"Altogether, we documented losses of more than 10 tons per acre of carbon and between 450 to 620 pounds per acre of nitrogen," Bormann said. "The loss of topsoil and combustion of organic materials together led to losses that are higher than most previous estimates."
The loss of topsoil and carbon from soil can negatively affect a range of processes, Bormann said, including nutrient retention and water infiltration. In the absence of special nitrogen-fixing plants, which are capable of converting atmospheric nitrogen into nitrogen compounds for growth, losses of nitrogen in the order of what he and his colleagues documented would require at least a century to be reversed.
Equally disconcerting is the role these released organic materials might have on the atmosphere, especially in the face of a warming climate. The burning of soil by wildfire may contribute to global warming, in the short term, by releasing carbon as a greenhouse gas and, in the long term, by reducing soil productivity through losses of organic matter and nutrients. With less productive soils, Bormann said, a forest will not grow as quickly nor reabsorb as much carbon as before a burna process critical to mitigating the accumulation of atmospheric carbon, which traps heat in the atmosphere and can, thus, raise temperatures.
"Our findings suggest that forest managers should carefully consider the effects of wildfire on soils when planning to reduce fuels, suppress future fires, and help trees and habitat recover after fire," Bormann said.
|Contact: Yasmeen Sands|
USDA Forest Service, Pacific Northwest Research Station