Abstract:
Although dung beetles are known to perform a multitude of ecosystem services, their effects on water
infiltration, runoff, porosity, moisture and erosion of soil have never been thoroughly researched. Maintenance of these hydrological properties is important in
agro-ecosystem functioning where over grazing
results in negative impacts on the soil. The study site was located in the Potshini catchment in Kwazulu-
Natal (South Africa), an area heavily grazed by livestock. We conducted two rainfall simulations on three
1m−2 control (no dung) and six dung-treated plots in December 2008, and repeated the study in June
2009 on the same plots. Natural populations of dung beetles were allowed to colonise the dung. Simulations were conducted for 30 min at an intensity of 30 mm h−1. Key variables calculated were pre-runoff
amounts (Pi), infiltration ratios (Ki), and soil losses. Samples were collected for bulk density determination during the same time periods in order to measure differences in porosity and moisture in control
and dung treated plots at different depths. Using multivariate statistics we found significant differences
between dung-treated and control plots in three of four simulations. After 48h of beetle activity, Pi and
Ki values were significantly increased and remained at elevated levels six months later. Soil losses were
initially higher in dung-treated plots than controls, but had declined to less than control values after
six months. Bulk density in the A -horizon (0–10cm) was significantly reduced after 48 h of beetle activity and remained so for six months. No difference in bulk density was observed at greater depths. Soil
moisture initially increased significantly in the A-horizon, as well as at 20 and 30 cm depths after six
months of activity. We conclude that dung beetles positively influence hydrological properties of the soil
by increasing water infiltration and soil porosity, and reducing surface water runoff. Contrasting effects
on soil losses are problematic to reconcile from this study. High losses initially observed may be offset in
the long-term by reductions associated with the increased infiltration ratios, though this remains to be
confirmed.
