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