Factors contributing invasion of Alien Invasive Species prosopis juliflora in Bundala National Park in Sri Lanka

Abstract

Bundala National Park (BNP) is a thorny shrub forest with a total extent of 6210 ha, consist of 13 habitat types; seven terrestrial types and six wetland types. Because of its precious biodiversity, Ramsar Convention considered the park as the first Ramsar site in Sri Lanka declared in 1990, and a Man and Biosphere reserve declared by UNESCO in 2005. Considering the threats, which have BNP faced, spreading of alien invasive species inside the park is considered as the most serious. Among them, Prosopis juliflorais considered as the most dangerous which has almost covered over 60% of the entire park. The study was conducted to evaluate the factors contributing to invasion of invasive Prosopis juliflora in Bundala National Park by understanding the factors enhancing invasiveness and suppressing native vegetation, allelopathic effects and mode of dispersion of P. juliflora. Our results strongly inferred that spreading of invasive P. juliflora has been imposed a significant ecological damage by suppressing native vegetation. The environmental and soil factors (salinity) enhance the P. juliflora growth while low sunlight and salinity are key external factors suppressing native vegetation in BNP. In addition, P. juliflora has allelopathic effects on native vegetation but impact is species dependent. Asian elephants and other ruminants fed on P. juliflora have great impact on P. juliflora seed dispersion throughout the BNP. The saline soil and high temperature regimes with other microclimatic conditions enhance the germination of dispersed P. juliflora seeds. Therefore, above factors should be taken into consideration for implementing effective management programs of P. juliflora.