Duff moisture dynamics in black spruce feather moss stands and their relation to the Canadian forest fire danger rating system

Brenda Wilmore
Wed, 22 Apr 2026 17:52:12 PDT

The Canadian Forest Fire Danger Rating System's Fire Weather Index (FWI) system models 3 levels of fuel moisture within the forest floor using simple environmental inputs. Wildland fire managers in interior Alaska have expressed concern that the FWI System does not take northern latitude factors such as long day lengths and permafrost into account. During the 1999 fire season destructive sampling methods were employed to monitor moisture content throughout the feather moss profile in 3 interior Alaska black spruce stands. Measured moisture contents were compared to the FWI System's fuel moisture predictions. The FWI System followed general trends of the seasonal fuel moisture within the feather moss profile. However, the short-term response of the interior Alaska moss profile is more dynamic than the FWI System's fuel moistrue code predictions. Hydraulic properties that have been linked to bulk density may be the causative agent for the observed short-term discrepancy.