Geochemical control of organic matter turnover in peatlands: Long-term security or short-term vulnerability of a major carbon store?

Lead Research Organisation: Queen Mary, University of London
Department Name: Geography

Abstract

Peatlands cover vast areas of the world - around 4 million square kilometres - and store about as much carbon as do the living plants in tropical rainforests. For the past 5,000-10,000 years, the plants living on peatlands have been fixing carbon dioxide from the atmosphere and storing it as dead plant matter - 'peat'. In a future warmer, and possibly drier, climate, this stored carbon could be respired back to the atmosphere or leached into rivers. Will increased temperatures and decreased rainfall lead to rapid loss of the peatland carbon store? If so, then the extra carbon released from peatlands could enhance 'greenhouse' warming further, leading to a runaway positive feedback on global climate. Or will rapid climate change trigger a shift to peatland types that accumulate peat (and store carbon) at a faster rate than present-day peatlands? If the latter, then peatlands could buffer further climate change. In this project, we will investigate the three-way interactions between plants, decomposition of peat and environmental factors such as temperature. Although there have been many studies on decomposition of forest and grassland soils, surprisingly little is known about how peat decays. We are particularly interested in how differences in the chemistry of different types of plants (and of the peat they produce) affects how quickly the peat decomposes and how it responds to changes in temperature. Of special concern is the bog-moss, Sphagnum, which has a unique chemical composition that makes it very resistant to decomposition. Our field site is a peatland in central Sweden that shows a great variety of plant types and environmental conditions, ranging from swamp forest to fen to bog. Using the full range of variation, we will analyse in detail the chemistry of a wide variety of living plants and their recently dead remains. We will also examine changes in chemistry and rates of peat accumulation in short cores that provide a historical record of the past 300 years or so. In addition, we will track how the chemistry of new and old peat changes as it decomposes, under higher temperatures and under drier conditions. The results of these studies will help us to predict how the peatland carbon store will fare in the face of future climate change.
 
Description In this project, we investigated the three-way interactions between plants, decomposition of peat and environmental factors. Although there have been many studies on decomposition of forest and grassland soils, surprisingly little is known about how peat decays. We were particularly interested in how differences in the chemistry of different types of plants (and of the peat they produce) affect how quickly the peat decomposes. Of special concern was the bog-moss, Sphagnum, which has a unique chemical composition that makes it very resistant to decomposition. Our field site was a peatland in central Sweden that shows a great variety of plant types and environmental conditions, ranging from swamp forest to fen to bog. Using the full range of variation, we analysed in detail the chemistry of the recently dead remains of the main plant types. We also examined changes in chemistry and rates of peat accumulation in short cores that provide a historical record of the past 100 years or so. In addition, we tracked how the chemistry of new and old peat changes as it decomposes under controlled conditions in the laboratory.



We found that Sphagnum traits vary along gradients of water- and light-availability, and these traits can be used to predict rates of litter production and decomposition. The litter of vascular plants, Sphagnum and other mosses differed substantially in chemical composition when it was newly-produced. We found four phenol derivatives specific to Sphagnum litter and, along with other phenols specific to vascular plants, these were useful biomarkers for tracking past changes in plant inputs and decomposition. In peat cores spanning about 100 years, Sphagnum components became preferentially preserved in older peat, and there was a gradual shift in geochemical composition, reflecting loss of easily-decomposed components and accumulation of more resistant components over time. These profiles allow us to test physically-based models of peat carbon dynamics, providing important process understanding and allowing robust estimation of model parameter values.
Exploitation Route The results of these studies will help us and other researchers to predict how the peatland carbon store will fare in the face of future climate change. In addition to enhancing understanding of fundamental processes, the research has uncovered key traits and geochemical biomarkers for Sphagnum, an under-studied genus that is the keystone in peatland carbon cycling.
Sectors Environment

 
Description (Note: This grant was awarded before NERC introduced 'Pathways to Impact' as part of the application process.) The main users of this research are other academics, particularly those with interests in the terrestrial biogeochemistry of carbon and in turnover of soil organic matter. As such, most of the impact of the research has been academic, i.e., enhancing scientific understanding of the controls on a major carbon store; development and utilisation of innovative approaches which cross disciplinary boundaries of ecology, soil science and geochemistry; contributing towards the health of soil science as an academic discipline; training highly skilled researchers. The principal economic and social impact has been in training of skilled people for non-academic professions. One of the PDRAs employed on the project is now the Executive Officer of the British Society of Soil Science. As such, she has an influential role in policy and education related to soil science.
First Year Of Impact 2009
Sector Environment
Impact Types Societal,Policy & public services

 
Description Open CASE Studentship
Amount £80,876 (GBP)
Funding ID NE/J016608/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2012 
End 09/2016
 
Description Open CASE Studentship - Partner funding
Amount £14,999 (GBP)
Organisation Broads Authority 
Sector Public
Country United Kingdom
Start 10/2012 
End 09/2015
 
Title Sphagnum functional traits database 
Description The dataset reports morphological and physiological traits of Sphagnum shoots, with associated canopy variables. The data are associated with the following publication: Laing, C. G., Granath, G., Belyea, L. R., Allton, K. E., & Rydin, H. (2014). Tradeoffs and scaling of functional traits in Sphagnum as drivers of carbon cycling in peatlands. Oikos, 123(7), 817-828. doi:10.1111/oik.01061 
Type Of Material Database/Collection of data 
Year Produced 2014 
Provided To Others? Yes  
Impact The database has been made publicly available via an institutional repository, Queen Mary Research Online. Morpological and physiological traits of plants, such as those reported in this database, are key to understanding and predicting carbon cycling in ecosystems, as well as ecosystem responses to climate change. 
URL http://qmro.qmul.ac.uk/jspui/handle/123456789/6179
 
Description Holocene Peatland Database 
Organisation Lehigh University
Country United States 
Sector Academic/University 
PI Contribution I contributed data to the Holocene Peatland Database and participated in a NSF-funded workshop to explore ways of analysing the data.
Collaborator Contribution The partner set up and maintains the Holocene Peatland Database, organised an international workshop and led on analysis of the data.
Impact The collaboration is multi-disciplinary; participants and co-authors have expertise in palaeoecology, ecology, hydrology, and palaeoclimate. Loisel J, Yu Z, Beilman DW, Camill P, Alm J, Amesbury MJ, Anderson D, Andersson S, Bochicchio C, Barber K, Belyea LR, Bunbury J, Chambers FM, Charman DJ, De Vleeschouwer F, Fialkiewicz-Koziel B, Finkelstein SA, Galka M, Garneau M, Hammarlund D, Hinchcliffe W, Holmquist J, Hughes P, Jones MC, Klein ES, Kokfelt U, Korhola A, Kuhry P, Lamarre A, Lamentowicz M, Large D, Lavoie M, MacDonald G, Magnan G, Mäkilä M, Mallon G, Mathijssen P, Mauquoy D, McCarroll J, Moore TR, Nichols J, O Reilly B, Oksanen P, Packalen M, Peteet D, Richard PJH, Robinson S, Ronkainen T, Rundgren M, Sannel ABK, Tarnocai C, Thom T, Tuittila E-S, Turetsky M, Väliranta M, van der Linden M, van Geel B, van Bellen S, Vitt D, Zhao Y, Zhou W (2014) A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation. The Holocene 24(9), 1028-1042.
Start Year 2013
 
Description Uppsala University collaboration 
Organisation Uppsala University
Country Sweden 
Sector Academic/University 
PI Contribution The research team carried out field and lab experiments on carbon turnover, monitored environmental conditions at the field site, and analysed samples for biogeochemistry.
Collaborator Contribution The partners provided local expert knowledge and logistical support for fieldwork in Sweden, where they have been carrying out research at this site for decades. Their on-going research on plant ecophysiology and interspecific competition in peatland bryophytes formed a part of the work on the inter-relationship of plant traits, litter geochemistry and environmental constraints.
Impact The collaboration is interdisciplinary. The Swedish partners (Rydin and Granath) have expertise in plant ecology and plant physiology; the QMUL team members have expertise in ecosystem ecology, soil science and biogeochemistry. Laing, C. G., Granath, G., Belyea, L. R., Allton, K. E., & Rydin, H. (2014). Tradeoffs and scaling of functional traits in Sphagnum as drivers of carbon cycling in peatlands. Oikos, 123(7), 817-828. doi:10.1111/oik.01061 Sphagnum functional traits database: http://qmro.qmul.ac.uk/jspui/handle/123456789/6179
Start Year 2007
 
Description Factors affecting carbon cycling in Sphagnum 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Members of the team contributed a 'blogpost', which appeared on the website of a major international ecology journal (Oikos).

This activity increased awareness of the importance of Sphagnum in the global carbon cycle. The article level metric (Altimetric = 13) is amongst the highest ever scored in this journal (ranked #36 of 656).
Year(s) Of Engagement Activity 2014
URL http://www.oikosjournal.org/blog/factors-affecting-carbon-cycling-sphagnum
 
Description Member of 'Peatlands and Climate Change' Expert Group, International Peatland Society 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact The 'Peatlands and Climate Change' Expert Group was established by the International Peatland Society to disseminate current scientific, evidence-based understanding of peatlands and climate change to policy makers, NGOs, industry and the general public. Examples of future activities include running symposia or workshops for particular groups of end-users, and the production of position papers on particular themes, press releases and more general outreach material.
Year(s) Of Engagement Activity 2017,2018
URL http://peatlands.org/about-us/commissions-expert-groups-and-sab