Author
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O Neill, Katherine |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 11/15/2007 Publication Date: 12/10/2007 Citation: O Neill, K.P. 2007. Are boreal soils a net source of carbon after fire? A chronosequence approach to assessing soil C dynamics in interior Alaska. In: Proceedings of the Workshop on Global Soil Change: Initiating an International Long-term Soil-Ecosystem Observatories Network, December 10-13, 2007, Durham and Goldsboro, North Carolina. 2007 CDROM. Interpretive Summary: Technical Abstract: Boreal forests soils have one of the highest carbon (C) densities in the world and are highly susceptible to wildfire. Post-fire changes in soil temperature and moisture have the potential to transform large areas of the landscape from a net sink to a net source of C due to reduced inputs and increased rates of heterotrophic respiration. Understanding how these processes respond and interact in the decades following disturbance is critical to modeling changes in ecosystem carbon balance under future climate scenarios. This presentation summarizes findings from a series of papers by K.P. O’Neill, E.S. Kasischke, and D.D. Richter. Soil respiration, soil microclimate, carbon storage and moss succession were measured along a 140-yr chronosequence of burned black spruce stands. Bryophyte species exhibited a distinct successional pattern in the first five decades after fire that corresponded to decreases in soil temperature and increased C accumulation in organic soil profiles. Post-fire changes in temperature and substrate quality indicate increased modeled rates of decomposition in humic organic material by a factor of 0.6 to 4.0 in the first 10 years after fire. A mass-balance model based on field measurements suggests that post-fire changes in root and microbial respiration caused these soils to function as a net source of carbon for 7 to 15 years after fire, releasing between 1.8 and 11.0 Mg C ha-1 to the atmosphere (12.4 to 12.6% of total soil organic matter). These estimates are on the same order of magnitude as C losses during combustion and suggest that current models have the potential to underestimate the effect of fire on C emissions by as much as a factor of two. |
