Simulating pyrogenic carbon in old growth Amazon forest sites with the RothC model

Pyrogenic carbon (PyC), the residues produced by the incomplete combustion of organic matter, is widely reported to play an important role in long term terrestrial carbon storing owing to its potential for millennial scale turnover when incorporated into soils.   

The Amazon has been subjected to infrequent anthropogenic fires within the past 10,000 years, as well as more recurrent and higher impact wildfires within the modern period. These fires have contributed PyC to the soil carbon stocks at varying rates across the Amazon basin, as revealed by extensive soil sampling across a range of locations with varying meteorological, soil, vegetation and land use conditions.

This dataset, accompanied by radiocarbon dating, reveals key information about the fire regime of the amazon basin (e.g. fire recurrence). However, some key aspects of the fire and PyC patterns require further investigation to gain further understanding of the Amazon fire regime and its carbon cycling significance. Additionally, research into the carbon cycling significance of PyC in the Amazon is currently limited and requires further assessment, as well as the role it may play under future climate changes.

Here, the RothC soil carbon model is used to evaluate:

• The specific conditions required to produce the observed soil organic carbon and PyC stocks per site
• The carbon cycling significance of PyC in the Amazon and under projected climate scenarios

This study uses site specific data (e.g. soil clay levels and site meteorology) as well as a range of modelled fire/PyC scenarios to reconstruct past conditions and evaluate soil PyC up to 2100. The investigation points to Amazon basin PyC stocks in the range of 100-1000’s of megatonnes with a millennial scale turnover rate, indicating that this is a key carbon store that needs to be considered under future climate modelling for the Amazon.