Charcoal and Carbon Storage in Forest Soils of the Rocky Mountain West

October 15, 2007

Charcoal produced during wildfire events represents an important form of long-term Carbon storage in forest ecosystems. Forest management practices, such as salvage logging or thinning without prescribed fire, may reduce soil charcoal content and, thus, long-term Carbon storage in mineral soils.

Conclusions
 

Charcoal represents an important component of the soil organic matter pool in temperate grasslands and forests. It contributes to the total water-holding capacity, ion exchange complex, and surface area of the soil environment.

Once deposited in soil, charcoal is highly stable, having mean residence times 30–100 times longer than that of woody materials and 5–12 times greater than humic materials. Contributions to this pool are dependent upon the occurrence of fire events in which biomass is partially consumed. The amounts of  charcoal formed during a given forest-fire event is highly variable and dependent upon fire severity and fuel composition; however, a safe estimate would be 1 to 4 Mg charcoal as C . This stable form of C may be ultimately mixed into the mineral soil or it may be lost, either to biomass burning in a subsequent fire event or an erosion event.

Erosion represents a loss only from the immediate ecosystem, as it will ultimately be deposited in a lake or marine environment, where it may remain for millions of years.

The role of charcoal in the forest ecosystem is just now being explored. The long-term implications of fire exclusion and the elimination of charcoal deposition in forests are not well understood. Timber harvest without prescribed fire may be applied as a forest restoration tool; however, under these conditions, charcoal, as a passive C contribution to the soil system, will be eliminated and will lead to a modest, but long-term loss of C from the forest ecosystem.

Conversely, restoration harvests that incorporate prescribed fire will more effectively emulate natural fire events and deposit charcoal across the activity unit. The importance of charcoal in soils and its contribution to long-term C storage requires greater consideration during ecological assessment, C modeling, and in forest management.  

This report appeared in Frontiers in Ecology and the Environment, a publication of the Ecological Society of America. The report was authored by Tom DeLuca and Greg Aplet of The Wilderness Society.