Carbon sequestration potential of rehabilitated and natural forest sites of bamburi cement limited, Mombasa County, Kenya
Mwikamba, Edward Mutwiri
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Deforestation in the tropical regions accounts for approximately 20% of carbon dioxide (CO2) emissions to the atmosphere. Restoration of mined areas through afforestation/reforestation (A/R) can potentially capture large quantities of atmospheric carbon dioxide if appropriate management strategies are applied. This will help reduce the rising CO2 levels in the atmosphere. The key challenge for successful implementation of A/R carbon project is the unreliable estimation of biomass carbon stocks in forests to find out their relative carbon accumulation potential. Bamburi Cement Limited (BCL), through its mining and cement production is a substantial CO2 emitter in addition to land degradation and transformation. To counter this, the company initiated quarry rehabilitation project through replanting of Casuarina equisetifolia and Conocarpus lancifolius to reduce their carbon footprint and conserve biodiversity. Despite their importance, carbon stocks in these rehabilitated forest sites have not been quantified to determine their potential in carbon offset. The current study aimed to estimate total carbon stocks and sequestration potential in natural and rehabilitated sites of BCL in Mombasa. Six carbon pools including aboveground biomass, belowground biomass, herbaceous biomass, litter biomass, deadwood and soil organic carbon were sampled in 137 plots of 10 x 10 m. One way ANOVA and t – test analysis were carried out using MINITAB software (version 14) to compare carbon means in different sites and forest blocks respectively. The average carbon density for BCL was 126.4±9 Mg C ha-1 with a range of 52.24 to 177.42 Mg C ha-1 and was within the range of tropical forests of 120 Mg C ha-1. Aboveground biomass carbon pool stored the highest carbon stock (58%) followed by soil organic matter (25%), then belowground biomass carbon with 8%, litter carbon pool 5%, deadwood biomass carbon 3% while herbaceous biomass carbon contributed the least (0.2%). Rehabilitated areas had more carbon stock compared to natural lands. The carbon densities in the rehabilitated sites increased with increase in stand age. The results show that, with better forest management practices, quarried areas can be carbon storage hotspots hence contributing to climate change mitigation. It is recommended that harvesting of mature trees and improved management of the rehabilitated areas be adopted to increase carbon capture and storage. In addition, further research needs to be carried out on net ecosystem carbon balance and developing species specific allometric equations is recommended to upscale the findings of this study.