Do plant communities manipulate soil for drought resistance?

Plants have differing abilities to engineer soil to make them more productive and stable under stress, but the mechanisms that underpin processes remain poorly understood, despite their significance to soil sustainability, food security and climate change. Some of the most dramatic evidence comes from environmental disasters like the Great Dust Bowl, where the transition from diverse prairie grasses to monoculture maize led directly to devastating wind borne soil erosion during drought. Roots act like reinforcing rods in soil and exude compounds that aggregate soils, increase water storage and help release nutrients. By clogging pores or creating an aggregated structure, roots also have a large impact on water transport. The ability of different plant species to engineer soil therefore has significant benefits to their own productivity but also impacts to the wider environment. In a diverse plant community, root traits of one species create complementary effects within the soil that might be beneficial to another species.

This PhD project will disentangle a range of processes that drive soil structure formation by diverse communities of plant roots, and then explore the knock-on beneficial effects that enable plants to resist, recover and adapt to drought. You will be answering these scientific questions:
1. How do root traits of different species of plants drive soil structure to their own advantage?
2. Do communities of plants drive complementary changes to soil structure, in terms of root growth and resource capture?
3. Does plant biodiversity decrease drought impacts by modifying soil physical structure?
Using small-scale testing methods developed by the team, you will be able to perform measurements of water transport and mechanical behaviour from the root-interface up to the root zones of plant communities. X-Ray CT enables measurement of root growth and pore structure changes over time, which will be complemented with traditional soil physical measurements. You will have the opportunity to explore the effects of different plant species, communities of plant species and different soil conditions. Experiments will first be conducted in controlled conditions where species composition and imposed stresses such as drought can be carefully manipulated. It may then move to field experiments exploring species composition impacts in grasslands and croplands, potentially drawing on established platforms at the James Hutton Institute and the Agri-Food and Biosciences Institute. The research is very relevant to exploring the sustainable management of soils, including management options such as cover crops, intercropping and grass sward species richness.

You will learn a range of specialist soil physical and biological laboratory testing approaches, including the use of state-of-the-art X-Ray CT to visualise inside the soil. The University of Aberdeen retains the only MSc in Soil Science in the UK, which could be useful if you come from another discipline. Soil science has been identified as a major skill-gap in the UK and has experienced increased funding opportunities and research employability due to concerns about food security and environmental sustainability. Collaborative supervision from Queens University of Belfast provides training opportunities in advanced statistics and ecosystem modelling of stability.