Carbon Down the Drain: Controls on DOC production and transport in oil palm plantations and forests on tropical peatland

Tropical peatlands are dense, long-term stores of carbon (C) that are vital components of global C soil-atmosphere exchange processes. They contain ~130 Gt C (20% of global peat C; Page et al. 2011, Dargie et al. 2017) but are very vulnerable to destabilisation through human- and climate-induced changes, including deforestation, drainage and fire, which enhance peat oxidation and convert long-term CO2 sinks into globally significant CO2 sources (Mietinnen et al 2017).

In SE Asia, plantation agriculture of oil palm is a key driver of peatland drainage and peat soil C loss. Although most of this C is lost to the atmosphere directly from the peat surface, dissolved organic carbon (DOC) in drainage water can also represent a significant loss process, and is a contributor to indirect CO2 emissions (Cook et al., 2018; IPCC, 2014). DOC fluxes vary with land use history but also with factors like water table depth (which can influence the rate of peat decomposition in the unsaturated zone) and water movement (which controls DOC translocation and removal rates).

Fluxes tend to be higher in more deeply drained sites. Understanding of the drivers of patterns of DOC concentration change remains uncertain but likely relates to a) DOC production and consumption processes within the peat column that are dependent upon various factors linked to water table position, including peat moisture, peat substrate quality and redox potential, and b) alterations in discharge, which may result from variations in rainfall and evapotranspiration, but also differences in plantation management.

This project will investigate the physical, hydrological and chemical interactions which control DOC losses from tropical peat under oil palm and forest in Sarawak (Malaysia Borneo). The project outputs will improve our knowledge of carbon dynamics in drained tropical peatlands, and underpin the development of practical land-management measures to reduce overall CO2 losses from peat plantation systems, contributing to emissions mitigation and to more responsible peatland management.

Previous work on fluvial C fluxes in oil palm plantations employed field-scale temporal and spatial measurements of drainage water discharge and organic C (quantity, quality) to estimate DOC fluxes. This PhD will use the same study site in Sarawak, Malaysia and take this work forward by investigating, for the first time, how short- and medium-term water table fluctuations and associated changes in the peat physical and chemical environment influence DOC production and consumption, transport and quality.

The student will design and conduct novel manipulative experiments to explore detailed dynamics of DOC production and transfer. Specifically, a) the extent to which water table fluctuations influence accumulation, residence time and quality of DOC within the peat column; and b) the influence of increased peat bulk density (a consequence of peat subsidence and plantation operations) which likely decreases peat pore volume and increases DOC residence time.

The research will be a carried out in close collaboration with the Malaysian Palm Oil Board who manage the field study facilities at the plantation site in Sarawak under their Tropical Peat Research (TROPI) programme. The student will also interact with other field scientists (Malaysian and international) using the same site to study ecosystem carbon balance (e.g. using eddy covariance flux towers).

The supervisory team includes the scientist in charge of the MPOB’s peat research programme, Dr Lip Khoon Kho, providing an exceptional pathway for research impact.

Entry requirements
Applicants are required to hold/or expect to obtain a UK Bachelor Degree 2:1 or better in a relevant subject. The University of Leicester English language requirements apply where applicable.

How to apply
Please refer to the CENTA Studentship application information on our website for details of how to apply.

As part of the application process you will need to:
• Complete a CENTA Funding form – to be uploaded to your PhD application
• Complete and submit your PhD application online. Indicate project CENTA2-GGE20-PAGE in the funding section.
• Complete an online project selection form Apply for CENTA2-GGE20-PAGE