Tuesday, February 23, 2010

Dipterocarp Mast Fruiting in Lambir Hills

Trees . . . they are everywhere in Lambir Hills National Park (Lambir Park), not only are they in great number buts also in species count.

Let’s see . . . everybody knows there is a 52-hectare research plot somewhere within the Park. Well, in that small plot some scientists decided to make a census count and they found a staggering 1,173 tree species in 286 genera and 81 tree families! Talk about diversity, Lambir definitely tops the list as the richest forest in Malaysia!

Two major types of forest are found in Lambir Park, the mixed dipterocarp forest and the kerangas forest. Kerangas forest is mainly found near the north-eastern part of the Park around Bukit Lambir peaks, while the majority of forest in other parts of Lambir is covered by mixed dipterocarp forest.

For the past few months starting October 2009, something wonderful has been taking place in the mixed dipterocarp forest of Lambir Park: the dipterocarp trees have been producing and releasing enormous amounts of winged fruits onto the forest floor. This special event is called dipterocarp mast-fruiting.

A carpet of dipterocarp flowers on the trails.

During this period many species of dipterocarps come into flower almost simultaneously, followed by mast-fruiting for a period of several months. Unlike other tree families, dipterocarp mast-fruiting only occurs at irregular intervals of anything between 2 – 10 years, a phenomenon that is very unique to dipterocarp forests of South-East Asia.

The different types of winged fruit found on the forest floor of Lambir.

The only spot not covered by the winged fruits is pool.

A few hypotheses have been proposed to explain this distinctive feature of dipterocarp forests, but the most widely accepted must be the predator-satiation theory which suggests that through synchronization of fruiting at around the same time by many dipterocarp species at irregular intervals of several years, it not only prevents the build-up of seed predator population, the heavy fruiting is also a means of defense to prevent seed predators from wiping out the whole crop of seeds, thus ensuring survival of some of the seeds to germinate and grow into seedlings.

A small group of MNS Miri Branch hikers who regularly visited the Park during weekends over the past four months saw first hand the chronological sequence of mass flowering and mast fruiting of several dipterocarp species along the trails they regularly walked.

Peter admiring the young seedlings taing their rightful places on the forest floor.

February month appears to be the height of the dipterocarp mast-fruiting, as the trails are literally covered with thousands of fallen dipterocarp winged fruits, and at some places it is so dense that walking on them makes quite treacherous as it is really slippery underfoot especially on a descend. It is also observed that many of the other plant species were busily producing bountiful fruits and seeds along side with dipterocarp trees. The forest has certainly never been seen so busy with all these reproductive activities!

Come and visit Lambir Hills National Park now and see for yourselves this special miracle before it is all over. You may not easily see it again in the next few years!

Write-up and photographs by Sara Wong.

Hazebroek, H. P., and Abang Morshidi, A. K. 2006. National Parks of Sarawak. Sabah: Natural History Publications (Borneo).

Sakai, S. 2002. General Flowering in Lowland Mixed Dipterocarp Forests of South-east Asia. Biological Journal of the Linnean Society 75(2): 233-247.

No comments:

Post a Comment