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The competitive response of meadow species along a hydrologic gradient is well established. Field and mesocosm experiments have shown species segregate along a hydrological niche gradient. However the synergistic aspect of increasing species richness hasn’t been tested along hydrologic gradient.  In addition the response of the soil carbon cycle to changing plant species composition and biomass along a hydrologic gradient is of great interest in the context of current global changes and the likely impacts on local hydrology. This link between biological species composition and the flows of carbon to and from the soil and the resulting impacts on carbon sequestration is one of the great challenges in ecology. With changing climate and water availability impacting terrestrial communities across the world, this question of how the changes in biodiversity affect ecosystem function and the soil carbon cycle in particular is of paramount importance to ecosystem stability. We intend to investigate the species response, carbon balance and resilience of multi-species plant assemblages to imposed hydrological change.

Figure 1. OU controlled water table Mesocosm array


The work will involve two aspects: a mesocosm experiment and a field experiment. In the mesocosm: 1, 3, and 7 species mixtures will be grown along 4 water table depths at the OU’s experimental mesocosms. Carbon flows from plant to soil and back to the atmosphere will be monitored by labelling the plant-soil system with 13C-CO2 at 99atom% 13C and then tracking the carbon through the various components of the plant-soil system, including plant shoot and root, bulk soil and soil-respired CO2. In addition there is the potential for stable isotope of PLFA/NLFAs probing will be used to identify 13C taken up by different groups of soil organisms, which determine to a large degree the below ground processes involved in either sequestering to or releasing carbon from the soil. Plant species cover, biomass production will be also be monitored.

Training and Skills

Student will be trained in practical ecohydrological techniques within the OU group and Floodplain Meadows Partnership team.  Training in laboratory skills such as soil microbiological methods will also be arranged with collaborators.

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:

Pilot monitoring of field site and sampling. Laboratory analysis of samples. Attend British Ecological Society meeting.

Year 2:

Set-up of experimental mesocosms with species, hydrology combinations. Main sampling of both vegetation and soil undertaken.

Year 3:

Final season data collection and integration of experimental and field observations. Present at British Ecological Society Annual meeting.

Partners and collaboration (including CASE)

Collaboration with Dr. Karen Olsson-Francis of the microbiology lab, OU. Floodplain meadows Partnership (OU). Professor Pal-Axel Olsson (Lund University) and Prof. Jonathan Adams (Cranfield University).


Further Details

Students should have a strong background in ecology or plant biology and enthusiasm for both field and laboratory work. Experience of undertaking independent field work and laboratory experience of soil chemistry / microbiology methods is desirable. The student will join a well-established team researching plant ecology/ecohydrology at the Open University.

Please contact Yoseph.Araya@open.ac.uk for further information.

Applications should include:

 Applications should be sent to


by 5 pm on Monday 22nd January 2018