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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Plantations 168<br />
intervention. Sanger-Davies (1937) carried the ideas<br />
further and <strong>for</strong>mulated a guide <strong>for</strong> the tending <strong>of</strong> more<br />
or less even aged stands <strong>of</strong> S. leprosula. In his technical<br />
recommendations, he proposed starting tending while the<br />
shelterwood is still standing.<br />
When designing research it should be kept in mind<br />
that the beneficiary <strong>of</strong> the thinning operation is the crop<br />
tree and, there<strong>for</strong>e, indiscriminate elimination <strong>of</strong> noncrop<br />
vegetation is unnecessary. Non-crop trees have<br />
beneficial ecological functions. Mead (1937) discusses<br />
the <strong>for</strong>mation <strong>of</strong> mixed stands <strong>of</strong> <strong>dipterocarps</strong> and shadebearing<br />
non-dipterocarp understorey species with dense<br />
crowns. The species Scorodocarpus borneensis, Mesua<br />
ferrea, Randia scortechinii, Randia anisophylla,<br />
Greenia jackii etc. were planted in mixture with Shorea<br />
leprosula, which <strong>for</strong>ms a rather open crown, to prevent<br />
the invasion <strong>of</strong> light demanding pioneer vegetation which<br />
impede the establishment <strong>of</strong> natural dipterocarp<br />
regeneration. Tending has, there<strong>for</strong>e, to consider also<br />
the secondary vegetation. Any inconsiderate felling<br />
should be avoided and instead it should be asked, whether<br />
such vegetation could assist in keeping the <strong>for</strong>est floor<br />
conducive to natural regeneration.<br />
Re-establishment by Natural Regeneration<br />
Embarking on plantations with dipterocarp species which<br />
grow relatively slowly compared with fast-growing<br />
exotics needs strong economic backing. Recent<br />
economic calculations (Kollert et al. 1993, 1994) have<br />
shown that it only makes sense, if at the end <strong>of</strong> the first<br />
rotation the new stands are established by natural<br />
regeneration. It is in this context that some comments<br />
are given on regenerating naturally even-aged planted<br />
dipterocarp stands, although on an operational scale this<br />
will be only a problem <strong>of</strong> decades from now. Systematic<br />
assessment <strong>of</strong> the regeneration situation and initiation<br />
<strong>of</strong> natural regeneration procedures are urgently needed<br />
<strong>for</strong> all species identified <strong>for</strong> plantation programmes and<br />
<strong>for</strong> which stands near rotation age exist. This should<br />
include research on the harvesting techniques required<br />
to reduce negative impacts on stand regeneration.<br />
The natural regeneration <strong>of</strong> even-aged planted stands<br />
will most likely be carried out as some kind <strong>of</strong><br />
shelterwood system. Shelterwood systems are ‘evenaged<br />
silvicultural systems, in which, in order to provide<br />
a source <strong>of</strong> seed and/or protection <strong>for</strong> regeneration, the<br />
old crop (the shelterwood) is removed in two or more<br />
successive shelterwood cuttings, the first <strong>of</strong> which is<br />
ordinarily the seed cutting (though it may be preceded<br />
by a preparatory cutting) and the last is the final cutting,<br />
any intervening cuttings being termed removal cuttings’<br />
(Ford-Robertson 1983). Where there is adequate<br />
regeneration the old crop may be removed in a single<br />
cut (e.g., Malayan Uni<strong>for</strong>m System). Preparatory felling<br />
means removing trees near the end <strong>of</strong> a rotation so as to<br />
open the canopy permanently and enlarge the crowns <strong>of</strong><br />
seed bearers, with a view to improving conditions <strong>for</strong><br />
seed production and natural regeneration. Here, no<br />
adequate regeneration is on the ground. Seeding felling<br />
is removing trees in a mature stand so as to effect<br />
permanent opening <strong>of</strong> its canopy (if there was no<br />
preparatory felling to do this) to provide suitable<br />
conditions <strong>for</strong> regeneration from the seed <strong>of</strong> trees that<br />
are retained. Removal felling is removing trees between<br />
the seed cutting and the final cutting, so as gradually to<br />
reduce the shelter and admit more light to aid the<br />
regeneration crop and to secure further recruitment. This<br />
type <strong>of</strong> felling is carried out over adequate regeneration.<br />
There is almost 80 years <strong>of</strong> experience with the<br />
regeneration <strong>of</strong> natural dipterocarp <strong>for</strong>ests. Experience<br />
on individual aspects <strong>of</strong> natural regeneration gained is<br />
with modification applicable to even-aged stands <strong>of</strong><br />
<strong>dipterocarps</strong>. This does not mean regeneration systems<br />
<strong>for</strong> even-aged stands can be derived from the knowledge<br />
available now but it is possible to outline some general<br />
directions.<br />
One important aspect <strong>of</strong> the establishment <strong>of</strong> a new<br />
generation by natural regeneration is, whether or not the<br />
stands will fruit well be<strong>for</strong>e the rotation has ended. A<br />
few observations have been made. Ng (1966) concluded<br />
from his work on age <strong>of</strong> first flowering <strong>of</strong> <strong>dipterocarps</strong><br />
that many species begin to flower and bear good seed<br />
be<strong>for</strong>e their 30th year. Tang (1978) found three trees <strong>of</strong><br />
Shorea leprosula planted in a taungya stand had fruited<br />
at the age <strong>of</strong> 7 years. Similar early ages <strong>of</strong> flowering/<br />
fruiting were reported by Lee (1980) <strong>for</strong> Shorea pinanga<br />
(flowering 6 years after planting) and by Suziki and<br />
Gadrinab (1988/1989) <strong>for</strong> S. stenoptera (fruiting 6 years<br />
after planting). Ardikoesoema and Noerkamal (1955)<br />
described a S. leprosula stand in Java that had fruited<br />
aged 13 years producing a moderately dense seedling<br />
crop. Appanah and Weinland (1996) evaluated the field<br />
files <strong>of</strong> the dipterocarp plantations at the Forest <strong>Research</strong><br />
Institute Malaysia and fruiting was reported <strong>for</strong> Shorea