Browsing by Author "Gunaratne, A.M.T.A."

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    Does Clidemia hirta (L.) D. Don Affect Natural Regeneration from Soil Seed Bank in Halgolla Forest, Sri Lanka?
    (Uva Wellassa University of Sri Lanka, 2020) Wanigasinghe, I.M.; Gunaratne, A.M.T.A.
    Invasive plant species exert a significant impact on natural regeneration of tropical forests causing drastic changes in the future stand composition. Small isolated forest fragments surrounded by human habitation are more prone to plant invasions. Halgolla Forest Reserve (7018’N; 80031’E) is an isolated tropical lowland rainforest fragment in central Sri Lanka which is highly disturbed due to logging and illegal land encroachment. Clidemia hirta (L.) D. Don has established densely at the forest edges of this lowland forest fragment. Although, many studies have investigated the effect of this invasive species on standing vegetation, its effect on soil seed banks is poorly understood. Thus, this study investigated the impact of C. hirta on a seed bank in three habitat types in the forest; highly disturbed forest edge, less disturbed riverine area, and undisturbed forest interior. In each habitat type, 30 soil samples (10 × 62.8 cm3 ) were collected using stratified random sampling during dry and wet seasons. The seed bank was estimated by the germination method. Out of all emerged seedlings, 40.7% was represented by C. hirta seedlings while identified native seedlings represented 35.7%. The highest seedling density of C. hirta in the dry and wet season was recorded in riverine and edge habitats, respectively, though the values were not statistically significant between habitats. Species diversity and evenness were lower in highly disturbed forest edge in which the highest relative abundance of C. hirta was observed. The percentage emergence of native seedlings was negatively correlated with the emergence of C. hirta seedlings during both seasons. Low representativeness of native plant species in seed banks compared to C. hirta indicates the threat exerted by this invasive species on the natural regeneration of tropical lowland forests. Thus, it is crucial to eradicating this species to conserve the biodiversity of Halgolla Forest Reserve. Keywords: Clidemia hirta, Invasive species, Regeneration, Soil seed bank, Tropical lowland rainforest
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    Effects of Rainfall on Plant Survival in Restored and Unrestored Pine Stands in Lower Hanthana, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Lakmali, S.M.M.; Jayawardhane, J.; Gunaratne, A.M.T.A.; Nawarathna, L.S.
    Restoration is crucial to assist the recovery of degraded, damaged or destroyed ecosystems to promote biodiversity and ecosystem services. This study was conducted to identify the relationship between rainfall and plant establishment in an unrestored (UP) and a restored (RP) Pinus caribaea Morelet plantation, in lower Hantana, Sri Lanka. In RP, partial thinning of pines followed by enrichment planting of four broad-leaved tree species and total thinning of pines have been initiated. In both sites fifteen plots (5 m x 5 m) and within each of them three subplots (1 m x 1 m) were demarcated randomly. The number of leaves in plants, height, and diameter at breast height (DBH) in two sites were obtained (seedlings in sub plots and saplings and trees in plots). Effects of rainfall on the species density and survival of plant species in the two sites were investigated. Data were categorized as seedling (< 50 cm), saplings group I (50 - 129 cm in height), saplings group II (129 - 300 in height) and trees (> 300 cm in height). The rainfall data for the study period was obtained from the Meteorology Department, Sri Lanka. Data were analyzed using non-parametric statistical techniques using the SPSS statistical software. When comparing the establishment of woody plant species in the two sites, more species were recorded in the restored site for all categories except for saplings group II. However many plants died within the 6 months of the study period, due to various factors including herbivory damage and over dominance of Alstonia macrophylla. The mortality decreased with the increased rainfall in restored site than the unrestored site. According to Spearman's correlations coefficient of seedlings, the restored site has more powerful negative relationship between rainfall and mortality while mortality comparison with rainfall data shows that when rainfall is high, mortality of trees is tending to be low.