Prescribed burns in forests may decrease carbon sequestration in the short term, but they increase the forest’s ability to sequester carbon in the long term.
So says a recent literature review published by the Missouri Department of Conservation.
Readers of this blog may recall that almost 3 years ago I published an 8-part series on wildfire in forests, and the role fire can have in promoting the health of the forest. Since then, I have published several updates. In that series, I reported that the Missouri Department of Conservation uses prescribed burning as a forest management tool, and it encourages private landowners to do so, too.
The literature review concludes that, though forests are complex, and general principles will not hold true for every plot within them, in the Missouri Ozarks:
- Fuel-reduction treatment (e.g. prescribed burning) reduces the risk of a large stand-destroying fire. When a whole stand is destroyed, all of the carbon sequestered in the trees is released into the atmosphere. Further, the forest is slow to regrow.
- Thinning using prescribed fire reduces competition among trees and provides additional ground nutrients, resulting in better growth.
- Forests managed with a combination of thinning and prescribed burning have lower carbon emissions than other types of forests. (Yes, they actually get out there and measure the gases emitted by different types of forest land.)
- During a prescribed burn, large trees are generally not killed by the fire, but small sprouts and herbaceous understory are. Burning the leaf litter and herbaceous understory results in a short-term increase in carbon released into the atmosphere. This is more than made-up for, however, by the increased vigor and growth of the remaining forest. The increased growth sequesters more carbon than was released in the prescribed burn.
- The soil in forests consist of a rich mixture of plant roots, moss and other vegetation, bugs, worms, microorganisms, and chemical compounds, including carbon (partially decayed remains of living things that have worked their way into the soil). There has been concern that prescribed burning would release the carbon sequestered in the soil. So far, research indicates that there is no difference in the carbon sequestration of the soil in control plots vs. plots that have had prescribed burns applied. In addition, no difference has been found between plots that are burned annually vs. plots that are burned every 4 years. The concern is understandable, but so far it appears incorrect.
- Soil respiration (the ability of oxygen to penetrate to the roots of plants) is not affected by prescribed burning.
Forests have not traditionally been managed with increased carbon sequestration as a major goal. However, the literature review seems to indicate that prescribed burning may be a technique that can lead to increased carbon sequestration in forest, through increased vigor and growth of the trees in the forest.
Ball, Liz. Undated. “The relationship between prescribed fire management and carbon storage in the Missouri Ozarks.” Missouri Department of Conservation. Downloaded 8/22/2019 from https://pdfs.semanticscholar.org/acfb/673db5694db7389e7bf7190211fb5ec75885.pdf.