Bark char [Bole char]

n. The blackened residue resulting from incomplete combustion of the bark.

 

  • Discussion

 

Bark char, also called bole char, is used as an indicator of the length of time a tree bole has been exposed to the flames and high temperatures of a fire. Bark char correlates to the heat transferred into the tree and has been used to estimate cambium injury. Bark insulates the cambium and helps to protect it from heat injury. The greater the bark thickness, the longer a tree can be exposed to high temperature without cambium mortality. Bark char on trees with thin bark can indicate cambium injury. However, bark char on trees with thick bark is not always a reliable indicator of the condition of the underlying cambium (Hood and others 2007).

 

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Several studies have found bark char or bark char classes to be a significant predictor of post-fire tree mortality (see Peterson and Arbaugh 1986, 1989; McHugh and Kolb 2003; Keyser and others 2006; Sieg and others 2006).

Bark char classes were developed by Ryan (1982b) to aid in estimating cambium injury (see table below). The accuracy of these codes has not been fully tested, and they therefore should not be used as sole indicators of cambium status, especially for trees with thick bark.

 

from Ryan (1982b)

Unburned

Not burned. No evidence of flame having contacted the bole and no darkening of the bole.

Lightly charred

Bark is not completely blackened and species is still identifiable based on bark characteristics; edges of bark plates blackened.

Moderately charred

Bark is uniformly black except possibly some inner fissures; bark characteristics still discernable.

Deeply charred

Bark has been burned into, but not necessarily to the wood; outer characteristics are lost.

 

Light bark char. Bark is not completely blackened and species is still identifiable based on bark characteristics; edges of bark plates blackened.

 

Moderate bark char. Bark is uniformly black except possibly some inner fissures; bark characteristics still discernable.

 

Deep bark char. Bark has been burned into, but not necessarily to the wood; outer characteristics are lost.

 

  • See Also

  • References

    • Hood, S. M; Smith, S. L.; Cluck, D. 2007. Delayed Tree Mortality Following Fire in Northern California. In: Powers, R.F., ed. Restoring fire-adapted ecosystems: Proceedings of the 2005 National Silviculture Workshop; 2005 June 6-10; Tahoe City, CA. Gen. Tech. Rep. PSW-GTR-203. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 261-283.

    • Keyser, T. L.; Smith, F. W.; Lentile, L. B.; Shepperd, W. D. 2006. Modeling postfire mortality of ponderosa pine following a mixed-severity wildfire in the Black Hills: the role of tree morphology and direct fire effects. Forest Science. 52: 530-539.

    • McHugh, C.; Kolb, T. E. 2003. Ponderosa pine mortality following fire in northern Arizona. International Journal of Wildland Fire. 12: 7-22.

    • Peterson, D. L.; Arbaugh, M. J. 1986. Postfire survival in Douglas-fir and lodgepole pine: comparing the effects of crown and bole damage. Canadian Journal of Forest Research. 19: 1175-1179.

    • Peterson, D. L.; Arbaugh, M. J. 1989. Estimating postfire survival of Douglas-fir in the Cascade Range. Canadian Journal of Forest Research. 19: 530-533.

    • Ryan, K. C. 1982a. Evaluating potential tree mortality from prescribed burning. In: Site preparation and fuels management on steep terrain: proceedings of a symposium; 1982 February 15-17; Spokane, WA. Pullman, WA: Washington State University Cooperative Extension: 167-179.

    • Ryan, K. C. 1982b. Techniques for assessing fire damage to trees. In: Lotan, J., ed. Fire, its field effects: proceedings of the symposium sponsored jointly by the Intermountain Fire Council and the Rocky Mountain Fire Council; 1982 October 19-21; Jackson, WY: Intermountain Fire Council: 1-11.

    • Sieg, C. H.; McMillin, J. D.; Fowler, J. F.; Allen, K. K.; Negron, J. F.; Wadleigh, L. L.; Anhold, J. A.; Gibson, K. E. 2006. Best predictors for postfire mortality of ponderosa pine trees in the Intermountain West. Forest Science. 52: 718-728.

     

  • Notes

    • Author 

      Sharon Hood, Forester

      Rocky Mountain Research Station