£800k study to look at link between fire and climate change

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University of Stirling experts will lead a new £800,000 study investigating the behaviour of pyrogenic carbon – partly-burned plants left behind following fire – and its potential impact on climate change.

Fires affect more than 500 million hectares of the world’s surface each year – with the majority occurring naturally – and leave residues of pyrogenic carbon (PyC), similar to charcoal.

However, due to the lack of data available, it is not clear what proportion of soil carbon derives from PyC; by which processes PyC is incorporated into the soil; how quickly it returns to the atmosphere as carbon dioxide; and how these processes may be impacted by climatic conditions.

Funded by the Natural Environment Research Council, the new three-year project – led by Dr Jens-Arne Subke, Associate Professor in the Faculty of Natural Sciences – aims to address these gaps in knowledge by focusing on a tropical savannah in Gabon, Central Africa.

Jens-ArneSubke
With global models predicting that fire frequency and intensity will increase in many areas, it is important to understand how these carbon deposits behave, and ultimately what their impact is on ecosystems and climate change.
Dr Jens-Arne Subke Associate Professor

Dr Subke, Lead Principal Investigator, said: “It is estimated that pyrogenic carbon contributes between 116 and 379 teragrams of carbon to soils each year – a considerable amount given that the annual net increase of carbon to all of Earth’s ecosystems on land is around 4,300 teragrams. In some fire-prone ecosystems – such as tropical savannahs – deposits from fire can account for as much as half of total carbon stored in soils.

“With global models predicting that fire frequency and intensity will increase in many areas, it is important to understand how these carbon deposits behave, and ultimately what their impact is on ecosystems and climate change.

“Our project will gather new data on pyrogenic carbon and investigate how levels change with soil depth under contrasting positions within the landscape, and in relation to the return intervals of fires. We will also consider the role of soil animals and microbial organisms in processing – and potentially stabilising – pyrogenic carbon in the soil, and how long it remains in the soil at given depths.

“We will use our data to update models to enable forecasts of carbon cycle dynamics that reflect the input and turnover of pyrogenic carbon in soils – ensuring future research and policies are better informed.”

Collaboration

Dr Subke will work alongside fellow Principal Investigators: tropical ecologist Professor Kate Abernethy (University of Stirling); Dr Philippa Ascough (Scottish Universities Environmental Research Centre, University of Glasgow), an expert in global biogeochemical cycles and specifically pyrogenic carbon; and Professor Francesca Cotrufo (Colorado State University), an international leader in modelling soil organic matter dynamics.

Senior researcher Dr François-Xavier Joly (University of Stirling) will provide further critical expertise in soil organic matter formation and faunal processing of biomass, while Dr Kathryn Brun-Jeffery (National Parks Agency of Gabon) will link the findings to carbon accounting for the National Climate Council of Gabon.

The team will carry out a number of experiments in Gabon, where there is a significant abundance of PyC in the soil profile, and link the results to long-term studies at the country’s Lopé National Park. Previous work involving Professor Abernethy has established a significant carbon sink in mature tropical forests within the National Park, and the new project will inform understanding of carbon dynamics across the landscape, in both forest and savannah.

Experiments will include targeted soil coring, tracing of PyC using stable isotopic labelling in areas of known fire return intervals, and the dating of samples to understand turnover in soils. The scientists believe the work will help them to gain a better mechanistic and quantitative understanding of soil PyCdynamics.

Climate system

Dr Subke added: “Public understanding of the significance of climate change has probably never been greater than it is today – there’s a genuine interest in understanding ways in which natural and managed ecosystems respond and interact with the Earth’s climate system.

“The findings of our research will be directly useful to land managers working in fire-prone landscapes, who wish to maximise carbon storage as a critical ecosystem service, and will enable better predictions of carbon uptake and release by natural and managed ecosystems.

“This will help form the basis of an informed understanding by scientists, as well as the public, of how natural processes and active management of ecosystems affect future carbon dioxide concentrations in the atmosphere – and, ultimately, climate change.”

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