Overview

Project Highlights:

  • The project will address a significant knowledge gap in the tropical peatland carbon cyle: the influence of water table on DOC production/consumption and transport. It will inform one of the most pressing issues in global land-management, reconciling economic and social development in tropical forest regions with environmental and climate protection.
  • Multi-disciplinary, international supervisory team with strong publication track record, including a PhD student-led Nature paper on related work (Moore et al., 2013).
  • Fieldwork in Sarawak, Northern Borneo, with opportunity to gain first-hand experience of working in plantation and forest ecosystems and to use a range of field, analytical and data synthesis techniques.

Overview:

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.

Figure 1: Undrained peat swamp forest (a, left) and oil palm plantation (b, right) on tropical peatland. The land use change to plantation involves deforestation, drainage, mechanical compaction of the peat surface and the application of inorganic fertilizers.

Methodology

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.

Training and Skills

The student will acquire a wide range of biogeochemical, hydrological, ecological and modelling skills, and carry out field work in a tropical ecosystem setting. They will gain training and experience of research design and planning, writing peer-reviewed articles and presenting at conferences. Research objectives will be met using a mix of field experiments, hydrological measurements, various physical and chemical analyses, and modelling. The student will benefit from being part of a multidisciplinary team with a strong track record of publication and end-user engagement.

Timeline

Year 1: Undertake literature searches; define research plan & research questions; undertake basic research training; research and define methodologies; design experimental set up; visit field sites; carry out a relevant work placement (e.g. with a knowledge end-user organisation).

Year 2: Undertake field research programme, including setting up experiments & collecting initial results; carry out sample and data analysis and interpretation; use models as a framework for data interpretation; undertake iterative changes to research design, as required, and design additional analyses to address follow-on questions. Present initial results at a conference.

Year 3: Complete field research programme, data collection, analysis and modelling; start writing research chapters & first journal paper; present results at an international conference; produce guidance for plantation managers on minimising fluvial carbon fluxes from peatland plantations; complete thesis.

Partners and collaboration (including CASE)

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.

Further Details

Contact details: Prof Susan Page (sep5@le.ac.uk); Dr Mick Whelan (mjw72@le.ac.uk), both in School of Geography, Geology & the Environment, University of Leicester (https://www2.le.ac.uk/departments/geoggeolenv)