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AGU: Journal of Geophysical Research, Biogeosciences


Index Terms

  • 0428 - Carbon cycling
  • 0414 - Biogeochemical cycles, processes, and modeling

Paper in Press


Fuel moisture influences on fire-altered carbon in masticated fuels: An experimental study

Key Points
  • Increased fuel moisture led to increased Soot-BC in masticated fuels
  • Indiscriminate combustion of precursors at lower fuel moistures limits Soot-BC
  • Soot-BC production rates ranged from 0.02 to 0.05% relative to unburnt OC


Nolan W Brewer

Alistair Matthew Stuart Smith

Jeff A Hatten

Philip Edward Higuera

Andrew Hudak

Roger D. Ottmar

Wade T Tinkham

Biomass burning is a significant contributor to atmospheric carbon emissions, but may also provide an avenue in which fire-affected ecosystems can accumulate carbon over time, through the generation of highly resistant fire-altered carbon. Identifying how fuel moisture, and subsequent changes in the fire behavior, relates to the production of fire-altered carbon is important in determining how persistent charred residues are following a fire within specific fuel types. Additionally, understanding how mastication (mechanical forest thinning) and fire convert biomass to black carbon is essential in understanding how this management technique, employed in many fire prone forest types, may influence stand-level black carbon in soils. In this experimental study fifteen masticated fuel beds, conditioned to three fuel moisture ranges, were burnt and production rates of pyrogenic carbon and soot-based black carbon were evaluated. Pyrogenic carbon was determined through elemental analysis of the post-fire residues, and soot-based black carbon was quantified using thermo-chemical methods. Pyrogenic carbon production rates ranged from 7.23 to 8.67% relative to pre-fire organic carbon content. Black carbon production rates averaged 0.02% in the 4 to 8% fuel moisture group, and 0.05% in the 13-18% moisture group. A comparison of the ratio of black carbon to pyrogenic carbon indicates that burning in fuels ranging from 13-15% moisture content resulted in a higher proportion of black carbon produced, suggesting that the precursors to black carbon were indiscriminately consumed at lower fuel moistures. This research highlights the importance of fuel moisture and its role in dictating both the quantity and quality of the carbon produced in masticated fuel beds.

Received 21 May 2012; accepted 24 November 2012.

Citation: Brewer, N. W., A. M. S. Smith, J. A. Hatten, P. E. Higuera, A. Hudak, R. D. Ottmar, and W. T. Tinkham (2012), Fuel moisture influences on fire-altered carbon in masticated fuels: An experimental study, J. Geophys. Res., doi:10.1029/2012JG002079, in press.