Type
G: Dipterocarpus / Richetia Forest
The following is an excerpt of JED Fox's PhD
thesis. The article stays fairly true to the original with minor changes. Most
measurements are changed to the Metric System.
Quick Jump Sepilok
Elsewhere in the East Coast
In the north A
bit of advice...
This type is best known from the coastal locations
where it occurs on sandstone hills and ridges with dip and scarp slopes of high
amplitude. The soils are often comparatively deep red/yellow podsolic sandy
loams to sandy clay loams with depth. The type is often associated with Heath
forest on leached sandy soils on cuestas, ridges and steep slopes.
Sepilok
The best known examples of Type G forest are those of
Kabili-Sepilok VJR of which RP 17 has received the greatest attention. Stand tables for
two ten acre (4 ha) plots RP 292/2, 292/3 showed that in this Type of
dipterocarp forest, Parashorea
species, Dr. lanceolata and Eusideroxylon zwageri are scarce. A number of Rubroshorea species
are present of which S. smithiana and S.
macroptera are probably most typical, while others may be locally abundant,
and in Sepilok, S. beccariana falls
into this category. Anthoshorea and Shorea
(SB) sections of Shorea are
represented but the most typical
species is the Richetia S. multiflora.
The largest, dominant species forming the emergent canopy are Dipterocarpus,
and D. confertus, D. grandiflorus and D.
acutangulus are all represented in Kabili-Sepilok VJR.
The profile diagrams show the general structure of
the forests, with Dipterocarpus
emergent to 50 m, a main canopy largely composed of S. beccariana at about 36 m, a second layer at 18–24 m with
S. multiflora and an understorey.
Other species typically present include Gluta
renghas, Lophopetalum beccarianum, Tapoides villiamillii, Persea bancana, Ganua
kingii, Pentace borneensis
and Teijsmanniodendron glabrum. In
comparison with Parashorea and
Rubroshorea forests, this type often has a more even structure. Though gaps due
to lightning damage occur on exposed ridges, and patches may suffer landslides
from time to time, the characteristic occasional tangle of climbers and bamboo
of the lowlands are less noticeable, possibly due to lower mortality rate which
may be associated with slower growth of the dominant species. The largest trees
of this Type are shorter in height and smaller in girth than those of most of
the lowland Types, but stem numbers and basal area are high due to denser lower
canopies.
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Elsewhere in the E coast
The Type is mainly confined to the sandstone
exposures within these geological formations coloured yellow on Map 3. The
Sepilok occurrence is on the Sandakan formation which is allied to the Tanjong
Formation. Dryobalanops beccarii
occurs on the sharp ridges of exposures of the Tanjong formation at Bangon River,
West
Kuamut, as a scattered tree in the form of Dipterocarpus/Richetia forest where the common species are D.
acutangulus, the Richetia S.
faguetiana and the Rubroshorea S.
ovalis. Scaphium longipetiolatum is common here. Elsewhere in the Sandakan
area the main association of D.
acutangulus/S. multiflora is a feature of sandstone hills of the Tanjong
Formation impinging on the Kinabatangan River at Sukau, Bilit and
Batu
Putih and also east of Lumerau River in the Segama River delta on the
Ganduman Formation.
D. grandiflorus
is abundant on the long sandstone escarpment east of the lower Umas Umas
River. This species also occurs on coastal Chert-Spilite on Sakar Island
in Darvel Bay and on sandstone at Sungai Paliu in the Labuk River delta.
The Obar Ridge of the Bongaya Formation in the lower Sugut area has both Dipterocarpus/Richetia
forest on the less leached slopes and Heath
forest on the poorer soils. Species characteristic of Type G in this area
include D. confertus, D. stellatus the
Rubroshorea species S. macroptera, S.
smithiana, and S. ovalis with S.
kudatensis representing Richetia and
S. agami Anthoshorea. Both in this area and in the Serudong area of lower Kalabakan
FR the Type is marginal with Rubroshorea/Dipterocarpus,
but on some low-lying coastal areas, e.g. at Sungai Pirit, Mamahat it is
marginal with Dryobalanops beccarii swampy
padang forest.
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In the North
In the north of the State, the Type occurs on
sandstone hills of the Kudat Formation. For example, at the southern end of Bengkoka
Peninsula, the association D.
grandiflorus/S. kudatensis occurs with S.
ovalis, S. oleosa and S. cristata.
At Lajong FR near Kudat, the Richetia species
S. fagustiana and S. kudatensis
are found with S. smithiana and small
trees of Dacaspermum fruticosum,
Callophyllum obliquinervium, Buchanania arborescens and Eugenia (Syzygium)
palawanensis.
A coastal forest of similar type at Balembangan Island
on Chert-Spilite has D. grandiflorus and
S. kudatensis as large emergent to 36 m over a main canopy of Tristania (Tristaniopsis)
clementis, Oncosperma horrida, Shorea xanthophylla (Ri)
and Cotylelobium melanoxylon. The
latter species is typical of dry leached sites in general.
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A bit of advice...
The forests of this Type though difficult to
distinguish on aerial photographs from others, are inherently less valuable as
the larger trees are often hollow. The soil is unsuited to agriculture and
any canopy opening accelerates erosion.
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