Abstract:
Invasive alien species constitute a major threat to biodiversity, which includes incidents of
species extinctions caused by invasive animals. However, while invasive plants are known to
affect to ecosystems and their native biota, there exists a deficiency of studies demonstrating
their long-term impacts and regeneration after eradication attempts. Horton Plains National
Park (HPNP) is a hotspot of biological endemism in Sri Lanka. Central Highlands, including
HPNP was declared as a UNESCO World Heritage, owing to the large number of endemic flora
and fauna inhabits it. Invasive plants have rapidly spread in HPNP during the last few decades,
Ulex europaeus, Aristea ecklonii and Ageratina riparia being the dominant. It has reduced
the availability of grassland for sambar deer and other animals causing potentially significant
threats to biodiversity. Present study focused on quantification of habitat regeneration after removing Ulex in 2016 through a project that attempted to eradicate Ulex from HPNP. A systemic
ground survey following a quadrant design was carried out to quantify regeneration in Ulex removal area totaling to about 53.7 ha. Five out of eight cleared blocks were randomly selected to
estimate the relative coverage of Ulex and other species regenerated. A total 133 plots (1 m x 1
m plot per ha) were surveyed using the visual encounter method to count all invasive and native
plants regenerated. Known invasive plant Aristea ecklonii and Pteridium revolutum were heavily abundant in Ulex removal areas. Garnotia exaristata, Pennisetum clandestinum Taraxacum
javanicum and Emilia sonchifolia were the most abundant among non-invasive native species
found. Ulex regeneration was notably high in regeneration plots and there was significant difference in Ulex abundance between the plots that were cleared three months and six months ago
respectively (paired t-test; p = 0.034), regeneration being rigorous in the latter. Cluster analysis also supported the above conclusion with dissimilar associations of regenerating species
between two types of plots with different time since last removal. Therefore the study confirms
the need for continued removal programs for the success of controlling Ulex in HPNP. This
study facilitated to identify a proper management strategy for removal of IAS distribution and
establishment of controlling mechanism for IAS in HPNP.
