Within the forest canopy, especially in lowland forest, there live a large range of animals, vertebrates and invertebrates, some eating plant parts, same eating other animals. Complex interrelationships exist between plants and animals, for example, in relation to pollination of flowers and dispersal of fruits. Some plants, so-called myrmecophytes, provide shelter for ants in modified organs. Many plants, it is now believed, produce chemicals noxious to many insects and in this way attempt to protect themselves from being eaten.
The whole organic community and its immediate physical and chemical enviroment together make up tile ecosystem (Tansley 1935) of the rain forest. If part of the forest is destroyed plants (and attendant animals) recolonize the gap, others invade in competition with them; there is a secondary succession of seral plant communities, until eventually a community similar to the original is restored. This is called the climax. On bare land surfaces, for example, that created in 1963 by the eruption of Gunung Agong in Bali, a primary succession, or prisere, occurs leading also to the climax.
Over a sufficiently large area the climax itself is in a state of dynamic equilibrium. There is no net increase in the biomass of living plants and animals; deaths are more or less balanced by replacements. This is true on time-scales comparable to a man's life-span, and may he so too over a few centuries. But on a long, secular scale there may be change in the geographical range of species following alterations In climate such as have occurred during the Pleistocene period, and there are hints of this having happened. On a still longer time-scale new plants and animals have evolved and come to influence the ecosystem.
The synusiae
A synusia is a group of plants of similar life-form which fill the same niche and play a similar role in the community of which it forms apart (Richards 1952); that is, it is a partial life-form community.
Synusiae provide a good means for analyzing complex plant communities. Richards (1952) has introduced a convenient practical classification for the synusiae of tropical rain forest:
A. Autotrophic plants (with chlorophyll)
1. Mechanically independent plants.
(a) trees and treelets;
(b) herbs.
2. Mechanically dependent plants.
(a) climbers;
(b) stranglers;
(c) epiphytes (including semi-parasitic epiphytes).
B. Heterotrophic plants (without chlorophyll).
1. Saprophytes.
2. Parasites.
Species of very diverse taxonomic affinity make up the synusiae. As well as having a common life form, many also have very similar physiognomy. The relative representation of these ecological groups differs in the various Formations of the tropical rain forest and is important in their definition. They are all represented in tropical lowland evergreen rain forest. The synusiae occur throughout the tropics wherever the Formations are found.
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REFERENCE :
Whitmore, T.C, 1975, Tropical Rain Forests of the Far East , 1st Edition, Oxford University Press, Oxford.
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