Soil organic carbon dust emission: an omitted global source of atmospheric CO₂

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 (CO(2)) 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 an underestimated source of CO(2) and may accelerate SOC decomposition. Similarly, long dust residence times in the unshielded atmospheric environment may considerably increase CO(2) 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 CO(2)-e yr(-1)) and Australian agricultural soils (0.4 Tg CO(2)-e yr(-1)). These amount to underestimates for CO(2) emissions of ≈10% from combined C pools in Australia (year = 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 global source of uncertainty. Tracing the fate of wind-eroded SOC in the dust cycle is therefore essential to quantify the release of CO(2) from SOC dust to the atmosphere and the contribution of SOC deposition to downwind C sinks.

Wind erosion enhanced by land use changes significantly reduces ecosystem carbon storage and carbon sequestration potentials in semiarid grasslands

“…Wind erosion is one of the most important sources of uncertainty in terrestrial C accounting. Recent research on SOC redistribution within the landscape greatly improves our understanding on erosion's impact (Chappell et al, ; Van Oost et al, ; Wang et al, ). However, we still lack the basic field observations to constrain the causes, magnitudes, and consequences of soil erosion in the C cycle at the site level.…”

Monitor Soil Degradation or Triage for Soil Security? An Australian Challenge

“…A well-established dust emission model was used to show that between 2000 and 2011 mean dust (< 22 μm) emission was 1.34 TgC/year and 0.11 TgC/year for rangeland and agricultural Australia, respectively [36]. Despite smaller SOC dust emission and SOC contents than agricultural Australia, the largest loss of SOC dust emission is from rangeland Australia because of the large area affected by wind erosion and dust emission.…”

Australian net (1950s–1990) soil organic carbon erosion: implications for CO&lt;sub&gt;2&lt;/sub&gt; emission and land–atmosphere modelling

“…We account for all erosion processes (wind, water and tillage), specifically including wind erosion and dust emission, which has the potential to preferentially remove SOC rapidly from terrestrial ecosystems (Webb et al, 2012Chappell et al, 2013). Our estimates at the landscape or "catchment" scale (e.g.…”

“…193) suggested that a good approximation to the enrichment ratio is based on a comparison of the particle size composition of the eroded material with that of the topsoil. Chappell et al (2013) recently produced a map of SOC enrichment in dust for Australia by assuming that SOC enrichment is proportional to the enrichment of soil fines, estimated from a physically based model of particle size selectivity:…”