The most distinctive peatland in Singapore is the freshwater swamp forest at Nee Soon. This swamp system is extremely complex, and the all-important water regime must have drastically altered over time by changes both up and downstream of the existing remnants. Swamp forest occurs in low-lying areas where the water table is close to the soil surface and the soil is usually rich in organic matter. Many of the most characteristic tree species have striking stilt roots (e.g. Palaquium xanthochymun, Sapotaceae and Xylopia fusca, Annonaceae) and/or pneumatophores of various types (plank-like in Lophopetalum multinervium, Celastraceae), presumably as an adaptation this substrate and to the periodic floods to which most of the forest is subject.