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PEATland modelling for global carbon cycle and climate models

Periodic Reporting for period 1 - PEATmod (PEATland modelling for global carbon cycle and climate models)

Reporting period: 2016-03-01 to 2018-02-28

Peatlands are present in humid regions. In these ecosystems, water remains close to the surface and stagnates or flows very slowly. In peatlands, vegetation stores carbon through photosynthesis while the waterlogged conditions prevent this carbon to naturally decompose. This results in an accumulation of carbon and thus in peat growth. However, peatlands are also emit carbon, in form of methane and CO2 from respiration (Figure 1).

Since their development, the imbalance between carbon storage and release has allowed these ecosystems to accumulate large amounts of carbon. It is estimated that they contain 530-694 Gt of carbon, i.e. almost as much as the total amount of carbon in the atmosphere.
Changes in climate and atmospheric CO2 concentration affect photosynthesis, respiration and methane production in different ways and at different magnitudes. The effect of these changes in peatlands remains debated and there is a risk that peatlands could turn into net carbon sources, thus increasing the CO2 concentration of the atmosphere. Considering the amount of carbon that they store, it is important to assess whether large carbon quantities will be released or if carbon storage will be enhanced in the future. A better insight into this question can be gained from studying the feedback processes between peatlands, the atmosphere and hydrology.

Current knowledge on peatlands dynamics allows to adequately represent carbon exchanges in peatlands, especially for peatlands at high latitudes. This knowledge has been used to develop peatland modules in some of the existing global vegetation models in order to assess the role of peatlands at global scale. Although some models already include carbon functions and mechanisms in peatlands, the feedbacks between hydrology, vegetation and carbon are missing from most models, and this limits the accurate representation of the impact of peatlands on the atmosphere and the global carbon cycle.

The aim of the project was to take the firsts steps to include the necessary feedback mechanisms into the peatland modules in global vegetation models. We chose to focus on low-latitude peatlands, in order to integrate these important ecosystems into models.

Although peatlands are present at all latitudes, their properties change depending on the local topographical, climatic and geological conditions. To be able to represent peatlands in global models, the processes driving their functioning and resilience need to be identified.

The approach followed during the project included a wide range of peatland experts from different regions of the world. The results showed that low-latitude peatlands should be considered separately from high-latitude peatlands for modelling purposes. Key areas where research is needed were identified. The first steps toward the inclusion of low-latitude peatlands in global vegetation models were performed.

In conclusion, the project brought expertise in peatland modelling back to Europe and enabled to strengthen the links between the peatland science communities in North America, South America, Asia and Europe.
Acknowledging that processes understanding and expertise in northern peatlands is far more advanced than that for low-latitudes peatlands, we focused on low-latitude peatlands and reached out to establish new collaborations with experts in low-latitude peatlands.
Meetings with collaborators from Bern University and University of New Hampshire in Exeter were key to set-up the framework and methods used along the project.

We developed a new method to enhance collaboration between peers and integrate knowledge from the field into modelling. The approach highlighted that the main interactions between peat properties, vegetation, hydrology and the atmosphere remain the same as for high-latitude peatlands. However, it was identified that the hydrological processes are key in low-latitude areas and that more work is needed to comprehend the role of floods, droughts, seasonality and sea regressions. Moreover, it is crucial to gather more hydrological data from the field as well as data on hydraulics, decomposition and vegetation productivity. The result of this effort was the development of a new model framework for low-latitude peatlands to allow their integration in global models. This include the processes and feedbacks that are considered most relevant and the areas where more data is needed as well as the areas critically needing more research. Our results also include a new classification for low-latitude peatlands to allow better communication and comparison in the community. This classification is a useful tool for both ecological and modelling studies.

The project results represent an important step toward the assessment of tropical peatlands dynamics and their interactions with the atmosphere. The development of a conceptual model is key to grasp the most important components of the system in order to build a strong and useful model. It also is useful to develop a new tool to assess carbon fluxes to develop regional estimates, which are needed in countries part of the Kyoto protocol.

The project has been presented at different stages at international conferences in Vienna, Hawaii in 2017 and at the international PAGES C-PEAT workshop held in Exeter (2019). The project was also presented twice at the ecology group meeting of the Geography department in Exeter. Meetings with collaborators from Bern University and the University of New Hampshire were organized in Exeter.

Two publications are nearing completion. Experts knowledge proved really valuable and emphasized the need to convert field-based knowledge and expertise into a robust process-understanding base before developing algorithms.
We developed a new collaborative method applicable to all scientists consisting in stimulating reflexion, brainstorming and exchanges of ideas within a scientific community or reaching out to scientists in a related field. This approach allows to save time and logistics – people involved in the process being already at a conference - and therefore also saving money.

This method has enhanced collaborations among peat scientists across different regions and allowed the development of new collaborations between scientists working in high- and low-latitude peatlands.
Our new framework built the sound basis to develop models using cutting-edge understanding in the field. It also raises awareness of knowledge gaps and lack of resources allocated to low-latitude peatland research.
Comparing knowledge and functioning of low- and high-latitude peatlands and stimulating comparisons between these two very different ecosystems brought to the climate community an improved understanding of peatland dynamics as well as increased awareness of the role of peatlands on the global carbon cycle.

The project results are useful to the vegetation and climate modelling communities as they will strengthen the models and therefore improve carbon exchanges estimates between vegetation and the atmosphere. As a result, climate projections and regional assessments of the impact of climate change will be more accurate. An increased awareness of the role of peatlands in the global system as well as in local communities will enable to develop mitigation strategies for the local communities living in peatlands areas well as for national climate mitigation targets.
Peatlands carbon cycle