suggested that the species was probably extinct in Sabah due to loss of its habitat.

Fortunately, individuals of D. lamellatus were found in Sianggau Forest Reserve (Western Sabah, close to the Sarawak border) in 2011, after having not been seen for more than 50 years since the last record in 1955 at Beaufort Hill (Hinsley, 2011). However, the joy of this rediscovery may not last long as the species is still exposed to great threats. Sianggau Forest Reserve is highly vulnerable to fire and a large part of it has been burnt during several El Niño events (Maycock et al., 2012).

Dipterocarpus lamellatus is included in the list of the top 100 most threatened species (including animals, plants and fungi) in the world with only 12 recorded individuals remaining in the Sianggau Forest Reserve (Baillie & Butcher, 2012). On the IUCN Red List, it is classified as Critically Endangered with criteria A1cd+2cd, B1+2c, C1 and D. The Sabah state government is restoring its habitat and reintroducing the species to its previous range in efforts to sustain the long-term viability of the population.

References

  1. Ashton, P.S. (September 2004). Dipterocarpaceae. In Soepadmo, E., Saw, L.G. & Chung, R.C.K. (eds.) Tree Flora of Sabah and Sarawak, volume 5. Sabah Forestry Department, Forest Research Institute Malaysia (FRIM), Sarawak Forestry Department. pp. 113-114.
  2. Baillie, J.E.M. & Butcher, E.R. (2012). Priceless or Worthless? The World’s Most Threatened Species. Zoological Society of London, Regent’s Park, London NW1 4RY, United Kingdom. pp. 123.
  3. Hinsley, A. (14/06/2011). Rare Tree not seen since 1955 rediscovered in Sabah, Malaysia (June 2011). Global Trees Campaign. Retrieved May 29, 2017, from http://globaltrees.org/news-blog/rare-tree-seen-since-1955-re-discovered-sabah-malaysia/
  4. Maycock, C.R., Khoo, E., Kettle, C.J., Pereira, J.T., Sugau, J.B., Nilus, R., Jumian, J. & Burslem, D.F.R.P. (2012). Using high resolution ecological niche models to assess the conservation status of Dipterocarpus lamellatus and Dipterocarpus ochraceus in Sabah, Malaysia. Journal of Forest and Environmental Science (JFES) 28 (3): pp. 158-169
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