Invasive alien species in relation to edges and forest structure in tropical rainforest fragments of the Western Ghats

摘要

The impact of invasive alien species on native ecosystems is a major conservation issue in the tropics. This study in the rainforest fragments of Anamalai hills, in the Western Ghats biodiversity hotspot, assessed the effects of distance from edges and forest structure on the occurrence and abundance of three invasive alien species (Chromolaena odorata, Lantana camara, and Maesopsis eminii). Replicate line transects were laid from the edges into the interiors of four fragments varying in disturbance level and area (32 ha - 200 ha). Densities of alien species in the protected site were lower than in the three disturbed fragments. Maesopsis eminii occurred at highest density (382 trees ha(-1)) in the highly disturbed site where it also showed prolific regeneration (1510 saplings ha(-1)). The invasive alien species showed no clear edge-to-interior pattern, instead their abundance appeared to be localized and related in a site-specific manner to disturbances such as presence of Eucalyptus plantation, canopy openings, and trails.