Modifications to the hydrological cycle are expected as part of the on-going changes to the climate-system. Climate simulations indicate both an increased frequency of extreme events, such as droughts and flooding, as well as changes to mean rainfall amount. These new climate regimes will have uncertain impacts on terrestrial ecosystems, and thus knowledge of how they will affect plant function and ecosystem processes remain uncertain. This uncertainty motivated establishment of a large-scale, field-based climate-change experiment on a calcareous grassland, near Oxford (Fig. 1). Calcareous grasslands have high biodiversity but are becoming increasingly rare, and are therefore of high conservation importance. Understanding the impact of global change processes on these ecosystems is therefore central to their conservation. Located on a SSSI site, this experimental platform provides the opportunity to investigate the impacts of both decreased and increased rainfall on these species-rich ecosystems.
Plant-mycorrhizal symbioses are at the nexus of carbon-water-nutrient cycling and are recognised as drivers of many ecosystem processes. Mycorrhizal associations are also known to confer increased drought tolerance to their plant hosts, primarily via impacts on soil texture, but their role in ecosystem responses to environmental change is less well understood. The focus of this project is to improve our knowledge of the role that plant-mycorrhizal associations play in mediating responses to global change processes in a species-rich calcareous grassland, through a combination of both field-based and controlled environment experiments. The impact of changing precipitation will be investigated at the field site at Wytham, where mycorrhizal communities and plant physiological responses will be characterised under both drier and wetter conditions to tease apart the role of mycorrhiza in facilitating nutrient and water acquisition on plant physiological responses. The increase in atmospheric CO2 is an important global change process that will affect both carbon and water cycling through the biosphere. However, the response to CO2 depends on nutrient availability, and mycorrhizal associations may impact the magnitude of ecosystem response to CO2. This project will use advanced controlled-environment facilities in mesocosm experiments to investigate the influence of elevated CO2 on carbon-nutrient transfer in the grassland mycorrhizal associations under different water conditions.
The study site is a lowland calcareous grassland at the Wytham Upper Seeds Experimental site, near Oxford. Rainfall manipulation is performed using 5 m x 5 m rain-shelters and coupled irrigation systems to impose long-term drought and wetting treatments on replicated blocks. Mycorrhizal abundance will be assessed via microscopy techniques. Soil biota community structure will be determined using PLFA/NLFAs and molecular biology approaches. Field campaigns will be conducted over the growing season to collect samples and measure plant functional traits (e.g. gas exchange, water status, leaf chemistry and morphology). Continuous measurements of meteorological variables and soil-water status are available on site. Controlled environment studies will be conducted using advanced facilities on campus at the OU, using mesocosms of key plant-mycorrhizal associations. Split-plot experiments will investigate response to ambient and elevated CO2 concentrations under dry and wet conditions, and stable isotope 13CO2 labelling will be used to follow the fate of assimilated carbon.
Training and Skills
The student will receive full training in all necessary field and laboratory techniques and instrument use. The student will acquire specific skills in conducting field-based research and maintaining long-term experimental infrastructure; microbial ecology and molecular biology; plant ecophysiology; plant identification; scientific communication and networking.
NERC CENTA students are required to complete 45 days training throughout their PhD including a 10 day work placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes.
Year 1: Literature review, instrument and technique training, first season fieldwork and analyses.
Year 2: Set up mesocosm experiments, second season fieldwork, preparation of first manuscript, presentation at local conference.
Year 3: Complete analyses, write up thesis, presentation of results at international conference and second manuscript.
Partners and collaboration (including CASE)
The project will involve collaboration with Dr. Karen Olsson-Francis of the microbial ecology lab at the OU. There will be the opportunity for collaboration with other students at the site, including from the OU and Oxford University. The project will also link with the Drought-Net international network, providing the opportunity to join a network assessing responses of multiple types of ecosystems within an explicitly comparative experimental context.
We invite applications from students with a strong background in plant, soil or microbial ecology or physiology, an interest in global change processes and an enthusiasm for field work and independent research. Experience in experimental design and data analysis desirable. Clean driving licence preferred. The student will join a well-established team researching ecosystem processes, including a vibrant molecular ecology group, at the Open University.
Please contact firstname.lastname@example.org for further information.
Applications should include:
- a cover letter outlining why the project is of interest and how their skills match those required,
- an academic CV containing contact details of three academic references
- a CENTA application form, downloadable from: http://www.centa.org.uk/media/1202/centa-studentship-application-form.docx
- and an Open University application form, downloadable from: http://www.open.ac.uk/students/research/sites/www.open.ac.uk.students.research/files/documents/Application%20form.docx
Applications should be sent to
by 5 pm on Monday 22nd January 2018