Browsing by Author "Amarasinghe, M. D."

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An ethnobotanical approach to control Typha angustifolia: A case study from Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Madushani, K. P. K.; Amarasinghe, M. D.; Ratnayake, R. M. C. S.; Dahanayaka, D. D.G. L.
Typha is a cosmopolitan genus that is infamous globally for having nuisance plant species. In Sri Lanka, Typha angustifolia is distributed in both coastal and inland wetlands, including lagoons, paddy fields, and small reservoirs. Pervasive effects of Typha include hindrance to fishing activities, navigation, agriculture, human health, and ecosystem functions, especially provision of habitats for wading birds in coastal lagoons. The present study attempted to formulate an ethnobotanical strategy to control the distribution of Typha in Embilikala lagoon in Bundala National Park in Hambantota District in Southern Sri Lanka. T. angustifolia edible plant parts were tested for antioxidant activity to promote it as a phytonutrient that boosts the overall health of the body. Hexane, methanol, and aqueous extracts of leaf, leaf base, rhizome, and pollen of Typha were analyzed with DPPH and ABTS bioassays for the presence of antioxidants. Leaves were tested for their quality as raw material for making paper using the mould and deckle pouring method and couching technique. Methanol was found to be superior to hexane and deionized water as a solvent for both the assays. Leaf base (99.5±5.3 μg/mL) and rhizome (65.3±0.6 μg/mL) of T. angustifolia showed higher radical scavenging activity, and in some instances, higher than that of standard butylated hydroxytoluene (BHT) (119.3±4.5 μg/mL), indicating their potential as sources of bioactive compounds that can reduce free radicals. Contents of heavy metals (Arsenic: 0.338±0.040, Cadmium: 0.628±0.146, Chromium: 63.641±1.30, Lead: 15.657±1.70 ppb) in the rhizomes were below the standard permissible level (100.0 ppb). Pulp made with Typha leaves alone and a mixture of Typha (95%) and wastepaper (5%) were used successfully to produce writable paper. Findings suggest that T. angustifolia, which is widely considered as an invasive plant and marginally utilized currently, has a promising potential to be exploited as food and raw material to introduce new livelihoods to rural communities. This ethnobotanical approach may potentially be used to control the distribution of T. angustifolia in wetlands where it is found in invasive proportions.
Impact of climate and irrigation practices on hydrological aspects of Bundala wetlands in Sri Lanka
(Irrigation and Drainage, 2023) Patabendige, K. M. K.; Amarasinghe, M. D.; Ratnayake, R. M.
Bundala wetlands are the first to be declared a Ramsar wetland reserve in Sri Lanka. Two wetlands of this complex have transformed from seasonally inundated saline areas into permanent freshwater ecosystems, resulting in spatial and temporal changes that presumably have favoured plant invasions. We hypothesized that climate/rainfall changes and irrigation practices would be the most potential drivers of this change, and the objective of this research is to empirically determine the influence of rainfall and irrigation practices in the catchment on inundation pattern and plant nutrient availability that could potentially change ecology of these wetlands. Monthly rainfall data for the Bundala area (1988–2017) from Sri Lanka's meteorological department were analysed by parametric and nonparametric statistical methods, and a statistically significant change in rainfall was not discernible, confirming climate change is unlikely to be a driver to increase the lagoon water level. Irrigation data analysis revealed that these wetlands receive nearly 1.28 × 107 m3 of irrigation drainage annually from an irrigation scheme in the immediate catchment, which has resulted in decreased salinity, while inundation and plant nutrient content increased, changing the wetlands' ecology and socioeconomic status of the dependent rural communities.
Spatial distribution and dynamics of selected mangrove forests on the east and west coasts of Sri Lanka
(Sri Lanka Journal of Aquatic Sciences, 2022) De Silva, W.; Perera, K.A.R.S.; Amarasinghe, M. D.
The climate and edaphic characteristics primarily determine the spatial distribution and dynamics of mangrove forests. The present study was initiated to determine how species composition and structural characteristics vary along with climate and substrate salinity of six mangrove forests located on the west coast, i.e., Negombo estuary, Chilaw lagoon, and Malwathu oya estuary, and east coast, i.e., Batticaloa lagoon, Uppar lagoon, and Urani lagoon. The structural parameters in terms of tree height, basal area, biomass, and density were obtained to determine the vegetation structure of mangrove forests. The current study found that although the structure of mangrove communities of the two coasts does not differ significantly (P<0.05), plant diversity in mangrove areas on the west coast is significantly higher than that of the east coast mangroves. In contrast, the biomass accumulation in west coast mangroves is relatively lower than that of east coast. Tree height was found to influence the productivity in terms of biomass increment of mangrove forests under investigation. As such, our study suggests that regional variations in salinity, temperature, and rainfall primarily serve as drivers of variation in mangrove species composition and vegetation structure of mangrove forests along the coasts of Sri Lanka.