THE EFFECT OF ANT BIOPORES ON WATER INFILTRATION IN SOILS IN UNDISTURBED BUSHLAND AND IN FARMLAND IN A SEMIARID ENVIRONMENT

Data were collected on the morphology of selected ant species' nests i n farmland and naturally vegetated environments on two contrasting soi ls. The majority of ant nests have one central channel or biopore with chambers branching off the channel. The ant biopore ranges in diamete r from 1 - 200 mm and can extend to depths of 60 cm below the soil sur face. The nest entrance or biopore remains open virtually all through the year. Biopore densities range from 0.7 to 1.9 biopores m-2 in the vari us habitats with lower biopore densities in grey sandy loam compa red with yellow sand sites regardless of land use. The effect of ant b iopores on water infiltration was measured in situ using the disc perm eameter at negative (- 5, - 10, - 40 mm) tensions and at positive (+ 1 0 mm) pressure. The effect of ant biopores on steady-state water infil tration rates was not significant at - 10 and - 40 mm negative tension s. However, when tensions were raised to - 5 mm there was a detectable difference between water infiltration rates over the control area and the rates recorded over ant nests. But it was only under positive pre ssure that water infiltration over ant nests was significantly greater than the control soil. Hence ant biopores will only transmit water do wn the soil profile when the soil is saturated and water is ponding on the soil surface.