THE EFFECTS OF GRAZING PRESSURE ON SOIL ANIMALS AND HYDRAULIC-PROPERTIES OF 2 SOILS IN SEMIARID TROPICAL QUEENSLAND

A grazing experiment was used to examine the effects of high grazing p ressure on soil Acari populations, and on termite populations and acti vity, at two sites in semi-arid north Queensland. Changes in soil hydr aulic properties were also examined. Our investigations have shown tha t Acari populations were significantly lower in the heavily grazed tre atments at one of the sites. Termite species diversity and activity we re significantly lower in the heavily grazed treatments than in the li ghtly grazed treatments at both sites. The surface soils also had sign ificantly 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 t reatments appears to be associated with both increased trampling by ca ttle and decreased termite activity in the top 25 mm of soil. The surf ace and near surface galleries constructed by detritiverous termites t herefore have an important function in water movement in these semi-ar id soils.