A review of dipterocarps - Center for International Forestry Research

Management of Natural Forests
Table 1. Classification of Asian dipterocarp forests (after
Champion and Seth 1968, Collins et al. 1991).
I. Moist Tropical Forests:
1. Tropical wet evergreen-
1a. Evergreen dipterocarp-
Malaysia, Sumatra, Kalimantan, Irian Jaya,
Maluku (part), Papua New Guinea, Sri Lanka
(part), Peninsular Thailand, Tenasserim,
Andamans and Nicobar (part), Philippines
(part), Laos, Cambodia, Vietnam (part)
1b. Secondary dipterocarp (seral)-
Malabar coast
2. Tropical semi-evergreen-
North Thailand (part), Chittagong, Laos,
Cambodia, Vietnam (?) (part)
3. Tropical moist deciduous-
Maluku (part), Palawan (part), Zambales
mountains in Luzon, W. Mindanao
Moist sal- Terai, E. slopes of W. Ghats, Chota
Nagpur, Upper Burma, Assam (part)
II. Dry Tropical Forests:
4. Tropical dry deciduous (forests heavily degraded)-
Dry sal- Western India, Burma (part)
Indaing- Irrawaddy plains (part)
is the well known species of this zone. Sal occurs in the
Himalayan foothills from northwestern Himachal
Pradesh to central Assam and south to Tripura. It also
spreads south along the eastern part of India up to Andhra
Pradesh. Where sal occurs, it is the only dipterocarp in
the forest. These forests also have five other
dipterocarps, the majority of which are confined to the
Indo-Burma community. The Indo-Burmese species
include S. obtusa, S. siamensis, Dipterocarpus
obtusifolius, D. tuberculatus and D. intricatus. Many
of them occur as single species or codominant stands.
These dipterocarps have thick bark and are fire tolerant.
Today most of these forests have become more open as
a result of browsing of young regeneration by cattle and
felling.
Seasonal Evergreen Dipterocarp Forests
These forests are distributed north and east of the everwet
Malesian region of Malaya, Borneo and Sumatra. They
are found in places that experience a short but regular
dry season. The forests occur in western and southern
parts of Sri Lanka, western Ghats of India, the Andaman
Islands, eastwards from Chittagong (Bangladesh) to
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southernmost Yunnan and Hainan (China), and southwards
to Perlis, northwest of Peninsular Malaysia. In the
eastern parts of Malesia they occur again, in parts of
Sulawesi, the Moluccas, Bali, Lombok and New Guinea.
Only about a 100 species of dipterocarps are found in
this formation. They occur in the mature phase of the
forest, with no single species dominating the canopy.
About half of the canopy layer may consist of
dipterocarps. They tend to be found in gregarious stands,
and some like Anisoptera thurifera act like pioneers,
colonising sites that were cultivated. Details of the
species found in these forests are found in Ashton
(1982), Champion and Seth (1968), Chengappa (1934),
Rojo (1979), Smitinand et al. (1980), Vidal (1979),
Johns (1976) and others.
Aseasonal Evergreen Dipterocarp Forests
These are the forests that occur in the perhumid climate
of Malesia, with rainfall over 2000 mm annually, and no
pronounced seasonal water stress. These forests are
found all the way from southwestern Sri Lanka,
Peninsular Malaysia, Sumatra, Borneo, and the
Philippines. Similar but somewhat poorer forests can be
found in Irian Jaya in the east. The vast majority of the
dipterocarps, over 400 species, occur in this formation,
with Borneo having the biggest share. A complete list of
the Malesian species is given in Ashton (1982). The trees
dominate the emergent layer of lowland and hill forests,
but this is not the case in Irian Jaya where the dipterocarps
mainly make up the canopy species. Besides the lowland
and hill species, there are dipterocarp-dominated
montane formations, as well as several species adapted
to heaths, coastal hills, limestone cliffs, peat swamps
and freshwater swamp forests. Dipterocarps may
constitute between 50-60% of the emergent stratum in
the rich lowland formations, but under optimum
conditions, the trees may make up 80% of the emergent
individuals and occur as gregarious or semi-gregarious
populations.
Natural Regeneration
Dry Evergreen Forests
The best known dipterocarp forests of the dry zone are
the sal forests of India. Sal fruits annually, with heavy
fruiting at intervals of 3 to 5 years (Champion and Seth
1968). The flowering begins during the dry period, and
the fruits mature with the rains. A mature sal can produce