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Wildfire impacts on stream water quality in the Pacific Coastal Temperate Rainforest
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- Author / Creator
- Mahaux, Jeremie N
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Forests generally provide the highest-quality water among all land cover types, but they are highly susceptible to disturbances like wildfire. Climate change is driving a trend toward hotter, drier conditions that have been intensifying fire regimes worldwide. The Pacific Coastal Temperate Rainforest (PCTR), where severe fire has previously been rare, is the biome projected to experience the greatest proportional increase in area burned relative to past levels. Wildfires can alter dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) composition and nutrient concentrations in streams, affecting in-stream ecosystem function and aspects of drinking water quality. The extent of these effects varies with landscape making it crucial to understand localized impacts, but research has been focused heavily on historically fire-prone regions. To evaluate how burn-affected catchments in the PCTR propagate their impacts to low order streams and how those impacts differ between baseflow and stormflow, I sampled streams and soils within nine recent (2015-2022) wildfire and paired reference sites. Samples were assessed for DOC concentration and composition, nitrogen (N), phosphorus (P), suspended sediments, and a suite of cations and anions. At baseflow, I found lower concentrations of DOC (DOCref =2.5±0.2mg L-1, DOCburn = 1.8±0.2 mg L-1, p=0.085) and N (TDNref=187±30μg L-1, TDNburn=86±14μg L-1, p=0.002) in burned relative to reference sites, but greater concentrations of P (TDPref=3.7±0.3μg L-1, TDPburn=4.5±0.4μg L-1, p=0.024). Throughout storm events, constituents exhibited similar responses between burned and unburned catchments suggesting that the storms I sampled did not produce direct hydrologic connectivity between surficial soils and streams, perhaps due to high soil storage capacities enhanced by the historically dry sampling period. Finally, the effect of burn status was most pronounced in soil leachate samples, implying that the clear, direct impact of fire on terrestrial landscapes was poorly reflected in streams during my sampling period. The changes in nutrient concentrations I found may have implications for stream food web assemblages and drinking water treatability. Wildfire prevalence and severity is predicted to increase in this traditionally wet region; as a result, the results discussed here may be modest, compared to possible future effects.
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- Graduation date
- Fall 2024
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.