Fire | Carbon Cycle | PyC

Global fire emissions buffered by the production of pyrogenic carbon

Matthew W. Jones, Cristina Santín, Guido R. van der Werf and Stefan H. Doerr

Read our article in Nature Geoscience (2019)

A Global Dataset for Pyrogenic Carbon (PyC) Production Factors

The PyC in charcoal, ash and soot has unique biogeochemical properties that make it highly stable in soils and sediments.

PyC fluxes are typically on the order of 10-25% of the carbon emitted by fires, depending on the nature of the fuel and the fire.

We collated, screened and meta-analysed the production factors for specific fuel components observed in published studies.

There is variation across the fuel classes, with coarse woody (CWF) fuels producing more PyC per unit of carbon emitted than fine woody (FWF) and non-woody (NWF) fuels. No significant differences were observed within these fuel classes between aboveground (AG) and surface (S) fuel stocks.

Modelling the Global Production of Pyrogenic Carbon

We merged the PyC production factors with the Global Fire Emissions Database (GFED4.1s) to quantify the global PyC production flux.

Our central estimate for PyC production equates to 12% of the annual carbon emitted globally by landscape fires.

Regionality of PyC Production

PyC production per unit of vegetation carbon emitted is greatest in regions where large woody fuel stocks are burnt during fires.

Role of PyC in the Global Carbon Cycle

The production of PyC by fires may outweigh the decomposition fluxes of PyC produced in historic periods, resulting in a sink for atmospheric carbon.

However, our back-of-the-envelope estimates of decomposition suggest that the net flux could be either a source or a sink for atmospheric carbon at present.

Trends in vegetation burning can determine the balance of production and decomposition. When vegetation burning is on the rise, production fluxes can outweigh decomposition fluxes and “buffer” the loss of vegetation carbon stocks.

Global models do not currently include PyC fluxes. Models of the dynamics and decomposition of PyC will be critical to constraining the balance of the production and decomposition fluxes.

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