Translating Knowledge into Actions Tree hole aquatic habitat: a model for ecological experiments Letter to Editor

3 Division of Environment Impact Assessment, Salim Ali Centre for Ornithology and Natural History, Anaikatty P.O, 641 108 – Coimbatore, Tamil Nadu, India An ecosystem is a complex entity with several interacting components. Ecologists face problems of devising appropriate research design to understand complexity of ecosystem. It requires a realistic model to test the ecological theories. A large landscape is too big and too complex to conduct a good scientific research. Therefore, research experiments that miniature large ecosystems are often recommended to make a realistic prediction of ecosystem process. Natural small scale habitats such as tree hole aquatic habitats provide basic features of a large aquatic ecosystem and offer several methodological advantages over lakes, streams, and other comparatively large systems (e.g. Maguire 1971). First, tree holes can be treated as individual units for sampling. Second, they are rich in species diversity and abundance, mainly those of insects (e.g. Kitching 2000). Third, water-filled tree holes are the most tractable small aquatic systems, partly because they are relatively persistent, and can be mimicked with plastic cups, bamboo sections, or other inexpensive materials. Furthermore, tree holes have a defined boundary and size. In such habitats, both biotic condition (e.g., predation) and abiotic condition (physio-chemical characteristics) vary greatly, which makes them easily colonized by specialized communities starting from autotrophic fungi to predaceous amphibians (Yanoviak 1999). Tree holes have short period for community colonization/ generation and therefore they can be manipulated the energy source. They have a definitive ecosystem boundary. Laboratory microcosm has the limited overgeneralization potential of the ecosystem (Carpenter et al. 1998, Srivastava et al. 2004) (Figure 1). Tree hole habitats are similar to artificial one such as plastic containers that can maintain natural conditions by accumulating rain water and fallen leaf litter. The heterotrophic community in such habitats is easily manageable and mimics natural realism — the two main characteristics required for experimenting model ecosystems. The tree hole aquatic ecosystem can be a model to test two principle ecological mechanisms: complementarity and selection (Loreau and Hector 2001). The ‘complementarity mechanism’