Carbon emissions can be offset through controlled burning of natural areas

The carbon storage capacity of natural ecosystems is not maximized by planting trees or suppressing wildfires. A new study has shown that prescribed burning can actually lock-in or increase carbon in the soils in temperate forests, savannahs, and grasslands.

This finding points to a new way to manipulate the world’s natural carbon capture and storage capacity. It can also help maintain natural ecosystem processes. The journal Nature Communications published the results today. Nature Geoscience.

“Using controlled fires in forests to reduce wildfire intensity is a well-known practice. However, we have found that fire can stabilize or even raise soil carbon in ecosystems such as temperate forests, savannahs, and grasslands,” said Dr. Adam Pellegrini, University of Cambridge’s Department of Plant Sciences. He is the first author of this report.

He said: “Most fires in natural ecosystems across the globe are controlled burns. So we should view this as an opportunity. Humans manipulate a process. We may as well learn how to maximize carbon storage in soil.

The fire that burns plant matter and organic layer within the soil can lead to erosion and leaching carbon. It can take years, if not decades, for soil carbon that has been lost to reaccumulate. However, researchers believe that fires may also cause soil changes that can offset the immediate carbon loss and may stabilize ecosystem carbon.

In many ways, fire stabilizes the carbon in the soil. It forms charcoal that is resistant to decomposition and ‘aggregates’ soil clumps that can protect the carbon-rich organic matter in the center. Also, fire can increase the carbon-binding strength to soil minerals.

“Ecosystems can store large amounts of carbon when they are able to maintain a high level of fire frequency and intensity. It’s all about the balance between carbon going into soils as dead plant biomass and carbon going out through decomposition, erosion and leaching,” stated Pellegrini.

In densely planted forests, fires can be too intense or frequent. They burn all the plant material that has not decomposed and release carbon into soil. High-intensity flames can also destabilize soil by killing soil bacteria or fungi and breaking down carbon-based organic material from minerals.

The soil carbon, which is a recycledorganic matter from plants, is not able to be burned. Instead, microbes consume it and release it as carbon dioxide or methane. Cooler fires, however, can increase soil carbon retention by forming charcoal and soil aggregates that protect soil from decomposition.

Scientists believe that ecosystems can be managed to increase the carbon content of their soils. Most of the carbon found in grasslands is below-ground, in the roots. Controlled burning, which encourages grass growth, can increase root biomass to increase the carbon stored.

“FIRE is often seen as something bad when it comes to how ecosystems should be managed to capture carbon from the atmosphere. Pellegrini said that fire can be beneficial for both biodiversity preservation and carbon storage if it is managed correctly.

The study examined carbon stored in topsoils (those less than 30cm thick). The soils of the world contain more carbon than the entire global vegetation and atmosphere. Global carbon cycling is important because fire is a key component of most ecosystems.