Lowland forests
The lowland forests constitute freshwater and mangrove swamps which are regularly inundated with fresh water with high pH content and rich in minerals. The fluctuation of the water level allows periodic drying of the soil surface. In Peninsular Malaysia, most of these freshwater swamp forests, are found in Pahang and the southeastern part of Johor. There, in the sheltered coastal areas, stilt-rooted mangrove trees, which have adapted to tidal influence and saline waters, form an even, continuous canopy.
Further inland is found the nipa swamp forest. Uninfluenced by tidal movement, it is a unique brackish-water plant community dominated by nipa palm (Nypa fruiticans). On the landward fringes of the nipa swamp are clumps of nibong palms (Oncosperma filamentosum).The leaves of the nipa palm make good thatching material and the leaflets have been used for smoking tobacco long before the advent of cigarette paper. Its sap can be processed to obtain sugar and alcohol.
At one time, lowland peatswamp forests were a common feature on the coasts of Peninsular Malaysia and Sarawak. Their forest structure is identical to freshwater forests, in that there is also the canopy, the understorey and the shrub layers.
The highland peat forest, or kerangas, are mostly found in the Kelabit Highlands of Sarawak. Here, the upper tree canopy is consistently 30 metres above the ground. However, much of this forest, especially in Johor state, has been converted into plantation land mostly for growing oil palm and pineapple.
Along Malaysia’s lengthy coast, where soils are sandy and there is no mangrove, beach vegetation prevails. Stretching up to one kilometre inland, this thick, mat-like vegetation, including casuarina, cashewnut and simpoh trees, helps in controlling soil erosion. A typical beach forest is seen in Pulau Rumbia, Perak, where it merges well with coconut plantations.
The lowland dipterocarp forest, which is the most extensive type is found below the 300-metre line. The most important commercial timber species are found at this altitude where there is a considerable variation of dipterocarp species. There are also a variety of fruit trees with about 9 per cent of the tree flora, especially in Peninsular Malaysia, bearing edible fruits.
*Mangrove: There are about 20 to 30 species of mangrove trees and shrubs. In an established mangrove swamp, they are distributed in three distinct zones: the Avicennia-Sonneratia zone, the Bruguiera–Rhizophora zone and the back mangrove zone. In the Avicenna- Sonneratia zone, which is the most seaward fringe of the mangrove, the soil is soft and loose and flooded at all times during both low and high tides. The next immediate zone, the Bruguiera-Rhizophora zone, is situated on higher ground and is flooded only during high tide. Hence, the soil is relatively more compact than in the Avicenna-sonneratia zone. The soil in the back mangrove zone, which is inundated by equinoctial and other exceptionally high tides, contains more clay and is the most compact by comparison. The Bruguiera-Rhizophora wood is used to make piling poles, charcoal and firewood; while Rhizophora bark is a source of tannin.
**Sarawak: The largest area of wetlands in Malaysia, about 80 per cent, are found in Sarawak, the vast majority of which are peatswamp forests, covering more than 1.2 million hectares of land. Regarded as significant freshwater habitats which need protecting, these swamps are vital because they support many endemic plant species and endangered animals.
***Forest structure: In Peninsular Malaysia, the canopy layer is dominated by certain trees such as the ramin (Gonystylus bancanus), durian paya (Durio carinatus) and meranti. The middle understorey layer comprises smaller and medium-sized trees such as the kelat (Syzygium or Eugenia spp.) kayu arang (Diospyros spp.) and merbulan (Blumeodendron tokbrai). The shrub layer consists mainly of the kelubi (Eleiodoxa conferta) and pinang raja (Cyrtostachys renda) palms.
In Sarawak, the dominant tree species in the canopy layer are the sepetir paya (Copaifers palustris), ramin, jongkong (Dactylocladus stenostachys) and meranti (Shorea spp.). The understorey is the domain of the medang (Lauraceae), mangosteen (Clusiaceae), kedondong (Bursraceae) and mempisang (Annonaceae) families. The undergrowth in the shrub layer comprises the kelubi, pinang raja, jejarum (Ixora pyrantha), Tarenna fragans and groves of pandan (Pandanus andersonni, P. brevifolius and P. redleyi).