Tuaran Association occurs:
on the meander belts of the main rivers throughout the State with major developments along the Sugut, Labuk, Kinabatangan and Segama, which drain to east coast,
on the west coast the major developments are along the Padas, Papar, Tuaran and Wariu rivers,
along the rivers draining into Marudu Bay, and
on the meander belts of the Pagalan and Padas in the Tenom Plain.
The meander belts include levees, meander scrolls and cut-off lakes. The soils are formed on alluvium of variable texture. On the levees, for example, it is normally coarse-textured and on infilled cut-offs it is fine-textured.
This land has long been used by shifting cultivators and all the existing villages as far upstream as Kuamut on the Kinabatangan River are situated on it. As a result, much of the riparian forest is of secondary nature. On a sample plot on the Segama, Parkia javanica and Pterospermum sp. were common with many small Annonaceae and climbers and on the Kinabatangan at Subak, a vigorous riverside stand of Octomeles/ Anthocephalus regenerating forest with abundant grass and ferns was described.
At Subak, an open swamp forest was described; Baccaurea sp., Aporusa sp. and Xanthiphyllum sp. were common. Close by a rather denser swamp forest was recorded where Nauclea maingayi was dominant. Other species included Ficus sp., Glochidion breynoides and Colona seratifolia. In general, the tallest trees are on the levees and lines of tall trees away from the present river banks often indicate former levees. On the meander scrolls, trees are lower and less dense and have grass undergrowth. Meanders scars support grass vegetation with a few low trees.