Dung beetles as hydrological engineers: effects of tunnelling on soil infiltration

Abstract

1. Soil infiltration capacity determines the partitioning of precipitationinto infiltration and overland flow and is therefore an important soil hydrologicalcharacteristic. Water infiltration through soil is facilitated by macropores created byroots and soil macrofauna. In clay-rich soils, such as those of the tropical forests ofSabah, Malaysian Borneo, most infiltration occurs via these preferential flow pathways. 2. We evaluated the effects of dung beetle tunnelling on infiltration and macroporecreation (depth and width of the flow pathways) in tropical forest soils in Sabah. Usingmesocosms, we applied three treatments (i) soil-only, (ii) dung-only, (iii) dung+dungbeetles, and measured saturated hydraulic conductivity (i.e., the steady-state infiltrationrate) after 0, 5 and 10 days, and assessed depth and width of infiltration pathways byapplying a blue dye tracer. 3. The steady-state infiltration rate increased in the presence of dung beetles, thoughdifferences among treatments were only statistically significant after 10 days. After5 days of dung beetle presence, infiltrated water had reached a greater depth than thecontrol mesocosms without beetles. However, there were no differences in the width ofinfiltration pathways among treatments. 4. These results reveal the important, but under studied roles of dung beetles on soilhydrological functioning, that may have consequences for nutrient cycling and plantproductivity. Further, our findings indicate that the novel application of an establishedhydrological method–blue dye tracer–can provide interesting and reliable results formacrofauna–soil interaction studies