Rainfall and soil properties influence termite mound abundance and height: A case study with Odontotermes obesus (Macrotermitinae) mounds in the Indian Western Ghats forests

- Fungus-growing termite mounds are conspicuous features of tropical soils.
- Mounds provide an environment buffered against extremes of temperature and humidity.
- Odontotermes obesus is major mound building termite throughout India.
- Rainfall affects the abundance of O. obesus mounds in India.
- Amount of clay in the surrounding topsoil determines mound soil properties.

Several fungus-growing termite species build mounds, or termitaria, that are conspicuous features of African and Asian landscapes. Studies of the genus Macrotermes in Africa have established that their mounds provide an environment buffered against extremes of temperature and humidity, as well as protection from predators, and are correspondingly modified in composition. However, no studies are available in the specific context of the Asian continent where termite mounds are also abundant. Hence this study focused on the abundance and properties of mounds built by Odontotermes obesus in relation to rainfall and parent soil properties in southern Indian forests, in the Western Ghats area. Termite mound densities and sizes were measured in 18 forests along a rainfall gradient from 1160 to 3670 mm yr−1. The C and clay contents were analyzed in soil samples collected from mounds and the surrounding topsoil. Mound numerical density was positively correlated with mound height and rainfall had a negative relationship with the abundance. Neither vegetation type nor or rainfall influenced the clay content in the mound walls but a positive linear relation was observed between the clay content in the termite mound wall and that in the surrounding topsoil environment, suggesting a rather low impact of termites on the clay content in the mound soil. The C content in mound walls depended mainly on how much clay the termites used. In conclusion, this study shows that the amount of rainfall affects the abundance of O. obesus mounds in India while the amount of clay in the surrounding topsoil determines mound soil properties.