MSc and SIE projects

Mountain soils above the treeline store a majority of ecosystem carbon. Carbon accumulates in these systems mostly due to slow degradation rates in this harsh environment. Changes in temperature and precipitation patterns may shift this equilibrium, resulting either in organic matter accumulation or loss. Since both the formation and degradation of organic matter is governed by the soil microbiome, a detailed understanding of soil microbial processes is needed to project changes in soil carbon cycling in mountain soils. Soil moisture is the primary variable controlling microbial respiration pathways. The goal of this MSc thesis is to assess variations in the composition of the soil microbial community across a gradient of soil moisture conditions on selected field sites in the Swiss Alps.

The objectives of this thesis are:

1. Characterizing basic soil properties such as texture, elemental composition, pH, and cation exchange capacity across a gradient of soil moisture conditions.
2. Extracting DNA from soil samples and conducting qPCR to determine the abundance of bacterial and fungal genes.
3. Utilizing statistical methods to analyze the correlation between variations in microbial and fungal genes, landscape positions, and soil moisture. 

For further information, check out our project on Mechanisms of soil organic carbon stabilization in mountain soils and contact Kristina Bright for details. 

Mountain soils above the treeline store a majority of ecosystem carbon. Carbon accumulates in these systems mostly due to slow degradation rates in this harsh environment. In addition, carbon may be protected from microbial degradation through association with soil minerals. The extent to which this mechanism drives soil carbon stabilization in this system remains unknown. This MSc thesis aims to determine the contribution of soil minerals to organic carbon stabilization on selected field sites in the Swiss Alps.

The objectives of this thesis are:

1. Determine mineralogy using XRD across soils collected at various landscape positions
2. Perform sequential extractions to assess the reactivity of different mineral phases
3. Quantify mineral-associated organic carbon in different soil fractions

For further information, check out our project on Mechanisms of soil organic carbon stabilization in mountain soils and contact Bence Dienes for details.

Context:

Preserving soil organic carbon (SOC) stocks is essential for mitigating climate change. SOC decomposition is primarily driven by microbial activity, where microbes utilize oxygen as the preferred electron acceptor during decomposition processes. Agricultural practices, particularly tillage, directly influence soil aeration by altering oxygen availability, thus potentially impacting SOC decomposition and stabilization. Despite the apparent significance of this relationship, the connections between soil aeration metrics -such as oxygen levels, pore structure, and redox potential- and SOC decomposition under various tillage practices have not been systematically evaluated in field conditions.

Goals:

This study aims to assess the impact of different tillage practices, specifically conventional and no-till, on greenhouse gas emissions (carbon dioxide, nitrous oxide, and methane) using a long-term tillage experiment at Agroscope-Changins. The project will involve the use of water retention curve techniques to evaluate pore size distribution across different tillage treatments and soil textures. Additionally, training in X-ray µCT will support the 3D reconstruction of soil pore networks, allowing for analysis of pore metrics such as connectivity and tortuosity. The results will link soil aeration metrics with greenhouse gas emissions and SOC stabilization, offering insights into how tillage practices influence SOC dynamics under field conditions.

Knowledge and skills required:

• Interest in soil biogeochemistry.
• Good organisation skills.
• Enthusiasm for field work and soil lab analyses.
• Reasonable proficiency with written English.
• Willingness to participate in the scientific publication process.

Collaboration: This project will be co-supervised by Orly Mendoza ([email protected]), Stephanie Grand ([email protected]) and Meret Aeppli ([email protected])

Working place: Géopolis (UNIL Lausanne)

Context:

Tillage intensity has been widely implicated in promoting the mineralization of soil organic carbon, consequently leading to an increase in atmospheric carbon dioxide concentrations. However, conflicting findings from a limited number of studies exist. Most of the existing research has primarily focused on aggregate turnover, with a lack of a systematic approach to assessing soil organic carbon stabilization in relation to mineralogical properties across various soil types and depths, particularly under different tillage practices.

Goals:

We propose to use existing samples and collect samples from topsoils and subsoils, which exhibit variations in soil mineralogy and are subjected to different tillage practices -namely, conventional, reduced, and non-tillage- in long-term tillage trials conducted in Switzerland, Italy, and Japan. Through the utilization of soil fractionation techniques, routine mineralogical analyses, and nanoscale methodologies, the student will investigate the impact of tillage intensity on soil mineralogy and in turn on soil organic carbon stabilization. Ultimately, we aim to establish a systematic link between soil mineral composition and properties with the stabilization of soil organic carbon.

Knowledge and skills required:

• Broad interest in soil biogeochemistry.
• Good organisation skills.
• Enthusiasm for soil sampling and soil lab analyses.
• Strong base training in mineralogy.
• Reasonable proficiency with written English.
• Willingness to participate in the scientific publication process.

Collaboration: This project will be co-supervised by Orly Mendoza ([email protected]), Stephanie Grand ([email protected]) and Meret Aeppli ([email protected])

Working place: Géopolis (UNIL Lausanne) and ALPOLE (Sion)

Context:

Agricultural systems are under pressure to produce increasing amounts of food for a growing human population while preserving, and ideally enhancing, the capacity of soils to sequester carbon and provide a habitat for biodiversity. To address these challenges, Nestlé in collaboration with SOIL is supporting regenerative agricultural practices. One such practice is the application of non-harmful, cheap organic fertilizers in combination with additives. These combinations of fertilizers and additives have shown promise in laboratory studies, but it remains unknown if these positive effects manifest themselves when fertilizers plus additives are applied under real-world conditions on agricultural farms. This MSc thesis aims to evaluate the effects of organic fertilizers combined with additives on two different farms in Switzerland. The study will involve both fieldwork and laboratory analyses.

Goals:

The objectives of this thesis are to:

1. Conduct greenhouse gas (GHG) measurements from soils on two Swiss farms.
2. Collect and analyze soil samples from both farms, characterizing key properties such as texture, elemental composition, pH, and X-ray fluorescence (XRF).
3. Assess the impact of organic fertilizers and additives on GHG emissions and soil properties, comparing the results with existing data from previous studies.

For further information, contact Camila Morales for details.