Forests of the far north, or boreal forests, store immense amounts of carbon in their soils, including in permafrost. Release of this carbon to the atmosphere has the potential to worsen climate change. These soils have accumulated over hundreds and sometimes thousands of years, but they are increasingly vulnerable to the effects of climate warming. One major factor is wildfire, which is becoming more frequent and severe in many high-latitude forests. Fires directly emit soil carbon through the combustion process; however, what happens in the soil for years after a fire is just as important.
The global carbon budget is the balance between the carbon uptake by plants and algae and carbon emissions from humans, animals, and microbes. How soil microbes will respond to global change, including direct climate effects as well as land-use change and disturbances such as fire, is a major question. A study just published in Environmental Research Letters provides the first clue that in recently-burned boreal forests, the amount and type of microbes in the soil is highly dependent on the severity of the fire.
Using a combination of remote sensing techniques, field sampling, and laboratory analyses, a team of researchers sought to understand the response of soil and soil microbes following a 2010 forest fire in interior Alaska. Their study shows that the more severe the fire, the fewer the microbes, which, says WHRC scientist and co-author Brendan Rogers, “may be a good thing in the sense that decomposition and post-fire carbon emissions are more limited after severe fires.”
The story may not be so simple, however. In addition to decomposing soil organic matter, some types of microbes help trees acquire nutrients, which ultimately leads to higher productivity and long-term carbon storage. As it turns out, these microbes were the most sensitive to fire severity.
Although there is much more to uncover about the relationship between fires and soil microbes, this study was a big first step. Ultimately, says Dr. Rogers, “this type of information can improve our models and help us upgrade forecasting and manage boreal carbon cycling in an age of frequent fires.”
WHRC is an independent research institute where scientists investigate the causes and effects of climate change to identify and implement opportunities for conservation, restoration and economic development around the world.