A review of dipterocarps - Center for International Forestry Research

Plantations 171
fungal problems, bacterial and viral infections (Smits et
al. 1991). Heart-rot of dipterocarps has been
investigated, and is more serious in slow-growing than
in fast-growing species (Hodgson 1937b, Bakshi et al.
1963). Stand management strategies to control heartrot
have been developed for Shorea robusta (Bakshi
1957).
With establishment of large-scale plantations of
dipterocarps, susceptibility to diseases and pests is bound
to increase. The control of pests and diseases in
nurseries is well developed and advanced. Chemical
control is the prevailing method to fight the attack of
biotic agents. Chemical control is, however, not
practicable after field planting. Prevention has to be
secured by silvicultural means, e.g., species mixtures,
structural diversity, avoidance of damage to trees and soil,
etc. At present, there is an urgent need to survey diseases,
defects and damages in existing dipterocarp plantations,
particularly the incidence and possible causes of heartrot.
Gaps in natural forests and plantations are created
by natural mortality, biotic and abiotic agents. Lightning
is a major cause for the occurrence of gaps not only in
natural forests (Brünig 1964, 1973) but also in
plantations. While in natural forests such gaps drive the
regeneration dynamics, in plantations such gaps, first of
all, reduce the stocking. The effect of lightning can be
seen clearly in the plantation area of the Forest Research
Institute Malaysia (personal observation).
Management Aspects
The available information, here, can be combined under
the following categories: silvicultural systems, biological
production, (especially growth), thinning schedules,
stocking aspects, silvicultural diagnostics, and
economics.
‘A silvicultural system is a process, following
accepted silvicultural principles, whereby the crops
constituting forests are tended, harvested and replaced,
resulting in the production of crops of distinctive form.
The systems are conveniently classified according to the
method of carrying out the fellings that remove the
mature crop with a view to regeneration and according
to the crop produced hereby’ (Ford-Robertson 1983).
Silvicultural systems are discussed in the context of stand
regeneration of plantations after the first rotation.
In India, various silvicultural systems have been
applied to encompass the wide ecological variation in
the occurrence of dipterocarps. A selection system has
been applied in seasonal rain forests and moist deciduous
forests. Clearfelling and artificial regeneration have been
carried out in moist deciduous forests where frost is
absent. Various forms of shelterwood systems were
applied in regions where frost was experienced. Coppice
with standards was applied to Shorea robusta in dry areas
and simple coppice systems used in wood lots in
Karnataka.
While the silvicultural systems for Shorea robusta
forests in India are clearly formulated and understood,
there is little information in other parts of the region on
what the silvicultural system for dipterocarp plantations
should be. Most silviculturists would like to re-establish
an existing dipterocarp plantation at the end of the first
rotation by natural regeneration. In Malaya, Walton
(1933, 1936a), Watson (1935) and others have indicated
the possible species among the fast-growing lighthardwoods
which can regenerate naturally in the rotation
envisaged for plantations. Little is known about the
capacity of plantation-grown dipterocarp species to
regenerate naturally at a rotation of about 50 years. There
is already some information derived from planted
species, e.g., Shorea leprosula, Dryobalanops spp.,
Shorea spp. of the pinanga group and S. robusta, which
can be naturally regenerated during such a rotation time.
All the existing, mature, experimental, dipterocarp
plantations in the region should be assessed for natural
regeneration.
The growth of dipterocarps under natural forest
conditions has been observed early this century (e.g.,
Edwards and Mead 1930, Watson 1931/1932a, Rai 1996).
The observation of the growth of dipterocarps in plantations
commenced only later. Analysis of 29 dipterocarp species
in trial plots at the Forest Research Institute Malaysia
indicates rotation ages of 40 to 50 years for the best
performing species (Ng and Tang 1974). Individual volume
and growth plots have also been analysed (Vincent 1961 a, b,
c, d, Zuhaidi et al. 1994). The growth curves show a very fast
early height and diameter growth with distinct differences
between species in growth rates. Relatively impressive
growth rates of the light red meranti group (Shorea spp.)
have also been recorded in the Haurbentes experimental
plantation stands in Indonesia (Masano et al. 1987, see also
Ardikoesoema and Noerkamal 1955): a stand of Shorea
leprosula achieved an average height and diameter of 44.6
m and 77 cm respectively in 35 years. Shorea stenoptera
was similarly fast growing with an average height and