Termite activity in tropical and subtropical Brazilian soils

Termites, key members of the soil macrofauna, play a significant role in bioturbating soil through their construction activities, essential for their mobility and survival. Despite extensive studies on the alterations caused by mound construction, the full impact on soils, particularly in the Americas, remains inadequately understood. This study hypothesized that termites selectively engage with specific soil materials, a theory tested by comparing the sand and clay fractions of soils and mounds at six sites across five Brazilian states. Sedimentological analyses were performed on the sand fraction, while the mineral fraction underwent X-ray diffraction, magnetic susceptibility, and selective iron oxide dissolution tests. The findings reveal that termites prefer smaller sand particles when constructing mounds in sandier soils. In most locations, termites concentrated up to 79.9% of Fe and 65.3% of Al from pedogenic iron and aluminum oxides, and up to 31.1% of Fe from poorly crystalline forms. Magnetic susceptibility measurements indicated minimal differences in magnetic minerals between mounds and soils. Termites do not alter the mineral composition of highly weathered soils, which primarily consist of kaolinite, gibbsite, and iron oxides. However, they selectively target clay-sized particles in sandy soils. Therefore, termites are not considered weathering agents in highly weathered soils dominated by stable minerals. These results underscore the significant role of termites as bioturbators in soil dynamics.