The impact of fire on population density and canopy area of currant bush (Carissa ovata) in central Queensland and its implications for grazed woodland management

Abstract

Currant bush (Carissa ovata), where present in central Queensland beef cattle pastures, poses a severe constraint on the availability of herbage to domestic grazing animals and reduces the stock carrying capacity of the pasture. The impact of fire on population density and canopy cover of currant bush was investigated over 7 years. Seven burning treatments were imposed on plots heavily infested with currant bush and compared with an unburnt control. The treatments were: burnt once, burnt twice (12 months apart), burnt twice (20 months apart), burnt twice (24 months apart), burnt twice (32 months apart), burnt 3 times (20 months then 12 months apart) and burnt 3 times (32 months then 36 months apart).
Few existing currant bush plants died as a result of burning; however, fragmentation of the original plants increased plant numbers by an average of 22%. By greatly reducing the canopy of currant bush, fire gave cattle access to the pasture in those areas formerly occupied by currant bush. Measurements of canopy regrowth rates following burning indicate that regular burning, at least every 5 years, would contain the spread of currant bush without needing to attempt eradication of this native plant.