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Fire Effects on Stable Isotopes in a Sierran Forested Watershed
Author(s) -
Saito Laurel,
Miller Wally W.,
Johnson Dale W.,
Qualls Robert G.,
Provencher Louis,
Carroll Erin,
Szameitat Peter
Publication year - 2007
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0233
Subject(s) - soil water , environmental science , riparian zone , surface runoff , watershed , hydrology (agriculture) , litter , sediment , soil horizon , plant litter , soil science , environmental chemistry , geology , chemistry , ecology , nutrient , geotechnical engineering , machine learning , habitat , computer science , biology , paleontology , organic chemistry
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 ≥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 δ 15 N values in upland watershed analyses 1 yr postburn, while riparian zone analyses results indicated that δ 13 C values significantly decreased ∼0.71‰ over a 9 mo post‐fire period ( p = 0.015), and ash/sediment layer δ 13 C values were ∼0.65‰ higher than those in the A horizon. The lack of field confirmation may have been due to overall wildfire burn temperatures being <200°C and/or microbial recovery and vegetative growth in the field. Thus, the muffle furnace experiment supported the hypothesis, but it is as yet unconfirmed by actual wildfire field data.