A review of dipterocarps - Center for International Forestry Research

Plantations 161
and Noerkamal 1955, Krishnaswamy 1956, Sudiono and
Ardikusumah 1967). Dipterocarps, usually, are not
planted on completely cleared sites. In enrichment
plantings they are planted on lines cut into the forest and
in plantations the plants are usually planted under the
shade of a nurse crop.
Underplanting or sowing beneath a forest canopy is
important in restocking forests with valuable species.
Underplanting can be done in residual stands of logged
natural dipterocarp forests, in secondary forests, under a
planted nurse crop or in plantations where the stocking is
poor. The Experimental Forests of West Java (Darmaga
and Haurbentes) were established by underplanting.
Ardikoesoema and Noerkamal (1955) give an account of
the establishment of the Shorea leprosula stand in
Haurbentes. Two month-old seedlings were planted under
the shelter of 2 year-old Paraserianthes falcataria which
was removed after 5-6 years. At the age of 15 years the
stand had passed the pole stage. The experimental
plantations in the area of the Forest Research Institute
Malaysia were partially established under nurse crop,
either secondary vegetation or planted nurse trees
(Barnard 1954). Paraserianthes falcataria, Peltophorum
spp. and Adenanthera spp. were found to be useful as
nurse trees although the latter two species, which have
smaller and lighter crowns, were better suited.
Dryobalanops aromatica was established under a shelter
of Fragraea fragrans (Landon 1948b) and on lines in
secondary vegetation (Barnard 1949a). Doan (1985)
reported a planting trial in Vietnam, where Dipterocarpus
alatus, Hopea odorata and Anisoptera costata were
planted under shade of Indigofera teysmanii and Acacia
auriculiformis. Of the three species Dipterocarpus alatus
was more light demanding. Miyazaki (1989) found that
age of the nurse crop had an effect on survival of
Anisoptera thurifera. Seedlings were planted under 8-10
year old and 2-3 year old Acacia auriculiformis. Mortality
was higher for those seedlings planted beneath the
younger nurse crop. In a sowing experiment by Tomboc
and Basada (1978) seeds of Shorea contorta were sown:
under a secondary forest canopy which allowed the sun
to filter through the canopy for 1 hour daily, and in the
open. Survival was significantly higher under the forest
canopy, while height growth and leaf development were
better in the open. Wyatt-Smith (1947) reported a
successful sowing experiment with Dryobalanops
aromatica under a 1½-2 year old secondary forest while
sowing in cut lines proved a failure. The ecological role
of pioneer species in the natural regeneration of loggedover
dipterocarp forests is discussed. Wyatt-Smith (1947)
suggested that secondary vegetation can be cheaply
converted by line planting beneath its canopy in 5 to 10
years’ time (depending on the amount of soil degradation
that has taken place), when most of the herbs and ground
flora will have been shaded out. Rosario (1982) proposes
silvicultural treatments that preserve pioneer species.
These proposals are similarly valid for the treatment of
secondary vegetation into which dipterocarps are planted.
Other researchers have tested specific forms of site
preparation. Maun (1981) reported a sowing experiment
in a dipterocarp forest, where germination, survival and
early growth of Shorea contorta was tested. The
treatments were five different types of cover: (1) bare
soil, (2) soil with litter, (3) soil with litter and ground
cover, (4) soil with litter and underbrush, and (5) soil
with intact vegetation cover. Germination was best in
treatment (4), survival in treatment (4) and (5) and growth
performance was better in treatment (1) and (2). Ang
(1991) tested survival and growth of Shorea parvifolia
on three sites: (1) secondary forest with trees of >20 cm
girdled well in advance of planting, (2) open site (large
opening in forest) with 30 cm top soil removed, and (3)
open site (large opening in forest) with top soil retained.
Survival was similar in all three sites, but growth was
best in the open site where top soil had been retained.
Barnard (1949b) investigated the effect of two types of
planting site preparation on survival and growth of
differently prepared seedlings of Dryobalanops
aromatica. The test site was a natural forest with invasion
of Gleichenia spp. and Eugeissona triste. Part of the test
site was clear-felled and burnt. A control area remained
unburnt, where Gleichenia spp. and Eugeissona triste
were cut only. In the unburnt site all planting stock types
established, while in the burnt site only the potted
seedlings succeeded. Rowntree (1940) proposed grazing
as a means to control the growth of Imperata cylindrica
to secure the establishment of S. robusta regeneration.
Nykvist et al. (1994) have reported the impact of forest
harvesting and replanting on the forest site. They conclude
that burning should be avoided in order to reduce nutrient
loss and ensure better plantation growth. A similar view
was already voiced by Wyatt-Smith (1949a) for the same
reason. In the trial described by Barnard (1949b) in the
plots prepared by burning only potted seedlings of
Dryobalanops aromatica succeeded. As saplings they
developed strong stems and had good height growth.