An evaluation of large scale aerial photography for assessing range condition in central Australia.

Abstract

Largc scalc colour aerial photography was investigated as a method for assessing range condition of semi-desert rangelands in central Australia. Herbage layer spcics were selected which were good indicators of condition in three rangeland types, Open Woodland, Mulga with annual grasses and forbs and Mitchell grass Grassland. Two methods of photo interpretation were used in an attempt to distinguish between sites in different range condition on each of these rangeland types. These were: quantitative point counts on these indicator species; and qualitative visual rating scales of range condition. Both interpretation methods were successful on Mitchell Grassland where structure and colour of large tussock grass species aided photointerpretation. Smaller simd grass species, and differences between observers in their interpretations caused the methods to fail on the other rangeland types. This programme of testing was an intensive and thorou~rh one, and the results would indicate that further development of large scale aerial photography as a nionitoring tool for range condition is not warranted for rangelands in central Australia. In addition a comparison of both ground and aerial methods of range condition survey did not glve the aerial methods any advantage in time, cost or ease of operation.