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Title: The Ecology of Invase tree species in Singapore
Keywords: invasive, tree, Singapore
Issue Date: 19-Aug-2010
Citation: NGHIEM THI PHUONG LE (2010-08-19). The Ecology of Invase tree species in Singapore. ScholarBank@NUS Repository.
Abstract: Invasive species have been recognized as one of the main threats to biodiversity. Invasive trees, however, are relatively understudied compared to other taxa, especially in Tropical East Asia. This study was conducted on invasive trees in Singapore: an ideal study site for tree invasions in Tropical East Asia because it is a `worst case scenario? for invasibility, with a high level of deforestation, intensive land-use, and numerous deliberate tree introductions. Seventeen naturalized tree species were identified from a thorough literature review, communicating with local botanists and extensive field surveys in Singapore, and nine of these were considered invasive: Acacia auriculiformis, Cecropia pachystachya, Falcataria moluccana, Leucaena leucocephala, Manihot carthagenesis ssp. glaziovii, Muntingia calabura, Piper aduncum, Pipturus argenteus and Spathodea campanulata. These tree invaders were common in open sites, such as reclaimed land, wasteland, and forest fringes, but they were not found in native closed-canopied forests. The survival and growth of eight invasive tree species was investigated experimentally at an open site and in the understorey of a native closed-canopied forest. All species survived and grew well in the open, with Leucaena growing fastest and Spathodea slowest. No species grew significantly in the forest. For Acacia, Falcataria, Muntingia, and Manihot, 95-100% of seedlings died within 20 weeks after planting, but 10-25% of seedlings of Cecropia, Leucaena, Piper and Spathodea survived until the end of the experiment after 1 year. These four species are a potential threat to disturbed native forests. A comparison of functional traits showed that invasive tree species were not different from native pioneer tree species in terms of wood density, dry seed mass, height, leaf area, or flower sexual system. Invasive tree species differed from widely planted but non-invasive tree species in their lower wood density, smaller dry seed mass, larger distance to their natural range, and greater likelihood of being dioecious, but did not differ significantly in height, leaf area, residence time or dispersal mode. These results suggest that invaders are similar to native pioneer species and different from non-invasive species. The overall conclusion is that none of the invasive tree species studied is a serious threat to undisturbed native forest, although some of the naturalized but not yet invasive species may be so in the future. Of more immediate concern is the ability of invasive trees to dominate new successional forests outside the nature reserves. The long term trajectory of these forests is currently unknown and should be the subject of further research.
Appears in Collections:Master's Theses (Open)

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