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Date of Award


Document Type

Masters Thesis

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Homann, Peter S., 1953-

Second Advisor

Medler, Michael J.

Third Advisor

Sofield, Ruth M.


In the summer of 2002, the 200,000-ha Biscuit Wildfire consumed a portion of the 150-ha Long-Term Ecosystem Productivity (LTEP) experiment in the Siskiyou National Forest, Oregon. The wildfire burned previously established 100-year-old conifer control and thinned experimental units, which allows comparison with prescribed burn and unburned units. This research evaluates the O horizon and mineral soil charcoal, a key fire-related soil component that affects physical and chemical properties. Charcoal C was quantified by a peroxide-acid digestion method developed for forest soils. Charcoal C was 17% of the organic C for a reference Australian Vertisol soil and 9% for a German Chernozem, which are similar to published values from a dichromate digestion method. The charcoal C of the Siskiyou LTEP soils was quantified in hand-sorted charcoal from the O horizon and in the < 4-mm fraction of the A (0-3 cm depth) and B1 (3-15 cm depth) mineral soil horizons. The mineral soils contained substantial amounts of charcoal C and no changes were detected as a result of prescribed or wildfire. Concentrations were 10 g charcoal C/kg in A horizon and 7 g charcoal C/kg in B1 horizon and areal masses averaged 1,860 kg charcoal C/ha in A layer soils and 5,260 kg charcoal C/ha for B1 layer soils. Charcoal C in the O layer averaged 18 kg charcoal C/ha prior to the fire and was increased by a factor of 5 by both prescribed fire and wildfire. The effect of thinning on wildfire-induced charcoal C changes was non-significant. Charcoal was formed at a rate of 0.5 - 6.0% of surface woody fuels consumed in the wildfire. Long-term soil C sequestration in the Siskiyou - LTEP soils is greatly influenced by the contribution of charcoal C, which makes up 20% of mineral soil organic C. The significant effect of recent fire on the O layer soils demonstrates the significant short-term effects of the Biscuit Wildfire and the dynamic nature of the O layer. This research reiterates the importance of wildfire and prescribed fire to soil C in a Southwestern Oregon coniferous forest ecosystem.




Western Washington University

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