Lal. Debruyn et Aj. Conacher, THE EFFECT OF ANT BIOPORES ON WATER INFILTRATION IN SOILS IN UNDISTURBED BUSHLAND AND IN FARMLAND IN A SEMIARID ENVIRONMENT, Pedobiologia, 38(3), 1994, pp. 193-207
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.