- Title:
-
Thinning and Prescribed Fire Effects on Fuels and Potential Fire Behaviour in an Eastern Cascades Forest, Washington, USA
- Date:
- July 2006
- Organisations
- Association for Fire Ecology
- Authors:
James K. Agee and M. Reese Lolley
-
Location:
-
USA,
United States of America
Overview
Prescribed fire and low thinning were applied to dry forests dominated by ponderosa pine(Pinus ponderosa) and Douglas-fir (
Pseudotsuga menziesii) in the eastern Washington Cascades. Experimental design was an
unbalanced analysis of variance with 4 control units, 4 thin units, 2
burn units and 2 thin/burn units. Thinning was designed to reduce basal
area to 10-14 m2 ha-1 in a non-uniform pattern and burning was a low
intensity spring burn. Burn coverage was spotty, ranging from 23-51%,
and considered ineffective in reducing fuels at the time of application
by management and research personnel. Both thinning and burning had
effects on vegetation and fuels variables. Thinning reduced canopy
closure, canopy bulk density, and basal area, and increased canopy base
height. Burning had no influence on these canopy variables. Thinning
increased 10-hr timelag (0.62-2.54 cm) fuels. Burning decreased 1-hr
(0-0.62 cm) and 10-hr timelag fuels, forest floor depth and mass, and
increased fuel bed depth. There were interactions between thinning and
burning for 1-hr and 10-hr timelag fuels, and fuelbed depth. These
differences in fuel properties did not translate into differences in
simulated wildfire behavior and tree mortality. Thinning did increase
potential surface fire flame length under 97 percentile weather, and
active crown fire potential decreased on thinned units, but basal area
survival did not significantly differ between treatments under 80 and 97 percentile weather. The scale at which data are presented has a large
influence on interpretation of results. For example, torching fire
behavior, expressed as an average at the unit level, was low, but 17% of the individual plots (about 30 plots total per unit) across all
treatments didexhibit potential torching behavior.
