Fire effects on stable isotopes in a Sierran forested watershed

This study tested the hypothesis that stable C and N isotope values in surface soil and litter would be increased by fire due to volatilization of lighter isotopes. The hypothesis was tested by: (1) performing experimental laboratory burns of organic and mineral soil materials from a watershed at co...

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Bibliographic Details
Published in:Journal of environmental quality 2007-01, Vol.36 (1), p.91-100
Main Authors: Saito, L, Miller, W.W, Johnson, D.W, Qualls, R.G, Provencher, L, Carroll, E, Szameitat, P
Format: Article
Language:English
Subjects:
A horizons
Ash
carbon
chemical analysis
Fires
Food chains
Forest watersheds
forested watersheds
Isotopes
Marine pollution
nitrogen
organic horizons
riparian areas
runoff
soil chemistry
soil organic matter
Soil surfaces
Soils
Stable isotopes
temperature
Trees
upland soils
volatilization
Wildfires
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Summary:This study tested the hypothesis that stable C and N isotope values in surface soil and litter would be increased by fire due to volatilization of lighter isotopes. The hypothesis was tested by: (1) performing experimental laboratory burns of organic and mineral soil materials from a watershed at combinations of temperature ranging 100 to 600°C and duration ranging from 1 to 60 min; (2) testing field samples of upland soils before, shortly after, and 1 yr following a wildfire in the same watershed; and (3) testing field soil samples from a down-gradient ash/sediment depositional area in a riparian zone following a runoff event after the wildfire. Muffle furnace results indicated the most effective temperature range for using stable isotopes for tracing fire impacts is 200 to 400°C because lower burn temperatures may not produce strong isotopic shifts, and at temperatures > or = 600°C, N and C content of residual material is too low. Analyses of field soil samples were inconclusive: there was a slightly significant effect of the wildfire on delta ¹⁵N values in upland watershed analyses 1 yr postburn, while riparian zone analyses results indicated that delta ¹³C values significantly decreased approximately 0.71% over a 9 mo post-fire period (p = 0.015), and ash/sediment layer delta ¹³C values were approximately 0.65% higher than those in the A horizon. The lack of field confirmation may have been due to overall wildfire burn temperatures being
ISSN:0047-2425
1537-2537
DOI:10.2134/jeq2006.0233