Nick Ashton-Jones, with Oronto Douglas and Susi Arnott

“ The main palm species of the FAM are the oil and raffia palms. For a start, the ecozone is the endemic home of the Oil Palm (Elaeis guineensis) , which prefers the drier and lighter ground of swamp margins.
The Raffia Palms (mainly Raphia gigantia, R. hookei and R. vinifera) can tolerate longer periods of water-logged, reduced conditions and even short periods of salinity, if it is low; some Raffia species have breathing peg-roots (Pneumataphores) which makes them even more able to withstand reduced soil conditions.
Endemic: where a species is naturally unique to one region of the world. ”

“ The flood plain is under shallow water during the peak flow of the river. At these times, the soil has Illuvial characteristics. However, during the driest part of the year (December to March) when the flood recedes, the soils experience Eluvial and Colluvial processes as water drains down through them. The most recent silts are building up on the left flank of the young deposits; these are only exposed during the driest months when the river is at its lowest. The swamp to the far left of the diagram is not uniform, but is made up of permanent and seasonal patches. ”

“ The seasonal swamp soils have a higher clay content than the levee soils, with a thin peaty surface horizon; they are also relatively reduced.
Reduced soil conditions exclude many lowland tropical rainforest plants. However most palms, although not dependent on waterlogged conditions, are more tolerant of them than are the classic rainforest tree species. Palms cannot compete successfully for light in the LEM ecozones, but together with the bamboo they predominate in the swamps. ”

“ There are seven sub-ecozones in the Freshwater ecozone.
6.4.1 THE LEVEE TROPICAL RAINFOREST SUB-ECOZONE
#⁠This is similar to the LEM rainforest described but with three characteristic variations:
it tends to be long and narrow in shape, so that there is less 'deep forest' and a greater proportion is forest margins; on these forest margins, palm trees are more apparent than in the LEM because of their predominance in the adjacent sub-ecozones; and species requiring soils deeper than 1 metre, such as the Silk Cotton tree, are less common. ”

“ However, the trade-off is one sided, because the number of plant species tolerating reduced conditions are limited. Swamp plant communities have low biodiversity.
Biomass in the swamps is also limited, partly because tree height is limited. Palms never grow to a great height, and other trees cannot develop sufficiently deep taproots in the waterlogged soil to support massive growth. ”

“ Bird life is more prolific in the Fresh-water ecozone than in the natural LEM ecozone, because of the food and space provided by the water. The variety of subecozones and ecotones has produced a very high species diversity. ”

“ Lianas are woody, climbing plants found in all tropical rainforests. They use existing trees for support, and 'scramble' up them towards the light. They are particularly common in the flood plain tropical rainforest because of its broken canopy. They include the Rattan Palms (these are actually more common on the black-water flood plain) ; and the Swamp vine, Grewia coriacea.
#⁠Earthworm Ridges
An interesting phenomenon of the Freshwater ecozone, especially evident in the Floodplain sub-ecozone, is the Earthworm Ridges. ”

“ The white rivers move faster and have more dissolved oxygen but are more cloudy and are thus oligophotic or 'light-poor'. (A classic white-water animal is the 'electric eel', which provides its own light.) ”

“ Secondly, palms have only a single stem which does not bear branches. Palms are one of the few groups of monocotyledonous plants which grow tall enough to be called trees. Monocotyledons are normally shorter, because they do not develop the bark and cork layers that give dicotyledons the physical strength to support a tall plant body. ”

“ In evolutionary terms, palms are less advanced and need higher light intensities than the broad-leaved trees; they cannot compete with them and are not found in the taller-canopied climax rainforest.
#⁠Palms grow well in swamps for three reasons
These are all related to their fibrous root systems:
First, they have adventitious roots at the base of the trunk, parts of which can grow above ground, in some species acting as breathing roots ”

“ Obviously, reduction is greater in the permanent swamps, although seasonal rising and falling of water levels still allows some oxidation. The soils are likely to be peaty, organic matter building up in these reduced conditions. ”

“ They grow in clumps, and their extensive underground 'roots' are actually a form of stem supporting both roots and shoots. They proliferate mainly via these rhizome-like systems, but will eventually fruit and then die. ”