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The influence of fire and permafrost on sub-arctic stream chemistry during storms
|Title||The influence of fire and permafrost on sub-arctic stream chemistry during storms|
|Publication Type||Journal Article|
|Year of Publication||2007|
|Authors||Petrone, KC, Hinzman, LD, Shibata, H, Jones, JB, Boone, RD|
Permafrost and fire are important regulators of hydrochemistry and landscape structure in the discontinuous permafrost regionof interior Alaska.We examined the influence of permafrost and a prescribed burn on concentrations of dissolved organic carbon(DOC), dissolved organic nitrogen (DON) and other solutes (NO3 , Ca2C, KC, Mg2C, NaC) in streams of an experimentallyburned watershed and two reference watersheds with varying extents of permafrost in the Caribou–Poker Creeks ResearchWatershed in interior Alaska. The low-permafrost watershed has limited permafrost (3%), the high-permafrost watershed hasextensive permafrost (53%), and the burn watershed has intermediate permafrost coverage (18%). A three end-member mixingmodel revealed fundamental hydrologic and chemical differences between watersheds due to the presence of permafrost.Stormflow in the low-permafrost watershed was dominated by precipitation and overland flow, whereas the high-permafrostwatershed was dominated by flow through the active layer. In all watersheds, organic and groundwater flow paths controlledstream chemistry: DOC and DON increased with discharge (organic source) and base cations and SO24 (from weatheringprocesses) decreased. Thawing of the active layer increased soil water storage in the high-permafrost watershed from July toSeptember, and attenuated the hydrologic response and solute flux to the stream. The FROSTFIRE prescribed burn, initiatedon 8 July 1999, elevated nitrate concentrations for a short period after the first post-fire storm on 25 July, but there was noincrease after a second storm in September. During the July storm, nitrate export lagged behind the storm discharge peak,indicating a flushing of soluble nitrate that likely originated from burned soils. Copyright &\#63193; 2006 John Wiley & Sons, Ltd.