Response of Soil Bacteria to Wildfires

The Science

To better understand how wildfires may impact belowground processes in the boreal forest, researchers studied the role of three bacterial traits—fire survival, fast growth, and an affinity for post-fire soil conditions—in driving soil bacterial community composition years following wildfires. Following burning, fast-growing bacteria rapidly dominate soil communities but return to pre-burn levels by 5 years post-fire. While fire survival and affinity for post-fire soil conditions do influence post-fire soil community composition, neither trait is particularly influential. This study also found that post-fire soil respiration is unlikely to be limited by fire-induced changes in bacterial communities.

The Impact

Little is understood about the roles of soil bacteria in post-fire carbon cycling, which is important given the current shift in wildfire regimes in the boreal forest towards more frequent, higher severity fires. Researchers developed a traits-based framework of bacterial responses to wildfire that may be useful for understanding the impact of changing wildfire regimes on trajectories of bacterial community recovery and their functioning.

Summary

While ecological predictions can be made based on the genetic features of a given organism or community, the extraordinary diversity of soil bacteria impairs the ability to use taxonomy alone to confidently infer bacterial traits. This study used an uncommon approach to assign traits to bacteria in a high-throughput manner. Researchers first explicitly determined which individual bacterial taxa can survive fires, can grow quickly, and are well-adapted to the post-fire environment. To identify traits, scientists worked with soil cores collected from sites within the boreal forest of northern Canada that had not burned in the previous 30 years or more. Using a series of experiments with simulated burns and subsequent soil incubations, this study identified bacterial taxa with at least one of the following traits—fire survival, fast growth, or an affinity for the post-fire soil environment. These trait assignments were then applied to a field dataset of natural wildfires from the same region 1 and 5 years post-burn to evaluate the importance of each trait in the field. Finally, researchers used respiration data from the incubations of the experimentally burned cores to explore whether changes in microbial communities constrain soil carbon mineralization.

Principal Investigator

Thea Whitman
University of Wisconsin-Madison
[email protected]

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This work was funded by the Biological and Environmental Research (BER) Program within the U.S. Department of Energy’s (DOE) Office of Science (DE-SC0021022) and the University of Wisconsin–Madison Fall Research Competition Grant.

References