Browsing by Author "Kodikara, K. N."

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    Assessment of the potential distribution areas for two endemic plant species of Sri Lanka under climate change by species distribution modelling
    (Faculty of Science, University of Kelaniya Sri Lanka, 2022) Kodikara, K. N.; Vidanage, S. P.; Kadupitiya, H. K.
    Climate Change is arising as a major threat on biodiversity. Long term climatic conditions have direct links with the occurrence or prevalence of a species in a particular locality. Early predictions facilitate making necessary management options to reduce the negative impacts of this phenomenon. Calophyllum walkeri is a severely affected species from the dieback. It has a conservation status as vulnerable. Syzygium rotundifolium is a range restricted species. Both are endemic to Sri Lanka and dominant species in montane forests. The objective of this study was to predict the best suitable areas for both species currently and by 2070. Maximum Entropy (MaxEnt) modelling method was used, due to its accuracy and well performance even with small sample sizes as the number of records for Calophyllum walkeri was very low. Secondarily obtained data from the National Herbarium for the whole country were used for Calophyllum walkeri (n=29) and primarily obtained presence only data by field surveys covering the whole study area namely Horton Plains National park along with secondary data for less accessible places for Syzygium rotundifolium were used as species occurrence data (n=55). Climate data were obtained through the databases of WorldClim website which contains climate data as spatial data with high resolution, specifically have been developed for spatial modelling activities. Average monthly weather data for 2010-2018 with 2.5 minutes spatial resolution were used as current climate data and future climate data for 2070 for MIROC6, Global Circulation Model climate projection with 30s spatial resolution were used as future climate data. All the cllimate data were converted into ascii format by using ArcMap 10.2.2 and occurrence data were converted into csv format and introduced into the model while selecting random test percentage as 25%. Nuwara Eliya district along with some parts of Kandy and Matale districts were resulted as the best areas for Calophyllum walkeri currently, while Ratnapura and Kegalle districts show moderate suitability. There is a possibility in reduction of suitability in Kandy and Matale districts in 2070 while Nuwara Eliya district will remain as the best area. There is a possibility of wet zone of the country to become suitable for Calophyllum walkeri including Batayaya, Denuwakanda, Dolekanda. For Syzygium rotundifolium, Nuwara Eliya district was the best suitable area and Ratnapura district indicated slight suitability under both current and future climate conditions. The resulting value for the Area Under Curve test which is a main statistical test of this modelling method for Calophyllum walkeri was 0.947 and it was 0.968 for Syzygium rotundifolium. Since these values are greater than 0.5, the models have performed accurately. This study recommends further studies to check the possibility of the wet zone of the country including Western and Southern regions which was resulted as a suitable region with the changing climate, to introduce Calophyllum walkeri in a requirement to take more conservation efforts. Conservation efforts for Syzygium rotundifolium can be increased within the montane region, since it is the most suitable area for it, according to the results of this study.
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    Identification of soil erosion prone areas in Matale district in Sri Lanka using RUSLE model and bare soil index
    (Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayasekara, J. M. P. M.; Mendis, C. C. D.; De Silva, K. V. N. T.; Kodikara, K. N.; Weerasinghe, V. P. A.
    The Matale District is situated in the Central Province of Sri Lanka. It is roughly 1,993 km2 in size and is in the foothills of the central mountain range. Matale District is vulnerable to soil erosion, which causes serious problems for the local environment and agricultural activities. Soil erosion in Matale District is primarily caused by several factors, including rainfall, land use, slope, soil type and conservation practices. This study aims to assess the soil erosion vulnerability in Matale District, Sri Lanka, utilizing the Revised Universal Soil Loss Equation (RUSLE) model and Bare Soil Index (BSI). RUSLE Model, a Digital Elevation Model (15 * 15m), rainfall data, land use and land cover, soil maps, and cropping parameters were used to evaluate the severity of erosion throughout the Matale district. The RUSLE model was calibrated and utilized to determine the rates of soil erosion considering rainfall erosivity, soil erodibility, slope length and steepness, cover management, and conservation practices. Furthermore, the BSI was calculated using remote sensing techniques. The results of the study indicated that soil erosion vulnerability in Matale District varied significantly. The estimated annual average soil loss varied from 0 to 731.71t ha-1 yr-1 . Improved land management practices and forest cover were associated with lower rates of soil erosion, whereas steep slopes, poor vegetation cover, and intense land use practices were associated with higher rates. The BSI map further explains the soil erosion risk map. When comparing the BSI map with the soil erosion risk map, most of the areas with bare soil are prone to erosion. Paddy-cultivated areas, scrub lands, chena and other cultivated areas are prone to experience high levels of soil erosion when considering a land use map. The Red Yellow podzolic soil, Reddish Brown Earths, immature Brown Loams, Erosional remnants steep rock land, and various lithosols soil types are found in areas with severe soil erosion when comparing the soil and Soil Erosion Risk Maps. When comparing a slope map to a soil erosion risk map, areas with a high percentage of slope indicate high soil erosion. Areas with a low percentage of slope on a soil erosion risk map indicate less erosion. Based on the results, recommendations for soil conservation and sustainable land management strategies in the identified vulnerable areas in the Matale district include measures such as afforestation, contour farming, terracing, conservation agriculture practices, and education and awareness programs. This study contributes to understanding soil erosion vulnerability in Matale District and provides a foundation for further research and initiatives focused on sustainable land management and environmental conservation. Proper soil conservation practices should be implemented to safeguard natural resources, improve agricultural productivity, and assure long-term sustainability.