Gomantong Forest Reserve

The Gomantong FR is situated in the Lower Kinabatangan floodplains, surrounding the Class VI Gomantong VJR. It is accessible by the main gravel road to Sukau and by river transport along the Kinabatangan River. A  sealed road (about 4 km) from the Sukau road passes through the Gomantong Class I FR and leads leads to the Gomantong VJR and the main entrance to the caves. There is another unsealed gravel road from the Sukau road which enters the FR in the northwest and exits in the west to nearby Materis VJR.

These roads were part of an old network of unsealed roads that encircled the Gomantong VJR (Class 6) and within the Class 1 FR. The present condition of these roads is not known.

Road access to the Gomantong VJR (Class VI) and to the southwest of the FR.

Creation—Gomantong FR was first gazetted as a FR in  1925, surrounding the famous Gomantong Caves. Two extensions, to the south and west, were made to the reserve in 1971. It was reclassified and gazetted as Class I in 14/3/1984. At the same time, a smaller portion, about 1816 ha, was reclassified and gazetted as Class VI VJR. 

Management responsibility—Mukim Sukau, Kinabatangan District Forestry Office and the Sabah Wildlife Department.

Boundary matters—The boundary has yet to be demarcated.

Management plan—None.

Current use—None.

The FR is surrounded by oil palm estates. In the north, along the Sukau road, there is Kg. Bugis.

Topography—Most of the FR is formed on low hills and narrow alluvial flats with an amplitude of 15-30 m and short slopes ranging from 5-15° on the hills. In the south, the land is flat. The northwest is on moderate hills with amplitudes generally up to 75 m and slopes between 10° and 20°. The limestone outcrops have steep, often sheer, slopes. The southwest is rather flat on alluvial soil and minor hillocks with a relief amplitude which rarely exceeds 15 m and with slopes in the 0 to 15° range, the majority being less than 10°. The alluvial flats are often wide and include patches of swamp; they are subject to flooding.

Hydrology—

Soils—Mainly Rumidi, Lungmanis, Kinabatangan and Kretam Associations, with Gomantong, Klias and Sapi.

Meteorological data—The nearest meteorological stations are very close by at Bilit and Sukau. However, we do not have analysed data from these stations. See data from Bukit Garam (west), Sg. Sekong JUB Estate (northwest) and Tomanggong Estate (southeast) met stations.

The main vegetation types of the FR are MDF, MDF-limestone vegetation, seasonal freshwater swamp, freshwater swamp forest and peatswamp forest.

Mixed dipterocarp forest (MDF) – Large areas of the original MDF were selectively logged in the past. However, the old-growth secondary MDF has regenerated well with mean canopy height of 20-25 m. Dipterocarp recorded were Hopea beccariana, Hopea sp., Shorea atrinervosa, S. hypoleuca, Shorea sp1 and Shorea sp2. Common species were Polyalthia insignis (Annonaceae), Diospyros sp. (Ebenaceae), Magnolia sp. (Magnoliaceae) and H. beccariana (Dipterocarpaceae). Shrub layer was open.

MDF-limestone vegetation – Most of the MDF-limestone vegetation in the area is in the Gomantong VJR (Class 6). In this FR, there are outcrops in the mid-south, west and north, the former with some areas of primary vegetation.

The northern outcrop is about 3 km long but just about 0.3 km at its widest point. An old tractor path lead to the northern point of the outcrop where the vegetation was young secondary, probably affected by fires in 1997-98. Relatively fresh burnt scars were seen and causes unknown. The mean canopy height was 5 m at the slopes with the main species being Macaranga tanarius, Leea sp., Melicope sp., Ficus septica, Nauclea sp. and Pterospermum sp. At the summit, Chionanthus sp. was dominant. Other species included Macaranga tanarius, Ficus benjamina, Buchanania sp., Leucosyke capitellata, Melicope sp. and Homalantus sp. Lalang and ferns formed the ground cover for more open areas.

The western outcrop is about 4 km long, ending outside the FR, just north of the nearby Materis VJR. The vegetation is largely old secondary, similar to those at Bod Tai and Pangi FRs. On the ridges, the mean canopy height was about 20 m with mainly trees of 10-40 cm DBH. Common species included Saraca declinata, Drypetes sp. and 2 species of Hopea. Other species included Cynometra sp., Vatica sp., Dimocarpus sp., Lansium domesticum, Dimorphocalyx muricatus, Mangifera indica, Sindora sp., Enicosanthum, and Polyalthia sp. Trees 40-60 cm DBH were Drypetes sp., Hopea spp., Madhuca sp., Spathostemon sp., Mangifera indica, Diospyros sp., Magnolia condolii, Shorea falciferoides and Dialium sp. Only one species, Shorea falciferoides, grew to 90 cm DBH.

The southern outcrop had secondary and primary forests. The secondary forest was logged in the past and also affected by fire in certain places. Most of the trees were below 50 cm DBH. The most common species were Macaranga pearsonii, Melicope sp., Octomeles sumatrana, Endospermum sp. and Ficus septica. Other species included Teijmanniodendron, Rauwolfia reflex, Nauclea subdita, Neonauclea artocarpoides, Glochidion sp., Alangium sp., Cratoxylon arborescens, Macaranga hypoleuca, Ficus variegata, Diospyros elliptifolia, Hynocarpus woodii, Eusideroxylon zwageri, Canarium sp., Bridelia glauca, Ficus septica, Alstonia augustiloba, Pleiocarpedia sandakanenica, Eleaocarpus stipularis and Pterospermum elagatum. On the burnt areas with loose stones and little soil, species such as Lunasia amara, Muraya paniculata, Buchanania sp., Chionanthus sp., Cleistanthus sp., Antidesma sp. and Mallotus dispar were present. For dipterocarps, there were many Hopea nutans observed but the only other dipterocarp seen was Dryobalanops lanceolata. The primary forest on this outcrop was not surveyed as it was similar to the vegetation on the outcrop in the Gomantong VJR (Class 6).

Seasonal freshwater swamp forest. – This forest is located along the southern boundary of the FR with the slow flowing Sg. Menanggul flowing east through it. A large area on the southern portion is secondary while the southeast part is primary with patches of secondary vegetation. The primary vegetation, with a mean canopy height of 15 m, is almost a pure stand of Mallotus muticus. This species is well represented in all DBH classes up to 50 cm. Other species include Cordia sp., Nauclea subdita, Syzygium sp., Vatica rasak and Dillenia excelsa, with Excoecaria indica and Mitragyna speciosa (wetland species) reaching up to 60-80 cm DBH respectively. In areas more frequently inundated, common species are the sedge Thorostachyum, and the ferns Blechnum indicum, Cyclosours gongylodes and Nephrolepsis biserrata.

Peatswamp forest – This forest covers a large area southeast of the FR but only a small portion is within the FR boundary. The mean canopy height is 10-15 m with most of the trees at the 10-30 cm DBH range and only a few were above 40 cm DBH. The major species were Syzygium sp., Tristaniopsis sp., Campnosperma sp., Xylopia dehiscens and Garcinia sp. Other species include Baccaurea bracteata. The sedge Mapania is common.

Being part of the Kinabatangan Wildlife Sanctuary, the FR harbors a huge variety of wildlife. Common species are the larger mammals like elephants (migratory path), a few species of deer, orang-utans, clouded leopards and wild boars.

Aerial and ground surveys were conducted in the VJR and Gomantong FR in 2001. This was part of a statewide orang-utan census carried out by HUTAN (an NGO based in Sukau, Kinabatangan) and the Sabah Wildlife Department. Orang-utan population density was 3.8 individuals/km². The estimated population was 147 individuals.

Information not available.

Encroachment—The main concern here is the encroachment by illegal game hunters. Locals say that these hunters frequent the FR to hunt for wild boars and sambar deer. They normally hunt in the west and northwest where there is an unsealed road through the FR (see satellite image).

The FR is the largest protected forest in the Kinabatangan Floodplain. The peat swamps near Gomantong represents one of the largest, most intact, natural peatswamp vegetation in Sabah.