Plant–soil-water interactions play a central role in biogeochemical (carbon) and hydrological ecosystem cycling. These two cycles are also intimately linked because moisture availability is a key control on terrestrial carbon cycling and plant physiological traits (resulting in changes in biomass input and rate of turnover). In turn, plant water use and organic materials are major regulators of soil water storage dynamics. Changes in land cover, management and climate can cause significant perturbations in these interactions, in particular in tropical regions where water and carbon cycles are both highly dynamic but also not well understood. These cycles are typically studied separately, with the other poorly represented; there is a need for better integration of data collection and the development of modelling tools to test the hypotheses that the analyses of these data provide about the biogeochemical and hydrological interlinkages and feedbacks via plant-soil-water interactions. These are important prerequisites to be able to understand and predict future ecosystem functioning under changing conditions.
In many parts of the world, coffee agroforestry systems are the only remaining continuous green belts in formerly forested regions, and thus important water and nutrient regulators at local to landscape scales. However, common coffee varieties are gradually being replaced by those more resilient to diseases (e.g. coffee rust). There is a delicate balance in water use strategies of coffee plants and the trees that provide essential shading, with the former using more shallow soil water. However, the newly introduced coffee varieties are likely to use more water and compete for the same (deeper) water as shade trees. Moreover, inherent to these new coffee varieties are changes in above and below ground biomass and carbon storage. Over the long term, these changes could compromise the ecosystem’s growth and sustainability, especially under additional pressures from climate change towards more extreme dry periods. To aid management decisions that could mitigate against such scenarios, it is crucial to better understand the interlinkages between (changes in) water availability, plant water use and dynamics in carbon storage.
This PhD project seeks to better understand the interlinkages of water and carbon cycling in tropical agroforestry systems and responses to changes in management practices. It will address major knowledge gaps with respect to water and carbon cycling in agroforestry systems; how they respond under different climatological conditions, especially those that induce stress; and how this is affected by the introduction of new coffee varieties. For the first time in these regions, it will quantify plant water availability and combine data and models of water use with carbon cycling and also consider plant physiology. This will be studied at sites in Mexico’s coffee region which represent the extreme climatological limits (evapotranspiration close to total rainfall) under which coffee is grown, and which are understood to be most at risk given future land use and climate projections. As such it will provide new insights into the functioning of agroforestry ecosystems and sustainability under different management strategies and climates.
The project will involve coupled hydrological and ecological approaches and integration of empirical data collection and analysis and environmental modelling. This will include hydrological and biogeochemical modelling tools, the stable water isotope laboratory facilities in the School of Geosciences and in the School of Biological Sciences, and hydrometric and plant physiological trait monitoring equipment. It is expected that the candidate has close engagement and communication with stakeholders and colleagues in Mexico and the UK.
Candidates should have (or expect to achieve) a minimum of a 2.1 BSc Honours or MSc degree or equivalent in a relevant subject. This project requires strong numerical and analytical skills. A full driving licence would be desirable. Applicants must also be comfortable in undertaking and coordinating team fieldwork in Mexico.
• Apply for Degree of Doctor of Philosophy in Geography
• State name of the lead supervisor as the Name of Proposed Supervisor
• State the exact project title on the application form
Application closing date is 12:00pm (GMT) on 22 February 2019. Applications received after this time will NOT be considered. Additionally, incomplete applications will NOT be considered.
When applying please ensure all required documents are attached:
• All degree certificates and transcripts (Undergraduate AND Postgraduate MSc-officially translated into English where necessary)
• 2 References (Academic, where possible)
Informal inquiries can be made to Dr J Geris ([email protected]
) with a copy of your curriculum vitae and cover letter. All general enquiries should be directed to the Postgraduate Research School ([email protected]