Science
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/1
Browse
2 results
Search Results
Item Derive and validate an allometric model for the biomass gain of Tectonia grandis (Teak) in Sri Lanka(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Wijayasenarathne, K. A. S. H.; Bandara, W. A. R. T. W.Forest plantations play a crucial role in mitigating climate change. Tectonia grandis has the highest occupancy among plantation species in Sri Lanka, expanding into 23266.5 ha in 2018. Objective of this study was to develop and validate an allometric equation for the above ground biomass gain of Tectonia grandis. . Generally, commercial Tectonia grandis plantations are confined into intermediate zone and dry zone of Sri Lanka. Therefore, four study sites were selected from Kurunegala district (Athagala, Iriminna) and Anuradhpura district (Ashokpura, Palagala). Due to variations in the selected plantations, two 0.05ha squared plots with 10 trees were laid out from each plantation by using random sampling method. Sixty trees were used for model construction and 20 trees were kept for the model validation. Total tree height, merchantable tree height, crown diameter and diameter at breast height were measured from each individual in each plot as independent variables. Stem carbon content as the dependent variable was estimated by analyzing the carbon content in the extracted core samples at breast height through the loss an ignition method by oven-drying at 105˚C and igniting at 450˚C and extrapolating that value to estimate the carbon content in the stem. Stepwise regression method in the MNITAB 17 statistical software package was used for the model construction and validated with Model Bias (MB) and Model Efficiency (ME). After considering the mutlicollinearity, merchantable tree height and crown area were removed from the model construction. The constructed model to predict the carbon content of stem of Tectonia grandis is; Ln CC(kg) = −4.06 + 1.92 Ln dbh(cm) + 0.758 Ln TH(m) The final model was able to predict the stem carbon content of Tectonia grandis up to 76.1% reliability. According to the model validation, the model was to be proved to be applied to predict carbon content in the real world.Item Modelling of Changes in Evapotranspiration for an Area in Peninsular Malaysia(Pertanika Journal of Science and Technology, 2005) Najim, M.M.M.; Lee, T.S.; Haque, M.A.; Feng, H.Y.A study was carried out to check the sensitivity of evapotranspiration estimation due to changes in climate. The study used 30 years of data from the meteorological station in the FELCRA paddy estate, Seberang Perak, Peninsular Malaysia. The effect of changes in the climatic variables, temperature, solar radiation, relative humidity and wind speed on evapotranspiration were analyzed. Results showed that the mean temperature, mean relative humidity, mean wind speed, and net global radiation have changed by + 0.182 oC, -0.73%, -0.0365 mis, and +0.146 MJ/m2 respectively per decade, while the short wave radiation received has decreased by 0.0037 MJ/m2 per decade. The statistical analysis of the evapotranspiration estimations using selected methods showed that the Penman-Monteith, Blaney-Criddle and Pan evaporation methods give similar estimations (P = 0.05) and are suitable for the study area. When changes to the present climate are imposed for future decades, the over-estimation rate is linear with the Blaney-Criddle and Penman methods whereas for the PenmanMonteith method it is exponential. The overall increment expected after 5 decades is 5.3% and 6.9% with Penman and Blaney-Criddle methods respectively. The Penman-Monteith shows a 74.4% increment in the evapotranspiration over the next five decades.