A review of dipterocarps - Center for International Forestry Research

Management of Natural Forests
4. Clearfelling System
This system is used when there is a need to change the
composition of the crop to a more valuable species. The
restocking is through natural or artificial regeneration,
the latter used to introduce a new species or to change
the forest composition. As a consequence, the more
valuable teak is introduced into sal forests. The trend is
to convert most of these forests into plantations, making
the future of sal forests uncertain.
Peninsular Malaysia
Forest Management Systems
Forestry in the modern sense was started in 1883 with
the establishment of the forestry service. Prior to
introduction of forest management, logging was very
selective, principally limited to the heavy hardwoods
(mainly several dipterocarp secies), and only about 7m 3 /
ha was taken out (Barnard 1954). Silvicultural operations
were limited to enrichment plantings of the heavy
hardwood, chengal (Neobalanocarpus heimii), which
failed from lack of further tendings. But the demand for
timber increased, leading to over-exploitation of the
select timbers. This prompted the authorities to develop
a series of silvicultural systems.
1. Regeneration Fellings
In the beginning (1910-1922) Departmental
Improvement Fellings were implemented. All species
whose crowns interfered with the poles of any valuable
timber species were removed. It was subsequently
realised that such treatments had no impact on the
immature trees. However, they resulted in profuse young
regeneration (Hodgson 1937). The improvement fellings
had in fact been regeneration fellings. After 1932,
Regeneration Improvement Fellings (RIF) came in to
vogue. Inferior species were gradually removed over a
series of fellings. If the regeneration was verified as
successful, final felling of the valuable species was
carried out. This in fact resembled the classical
Shelterwood Systems.
2. Malayan Uniform System
As a rule, no forests were harvested without first carrying
out RIF. During the Japanese Occupation (1942-1945)
many forests were clearfelled without the benefit of RIF.
After the war, extensive surveys revealed that these areas
contained adequate advanced regeneration without any
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assistance. It was realised that if the forest had adequate
regeneration of the fast growing dipterocarp species, a
single clearfelling release could result in a greater
stocking of a more uniform crop of commercial species.
This became the basis for the Malayan Uniform System
(MUS), which was introduced in 1948 for managing
Lowland Dipterocarp Forests (Wyatt-Smith 1963).
A detailed silvicultural system was developed (Wyatt-
Smith 1963). It consists of felling the mature crop of all
trees above 45 cm dbh, poison girdling all defective
relics and non-commercial species down to 5 cm dbh,
and releasing established seedlings. Seedling adequacy
and suitable tendings underpinned the success of MUS.
3. Modified Malayan Uniform System
In the mid-1970s, most of the lowland dipterocarp
forests were alienated for agricultural programmes, and
forestry was confined to the hills and rough terrain
unsuitable for agriculture. Under these new conditions
it was considered difficult to apply the MUS. The
principal problem was the lack of uniform stocking of
natural regeneration. It was thought that enrichment
planting could overcome this deficiency (Ismail 1966).
This allowed all forests to be opened up for logging,
regardless of adequate seedling stocking, a prerequisite
with MUS. Planting up understocked areas was carried
out in the beginning, but their performance was very
variable and unsatisfactory. Now, artificial regeneration
is rarely carried out, or the practice is abandoned entirely.
4. Selective Management System
In the late 1970s, the Selective Management System
(SMS) was introduced. This is a simplified version of
the Philippine Selective Logging System (see Appanah
and Weinland 1990). The MUS was already discarded
for working in the hillier terrain, and the modified-MUS
proved unsatisfactory. The felling regime is formulated
on the basis of a pre-felling inventory. All commercial
tree species above a certain size (ideally nondipterocarps,
45 cm dbh; dipterocarps, 50 cm dbh) are
felled, provided a sufficient number of residuals are left
behind to form the next cut in ca 30 years (Thang 1987).
Therefore the SMS relies on adequacy of healthy
residuals which will respond to the cutting release for
the next cut some 25-30 years later. Seedling stocking
is assumed to be present, or will be replenished by the
maturing residuals. The SMS is regarded as more flexible
for managing the highly variable forest in the hillier