科研之友
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摘要
Increasing emphasis has been placed on identifying traits of introduced species which predispose them to invade, and characteristics of ecosystems which make them susceptible to invasion. Habitat disturbance such as floods, fires and tree-falls may make ecosystems more prone to invasion. However, in this study the absence of fire was considered to be a factor in facilitating the invasion potential of a Madagascan endemic, Bryophyllum delagoense. Fire trials in South Africa killed 89 and 45% of B. delagoense plants in a high and low intensity controlled fire, respectively, with tall plants and those growing in clumps more likely to escape being killed. A reduction in the incidence and intensity of fires may therefore facilitate the invasion of B. delagoense and contribute to its invasive potential. Overgrazing, which reduces the frequency and intensity of fires probably facilitates the invasion of large and small succulent species. In South Africa, B. delagoense is still considered to be a minor weed or garden escape, despite its introduction to southern Africa 175 years earlier than in Australia, where it is extremely invasive. However, other succulents such as Opuntia species have become invasive on both continents, confounding our hypothesis that fire may be inhibiting B. delagoense from becoming invasive in southern Africa. However, closer analysis of Opuntia literature indicates that smaller species, similar in size to B. delagoense, are more likely to be killed, even by low intensity fires. We speculate that B. delagoense is more invasive in Australia because of a reduction in the frequency and intensity of fires and that fire is, amongst other factors, largely responsible for inhibiting its invasion potential in southern Africa.
- 出版日期2011-1
