Spatial distribution of invasive alien plants in Pokhara valley, Nepal.
Urban areas often provide suitable microhabitats for the establishment of invasive alien plants (IAPs), which subsequently disseminate their propagules for further spread in surrounding landscape. Periodic survey of IAPs in urban areas not only brings opportunities for early detection and eradication of the invaders but also generate science-based information for the management of established IAPs. In this study, we inventoried IAPs and documented their spatial distribution in Pokhara valley, a popular tourist destination in Nepal. Using a checklist of 26 IAPs that have been reported from Nepal, we examined roadside vegetation in 201 plots (size: 5 m x 5 m) located at the interval of ca. 500 m in the valley. In each plot, the IAPs present were recorded along with geographic coordinates and land use type. Field data were used to calculate species richness, frequency, and prepare distribution maps of the IAPs. In Pokhara valley we recorded 20 IAPs, i.e. 77% of the total number of IAPs reported from Nepal. Four of the recorded IAPs: Chromolaena odorata, Eichhornia crassipes, Lantana camara and Mikania micrantha were among the 100 of the world's worst invasive species. Bidens pilosa had the highest frequency (63%), followed by Ageratum houstonianum (61%) and Lantana camara (44%). Small population of Alternanthera philoxeroides, and Mesosphaerum suaveolens were spotted at a single locations and Mikania micrantha at two locations, suggesting that they were at the early stage of invasion in the valley. Richness of IAPs was the highest in shrub land, followed by agriculture fallow land, and forest. Our data revealed that the Pokhara valley has already been invaded by a large number of IAPs, with possibility of arrival of new IAPs in near future. Periodic inventory and mapping of the IAPs would be helpful in identifying new IAPs and making management decisions timely.