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Investigation of peatland restoration (grip blocking) techniques to achieve best outcomes for methane and greenhouse gas emissions / balance - SP1202

Peatlands are large stores of carbon (C). During photosynthesis, peatland plants take up atmospheric carbon dioxide (CO2), the carbon from which is ultimately converted into plant tissue. As peatland plants die, they partially decay which releases some of their 'locked up' carbon back into the atmosphere (in the form of the decay gases carbon dioxide (CO2) and methane (CH4)). However, when plants don't fully decay peat is formed. Over the last 4000-10000 years peatlands have expanded and thickened, thus taking up more carbon from the atmosphere than they have returned. As a result, they have had a net cooling effect on global climate by lowering greenhouse gas concentrations.

Many peatlands in developed countries such as the UK have been drained for agricultural activity. In the UK the most extensive peatland type is blanket bog, found mainly in the uplands. Between the 1960s and the 1980s many blanket bogs were drained using shallow ditches called grips in an attempt to improve grass yields for grazing animals. Although such drainage proved ineffective at improving agricultural yields, it led to the drying of the peat. Peat decays slowly in natural waterlogged conditions but much more rapidly when it is drained, such that the peatland becomes a strong net emitter of CO2, thus contributing to global warming.

Restoration of drained or gripped peatlands is promoted as a means of restarting their carbon sink function. However, very few restoration schemes have considered the release of CH4 from peatlands. CH4 is a much more potent greenhouse gas than CO2, with a ‘global warming potential’ that is about 25 times higher. Therefore, although CH4 is emitted from peatlands in relatively small quantities, its effects must be considered when judging the success of peatland restoration from the perspective of climate change. A recent review of the academic and research literature carried out for Defra (project SP0574 - A Literature Review of Evidence on Emissions of Methane in Peatlands) noted that (i) very little is known about how restoration affects CH4 emissions from restored peatlands and (ii) there is a need to identify those restoration methods that produce the best return in terms of reducing CH4 emissions and maximizing net CO2 uptake.

The proposed project will address both (i) and (ii). It will do so by updating and expanding the literature review carried out for Defra project SP0574 (in particular in the context of restoration of blanket peatlands) and by undertaking a comprehensive set of laboratory experiments and field trials that investigate how the range of restoration measures used on drained blanket peatlands affect greenhouse gas (GHG) emissions. The laboratory experiments will be carried out at the Open University’s Ecosystem Research Group’s world-class laboratory facility. Samples of peat taken from a typical drained peatland in the Upper Conwy in North Wales (the Migneint) will be subjected to a range of ‘treatments’ that replicate different restoration measures used in the field. The peat samples will be maintained in state-of-the-art environmental cabinets that reproduce real-world weather conditions. Measurements will be taken of the CO2 and CH4 emissions from these samples (and also of another greenhouse gas – nitrous oxide – N2O) to see which restoration measures are best at reducing or stopping GHG emissions.

The laboratory study will feed into a field trial of the most promising restoration measures. Field trials will be carried out at the same location from which laboratory cores were obtained at the National Trust owned Migneint blanket peatland in North Wales. The experiments will build on a major peat monitoring and experimental infrastructure established by the Centre for Ecology and Hydrology for their Carbon Catchments programme. The rigorously designed field experiments will exploit ongoing peat restoration work by the National Trust, establishing controlled, replicated manipulations with full pre-treatment measurements within a large area of grip blocking planned for late 2010 / early 2011. We will measure how much CO2, CH4 and N2O is emitted from the various types of restored peatland over a period of three years so as to allow for inter-annual variability in weather conditions, with supporting measurements including water-table position, meteorological variables, dissolved carbon fluxes and detailed identification of the mechanisms by which CH4 is produced and consumed. We will reference the emissions of CO2, CH4, and N2O from the different restored areas to those from a nearby area of near-natural peatland and will also compare them with fluxes from an area that is still actively drained.

The combination of the laboratory and field experiments will allow us to identify those restoration options which produce the greatest benefits in terms of conserving the peatland carbon store and minimising GHG emissions. We will also evaluate the potential of mitigation options, including vegetation management and sulphur amendment, to reduce CH4 release from restored peats.
The project has four main objectives:
1. To undertake a literature review of the materials and methods for grip blocking and peatland restoration currently in use in the UK and the impacts of the techniques on GHG emissions.
2. To undertake controlled, small-scale laboratory experiments to see how different grip blocking techniques might affect GHG emissions from restored blanket peatland.
3. To conduct larger-scale field trials of different grip blocking methods to see how these affect GHG emissions from restored blanket peatland.
4. To report the results of (i) to (iii) in a format that can be easily understood by site managers and also in the international scientific literature.

Objective 1 feeds into both Objective 2 and Objective 3 and will help us decide which grip blocking methods and which factors affecting GHG losses from restored blanket peatlands to investigate most closely. Objective 2 will provide important context for Objective 3. For example, the laboratory experiments may suggest that water-level regime is an important control on rates of methane production in blocked grips, in which case greater attention will be given to the factors affecting water-table regime in the field trials.
Project Documents
• FRP - Final Report : SP1202 FinalReport   (861k)
• ANX - Annex : SP1202 FinalReport AppendixA   (629k)
• ANX - Annex : SP1202 FinalReport AppendixB   (52k)
• ANX - Annex : SP1202 FinalReport AppendixC   (2389k)
• ANX - Annex : SP1202 FinalReport AppendixD   (1490k)
• ANX - Annex : SP1202 FinalReport AppendixE   (1391k)
• ANX - Annex : SP1202 FinalReport AppendixF   (784k)
• ANX - Annex : SP1202 FinalReport AppendixG   (645k)
• IR - Interim Report : Controlled Environment (Mesocosm) Experiment results   (1459k)
Time-Scale and Cost
From: 2010

To: 2015

Cost: £1,130,606
Contractor / Funded Organisations
University - Leeds
Environmental Protection