Geoscience Reference
In-Depth Information
Dipterocarps can be immense trees, exceeding 200 ft (62 m) in height; they pro-
trude out of the canopy. They have smooth straight trunks without side branches
until they reach the canopy. The base is often buttressed. In the canopy, these trees
produce a crown shaped somewhat like a cauliflower. They rarely fall like the
emergent trees of the Neotropics. Instead, they die standing in place. Dipterocarp
trees produce an oily resin useful in the defense of bacteria, fungi, and animals.
This resin accumulates wherever the bark is bruised. When hardened, it is called
''dammar'' and used by local people as a varnish or a boat caulking agent. The
kapur or camphor tree, a dipterocarp common in Borneo, produces camphor, an
essential oil used in medicines and as a preservative.
Flowers of the dipterocarps vary in size from small to large; they have five pet-
als and many stamens and are scented to attract the thrips, beetles, moths, and bees
that pollinate them. The fruit produced is a single-seeded nut with a wing-like cov-
ering that allows the seed to spin to the ground (see Figure 3.18). These winged
seeds were probably helpful in the dispersal of this plant family throughout South-
east Asia and into New Guinea. Many dipterocarps share a regeneration strategy
that involves gregarious flowering and consequent mass fruiting. This often occurs
in two- to seven-year intervals. Flowering occurs at the same time in different spe-
cies among multiple layers of the canopy. A succession of flowers occurs over
about one month's time. The flowering is thought to be cued by brief episodes of
cooler night temperatures or by drought (such as that during an El Nino year),
although more research is needed on this subject. After flowering, an abundance of
fruit appears, providing food for many resident forest animals as well as those that
migrate to the area to feed. The seeds germinate quickly, forming a bed of seedlings
on the forest floor. These seedlings start out tolerant of shade and may be able to
survive several years under the dense canopy. Long-term seedling survival in the
Figure 3.18 Dipterocarp seeds have wing-like appendages that allow them to disperse
away from the parent tree. (Illustration by Jeff Dixon.)
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