In many regions fires are a part of the natural ecosystem, but a wildfire can sometimes also severely diminish the quality of the soil. Especially when a wildfire causes an increase in soil temperature the quality of the soil often severely declines. You would expect the places where fires are the most intense to have a higher soil temperature, but a recently published study shows that this is not the case. In fact, the areas where the flames were at their most intense actually showed lower soil temperatures than the areas where the flames burned more moderately.
As part of her PhD research at Wageningen University Cathelijne Stoof and her colleagues installed instruments across a 22-acre test area in Portugal, and subsequently set the area on fire. While the fire was raging the team monitored the intensity of the fire and the soil temperatures. The fire was most intense in vegetated areas, yet the soil temperatures in these areas remained relatively low. The team discovered that the vegetated parts of the area were moister, and that the moisture protected the soil.
Based on these findings Stoof, now a researcher at Cornell University, has devised a strategy to minimise soil damage during controlled burns “Burn the driest area first when it has some moisture” she told a American Geophysical Union reporter, “The damp area will be too damp, and therefore will not carry fire. Then go back and burn the damp area when it’s dried out enough so that it will burn. This way you end up with minimum soil damage.”
- Press release: Wildfires can burn hot without ruining soil, new study finds
- Article: Hot fire, cool soil, Stoof et. al. Geophysical Research Letters, 2013