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Title: Fractionation methods to estimate the carbon sequestration potential of highly organic soils impacted by regular burning
Author: Beckert, Marvin R.
ISNI:       0000 0004 9355 7034
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2020
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While carbon fractionation approaches for mineral soils are well established, methods suitable for organic soils are lacking. This research addresses this gap and attempts to devise methods for comparison to model pools, such as used in RothC. It examines impacts on rate of decomposition of burning, as this is likely to increase the inert fraction and impact rate of decomposition. Field sites were established in a Scottish heathland and a Tasmanian buttongrass moorland, both sites being managed by regular burning. Surface samples were taken from plots burned at varying times in the past, and labile fractions were measured by fractionating with hot water and sulphuric acid. There was a greater amount of labile-carbon extracted in plots not recently burnt at both sites, suggesting labile-carbon was either lost or converted to recalcitrant-carbon by fire. The fractions obtained were compared to RothC pools derived by an equilibrium-run, the usual model initialisation approach. There was a larger proportion of labile-carbon measured than predicted by the model, suggesting the equilibrium-run is overestimating inert carbon. Attempts were made to isolate inert carbon in charcoal using chemical and visual methods, but results from both methods were highly variable, so no direct comparison could be made with model pools. Respiration measurements of incubated samples were used to derive carbon pools by inverse-modelling. Again, results showed more labile-carbon than predicted by the equilibriumrun and less labile-carbon in most recently burned treatments. Inverse-modelling shows great promise to provide more accurate model initialisation, so a MicroResp approach was developed as a rapid alternative to gas chromatography and verified using known additions of charcoal. Addition of 1% charcoal lowered respiration rates, whereas 5% and 10% increased them, suggesting the presence of labile carbon in charcoal. Future work should quantify the labile carbon in charcoal and further develop the promising MicroResp approach.
Supervisor: Smith, Jo U. ; Smith, Peter ; Anderson, Ian ; Chapman, Steve Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Soil mineralogy ; Histosols ; Carbon sequestration