Document: SAN-3-68-15

Duff moisture dynamics and duff consumption by fire in the Canadian boreal forest.

VO, S.T.K.* ¹, K.MIYANISHI ² and E.A.JOHNSON ¹

University of Calgary, AB T2N 1N4, Canada ¹
University of Guelph, ON N1G 2W1, Canada ²

Abstract:
Wildfires in the boreal forest remove the organic soil horizon (duff) and create suitable seedbed conditions for tree regeneration. The objective of this study was to describe and explain within- and between-stand duff consumption patterns. The extent of duff consumption by smoldering combustion depends on duff moisture content and depth; the greater the moisture content, the greater the minimum depth required to propagate smoldering. We studied duff consumption patterns in mature stands of Pinus banksiana and Picea mariana within two fires (June 1996 and July 1998) and duff moisture patterns in comparable unburned stands. All stands occured on glaciofluvial substrate with Pinus on the upper and Picea on the lower hillslope. Patterns of duff consumption exhibited within-stand patchiness and between-stand-type differences. Duff directly beneath tree crowns was significantly drier due to precipitation interception and limited dew formation. Thus, in all burned stands, duff was preferentially consumed around the bases of standing trees. Early in the season (June), with lower evapotranspiration, duff is not excessively dry; smoldering is not propagated in the thinner duff of Pinus stands and the total area of consumption is less than in Picea stands. Later in the season (July), with higher evapotranspiration and drier duff, the minimum depth required for smolder propagation decreases; duff depth becomes less important and total areas of consumption in both stand types are similar. Thus, seasonal duff consumption patterns are explained by within-stand variation in duff moisture and between-stand-type variation in duff depth.

Keywords:

This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.