N.M. CLARKSON¹ and G.R. LEE²

¹Queensland Department of Primary Industries, Toowoomba, 4350.
²Queensland Department of Primary Industries, Bundaberg, 4670.

Abstract

Changes in ground cover, botanical composition and dry matter vield of a native pasture, grazed with sheep at 4 stocking rates in the traprock region of southern Queensland, were followed from 1962 to 1969. This period included a record drought throughout 1965.
Heavy stocking (0.27 ha/sheep with one sixth of the area lucerne) reduced ground cover but the greatest reduction was caused by the drought. Cover declined from 13.9% in 1962 through 9.6% in 1966 at the lowest stocking rate (0.8 ha/sheep) and 6.1 % at the highest, to an average of 7.6% in 1969.
Heavy stocking reduced the content of Dichanthium affine, Sporobolus elongatus and Aristida ramosa whereas Dichondra repens temporarily increased. Drought caused major reductions in the dominant and most valuable species Bothriochloa decipiens and Dichanthium affine. Increases in the less productive Chloris divaricata, Tripogon lohiformis, Enneapogon gracilis, and Dichondra repens occurred after the drought ended.
Pastures showed no recovery towards their pre-treatment levels of ground cover and botanical composition after 12 months free from grazing. At the lighter stocking rates dry matter yields had increased considerably, but at heavier stocking rates they remained depressed.