Location: Range Management ResearchTitle: Soil organic carbon dust emission: an omitted global source of atmospheric CO2?) Author
|Riscarra Rossel, Raphael|
Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2013
Publication Date: 7/30/2013
Citation: Chappel, A., Webb, N., Butler, H., Strong, C., McTainsh, G., Leys, J., Riscarra Rossel, R. 2013. Soil organic carbon dust emission: An omitted global source of atmospheic CO2? Global Change Biology. 19:3238-3244. Interpretive Summary: There is on-going uncertainty and debate about the impact of soil erosion on the global carbon budget, and in particular whether erosion is a net source or sink of CO2 emissions. Carbon fluxes due to dust emission are largely unknown and neglected in this debate, but may be an accelerant of SOC decomposition. We develop a process-based model of SOC dust enrichment and show that SOC dust emissions for Australia (5.83 Tg CO2-e y-1) amount to substantial under-estimates for CO2 emissions. Tracing the fate of SOC dust will be essential for quantifying the impacts of the dust cycle on the carbon cycle and Earth climate system.
Technical Abstract: Soil erosion redistributes soil organic carbon (SOC) within terrestrial ecosystems, to the atmosphere and oceans. Dust export is an essential component of the carbon (C) and carbon dioxide (CO2) budget because wind erosion contributes to the C cycle by removing selectively SOC from vast areas and transporting C dust quickly offshore; augmenting the net loss of C from terrestrial systems. However, the contribution of wind erosion to rates of C release and sequestration is poorly understood. Here we describe how SOC dust emission is omitted from national C accounting, is a neglected source of CO2 and a likely accelerant of SOC decomposition. Similarly, long dust residence times in the unshielded atmospheric environment may considerably increase CO2 emission. We developed a first approximation to SOC enrichment for a well-established dust emission model and quantified SOC dust emission for Australia (5.83 Tg CO2-e y-1) and Australian agricultural soils (0.4 Tg CO2-e y-1). These amount to under-estimates for CO2 emissions of ~10% from combined C pools in Australia (yr=2000), ~5% from Australian Rangelands and ~3% of Australian Agricultural Soils by Kyoto Accounting. Northern hemisphere countries with greater dust emission than Australia are also likely to have much larger SOC dust emission. Therefore, omission of SOC dust emission likely represents a considerable underestimate from those nations’ C accounts. We suggest that the omission of SOC dust emission from C cycling and C accounting is a significant source of uncertainty. Tracing the fate of wind-eroded SOC in the dust cycle is therefore essential to quantifying the release of CO2 from SOC dust to the atmosphere and the contribution of SOC deposition to downwind C sinks.