Bellyache bush: a resilient shrub in northern Australia

摘要

Bellyache bush (Jatropha gossypiifolia L.) is a perennial native shrub of South America that has become naturalised in northern Australia. It is now a major weed across the tropical regions of Queensland, Northern Territory and Western Australia. Theplant population dynamics of a dense bellyache bush infestation in north Queensland have been studied from September 2001 until August 2005. Density of bellyache bush plants >20 cm high declined from 20 plants m~(-2) to 5 plants m~(-2) during the low rainfall years (<400 mm year~1) from August 2001 to May 2003, but increased to 10 plants m~(-2) in subsequent years when rainfall was higher (>400 mm year~1). This increase is due to the survival of replacement plants (>20 cm high), which is highly correlated (R~2 = 0.96) with annual rainfall. Mean seedling (<20 cm high) densities as high as 61 plants m~(-2) were reached during the peak of the wet season but declined to zero and almost zero during the long dry seasons of 2002 and 2004 respectively. However, in the shorter dry seasons of 2003 and 2005 some seedlings were able to survive and grow. This study indicates that the density of bellyache bush populations declines during low rainfall years and rapidly regenerates when rainfall improves. This studyalso suggests that while plant densities can change significantly from year to year in response to moisture conditions, bellyache bush infestations are resilient and are likely to be permanent fixtures in the landscape unless control activities are initiated.