Determination of the Roles of Pyrophilous Microbes in the Breakdown and Sequestration of Pyrolyzed Forms of SOM
Thomas D Bruns, Dept. Plant & Microbial Biol., Univ. Cal., Berkeley, (Principal investigator)
Matthew Traxler, Dept. Plant & Microbial Biol., Univ. Cal., Berkeley, (Co-Principal investigator)
Thea Whitman, Dept. Soil Science, Univ. Wisconsin, Madison (Co-Principal investigator)
Igor Grigoriev, US DOE Joint Genome Institute, Walnut Creek, CA, (Co-Principal investigator)
The work will investigate the effects of pyrophilous (“fire loving”) microbes on post-fire soil carbon dynamics. The three objectives of the work are:
To develop improved genomic and other -omic resources for the dominant microbes in post-fire soil.
To determine the temporal response of soil microbes to fire and to additions of burn substrates under controlled conditions.
To chemically characterize the extractable fractions of burnt substrates, their temporal patterns of degradation, and their effects on soil organic carbon mineralization, and to determine the soil microbes driving these processes.
The methods include: 1) the development of small experimental units that allow precise replication of fire effects on soil; 2) highly controlled production of 13C-labeled burnt substrates that in combination with stable isotope techniques will allow us to trace the breakdown of burnt substrates through the microbial food chain; 3) genomics and transcriptomics methods that will allow us to determine the precise way in which microbes degrade partially burnt materials; and 4) mass spectrometry to enable the complex chemistry of burnt soil to be characterized in detail.
This work is important because the size and frequency of large catastrophic forest fires are increasing. Soil effects from such fires are important to understand, because they have significant direct and indirect effects on global carbon storage. For example, fires result in a large amount of carbon that remains resident on the site as dead and partially burned material that has long residency times and constitutes a significant pool in fire-prone ecosystems. In addition fire induced hydrophobic soil layers, caused by condensation of partially burned waxes and lipids, increase post-fire erosion and lead to long-term productivity losses. Soil microbes are likely to be involved with the degradation of all of these compounds, and it is known that a specific set of pyrophilous microbes are associated with post-fire soils. Yet almost nothing is currently known about what these organisms do or the metabolic processes they use.
The ultimate goal of this work is to understand how the post-fire microbial community affects the fates of partially burned carbon and unburned soil carbon in the early post-fire soil environment. With this understanding comes the potential to manipulate conditions to achieve goals of greater post-fire carbon storage and improved soil productivity.
