A review of dipterocarps - Center for International Forestry Research

Plantations 157
Malaysia, flowering and fruiting are regularly observed
over a wide geographical and climatic range and reliable
records are available. Darus et al. (1994) proposed the
establishment of seed production stands in the main
climatic regions of Peninsular Malaysia and a
corresponding tree selection and tree improvement
programme. Similar efforts on tree improvement
involving dipterocarps have been made in Bangladesh
(Nandy and Chowdury 1994), India (Negi 1994),
Philippines (Rosario and Abarquez 1994) and in Thailand
(Sa-Ardavut 1994). Much of the improvement work in
the region is coordinated within the Species Improvement
Network (Anon. 1994).
Seedling planting stock
‘In nursery practice, a seedling is a very young tree that
has not been transplanted, i.e. is growing where it
germinated’ (Ford-Robertson 1983). Seedling planting
stock for most dipterocarp species is usually potted and
leaves the nursery after about 9 months. The seedling
height is about 25-50 cm.
Generative propagation is still the prevailing method
of plant production in dipterocarps and is technically not
a problem if seeds are planted immediately after
collection. Timber companies involved in propagation
of dipterocarp seedlings have the expertise to run largescale
dipterocarp nurseries professionally e.g., in
Indonesia or Sabah (Moura-Costa 1993). The literature
on the propagation of dipterocarp seedlings deals mainly
with planting stock type (e.g., Walton 1938, Barnard
1954, Pande 1960, Joshi 1959), sowing position of
seeds (Serjuddoula and Rahman 1985), response of
potted seedlings to fertilisers (Kaul et al. 1966, Bruzon
1978, 1982, Sundralingam 1983, Sundralingam et al.
1985), controlled mycorrhization (Garbaye 1989,
Santoso 1989, Santoso et al. 1989), the use of bare-root
plants (Sasaki 1980b, Mori 1981).
As far as the age of the planting stock is concerned
Barnard (1954) found that for most of the dipterocarp
species planting stock between 3 and 8 months old is
the best (e.g., Dryobalanops aromatica, Shorea
leprosula and S. pauciflora). Hodgson (1937a)
concluded that planting stock only a few months old is
more likely to survive than older material. Seedlings of
Anisoptera sp., Dryobalanops aromatica and
Neobalanocarpus heimii were planted with cotyledons
still attached. While D. aromatica was destroyed by
rodents, the two other species survived. Kuraishy (1942)
transplanted 6-week old seedlings of Shorea robusta
successfully.
Lamprecht (1989) proposes the use of 15-20 cm
tall planting stock for economic and handling reasons.
Which plant size to choose, should depend on the
condition of the planting sites, that is, those with
intensive weed growth require larger planting stock. To
reduce the amount of weeding it is preferable to plant
seedlings which are large enough to overcome weed
competition at an early stage although growth rates might
not be better than those of smaller planting stock. Planting
stock size is an important aspect but root:shoot ratio,
leaf area and diameter:height ratio are as important.
Sturdy plants with a low root-collar:shoot ratio tend to
form roots faster and are better equipped to withstand
drought stress. In a trial carried out by Moura-Costa (not
dated) initial height growth rates were significantly better
for sturdier plants. Species tested were: Dipterocarpus
gracilis, Dryobalanops lanceolata, Parashorea
malaanonan, Shorea johorensis, S. leprosula, S. ovalis
and S. parvifolia.
Type of planting stock is another factor to be
considered. Potted seedlings proved to be superior to
bare-root planting stock (e.g., Anon. 1948a, Barnard
1949b). With the exception of a few hardy species, the
survival of bare-rooted stock seems to be low (e.g., Cerna
and Abarquez 1959). Rayos (1940) tested the survival
of bare-rooted seedlings of Hopea pierrei of different
sizes with their roots stored in moist sawdust before
planting out. Survival was inversely proportional to
storage period and seedling size. The smallest height
tested was 10-20cm. Prasad (1988) found in a plantation
trial on bauxite mining land that survival and growth of
potted S. robusta plants were superior to that of plants
from direct sowing.
Specific treatment of seedlings, such as shoot and
root-pruning and the effect on growth and survival have
been investigated. Root-pruning gave better survival and
growth of planting stock. Walton (1938), Landon (1948b)
and Barnard (1954) showed that survival and growth of
Dryobalanops aromatica seedlings were superior when
seedlings were wrenched (tap root severed) compared
to unwrenched seedlings. The effects of shoot-pruning
and stripping of the leaves on survival were inconclusive.
Landon (1948b) planted Dryobalanops aromatica under
the shade of a 20-year old Fragraea fragrans stand and
topping, partial or total stripping of leaves had no effect
on survival. Sasaki (1980a) pruned bare-rooted seedlings
Shorea talura and Hopea odorata (removal of all leaves,
all young parts of the stems and the tap root) and was