Project

Elucidating the controls on enhanced rock weathering using reactive transport modelling

Soil organic matter (SOM) stores large amounts of organic carbon. Under the influence of climate change, higher temperatures have the potential to stimulate SOM decomposition, accelerating the release of carbon dioxide into the atmosphere. If carbon loses are higher than photosynthetic inputs, increased SOM decomposition can positively reinforce the feedback to climate change.

Background

Decomposition rates of SOM are commonly assessed through laboratory incubations. One widely use method for preparing soil samples in the laboratory is the air-drying and subsequent re-wetting process. Air-drying soils is a well established technique that allows to preserve soil samples for long periods of time. Long-term storage and archiving air-dry soil samples is highly valuable and cost-effective way of preserving irreplaceable knowledge spanning decades of change in land use and climate. While air-drying and re-wetting process can change SOM biological, chemical, and physical characteristics, the translation of these changes into SOM decomposition rates and its temperature response remain uncertain.

In this thesis, you will evaluate the temperature response of fresh, air-dry, and re-wetted soil samples stored for different periods. You will incubate these different samples in a temperature gradient block and measure CO2 production. Additionally, you will conduct measurements on soil pH, DOC, microbial community composition, and depending on your interest, possibly other techniques. You will learn to analyse complex datasets and use multiple statistical approaches.

Literature:

Conant, et al. Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward. Glob. Chang. Biol. 17, 3392–3404 (2011);
Robinson, et al. Rapid laboratory measurement of the temperature dependence of soil respiration and application to changes in three diverse soils through the year. Biogeochemistry 133, 101–112 (2017);
Jones et al. Drying and rewetting effects on organic matter mineralization of contrasting soils after 36 years of storage. Geoderma 342, 12-19. (2019).