The role of termites and ants in soil modification - a review

Abstract

The review examines the literature concerning the effects on soil profile development of ants (Hymenoptera: Formicidae) and termites (Isoptera), two prominent insect groups in the Australian environment. Their pedological influence is largely through the construction of nests, galleries, soil sheetings and mounds. Some of the pedological effects are manifested in the physical modification of the soil profile through selecting, transporting and rearranging soil particles. Within this group, findings in areas such as soil turnover, mound longevity, bioturbation, soil structure and water infiltration are discussed. Termites contribute actively to soil turnover, and the contribution of termite sheetings and ant mounds to soil turnover is also being recognized. Termite mounds may persist in the landscape for more than two decades, while ant mound longevity varies from weeks to decades. Information on the effects of ants and termites on soil structure and water infiltration is sparse; but ants and termites seem to either increase infiltration by improving soil structure and porosity, or to decrease infiltration by producing compact surfaces which assist runoff and erosion. Other effects involve the chemical alteration of the soil profile by ants and termites collecting and transporting live and dead animal and plant materials to their nest structures, and by the additions of secretions and excreta in nest construction. The majority of ants and termites probably increase carbon and nutrient levels, especially nitrogen, phosphorus and potassium, as well as exchangeable magnesium and calcium. The extent of the increases depends greatly on the type of mound construction and the degree to which organic material is incorporated. Problems with research techniques include the use of a variety of sampling techniques by different researchers, lack of detailed soil description or classification, and inadequate description of location of sampling points. These deficiencies make it difficult to draw valid comparisons between research projects. Many researchers also base their generalizations on ant or termite soil modifications on a small number of samples, although during the 1980s there has been an increase in sample sizes. Contradictory data often result from projects being undertaken on different species and in different environments. Future research directions need to include a greater concentration on the morphology of ant nests, more detailed assessment of the influence of ants and termites on soil structure and water infiltration, an increase in biopedological research in human-modified environments, a greater emphasis on termites and ants other than the most dominant or prominent species, and a focus on community as distinct from single-species effects.