INVASIVE PLANT SPECIES IN THE DISTURBED FOREST OF BATUKAHU NATURE RESERVE, BALI, INDONESIA
Patterns of invasive plants distribution and their underlying mechanisms are complex and may vary with spatial scale. Within the mountainous tropical ecosystems of Bali Island, a local scale of patterns of invasive plants is still poorly understood. This paper aimed to detect and investigate the presence of invasive species and to evaluate their relative abundance linked to forest site condition along an elevation ranges on Mount Pohen, Batukahu Nature Reserve, Bali, Indonesia. To identify the importance of environmental disturbances on species invasion, the disturbance-environmental factors and the species-environmental relationship were also measured and examined. A total of 78 vegetation plots of 2x2 m size were established in four forest sites using the stratified random sample. Ten invasive plant species belonging to ten generaand five families in the study area were identified. Of these invasive species, 40% were herbs, while shrubs and grasses comprised 30% respectively. Austroeupatorium inulaefolium occurred at the highest frequency (45% of plots); followed by Ageratina riparia, and Brachiaria reptans (40% of plots respectively), Melastoma malabathricum(37%), and Calliandra calothyrsus (27%). Austroeupatorium inulaefolium was the most abundant invader, followed by Ageratina riparia, and the remaining invasive species were, in order, Pennisetum purpureum, Calliandra calothyrsus, Imperata cylindrica, Brachiaria reptans, Melastoma malabathricum, Lantana camara, Bidens pilosa, and Blumea lacera. The results demonstrated that the distribution of invasive plants was strongly linked to the disturbance level of the according habitat. The largest numbers of invasive plants were present in burnt sites close to the forest edges with direct anthropogenic influence, while the undisturbed forest was the least invaded site. Further, the results demonstrated that most invasive species were mainly occurred at low elevations up to 1600 m a.s.l. and were rarely found in higher elevations. However, few invasive species such as Austroeupatorium inulaefolium and Melastoma malabathricumwere also able to colonize the highest altitude (2035 m a.s.l.), and to a lesser degree, Ageratina riparia and Brachiaria reptans were also distributed into high altitude areas (1950 m a.s.l. and 1972 m a.s.l. respectively). This study provides a fine-scale analysis of invasive species distribution in this protected area which can be used as a reliable basis for conservation purposes, especially for strategic planning regarding the detection and management invasive alien plants.
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