The Impact Of Wildfire On Mobilization And Chemistry Of Dissolved Organic Material In The Arctic Tundra
Gabor, Rachel 1 ; Kling, George 2 ; McLoughlin, Rachel 3 ; McKnight, Diane 4
1 University of Colorado - Boulder
2 University of Michigan - Ann Arbor
3 University of Colorado - Boulder
4 University of Colorado - Boulder
One proposed impact of climate change is the mobilization of organic carbon in arctic tundra, which could be further accelerated by a climate-related increase in fires. A large tundra fire in the fall of 2007 near the Arctic Long Term Ecological Research site (LTER) at Toolik Lake provided the opportunity to study the effects of fire on mobilization of dissolved organic carbon (DOC) in tundra ecosystems. Pre-fire samples taken from the region in 2002 and 2003 were also available for comparison1. Intact tussocks and soil cores were removed from burned and unburned regions in early summer 2008 and leached in DI water for 3-4 days. The leachate was then filtered, fractionated using XAD-8 resin, and analyzed for DOC as well as with fluorescence and UV-VIS spectroscopy. Samples from the burned areas showed significantly higher DOC concentrations -- averaging around 85 mg/L for the burned tussocks -- than samples from unburned areas -- around 40 mg/L for tussocks from unburned areas. Fulvic acid content also increased in the burned areas, averaging around 56 % in the burned tussocks and 48% in the unburned tussocks. In addition, the chemical characteristics of the fulvic acids from the burned region were consistently different from those in the unburned regions, specifically displaying a higher degree of aromaticity as measured by Specific UV Absorbance (SUVA) at 254 nm – averaging 4.6 L mg-1 m-1 for the burned tussocks and 4.2 L mg-1 m-1 for the unburned. This study can advance the understanding of the impacts of fire on carbon cycling in other regions, such as the Colorado Front Range where the pine beetle infestation is likely to lead to increased wildfires.
Cory RM, McKnight DM, Chin YP, Miller P, Jaros CL, 2007, Chemical characteristics of fulvic acids from Arctic surface waters: Microbial contributions and photochemical transformations: Journal of Geophysical Research, v. 112, G04S51.