The dipterocarps are a family of hardwood, tropical trees comprising about 500 species, with about 300 species (if I’m not mistaken) located on the island of Borneo. Borneo is their center of gravity, followed by Peninsular Malaysia, South Thailand, and then Sumatra – basically the evergreen tropical rainforests of the Sunda region is where they thrive. There are many genera, like Shorea, Dipterocarpus, Anisoptera, Dryobalanops, Parashorea, Vatica, Hopea, Cotylelobium, and Neobalanocarpus, with Malay names like Meranti, Balau, Kapur, Chengal, and Keruing, among others.
Dipterocarps “can” grow very tall and large, and they form a very large proportion of the rainforest canopy here in Peninsular Malaysia. An extensive study showed that up to 57% of the emergent layer of the lowland forest in Peninsular Malaysia is composed of diperocarps. In Sarawak, dipterocarps comprise even more of the emergent and canopy layer, at 75%, while in Sabah, it can be as high as 90%. Little wonder then, that Sabah has the tallest dipterocarps ever found to date; in fact Sabah has the tallest tropical trees in the world!
The current tallest tropical tree in the world is a Shorea faguetiana in Danum Valley, Sabah, which was taped drop measured at 100.8 meters tall. This astounding find surpasses all the previous records and dispels previous notions scientists had of tropical tree height. In fact this tree which has been named as “Menara” (Malay for “Tower”) is the second tallest tree (so far found) in the entire world!
In central and east Sabah, are found many other dipterocarps that are over 80 m tall! So it is likely, that many dipterocarp species are able to attain great height or size, but due to soil conditions and local weather patterns, do not achieve such dimensions. [Edit: scientists have recently found 50 trees in Eastern Sabah that are believed to be around or more than 90 m tall!].
Another characteristic of dipterocarp forests is the group habit of the emergents. This means that the emergent trees will often be found in small groups, and not individuals, and since dipterocarps form the huge bulk of the emergent layer, it can be hypothesized that this is a habit of dipterocarps in primary forests – but that’s just my theory.
Every few years or so, there will be a mast flowering event in certain areas of the forest, where the dipterocarp trees all simultaneously flower and fruit. The “trigger” for such an event has been speculated to be a period of drought and sunspot activity. When such mast flowering occurs, the forest canopy is transformed into a brilliant mosaic of yellow, brown, orange and even purple, all in varying shades of colour.
Dipterocarp forests are already known among foresters as being the tallest and most diverse rainforests in the world. This also means – Great timber potential. Much of the lowland forests below 300 m asl that covered South East Asia have been logged or cleared for agriculture, namely palm oil. Borneo is now resembling one giant oil palm plantation, to put it mildly.
Generally, most mature dipterocarps in Peninsular Malaysia are about 35-60 meters tall, based on my experience, but in North Borneo, they regularly attain heights of 60-70+m, with some in the 80-90m range in Eastern Sabah, which unfortunately, have been mostly chopped down. [Edit: Recent finds using Lidar technology have come across superlative trees at around 100m tall).
Only a few remaining examples are left in the Tawau Hills Park, Danum Valley, Maliau Basin, and Imbak Canyon. Other “protected” areas in eastern Sabah, like the Tabin Wildlife Reserve that in the past harbored such impressive trees, are unfortunately, almost wholly secondary forest, having been entirely logged in the past. Another area adjacent to the Tawau area, the “proposed” Sembakung area in Kalimantan, has been subjected to intense logging as well, and is now a tattered “forest” where once tall trees stood proud.
So it is almost certain there are no more areas where you will find such impressive dipterocarp trees anymore, at least in an intact primary lowland forest area that isn’t a conserved park. Once a forest is logged, it will never regain its original height, as the new generation of trees will not regenerate to the previous height. In addition to that, dipterocarp trees take a VERY long time to grow to maturity. In fact, it takes on average, about 100 years for a dipterocarp to attain a canopy height of 30 m and 60 cm trunk diameter.This is based on long term observation work at FRIM (Forest Research Institute of Malaysia) and in jungle study plots.
That’s why most of the forests you see while traveling throughout Malaysia are pale shadows of their former selves, because almost all have been logged (but most people don’t realize that and often call them “virgin” forests). Taman Negara alone contains 80% of the remaining virgin lowland forests in Peninsular Malaysia while there are no more comparable areas like this (either protected or left to protect), in the WHOLE of Sarawak or Sabah.