Termites play a crucial role in forming major tropical soils: insights from a deep Ferralsol

Soil bioturbation is increasingly recognized as a key driver of pedogenesis in tropical ecosystems, influencing above- and below-ground biodiversity, nutrient cycling, and aggregate stability across different spatial and temporal scales. This ecological process may play a particularly critical role in the formation of deep, highly weathered soils, where the physical and chemical properties alone cannot fully explain the observed complexity. Ferralsols, which dominate tropical soils, are renowned for their micro-granular structure, which is fundamental to their high physical fertility. However, the mechanisms underlying the pervasive presence of this structure throughout the soil profile remain poorly understood. In this study, we document active termite bioturbation at depths of 10–14 m in a Ferralsol from the Brazilian Cerrado. We showed that the termite species Nasutitermes corniger builds chambers and galleries at these depths. Structural and microscopic analyses revealed that their activity penetrates the dense groundmass, producing and redistributing micro-granular fragments. We propose a novel conceptual model in which termite burrowing occurs near the weathered rock–soil interface, where termites excavate dense clayey material resulting from rock weathering, form galleries, and refill older voids with fragmented dense clayey material. Over geological timescales, this sustained biological activity drives the development and renewal of the micro-granular structure throughout the entire volume of the Ferralsol. Finally, our findings underscore the critical role of ecological/biological processes in soil formation and highlight the potential importance of preserving or emulating such biological processes in land management strategies. This may be essential for sustaining soil functions that are vital to global environmental stability.