X‐ray tomography analysis of soil biopores structure under wetting and drying cycles

Soil macroporosity is a highly dynamic feature driven by numerous physical and biological processes, of which bioturbation, the movement of water in soil and swelling and shrinking cycles are the main processes. To date, the interaction between these factors, especially how galleries produced by soil fauna respond to rainwater percolation and wetting-drying (WD) cycles, remains poorly known. A laboratory experiment was carried out to expose soil macrofauna galleries to 3 different consecutive water flow (simulated rain event of 50, 80 and 110 mm h-1 in one hour) and drying cycles in a clayey soil. X-ray computed tomography and image analyses were used prior and after each exposure to assess the water stabilities of galleries and created cracks. The 3D properties (volume, diameter, specific surface area and density) of the galleries produced by termites or ants were not statistically influenced by rainwater percolation and WD cycles, suggesting a high water stability and life expectancy under natural conditions. Conversely, the crack water stability was variable and was probably influenced by the presence of galleries in the same area. This study emphasizes that the macropores created by soil fauna may persist in clayey soil and that there is a need to better understand how cracks and galleries interact.