Tropical forest dynamics: the faunal components

Abstract

The form, diversity and dynamics of tropical forests are influenced by both abiotic factors, such as the physical environment and climate, and biotic factors, such as interactions between organisms. To most people forests are principally comprised of trees, large mammals and birds. But, tropical forests are comprised of many other smaller life forms including arthropods, fungi, nematodes and bacteria, and these too have an important part to play in forest dynamics. The relative importance of different groups of animals in tropical forests, as measured through abundance, biomass and species richness, is presented here. Because of the sheer diversity of the life forms in tropical forests, only a few of the complex webs of interactions between organisms of the different kingdoms have been determined with any accuracy. In spite of this fact, some general patterns have been recognised and the major components of trophic systems in tropical forests have been determined. Many detailed studies of large mammals and birds have shown the significance of their roles in the dynamics of tropical forests. What is less clear is the precise contribution of many groups of invertebrates such as arthropods and nematodes. In part this is because the abundance, species richness and sometimes biology of these groups is poorly understood. Data are presented on the (i) distribution, abundance and biomass of arthropod groups in the main habitats of lowland rain forest in Seram, and (ii) the species richness of different arthropod groups in lowland forest in Sulawesi. Arthropods are particularly important in two contrasting strata of tropical forests, the canopy and soil, where herbivory and decomposition, respectively, are the principal trophic processes. The importance of arthropods in these forest strata and to forest dynamics are discussed through examples of two groups of arthropods, ants and termites. An understanding of tropical forest dynamics may help in determining how biodiversity and sustainability may sit more easily together. This is discussed with suggestions as to how we can best use available information toward this end, what new information is needed, and which ideas require examining.