Understanding of coupled physicochemical and mineralogical mechanisms controlling soil carbon storage and preservation

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dc.contributor.author Pitumpe Arachchige, Pavithra Sajeewani
dc.date.accessioned 2016-08-15T17:28:15Z
dc.date.available 2016-08-15T17:28:15Z
dc.date.issued 2016-08-01 en_US
dc.identifier.uri http://hdl.handle.net/2097/32921
dc.description.abstract Soil carbon (C) sequestration has been recognized as one of the most effective potential mitigation options for climate change. Underlying mechanisms of soil C sequestration/preservation is poorly understood, even after decades of soil C research. The main research objectives of this dissertation were three-fold: (1) enhancing our understanding in mineralogical and physicochemical mechanisms of soil C sequestration in microaggregates, (2) understanding the chemistry of organic C sequestered in soil aggregates, and (3) to determine the resilience of C to different temperature-moisture regimes and physical disturbance in a six-month incubation. An integrated approach was used in obtaining a better picture on mechanisms of C preservation. Two long-term agroecosystems located at the North Agronomy Farm, Manhattan, KS (Mollisols) and the Center of Experimentation and Research Fundacep in Cruz Alta-RS, Brazil (Oxisols) were used. Main plots of both systems were till and no-till. Mollisols consisted of three fertilizer treatments; control, manure/compost and urea. Oxisols had three different crop rotations; simple, intermediate, and complex. Submicron level information gathered by spectromicroscopy approaches, identified the direct preservation of OC structures with the original morphology; suggesting that the preservation of OC is a primary mechanism of C sequestration in these soils. Physical protection and organo-mineral associations seemed to also be involved in OC preservation. Manure/compost addition and no-till favored labile C preservation in aggregates of Mollisols. Significant associations observed between reactive minerals and C pools in Mollisols indicated the significance of organo-mineral associations in OC preservation. Large microaggregates exerted strong C preservation through physical protection and organo-mineral associations. Unlike in Mollisols, Oxisols showed a poor correlation between reactive mineral fraction and organic C which indicated the significance of physical protection over organo-mineral associations. Resilience of sequestred C was significantly affected by temperature across both temperate and tropical soil ecosystems, directly and indirectly. High temperature influenced soil acidity and reactive minerals, ultimately affecting organo-mineral associations. Macromolecular propeties of humic acid fraction showed changes after six months. Overall, direct and indirect evidence from this study suggested that the preservation of SOC is an ecosystem property supporting the newly proposed theories in soil C dynamics. en_US
dc.language.iso en_US en_US
dc.publisher Kansas State University en
dc.subject Soil carbon en_US
dc.subject STXM-NEXAFS en_US
dc.subject Mollisol en_US
dc.subject Oxisols en_US
dc.subject Carbon sequestration en_US
dc.title Understanding of coupled physicochemical and mineralogical mechanisms controlling soil carbon storage and preservation en_US
dc.type Dissertation en_US
dc.description.degree Doctor of Philosophy en_US
dc.description.level Doctoral en_US
dc.description.department Department of Agronomy en_US
dc.description.advisor Ganga M. Hettiarachchi en_US
dc.date.published 2016 en_US
dc.date.graduationmonth August en_US


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