The effects of grazing pressure on soil animals and hydraulic properties of two soils in semi-arid tropical Queensland

A grazing experiment was used to examine the effects of high grazing pressure on soil Acari populations, and on termite populations and activity, at two sites in semi-arid north Queensland. Changes in soil hydraulic properties were also examined. Our investigations have shown that Acari populations were significantly lower in the heavily grazed treatments at one of the sites. Termite species diversity and activity were significantly lower in the heavily grazed treatments than in the lightly grazed treatments at both sites. The surface soils also had significantly lower steady-state how rates and hydraulic conductivities in the heavily grazed treatments than in the lightly grazed treatments. The deterioration in soil hydraulic properties in the heavily grazed treatments appears to be associated with both increased trampling by cattle and decreased termite activity in the top 25 mm of soil. The surface and near surface galleries constructed by detritiverous termites therefore have an important function in water movement in these semi-arid soils.