Project Details
Projekt
Soil structure turnover under various land uses and feedback to soil carbon turnover
Subject Area
Soil Sciences
Term
since 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 416883305
Soil structure, the three-dimensional arrangement of solid soil constituents and pores, results from the complex interplay of various physical, chemical, and biological processes. These processes continuously alter soil architecture with impacts on various soil functions, such as carbon and water storage and nutrient recycling. One key mechanism regulating soil organic matter turnover is physical protection by limited accessibility for microbial decomposers. Soil structure is often considered static but actually changes due to bioturbation, wetting/drying, freezing/thawing, and tillage activities. In the first phase of this project we established a new approach to measure soil structure turnover rate under natural conditions and to quantify the impact of different abiotic and biotic drivers. The approach is based on structure labelling where soil aggregates are coated with small inert garnet particles and their fate is studied using X-ray microtomography. The speed at which randomization with respect to particle‒pore distances is achieved is interpreted as structure turnover rate. Another achievement of the first phase was the detection of microscopic biogeochemical gradients based on multiple imaging techniques, where we could show that soil moisture regimes affect the establishment of gradients around pores and particulate organic matter of different morphologies. In the second project phase we focus on applying the new imaging methods to soils under different land uses (grassland, cropland, forest) by establishing new experimental field sites. This also allows to explore key mechanisms for structure turnover under various management practices and its impact on soil organic matter turnover. The derived soil structure turnover rates will be related to the turnover rates of different organic matter fractions and the establishment of biochemical gradients. We hypothesize that fast decomposable particulate organic matter will be strongly linked to structural turnover due to cycles of exposure and occlusion while biogeochemical gradients are expected to form when soil structure turnover is slow. Field experiments will be complemented by a mesocosm experiment studying whether the incorporation of particulate organic matter into soil by earthworm activity is linked to structure turnover. Overall, the second phase will provide a deeper insight into the effects of macrofauna on soil structure turnover. With our new field experiments we will derive relationships between soil structure turnover and soil functions depending on land use, management practices, and environmental factors, and explore the mechanistic link between soil structure turnover and organic carbon turnover.
DFG Programme
Research Grants
Co-Investigators
Professor Dr. Efstathios Diamantopoulos; Dr. Klaus Kaiser
