Biscuit Fire Study

Summary

The annual exchange of CO2 between forests and the atmosphere can be profoundly affected by wildfire, especially in regions like the Pacific Northwest where forest biomass potential is relatively high. The pulse of carbon released to the atmosphere by large-scale fire events such as the Biscuit may reduce the net annual uptake of carbon by Oregon forests by as much as 25%. Moreover, changes in the size of detrital pools and age structure of living plants that result from wildfire can influence the exchange of carbon between the forest and atmosphere for decades to come. A better understanding of how wildfire and subsequent salvage practices affect the transfer of carbon between living, dead, black, and atmospheric carbon pools is necessary in order to link disturbance and forest management practices to regional carbon balances.

The scale of recent high-severity wildfire events across the western U.S. has increased the focus on post-fire ecology and management. Much of this concern revolves around feedbacks between multiple fire events closely spaced in time and how forest ecosystems will respond to altered disturbance regimes under current trends in climate, fire behavior, and management objectives. Post-fire logging of burned trees is often presumed to moderate the feedback between two subsequent fires by reducing fire-generated fuel loads and thus the potential fire behavior/effects in the event of a reburn. However, the efficacy of post-fire logging in reducing fuel loading has never been tested and its ecological effects, such as potentially altered successional pathways, are virtually unknown. Moreover, recently burned areas represent an important type of habitat that many species of animals have evolved to utilize. Snags (standing dead trees) provide critical nesting and foraging habitat for birds and small mammals, and as they decay and fall, create additional habitat for small mammals and terrestrial amphibians as coarse woody debris. Removal of the largest wood from a site is likely to have large consequences for the species of wildlife that are able to persist there. Post-fire logging is thus likely to interact with several other management objectives on the landscape.

Objectives

The combination of fires we are sampling allows us to address these research questions:

• Quantify the transfer of carbon between living, dead, black and atmospheric pools resulting from the Biscuit event . With this information we can describe the pulse of carbon released as a result of the Biscuit and compare that quantity of carbon that exchanged regionally in the same year and historically in the Biscuit perimeter.
  
• Collect base-line measurements of post-fire carbon pools, vegetation/fuel profiles, and vertebrate composition. With this information we can, in future years, back-calculate the post-fire trajectory of NEP and biotic succession both above and belowground.
  
• How do communities (vegetation, birds, small mammals) and fuel structure/potential fire behavior change after high-severity fire and over early succession?
  
  a. 2-3 year time scale ? (empirical field data)
  b. 17-18 year time scale ? (empirical field data)
  c. And beyond ? (modeling exercise parameterized with above data)
  
  
• How does postfire logging affect the community/fuel/fire dynamics observed in question (1)?
  
• How do communities (vegetation, birds, small mammals) and fuel/stand structure respond to a repeat fire within 15 years (a.k.a. ‘reburn’ per Brown et al. 2003)? Is it fundamentally different than that following a single fire?
  
• How does postfire logging influence the response to repeat fire observed in question (3) ?
  
• What are early patterns of conifer regeneration in a landscape-scale fire?
  
  a. abundance, distribution, composition, associated vegetation
  b. early regeneration timing
  c. distribution of seed sources in a large mixed-severity burn
  d. dominant abiotic and biotic controls on regeneration levels