Impact of fire on rubber vine (Cryptostegia grandiflora R. Br.) and associated pasture and germinable seed bank in a sub-riparian habitat of north Queensland

Abstract

Effects of two annual late season fires on dense rubber vine (Cryptostegia grandiflora R.Br.) infesting a sub-riparian habitat in the dry tropics of north Queensland were investigated. Standing pasture biomass and quality and germinable seed bank of monocotyledons and dicotyledons (including rubber vine) were determined. The first fire significantly (P<0.05) reduced the rubber vine population by 80% (from 2560 plants ha-1 to 512 plants ha-1). A second fire a year later extended the kill rate to 99% (to 18 plants ha-1). The relative sensitivity to the imposed fire regime was juvenile >mature >old plants. No significant differences in standing pasture biomass occurred as a result of fire treatments. However, pasture quality was significantly improved after the first fire. Fire significantly affected the germinable seed bank of both dicotyledons and monocotyledons. The total germinable bank of dicotyledon and monocotyledon seeds was reduced by 52 and 78% after the first and second fire respectively. No rubber vine seeds were detected in the seed bank of either burnt or unburnt plots. We suggest that the present fire prescription may not only be a viable management method of reclaiming densely infested sub-riparian habitats but may also facilitate the use of mechanical or chemical control to clean up remnant infestations.