NESTS OF ANTS AND TERMITES INFLUENCE INFILTRATION IN A SEMIARID WOODLAND

The effect of nest structures of funnel ants (Aphaenogaster barbigula) and subterranean harvester termites (Drepanotermes spp.). on infiltra tion was studied in a semi-arid woodland in eastern Australia. Disc pe rmeameters were used to measure steady-state infiltration under tensio n (-40 mm) and under pending (+10 mm) on a red earth soil. Ponded stea dy-state infiltration averaged 1026 mm h-(1) on soils with nest entran ces, but only 120 mm h(-1) on soils without nest entrances. Using nest entrances of varying apertures, a significant relationship was found between nest entrance diameter and steady-state infiltration (R(2) = 0 .65). There was no significant relationship between depth to wetting f ront and diameter of nest entrances: Ponded steady-state infiltration on sub-circular pavements constructed by subterranean harvester termit es was significantly lower (6.7 mm h(-1)) than infiltration in the ann ular zone surrounding the pavement (113.2 mm h(-1)) or in the inter-pa vement soils (103.6 mm h(-1)). The ratio of infiltration under pending to that under tension indicated the abundance of macropores in the an nular and inter-pavement zones, compared with the low ratio on the pav ements (1:1.4). The cemented surface of the pavement increases redistr ibution of water and nutrients from the pavements to the surrounding a nnular zone. By controlling infiltration, ants and termites, through t he construction of surface soil features, accentuate the development o f moisture-rich patches in an environment where moisture is limited.