Bioturbation by dung beetles and termites. Do they similarly impact soil and hydraulic properties?

In the tropics, termites and beetles are considered key soil bioturbators regarding their impacts on many ecosystem services. The aim of this study was to compare the functional impacts of these two soil engineers in a seasonally dry tropical forest in southern India. The soil excavated by dung beetles and termite sheeting found at the soil surface were sampled and compared to the surrounding topsoil environment. We showed that soil sheeting had very similar soil particle sizes and C content as the surrounding topsoil while the soil excavated by beetles was enriched in C and gravels in comparison with the topsoil. Bioturbation by dung beetles was also associated with the production of vertical tunnels that significantly decreased soil bulk density and constituted a preferential flow path for water to infiltrate (37-fold increase in comparison with the surrounding topsoil). Termite activity was also associated with the production of macropores. However, termite galleries were narrower and less vertical than dung beetle macropores, consequently leading to a positive but rather limited impact on the water hydraulic conductivity (Ksat) in comparison with that of dung beetles (i.e. from 2 to 8-fold increase). In conclusion, this study showed that soil engineers have different bioturbation impacts, dung beetles having locally a larger impact on soil dynamics and properties than termites. More research is now needed to understand the consequences of these bioturbations on the fate of C in soil and on water dynamics at larger scales.