Mapping the distribution of invasive shrub Austroeupatorium inulifolium (Kunth) R. M. King & H. Rob: a case study from Sri Lanka

A light loving invasive shrub, Austroeupatorium inuli­folium has been spreading many land use types in the Knuckles Forest Reserve (KFR) in Sri Lanka, including man-made grass­lands. In developing countries, there are limitations of using novel technologies to quantify and track the distribution of invasive spe­cies due to high costs and lack of facilities. This is a setback for their early detection and to introduce effective control measures. This pilot study attempted to map the distribution of A. inulifolium in man-made grasslands in KFR using high spatial multispectral images. Unsupervised, supervised and knowledge-based classifi­cations were performed to quantify the spatial distribution of A. inulifolium in ERDAS Imagine. The results generated compara­ble results of the extent of area under A. inulifolium by using the unsupervised (108 ha), supervised (94 ha) and knowledge-based classifications (93 ha). They were 18, 15 and 15% from the to­tal area selected for the study (622 - 646 ha), respectively. The results indicated the suitability of high spatial multispectral imag­eries in quantifying the spatial distribution of A. inulifolium. Fur­ther studies are recommended to investigate long-term changes in invasive plant population using multi temporal satellite data.