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Gewählte Master / Diploma Thesis:

Markus Schartner (2015): IMPACT OF REPEATED DRY-WET CYCLES ON MACRO-AGGREGATE STABILITY AND ORGANIC CARBON STABILIZATION OF A BEECH FOREST SOIL.
Master / Diploma Thesis - Institut für Bodenforschung (IBF), BOKU-Universität für Bodenkultur, pp 103. UB BOKU obvsg

Data Source: ZID Abstracts

Abstract:: The aim of this work was to investigate changes in the release of DOC due to repeated DW events simulated in-situ on a silty-loam soil under a beech forest. Two drought and rewetting scenarios (moderate and severe) were implemented and seven samplings at dry and wet conditions conducted. Soil macro-aggregate stability (SAS) was determined according to Kemper. Ultrasonic (US) treatment on stabile aggregates at rising energy level was applied to investigate changes in DOC releases. Additional, the aromaticity of DOC was measured by UV-absorbance at 254 nm and accompanying FTIR measurements were conducted to show relative changes of hydrophobic substances. After the drought period in June SAS values decreased in all plots which was ascribed to the absence of organic binding agents. While SAS decrease was accompanied by a lower and highly aromatic DOC release after 30 seconds dispersion for severely stressed- and control plots, OC dynamics in moderately stressed plots seemed to be stabilized by shorter and more frequent DW cycles. After rain-simulation, which coincided with a natural rain event, SAS increased in all plots accompanied by a high DOC release in control plots. A low aromaticity of DOC at severely stressed- and control plots indicated a quick production of organic materials by micro-organisms. FTIR measurements found reactions only in control plots after dry period in June, where hydrophobic aromatic substances seemed to exceed a specific threshold and indicated a lower wettability of soil aggregates. Since no reactions were found for the last DW cycle in October we concluded that DW cycles had only disturbing effects on aggregates in the short term at early stages of the year. The ability of micro-organisms to adapt to changing environmental conditions may explain the stabilization of OC dynamics and aggregates in the long term and the generally low total DOC releases of the beech forest soil.; Beurteilende(r): Zechmeister-Boltenstern Sophie; 1.Mitwirkender: Zimmermann Michael; 2.Mitwirkender: Mentler Axel