In Sabah, subalpine forest (2800 – 3400 masl) occurred in Kinabalu National Park. Trees in this altitudinal band are gnarled and stunted shrubs with rhododendrons and conifers.
Montane forests can be categorized into lower montane forest (1,000 – 1,500 masl) and upper montane forest (1,500 – 2,800 masl). However, the altitudinal ranges of montane forests are greatly influenced by geographical conditions. For example, vegetation of the upper montane ultramafic forest in Mount Silam (880 masl) bears a striking resemblance to that of the Mount Kinabalu montane forest at 2,133 – 3,048 masl. Montane forests are usually characterized with high tree density but small tree basal area. The dominance of tree family Dipterocarpaceae is disappearing as the altitude increases.
Dipterocarp forests are naturally dominated by trees of family Dipterocarpaceae. In Sabah, typical dipterocarp forests are lowland mixed dipterocarp (up to 600 masl) and upland mixed dipterocarp forests (600 – 1,000 masl). Vegetations in dipterocarp forests are often complex of which the four major canopy layers are distinctive. However, this forest may also occur in unique habitats including ultramafic, limestone and kerangas. This forest harbours many interesting Bornean trees, for instance Shorea faguetiana (Seraya Kuning Siput), the tallest tropical tree in the world. Old-growth dipterocarp forest can easily be found in Tabin Wildlife Reserve, Danum Valley Conservation Area, Imbak Canyon Conservation Area, Maliau Basin Conservation Area, Tawau Hills Park, and Crocker Range Park.
The term kerangas is an Iban word that refers to infertile soils in which rice cannot grow. This forest occurred on site with predominantly podzolized, highly acidic and sandy soils. In general, its dense vegetation comprises trees with small diameter and uniform height. Tropical pitcher plants (Nepenthes) are well adapted to this low-nutrient habitat. Kerangas forests have been recorded in many reserves including Sungai Serudong Forest Reserve and Segaliud Lokan Forest Reserve.
Mangrove forests are also known as tidal forests. They exist as an interface between the land and sea, where plants have evolved special adaptive features to survive in such environment. The mangroves of Sabah can be divided into three broad mangrove zones, for examples seaward or riverine margin, main mangrove and back mangrove zones.
Peatswamp forests occurred where waterlogged soils prevent dead leaves and wood from fully decomposing, which over time creates thick layer of acidic peat. Peatswamp forest can be found in Binsuluk Forest Reserve.
Seasonal freshwater swamp forests are inundated with freshwater. They normally occur along the lower reaches of rivers and around freshwater lakes. Seasonal swamp forest can be found in Pin Supu Forest Reserve.
Limestone forests often occurred on limestone hills (karst). Limestone forest is distinct from the surrounding lowland forest, not only in its species composition, but also in its appearance. Limestone forest can be found in Bukit Punggul Forest Reserve.
Beach forests are ecosystems that can be found adjacent to beaches. Some fruits and seeds are adapted to be dispersed by sea currents by evolving seawater resistance fruits. To a certain degree, beach forest trees are able to prevent coastal erosion.
Ultramafic forests occurred on ultramafic rocks that can be found in few places in Sabah, including Kinabalu National Park, Mount Silam, and Tawai Forest Reserve. Plants found on ultramafics often have morphological adaptations to minimise water requirements and water loss in order to survive in water-limited environment. Such adaptations include a generally low stature, small-crowned growth-form and other characteristics such as glaucous leaves and sclerophyllous and microphyllous morphologies.
