Effect of spring wild fires on Iseilema (Flinders grass) populations in the Mitchell grass region of north-western Queensland

Abstract

The effect of spring wildfires and consequent ashbeds on the emergence and survival of the annual Iseilema spp. (Flinders grass) was studied in field and pot experiments during favourable growing conditions between December 1976 and April 1977. Emergence of Iseilema seedlings was lower on burnt than unburnt treatments when the amount of litter present at burning was 100 g m-2 or more. Litter had a major influence on emergence in unburnt areas. Initially there was a rapid increase in emergence with increasing litter followed by decreased emergence with a further increase in litter. Microtopography had no effect on emergence in unburnt treatments but there were significantly more seedlings in depressions (750 m-2) than on flats or rises (240 m-2) in burnt areas. The number of tillers per plant was greater in burnt areas than in unburnt areas at the same density, especially when the density was lower than 500 m-2. At higher densities, the number of tillers per plant decreased in both treatments. Seedling survival was greater in burnt areas in the early stages of establishment but, by maturity, survival was highest in the unburnt areas.