Estimation of N20 and NO emission from a tropical highland forest in Rwanda

Abstract

The research of this work fits within the broad subject of greenhouse gas emissions and climate change. More specifically, this work focuses on the contribution of tropical forest soils to the atmospheric N20 and NO budgets. Nitrous oxide has a global warming potential of 310 relative to CO2 and is one of the main greenhouse gases covered by the United Nations Framework Convention on Climate Change (UNFCCC). Nitrous oxide also plays a key role in modulating the stratospheric ozone layer. Tropical forest soils are considered to be the largest natural source of N20. Additionally, they can produce considerable amounts of NO. Estimates of the contribution of tropical rainforest ecosystems, which cover u50 x ro6 ha of the global land surface, to atmospheric N20 and NO have a high uncertainty. Despite the fact that tropical forest soils are considered to be a key source of N20 and NO2 only a relatively small number of detailed studies investigating the temporal and spatial variability of the N20 and NO soil-atmosphere exchange are available, particularly for Africa. Therefore the general objective of this research was to improve N20 and NO emission predictions from tropical forest. The research has been carried out in the Nyungwe forest in Rwanda for which a large number of legacy data are available. The results of this thesis led to (i) a better understanding of the N20 and NO source strength of a central African tropical forest soil, (ii) improved NO and N2O emission estimates from a central African tropical highland forest and more insight into the importance of soil properties controlling N20 and NO emissions and (iii) a better insight in those parameters that preferentially should be monitored to allow better global simulations of N20 and NO emissions from tropical forests.