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Rapid degradation of pyrogenic carbon

TitleRapid degradation of pyrogenic carbon
Publication TypeJournal Article
Year of Publication2012
AuthorsZimmermann, Michael, Bird Michael I., Wurster Christopher, Saiz Gustavo, Goodrick Iain, Barta Jiri, Capek Petr, Santruckova Hana, and Smernik Ronald
JournalGlobal Change Biology
Abstract

Pyrogenic carbon (PC- charcoal, biochar or black carbon) represents a poorly understood component of the global carbon (C) cycle, but one that has considerable potential to mitigate climate change through provision of long-term soil C sequestration. Mass balance calculations suggest global PC production and stocksare not in balance, indicating a major gap in our understanding of the processes by which PC is re-mineralized. Wecollected PC samples derived from the same wood material and exposed to natural environmental conditions for one year and 11 years.We subjected these materials to repeated laboratory incubation studies at temperatures of up to 60 °C, as ground surface temperatures above 30°C and up to 60°Coccur regularly over a significant area of the tropics and sub-tropics.

Mineralization rates were not different for the two samples and followed an exponential Arrhenius function that suggest an average turnover time of 67 years for conditions typical of a tropical savannah environment. Microbial biomass as measured by chloroform fumigation and DNA extractions was the same for the two samples, but abiotic CO2 production was lower for the fresh PC sample than for the aged sample. Nuclear magnetic resonance spectroscopy, hydrogen pyrolysis and scanning electron microscopy demonstrate thatthe measured CO2 production originates dominantly from polycyclic aromatic compounds rather than any minor labilecomponents. Therefore, rapid, sub-centennial rates of re-mineralizationof PC on the soil surface in tropical and sub-tropical environments may represent a major and hitherto unidentified mechanism for balancing the PC production at the global scale.

DOI10.1111/j.1365-2486.2012.02796.x