Influence of mechanical loading on static and dynamic CO2 efflux on differently textured and managed Luvisols.

Mordhorst, A., Peth, S. and Horn, Rainer (2014) Influence of mechanical loading on static and dynamic CO2 efflux on differently textured and managed Luvisols. Geoderma, 219 . pp. 1-13.

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Mechanical disturbance of soil structure is commonly related to altered physical changes in pore systems, which control CO2 effluxes e.g. by changes in gas transport properties and in microbial activity. Soil compaction mostly leads to reduced CO2 fluxes. In contrast, structured soils can also release physically entrapped CO2 or give access to protected carbon sources inside aggregates due to aggregate breakdown by disruptive forces. In this study it was investigated how far arable soil management affects structure- and compaction-related CO2-releases using incubation experiments and CO2 gas analysis under standard matric potentials (-6 kPa). CO2 efflux was analyzed before, during and after mechanical loading using the alkali trap method (static efflux) and a gas flow compaction device (GaFloCoD, dynamic efflux). Intact soil cores (236 and 471 cm(3)) were collected from a Stagnic Luvisol with loamy sand (conservation and conventional tillage systems) and a Haplic Luvisol with clayey silt (under different fodder crops) from the topsoil (10-15 cm) and subsoil (35-45 cm). Mechanical stability was reflected by the pre-compression stress value (P-c) and by the tensile strength of aggregates (12-20 mm). Changes in pore systems were described by air conductivity as well as air capacity and total porosity. While CO2-releases varied highly during the compaction process (GaFloCoD) for different stress magnitudes, soil depths and management systems, basal respiration rates were generally reduced after mechanical loading by almost half of the initial rates irrespective of soil management. For both methods (dynamic and static efflux) restriction in gas transport functionality was proved to have major influence on inhibition of CO2 efflux due to mechanical loading. GaFloCoD experiments demonstrated that decreases in CO2 efflux were linked to structural degradation of pore systems by exceeding internal soil strength (P-c). Otherwise, re-equilibrating matric potentials to 6 kPa and re-incubating offset inhibition of soil respiration suggest a re-enhancement of microbial activity. At this state, physical influences were apparently overlapped by biological effects due to higher energy supply to microbes, which could be offered by spatial distribution changes of microorganisms and organic substrates within a given soil structure. This implies the susceptibility of physical protection mechanism for carbon by disruption of soil structure. In future, special focus should be given on a clear distinction between physical and microbiological effects controlling CO2 fluxes in structured soils. (C) 2014 Elsevier B.V. All rights reserved.

Document Type: Article
Additional Information: Times Cited: 0 Peth, Stephan/A-2668-2009 Peth, Stephan/0000-0001-9799-212X 0
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
ISSN: 0016-7061
Projects: Future Ocean
Date Deposited: 30 Mar 2015 12:34
Last Modified: 23 Sep 2019 23:12

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