Long term changes in arid zone vegetation at Koonamore, South Australia.

Abstract

The vegetation of areas grazed continuously by sheep since 1870 and those protected from grazing since 1925, in the Koonamore Vegetation Reserve, South Australia were compared. Irrigated small plots were used to study possible mechanisms of development of observed vegetation differences between the 7 sites in Stipa nitida which was more abundant in protected areas and Schismus barbatus which was more abundant in grazed areas. The soils in the protected area were more fertile, less compact, higher in OM content and had a better developed lichen crust than in grazed areas. The difference in S. nitida was attributed to direct grazing selection, and in S. barbatus to physical or chemical properties of the lichen crust affecting its germination and growth. Most ephemeral spp. studied could germinate and establish in most seasons except mid-summer and mid-winter. Previous unevaluated data on longevity of Atriplex vesicaria, Acacia aneura and Kochia sedifolia showed they lived to max. of 30, 300 and several hundred yr, resp. In the latter 2 spp. mortality exceeded replacement even in protected areas and it was predicted that they would disappear under grazing.