The effect of fire regimes on carbon sequestration and stabilization in South African grasslands

Abstract

Grasslands are important ecosystems worldwide since they not only provide important ecosystem services such as biodiversity reserves and water catchments, but also play a large role in the cycling of carbon and nutrients. In general, the sequestration of carbon is in balance with respiration, but environmental conditions can dislodge this balance, resulting in a positive or negative impact on global climate change. A large portion of organic carbon is sequestered in soil organic matter (SOM) and the importance of SOM is recognized by science. The structure of carbon changes during the sequestration process, resulting in labile and recalcitrant carbon pools that determine the decomposition rate of the carbon. In South Africa, grasslands sequester a lot of carbon and have evolved over many centuries, creating unique ecosystems that can cope with disturbances. Fire regimes occur in these grasslands and influence the sequestration process of carbon. In this study, the effect of different fire treatments on soil carbon storage has been investigated. While fires increase the total amount of carbon stored in soils, it also affects the distribution of carbon and increases the amount of black carbon sequestered in soils. Combined, the changes in carbon distribution and the accumulation of black carbon increase the overall recalcitrance of carbon, resulting in longer residence times of carbon in soils. The role of fire in grassland ecosystems needs to be evaluated even further since fire could play a part in conserving grasslands and could aid as a potential climate mitigation option.