The Koompassia excelsa tree is among the tallest trees in the world, and also one of the most prominent trees in the tropical rainforests of the Sunda Shelf. It is found in Sumatra, Borneo, South Thailand, and Peninsular Malaysia. The grey, whitish bark of the tree, large bole, and often handsome crown makes it stand out amongst the other trees (usually). It is known by different names in different regions – Mengaris in Brunei and Sabah, Tualang in Peninsular Malaysia, Sialang in Indonesia, and Tapang in Sarawak. The name tualang comes from the Malay words of tua – old, and helang – eagle.
In Peninsular Malaysia, the tualang tree is only found north of an imaginary line that connects Kuala Lumpur (KL) with Kuantan. It has never been found south of that “line” for unknown reasons. If you drive north towards Frasers Hill, you should be able to see some small specimens in the forests of the lower portion of the Main Range, although they are not conspicuous.
I’ve not noticed tualang trees in the forests north of KL on the way to Genting Highlands. They only seem to appear after the boundary with Pahang is crossed (especially around Bentong). That said, tualang trees are not found in higher altitudes above 500 meters asl. It is mostly limited to lowland forests up into the lower portion of hill dipterocarp forest.
The tualang is a member of the legume or bean family. Maybe surprisingly, it is not a dipterocarp. There is another closely related species, the Kempas, or Koompassia malaccensis. The kempas is a big tree widely distributed throughout the country, in all lowland forested areas, especially near riverine areas, although it does not grow as large, nor as tall, as the tualang.
There are legends and lore regarding the tualang tree. Aborigines believe this tree is inhabited by spirits, and it is often left alone in heavily logged areas for that reason. Of course, it being the favorite tree for the Asian Giant Honeybee (Apis dorsata) to build their nests on, is part of the reason why the tualang is often left alone. The bees choose the tree for its smooth bark which is tough for predators like the sun bear, to climb.
Its wood is hard, but decays quite rapidly unless treated, which means it doesn’t have much commercial value. However, as logging has stripped out virtually all the valuable timber there is left, even tualang trees these days are fair game to logging companies.
Tualang trees can grow more than 80 meters in height, but this is largely limited to Bornean specimens; more specifically Sabah specimens. Sabah’s rich volcanic soil (in the eastern half) produces very tall and large trees of all species; not just limited to tualang. However, Foxworthy (a British forester conducting work largely in the then Malaya during the 1920s) presumably found a tualang 80 meters tall somewhere in Peninsular Malaysia. This find is intriguing, as all the tualang trees I’ve seen here in Peninsular Malaysia (and I’ve seen a lot) have never really exceeded 50-something meters in height, at most. However, the Sabah specimens are really awesome in height and size, as this little known (but excellent) link, points out, obviously due to the lengthy boles (trunks) of the trees there.
Sadly, as most of Sabah and Kalimantan have already been logged out, there is really no way now to find out if tualang trees that exceed 90 meters in height really did exist or not. In Pahang, north Perak, inner Kedah, and Kelantan, tualang trees are very conspicuous, even by the roadsides. You will certainly be able to spot them in many a secondary forest or even in overgrown, old rubber plantations where the original loggers or forest clearers have not bothered with cutting them down, 40 or 50 years ago. You will also be able to see young tualang trees grown in the grounds of FRIM. Up north in Perak and Kelantan, the locals often nail wooden “ladders” up trees that have honeybee nests, to harvest the honey. A dangerous process worth viewing, if you get the chance.
Flowering occurs once every few years, often during mast flowering periods (when other trees in the rainforest are also flowering). The flowers are small, and yellow colored, often taking up the entire crown of the tree. It is not a common occurrence (at least back then), so consider yourself lucky, if you have seen a tualang flowering!
Another curious aspect of the tualang tree is it sheds its leaves during February-April. However, as the global climate is so variable these days, I won’t be surprised if tualang trees now shed their leaves outside this period. It certainly varies from place to place.
This deciduous behavior is not really common in the evergreen rainforests of Malaysia, so it may indicate the tualang being a “relic” of a more variable, drier climate in the past. Certainly, we know that in the last Ice Age, there were a lot of open woodland areas and the tropical forests then, were not as “tropical” in the sense of the word, as they are today. When tualang trees are in deciduous mode, the lowland rainforest from the air looks peppered with their whitish, fluffy crowns devoid of leaves, and you can easily pick them out from a helicopter.
In Thailand, there are petrified trunks of an ancient cousin of the tualang tree that were found by accident in 2003. Today, these fossilized trunks are preserved for tourists to view at the Ban Tak Petrified Forest Park. These are some of the best preserved and largest fossilized tree trunks in the world to date. Scientists estimate the heights of some of these trees to be well over 100 meters tall, making them one of the tallest trees in the world alongside the redwoods – if they were growing today.
It might be interesting to know that another tree with similar dimensions to the tualang, the Mengkundur or Tetrameles nudiflora is also commonly associated with the tualang where it is found and often mistaken for it as well. The mengkundur tree grows to huge size and develops large buttresses, just like the tualang, and seems to be restricted to drier areas of Peninsular Malaysia (like the tualang too). The mengkundur is also common in the drier states of Negeri Sembilan and Malacca (but the tualang is not found there). All these are further evidence of past climatic differences between then, and now.