Event Title

Forest Soil Response to Wildfire: Relation to Woody Surface Fuels

Event Website

http://www.nafew2009.org/

Start Date

25-6-2009 9:20 AM

End Date

25-6-2009 9:40 AM

Description

The 2002 Biscuit wildfire burned 200,000 ha of conifer forest in southwest Oregon, including previously established experimental plots of the Long-term Ecosystem Productivity Study. Prefire manipulations had resulted in substantial heterogeneity among plots with respect to vegetation composition, structure, and woody surface fuel loads. The Biscuit fire resulted in nine plots burned by the wildfire, one plot previously burned by prescribed fire then by the wildfire, and three plots back-burned in the establishment of a fire line. Pre- and postfire sampling allowed direct measurement of soil change, and unburned plots exhibited minimal or no soil change. The soil C loss due to wildfire varied among plots from 3 to 21 Mg C per ha, and the N loss from 0.03 to 0.60 Mg N per ha. On the most severely burned plots, soil C and N losses occurred not only from the O horizon, but also from the mineral soil. Soil C and N losses were positively and curvilinearly related to woody fuels consumed, which varied among the plots from 14 to 80 Mg per ha. This suggests woody fuel loads and their subsequent combustion influenced soil C and N reduction via volatilization, particulate loss, or post-fire erosion. The combination of prescribed fire followed by wildfire resulted in 30% less soil C and N loss than wildfire alone. The three back-burn plots exhibited soil C and N losses comparable to high-severity wildfire plots, in spite of widely varying fuel losses. Overall, the rare occurrence of previously sampled plots being burned by wildfire allowed direct evaluation of wildfire-induced soil changes. More importantly, the prefire heterogeneity of woody fuels resulted in an unprecedented quantification of the relation between soil changes and the magnitude of wildfire fuel consumption, which will be useful in evaluating potential impacts of wildfire on forest soils.

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Jun 25th, 9:20 AM Jun 25th, 9:40 AM

Forest Soil Response to Wildfire: Relation to Woody Surface Fuels

The 2002 Biscuit wildfire burned 200,000 ha of conifer forest in southwest Oregon, including previously established experimental plots of the Long-term Ecosystem Productivity Study. Prefire manipulations had resulted in substantial heterogeneity among plots with respect to vegetation composition, structure, and woody surface fuel loads. The Biscuit fire resulted in nine plots burned by the wildfire, one plot previously burned by prescribed fire then by the wildfire, and three plots back-burned in the establishment of a fire line. Pre- and postfire sampling allowed direct measurement of soil change, and unburned plots exhibited minimal or no soil change. The soil C loss due to wildfire varied among plots from 3 to 21 Mg C per ha, and the N loss from 0.03 to 0.60 Mg N per ha. On the most severely burned plots, soil C and N losses occurred not only from the O horizon, but also from the mineral soil. Soil C and N losses were positively and curvilinearly related to woody fuels consumed, which varied among the plots from 14 to 80 Mg per ha. This suggests woody fuel loads and their subsequent combustion influenced soil C and N reduction via volatilization, particulate loss, or post-fire erosion. The combination of prescribed fire followed by wildfire resulted in 30% less soil C and N loss than wildfire alone. The three back-burn plots exhibited soil C and N losses comparable to high-severity wildfire plots, in spite of widely varying fuel losses. Overall, the rare occurrence of previously sampled plots being burned by wildfire allowed direct evaluation of wildfire-induced soil changes. More importantly, the prefire heterogeneity of woody fuels resulted in an unprecedented quantification of the relation between soil changes and the magnitude of wildfire fuel consumption, which will be useful in evaluating potential impacts of wildfire on forest soils.

http://digitalcommons.usu.edu/nafecology/sessions/fuel/3