Termite mounds impact soil hydrostructural properties in southern Indian tropical forests

Mounds built by fungus-growing termites are often considered to be patches or fertile areas in tropical ecosystems because they contain more nutrients than the surrounding soil environments. However, the mechanism of how these habitats influence soil physical properties remains unknown. Therefore, this study aimed at comparing the soil hydrostructural properties of two common termite mounds in southern India, namely, cathedral and lenticular mounds. The shrinkage curves of the soil eroded from three cathedral mounds and of the soil sampled in the center or in the periphery of three lenticular mounds were measured and compared to those of their surrounding soil environment. This study revealed that the soil in the periphery of cathedral mounds was compact with a lower soil specific volume and macroporosity than the control soil. On the other hand, the accumulation of clay in lenticular mounds was associated with a lower soil specific volume at the end of the shrinkage period, higher microporosity, increased swelling capacity and higher water holding capacity than the control soil. These parameters reached intermediate values in the periphery of the lenticular mounds between those of the lenticular mound soil and the surrounding control soil. In conclusion, this study showed that cathedral and lenticular mounds impacted soil hydrostructural properties in two opposing directions. It also highlighted the link between the impact of termites on the clay and carbon contents of soil and their influence on soil porosity and water dynamics, and then the need for a better understanding of the influence of termites on the dynamic of carbon and clay in ecosystems