Carbon Storage and Fluxes from a Tropical Freshwater Wetland in Uganda: Implications for Climate Change Mitigation
| dc.contributor.advisor | Kansiime, Frank (Professor) | |
| dc.contributor.advisor | Fetahi, Tadesse (Professor) | |
| dc.contributor.author | Were, David | |
| dc.date.accessioned | 2021-09-16T07:28:46Z | |
| dc.date.accessioned | 2023-11-18T09:52:22Z | |
| dc.date.available | 2021-09-16T07:28:46Z | |
| dc.date.available | 2023-11-18T09:52:22Z | |
| dc.date.issued | 2021-06-26 | |
| dc.description.abstract | Natural wetlands have been shown to be among the most important ecosystems in climate change mitigation, through carbon (C) sequestration. However, natural wetlands also act as C sources, emitting part of the sequestered C back into the atmosphere, in form of carbon dioxide (CO2) and methane (CH4). Storage and emission of C are of interest in tropical wetland studies because the high and relatively stable temperatures year-round enhance both primary productivity and organic matter decomposition. However, most of the studies on C sequestration and emission have mainly focussed on temperate and boreal wetlands. Further, many natural tropical freshwater wetlands are increasingly being converted into rice paddies, with limited knowledge on its impact on wetland C balance. This study investigated soil organic carbon (SOC) storage and emission of CO2 and CH4 from a tropical freshwater wetland in Uganda, under natural and rice paddy conditions. The natural section is dominated by Cyperus papyrus (Papyrus), Typha latifolia (Typha) and Phragmites mauritianus (Phragmites) vegetation communities. Soil samples for determination of SOC were obtained up to 50 cm depth, using a Russian peat borer, while CO2 and CH4 gas samples were obtained using static flux chambers. Within the natural wetland section, SOC content (123.7±2.6 [mean±SE] g C kg-1 dry soil) in Papyrus was significantly higher (p < 0.05) than those obtained in Typha and Phragmites. On the other hand, there was no significant variation (p > 0.05) in SOC contents of Typha and Phragmites. Comparing SOC contents of the natural and rice paddy wetland sections, all the three vegetation communities of the natural section had SOC contents (Papyrus = 123.7±2.6, Typha = 85.3±1.1 and Phragmites = 78.2±3.4 g C kg-1 dry soil) significantly higher (p < 0.05) than that recorded in the rice paddy section (39.7±0.7 g C kg-1 dry soil). Considering fluxes of gases from the wetland, variation among the vegetation communities of the natural section was only noticed in Phragmites during the dry season. During this season, Phragmites showed significantly higher flux (p < 0.05) of CO2 (871.8±56.7 mg C m-2 h-1) and lower (p < 0.05) flux of CH4 (8.7±0.5 mg C m-2 h-1) than those measured in both Papyrus and Typha. No significant variation in gas fluxes (p > 0.05) occurred among the vegetation communities during the wet season, for both CO2 and CH4. Further, comparing the natural and rice paddy wetland sections, variabilities in gas flux rates were observed. CO2 fluxes (mg C m-2 h-1) from the rice paddy section during the dry and wet seasons were 1045.4±46.6 and 804.4±50.2 respectively, both significantly higher (p < 0.05) than those obtained in all the three vegetation communities of the natural section. However, CH4 fluxes from the rice paddy section during the dry and wet seasons were 2.1±0.4 and 5.1±0.5 mg C m-2 h-1 respectively, both significantly lower (p < 0.05) than those observed in all the three vegetation communities of the natural section. Nevertheless, considering total C flux (summation of CO2 and CH4 fluxes), it was observed that the rice paddy wetland section emitted significantly higher (p < 0.05) C than the natural section. Plant biomass density, and soil physico-chemical characteristics: bulk density, salinity, pH and temperature significantly correlated (p < 0.05) with SOC, while water level had a significant correlation (p < 0.05) with CO2 and CH4 fluxes in both sections of the wetland. The observation of significantly higher SOC content and significantly lower total C flux from the natural wetland section compared to the rice paddy section suggests that conserving a natural tropical freshwater wetland is a better climate mitigation option than converting into a rice paddy wetland. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/12345678/27915 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Carbon Storage | en_US |
| dc.subject | Fluxes from a Tropical Freshwater Wetland | en_US |
| dc.subject | Uganda | en_US |
| dc.subject | Implications for Climate | en_US |
| dc.subject | Change Mitigation | en_US |
| dc.title | Carbon Storage and Fluxes from a Tropical Freshwater Wetland in Uganda: Implications for Climate Change Mitigation | en_US |
| dc.type | Thesis | en_US |