Submitted to: Scientific Research and Essays
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/25/2012
Publication Date: 10/1/2012
Citation: Nyamadzawo, G., Gotosa, J., Muvengwi, J., Wuta, M., Nyamangara, J., Nyamugafata, P., Smith, J.L. 2012. The effect of catena position on greenhouse gas emissions from Dambo located termite (odontotermes transvaalensis) mounds from Central Zimbabwe. Atmospheric and Climate Sciences. 2:502-509. Interpretive Summary: Nitrous oxide is one of the greenhouse gases (GHG) which cause global warming (IPCC, 2007). The greenhouse effect occurs when GHG trap long waves radiated from the earth’s surface, hence affecting the balance of heat radiation through the entire atmosphere, resulting in rising temperatures. The global warming potential (GWP) of nitrous oxide (N2O) is 310 more, than that of CO2. Central and Southern African regions are occupied by some of the largest seasonal wetlands in Africa, which are potential natural sources of greenhouse gases. These seasonal wetlands, also called dambos, constitute the largest geographic extent of seasonal wetlands on the elevated plateaus of Africa. Termite mounds are a common feature of dambos of central and southern Africa and estimates are that they contain millions of termite mounds which are scattered throughout these gently undulating floors. The N2O fluxes from dambo located termites mounds were high compared to agricultural land. Fluxes were highest in the margin areas of the dambos, compared to the mid-slope, lower slope and the bottom positions. It was concluded that dambo located termite mounds are an important source of N2O which should be accounted for when making estimates of N2O emissions from tropical Africa. The estimates can be used by policy makers, land managers and scientists when evaluating methods of greenhouse gas mitigation for a region.
Technical Abstract: Nitrous oxide (N2O) is one of the most important greenhouse gases. The global warming potentials (GWP) of nitrous oxide (N2O) is 310 more, than that of carbon dioxide (CO2) during a 100 year time scale on molecule for molecule basis. Natural sources of N2O include wetlands. Sub-Saharan Africa is occupied by some of the largest seasonal wetlands (dambos) which are conservatively estimated to be 135 million hectares (ha). In Zimbabwe dambos occupy 1.28 million ha, but to date the potential of millions of dambo located termite mounds as a source of N2O has not been investigated. This study conducted in dambos at the University of Zimbabwe farm is reporting the first estimate of N2O emissions from seasonal wetlands (dambos) located termite mounds from Zimbabwe and whole of Central Africa. The mean N2O fluxes from dambo located termites mounds were 88 µg m2 h-1, with a range of 9-324 µg m2 h-1. Fluxes were 50, 100, 115 and 74 µg m2 h-1 for the margin, mid-slope, lower slope and the bottom positions respectively. Using a mound based up scaling, estimated emissions from dambo termite mounds alone were 7.7 g of N2O-N ha-1 yr-1. Estimated N2O emitted from 0.128 million ha of clayey dambos, ~10% of Zimbabwe’s dambos was 1x106g N2O-N, emissions from all dambos from Zimbabwe is estimated at 0.01Gg, and emissions from Sub-Saharan Africa are estimated to be 1Gg. It was concluded that dambo located termite mounds are an important source of N2O which should be accounted for when making estimates of N2O emissions from tropical Africa.