Carbon Stock in Plantations of Indigenous Tree Species in the Wet Evergreen Vegetation of Ghana

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Carbon sequestration is one of many valuable environmental facilities that forests provide. Traditionally, society has enjoyed the benefits of environmental conditions such as clean air, nutrient cycling, and watershed protection without any payment. The role of terrestrial ecosystem in mitigating the effects of climate change entails the assessment of carbon stocks in various pools. This thesis seeks to provide information about growth and carbon stock of thirteen indigenous and one exotic tree species (Terminalia ivorensis, Terminalia superba, Milicia excelsa, Ceiba pentandra, Entandrophragma angolense, Aningeria robusta, Heritiaris utilis, Khaya ivorensis, Antiaris toxicaria, Mammea africana, Triplochiton scleroxylon, Pycnanthus angolensis and Cedrela odorata) in agroforestry, mixed and pure plantations in the wet evergreen vegetation of Ghana. A three (3) hectare plot was evaluated at the Oda Kotoamso Agroforestry Project site in the Western Region of Ghana. Results revealed that carbon accumulation and growth performance per tree species increased from trees in pure to mixed and to agroforestry plantations. Results from this study also indicated fast growing species (Ceiba pentandra, Milicia excelsa, Terminalia superba and Terminalia ivorensis) had the highest carbon accumulation per tree. Also shade, age and initial planting distance were observed as key factors that influenced growth parameters among tree species in plantations. Among the tree species studied, Ceiba pentandra recorded the highest amount of carbon per tree in pure plantation (52.2 kg C), 95.6 kg C in mixtures and 184.9 kg C in agroforestry plantation. The volume growth performance of Ceiba pentandra was the best among the remaining tree species with the highest volume of 0.4 m3 in the agroforestry plantation. Four different allometric equations were used in calculating amount of carbon in tree species. Results indicated variations in all four allometric models used for estimating carbon. Lastly, an assumed carbon concentration (50%) and specific carbon concentrations were used to convert tree biomass to carbon stored. It was observed that the assumed carbon concentration overestimated the carbon stock by 1.8% to 3.6% per tree species and 3.0% on substantial scale (per hectare) compared to specific carbon concentration of the same tree species. This research therefore supports the concept that tropical plantations can serve diverse economic, social, and ecological functions while also ultimately helping reduce atmospheric CO2 accumulation.
A Thesis Submitted to the Department of Environmental Science, College of Science, Kwame Nkrumah University Of Science and Technology, in partial fulfilment of the requirements for the award of Master of Science Degree In Environmental Science, June-2012