Biophysical effects on soil crack morphology in a faunally active dryland vertisol

Abstract

Abstract Faunal behavior in dryland ecosystems may physically influence swelling soil hydrologic and pedologic processes due to its contributions to soil crack formation. In order to provide a physical link between this faunal activity and pedological processes, we use a resin visualization technique and X-ray imaging to characterize the biomechanical influences of biocompaction (mega/meso-herbivores) and bioturbation (termites) on 3D crack morphology and topology in a faunally active dryland vertisol system. Results show increased soil cracking intensity due to faunal influence. However, this increased cracking diverged by faunal influence: bioturbation creates “surficial” (shallow, extensive) crack networks while biocompaction creates “systematic” (deep, narrow) crack networks, compared to a reference soil. Biocompacted soils also exhibit a memory of past wetting and drying events via vertically layered crack morphologies. Despite differences in these crack magnitudes between the faunal influences, crack structures show morphological and topological similarity as a topological network. These persistent differences in field crack systems may potentially create convectively-driven “hotspots” of enhanced water and carbon gas transport in dryland ecosystems as a result of crack formation, highlighting the importance of considering fracture behavior in both an ecological, atmospheric, and pedologic context.