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Impacts of Forest Fire on Boreal Lakes

This article explores the effects of forest fires on boreal lakes, covering topics such as devegetation, hydrophobic soils, ion and nutrient transport, aquatic ecology, recovery rates, and management implications. Forest fires can lead to increased nutrient transport, changes in water quality, reduced algal species richness, and long-term impacts on lake ecosystems. Understanding these environmental consequences is crucial for effective forest fire management and conservation efforts.

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Impacts of Forest Fire on Boreal Lakes

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  1. Impacts of Forest Fire on Boreal Lakes Tess Chadil Source: http://blog.e-democracy.org/posts/91

  2. Impacts to Physical Watershed Processes http://wwwbrr.cr.usgs.gov/projects/Burned_Watersheds/Rll_IntR.jpg Devegetation Hydrophobic Soils ↓interception ↓ transpiration ↑ runoff ↑ erosion ↑ sediment transport ↑ion and nutrient contributions to lakes Source: http://www.wrh.noaa.gov/wrh/02TAs/0212/figure23.gif

  3. Ion and Nutrient Transport • Magnitude of flux into lake depends on • Severity of fire • Depth of organic layer in soil • P and N transport have most significant impacts to lake water quality • Fire leads to increased concentrations of K+, Ca2+, Mg2+, Cl-, SO42- • Local deposition of particulate Hg

  4. Phosphorous and Nitrogen • Significant increases in total, total dissolved and soluble reactive phosphorous • 74% of variance in TP can be explained by percent of basin burned, and time elapsed since fire • Most boreal lakes are naturally P-limited • Significant increases in total and total dissolved nitrogen, nitrates and ammonium • Primary source for nitrates is ash • Persistent nitrate contamination sustained by contaminated groundwater inflows

  5. Additional Effects of Fire • Increased concentration of inorganic suspended solids • Mean light extinction nearly doubled in some cases • No significant increases to DOC • Increases in pH varied among studies • some lakes experience permanent increases in pH

  6. Aquatic Ecology • Reduced algal species richness • Increased Hg concentrations reported in fish • Hg concentrations limited by “growth-dilution” effect • Boreal lakes in burned watersheds tend towards eutrophy • Lakes in burned watersheds reported TP:TN ratios between 10 and 20 • Cyanobacteria blooms lead to diminished water quality • Reduced clarity helps to limit chlorophyll-a concentrations Source: http://biology.mcgill.ca/grad/alison/photos/researchInterest1.jpg

  7. Recovery Rate • Recovery rate dependent on: • Ratio of burned watershed area to lake surface area • Predominant vegetation Source: http://barbagallo.files.wordpress.com/2009/09/img_4721.jpg • Recovery to pre-burn conditions takes decades • Most studies are short-term (less than 10 years), or • Paleolimnological Investigations (100s or 1000s of years) Source: http://interwork.sdsu.edu/fire/resources/images/MiddlePeak2.jpg

  8. Paleolimnology Source: http://www.biol.canterbury.ac.nz/ferg/Images/Sediment-core-lake-Rotorua-(Kaikoura)-lg.jpg Source: http://www.pc.gc.ca/eng/pn-np/bc/kootenay/natcul/natcul23.aspx Source: http://post.queensu.ca/~low/Research%20Page.html Source: http://www.scielo.br/img/revistas/bn/v6n1/a01f06.gif

  9. Management Implications • Climate change • Increased incidence of fire • Increased nutrient transport potential • Fire Management Practices • Fisheries value • Need for further long-term studies Source: http://www.ec.gc.ca/INRE-NWRI/0CD66675-AD25-4B23-892C-5396F7876F65/ch8-forestfire%5B1%5D.jpg

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