A review of dipterocarps - Center for International Forestry Research

Management of Natural Forests
which may become marketable in the future. But
maltreatment of the forest has become commonplace.
The short cutting cycles have resulted in doubling of
coupe areas, but almost as much timber as in a
shelterwood cutting has been harvested. So are the
problems of re-entry to logged over coupes as timber
scarcity develops. Next, selection felling is regularly
abused with the removal of the best stems without any
attempt to redress the balance by simultaneous removal
of the poorer material that can lead to genetic
impoverishment of the forests. Perhaps the stage has
arrived where management in the true sense can be
introduced. This of course requires that besides paying
proper attention to the silvicultural systems and
harvesting methods, management must pay heed to other
aspects like the preservation of ecological functions,
conservation of biodiversity, and maintaining the integrity
of the forest. In addition, the social issues that may
impact on the management of a forest must be given a
higher priority.
Good management is indispensable whatever the
silvicultural systems. An inappropriate silvicultural
system may mean that the maximum productivity of the
forest has not been captured. But what really sets back
tropical forests is poor harvesting practices. Usually,
harvests exceed growth rates. Few of the silvicultural
tendings are done, further delaying the growth of the crop.
Logging using skidder-tractor systems is exceedingly
damaging to the soil and the standing residuals. Soil
damage, in terms of erosion and compaction is
exceedingly heavy. The immediate need is to adopt
harvesting practices that minimise such damage. A swing
in that direction has begun in Sabah. Already, one forest
reserve is being managed under tight prescriptions.
Skidder-tractors are heavily controlled and limited to prealigned
trails only, and are only operable on slopes below
15 o . On steeper slopes, a long range cable crane system
is used which does only limited damage to the soils and
residual trees. Such developments provide us with the
optimism so much needed in tropical forest management.
Additional Research Needs
1. Management systems have been applied universally
over the landscape without regard to site and timber
stand characteristics. This cannot be ecologically
optimal. Intensive management procedures should be
developed whereby silvicultural systems are applied
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that are more specific to the site (site categories,
floristic groups, etc.).
2. Harvesting damage can be easily controlled, and the
improvements realised will be immediate and several
fold. Besides research to lower harvesting damage,
standards for allowable harvesting damage should be
drawn.
3. There is still much uncertainty about cutting cycles
in selection fellings. The growth data available from
few sites are broadly applied to large areas. Not only
should existing growth data be reviewed rigourously
so as to derive more appropriate cutting cycles,
additional growth plots should be set up so all the
different forest types are included.
4. In selection fellings, seedling regeneration and
growth are often not given attention. Studies should
be initiated to determine post-harvest fruiting and
seedling regeneration characteristics, and tending
procedures.
5. The response of advance growth to liberation
treatments requires further investigation. Their
reaction to heavy isolation, injury, soil disturbances
and water stress should be studied. Will selectively
logged forests require further crown liberation to
optimise growth? Will promoting dense crop
regrowth affect soil-moisture balance?
6. No data are widely available on regenerated stands
managed under Shelterwood Systems. Such stands
should be reexamined. The structure of the stand and
regrowth composition would help illuminate the
effect of improvement fellings and climber cutting
treatments.
7. The basis for sustaining long-term forest production
depends on the soil characteristics and organic matter
accumulation. The impacts of harvesting on the
nutrient cycles have to be further investigated. What
will be the impacts of whole tree harvesting on
nutrient cycles?
8. With increase in utilisation of lesser-known or lesserused
species, will selective logging be the same as
in the past? How will this affect regeneration and
composition of future crops?
9. With changes to the future crops likely to take place,
gregarious and very common species may become
even more important for management. Autecological
studies of these species are needed to fine-tune the
management to favour such species for future crops.