Studies in the ecology of the Riverine Plain. V. Plant density response of species in a Danthonia caespitosa grassland to 16 years of grazing by Merino sheep

Abstract

The species density of 252 permanent quadrats set in plots which were ungrazed and lightly, moderately, and heavily grazed, in a Danthonia caespitosa Gaudich. grassland, was measured on seven occasions between October 1949 and October 1965. The field data were analysed by means of a Response Index and a Grazing Pressure Index to give the grazing responses of 41 individual species. Those species favoured either by grazing or by non-grazing are listed, and their performance examined in relation to published data on the dietary selection exercised by Merino sheep. The present D. caespitosa grassland is a disclimax one resulting from the grazing of domestic and feral animals, and most species have already come into equilibrium with the total environment. It is suggested that the observed reductions in plant density, size, and the seed crop of annual species in the grazed plots was not followed by the elimination of any species because stocking rates applied in the experiment were no more severe than those which brought about the development of the grassland. The possible unique nature of long-term exclosures in a disclimax grassland is noted.