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Faculty for Biology, Chemistry, and Earth Sciences

Soil Physics

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Efstathios Diamantopoulos: Theses supervised



Bachelor's Theses
Anna Dürringer The effect of Arbuskular Mikoriza Fungi (AMF) on root water uptake and on soil hydraulic properties

The growing world population and increasing demand for food present significant challenges, especially in the context of climate change. As freshwater resources become increasingly scarce, particularly in already arid regions, and with agriculture responsible for approximately 70% of global freshwater consumption, there is a growing need to find sustainable solutions for agriculture and food production. One approach is to investigate the interactions of soil-dwelling microorganisms with plants and their roots. The symbiosis between plants and mycorrhizal fungi affects around 90% of land plants, with the association with arbuscular mycorrhizal fungi (AMF) being particularly relevant for crop plants. AMF not only enhances plant nutrient uptake but also improve the water status, especially in dry soils, leading to plants in symbiosis exhibiting lower negative leaf water potentials and prolonged water uptake compared to plants without fungal partners. Based on this background knowledge, two hypotheses were formulated:

 

  • H1: The presence of arbuscular mycorrhizal fungi (AMF) influences the water uptake of plant roots, leading to increased water uptake by the roots and consequently positively affecting the leaf water potential of the plants. (Anna Dürringer)
  • H2: The symbiosis between plants and AMF alters soil hydraulic properties, improving water retention and hydraulic conductivity in the soil, resulting in increased water availability for the plants. (Ilvy Steinlein)

To test these hypotheses, an experiment was conducted with Sorghum plants under controlled laboratory conditions, where representative Sorghum plants of the same variety were divided into two groups. One group was planted in sterilized soil without AMF spores, while the other group was planted in sterilized soil with AMF spores. This setup ensured comparable growth conditions for plants with and without AMF symbiosis in a climate chamber. The experiment involved a dry-down phase during which leaf water potentials and leaf areas were measured. After the experiment, root colonization rates by AMF were evaluated using potassium hydroxide (KOH) and subsequent root staining with an ink-vinegar solution. Additionally, soil hydraulic properties were examined for both soil treatments using Hyprop and WP4C measurements to identify potential changes in soil hydraulic parameters.



Supervisor: Anna Sauer, Mutez Ali Ahmed, Efstathios Diamantopoulos
Ilvy Steinlein The effect of Arbuskular Mikoriza Fungi (AMF) on root water uptake and on soil hydraulic properties

The growing world population and increasing demand for food present significant challenges, especially in the context of climate change. As freshwater resources become increasingly scarce, particularly in already arid regions, and with agriculture responsible for approximately 70% of global freshwater consumption, there is a growing need to find sustainable solutions for agriculture and food production. One approach is to investigate the interactions of soil-dwelling microorganisms with plants and their roots. The symbiosis between plants and mycorrhizal fungi affects around 90% of land plants, with the association with arbuscular mycorrhizal fungi (AMF) being particularly relevant for crop plants. AMF not only enhances plant nutrient uptake but also improve the water status, especially in dry soils, leading to plants in symbiosis exhibiting lower negative leaf water potentials and prolonged water uptake compared to plants without fungal partners. Based on this background knowledge, two hypotheses were formulated:

 

  • H1: The presence of arbuscular mycorrhizal fungi (AMF) influences the water uptake of plant roots, leading to increased water uptake by the roots and consequently positively affecting the leaf water potential of the plants. (Anna Dürringer)
  • H2: The symbiosis between plants and AMF alters soil hydraulic properties, improving water retention and hydraulic conductivity in the soil, resulting in increased water availability for the plants. (Ilvy Steinlein)

To test these hypotheses, an experiment was conducted with Sorghum plants under controlled laboratory conditions, where representative Sorghum plants of the same variety were divided into two groups. One group was planted in sterilized soil without AMF spores, while the other group was planted in sterilized soil with AMF spores. This setup ensured comparable growth conditions for plants with and without AMF symbiosis in a climate chamber. The experiment involved a dry-down phase during which leaf water potentials and leaf areas were measured. After the experiment, root colonization rates by AMF were evaluated using potassium hydroxide (KOH) and subsequent root staining with an ink-vinegar solution. Additionally, soil hydraulic properties were examined for both soil treatments using Hyprop and WP4C measurements to identify potential changes in soil hydraulic parameters.



Supervisor: Anna Sauer, Mutez Ali Ahmed, Efstathios Diamantopoulos
Lara Kersting The impact of root exudates on the soil hydraulic properties of soil and root water uptake

Securing food availability foran  increasing global population is a major challenge.Water shortage and degradation are already limiting crop yields, and this problem will further intensify due to the expansion of agricultural areas into less fertile locations and the impact of climate change itself. The rhizosphere, the interface between roots and soil, represents a unique environment enriched with a diversity of substances like mucilage exudated from plant roots. Mucilage is a gel-like substance released from the tips of the roots and provides several benefits.

 

  • We hypothesized that root exudates alter the pore space of the soil, thereby improving the soil hydraulic properties, increase available water in the rhizosphere and/or prolonging the contact of the roots with the soil matrix.

To assess the potential of mulicalge on reducing water stress, two different soils (loam and sand) are being tested for their drying properties with varying concentrations of mucilage. For this purpose, the study makes use of HYPROP and WP4C instruments. Maize mucilage is introduced into the soil at various concentrations.



Supervisor: Asegidew Akale, Mutez Ali Ahmed, Efstathios Diamantopoulos
Lara Ketterer (2024) The effect of fluorinated ski wax on the wetting properties of sandy and loamy soils

Ski sports like cross-country skiing, downhill skiing, and biathlon are popular winter sports. Applied ski waxes reduce the friction between snow and ski and therefore increase the ski gliding. Parts of the ski waxes can enter the soil due to snow melting.

 

  • We hypothesize that ski wax increases the soil-water contact angle and consequently the water repellency of soils.

To test this hypothesis the contact angle is measured directly with the sessile drop measurement and indirectly by the Washburn method with the DCAT 11 advice. Two PFAs containing wax products (powder and liquid) are applied to sandy soil in various concentrations. The concentrations are based on their PFAs content and the PFAs concentrations measured directly in Nordic Skiing areas.  



Supervisor: Frederic Leuther, Efstathios Diamantopoulos


Master's Theses
Adina Rauscher Experimental and numerical investigation of the fate of insoluble pollutants in the rhizosphere

Polycyclic aromatic hydrocarbons (PAHs) occur ubiquitously in terrestrial and aquatic ecosystems all around the world and are a group of chemicals among the so called “persistent organic pollutants” (POPs). PAHs comprise several hundred chemically related compounds and some of them are known to have toxic, mutagenic, and carcinogenic effects on humans and other living organisms Although PAHs are considered to be very poorly soluble in water, there appears to be transport of molecules in soil that allow them to be distributed, clog pores, or accumulate at the soil plant interface. Especially for high molecular weight PAHs, colloidal and particulate transport is assumed to be an important process. Little is known about the exact transport processes in soil and whether plants can influence this transport by suction

Hypotheses

  • H1: PAHs bind to soil particles and can thus be transported in the soil despite their low water solubility.
  • H2: Plants influence the distribution of the particle bound PAHs in the soil through their water uptake at the roots, which leads to the accumulation of these particles in the rhizosphere.

Methods

To test the first hypothesis an experiment is to be carried out with undisturbed soil columns without plants. An irrigation head with needles will be used to supply water to the columns, which will also contain any tracers and particles. Three steps are planned: i nvisible tracer (e.g., chloride) chloride), p articles + PAH s, inv isible and visible tracer (brilliant blue) blue). For each step, the drainage at the bottom of the column will be collected and analysed, and at the end the distribution of the particle bound PAHs in the column will be investigated. To test the second hypothesis, undisturbed soil columns with maize plants are to be used. Again, particle bound PAHs will be supplied via the irrigation system; then drying and rewetting phases will follow. The drainage will be collected and analysed and the distribution of particle bo und PAHs around the root will be studied.



Supervisor: Frederic Leuther, Efstathios Diamantopoulos, Eva Lehndorff
Hai Anh Nguyen (2024) Simultaneous quantification of water states, fluxes and bVOCS emissions in agriculture soils

Volatile organic compounds (VOCs) produced by living organisms via biological processes, which are known as biogenic volatile organic compounds (BVOCs), are an important group of chemicals that has significant influences on atmospheric chemistry, climate system, as well as the bioactivities of plants and animals. Whereas plant-emitted BVOCs have been widely studied for the past decades, the understanding of soil related BVOCs remains inadequate.  A variety of abiotic and biotic processes taking place beneath the ground makes soil both a sink and a source for BVOCs.

Hypotheses

  • BVOCs emission and/or uptake are highly affected by the percent of organic matter in the soil and the water content.
  • The dynamics of BVOCs exchange are subject to memory effects, following the hysteretic water content vs matric potential relationship.

Methods

To test the two hypotheses, we conduct transient water drying and wetting experiments, and we quantify simultaneously BVOC sources and sinks, as well as soil water states and fluxes.



Supervisor: Frederic Leuther, Anke Nölscher, Efstathios Diamantopoulos
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