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INTRODUCTION
Termites are intimately associated with soils through their nesting, tunnelling and feeding activities. Most species build subterranean or epigeal nests, and most wood-nesting species maintain some contact with the soil substratum. While many termites feed on dead wood, and some forage on grass or leaf litter, around 50% of species feed directly on mineral soil or humus (Brauman et al. 2000). Termites can achieve very high population densities in tropical soils (Bignell & Eggleton 2000), and are known to have a major influence over decomposition, mineralization, the redistribution of organic matter, soil structure and soil quality (Brauman 2000, Holt & Lepage 2000, Ji & Brune 2006, Lee & Wood 1971, Mando et al. 1996).
In contrast to the considerable amount of research investigating how termites affect soils and soil processes, there has been surprisingly little research on the extent to which soil type and soil properties influence termite distribution and ecology. Many studies have assessed termite assemblages (Bignell & Eggleton 2000) but most of these have not characterized the local soil. Only a few studies have shown that termites avoid soils with particular physical or chemical properties. Wild (1975) reported that termites are mainly absent from grassland on ultramafic (also known as serpentine) soils in Zimbabwe, where only two species were found, in stark contrast to neighbouring areas on non-ultramafic soils where termites were much more abundant and diverse. Harris (1963) compared eight woodland and savanna sites in Congo, and found relatively high species richness and frequency of termites in soils at all sites, with the exception of one site on sandy soil in which termites were absent. Very sandy soils may have insufficient cementing agents, such as clay and other fine colloid material, to allow termites to build mounds and subterranean galleries (Lee & Wood 1971). Ratcliffe et al. (1952) reported termites as virtually absent from the heavy clay soils of inland north-eastern Australia. The physical characteristics of these soils, which crack deeply and widely in dry periods and become waterlogged in wet periods, are thought to preclude termite survival, although this has been partly refuted by Holt & Coventry (1982). Finally, in habitats that have a high water table or are regularly inundated,...