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Impacts of Forest Fire on Boreal Lakes

Impacts of Forest Fire on Boreal Lakes. Tess Chadil. Source: http://blog.e-democracy.org/posts/91. Impacts to Physical Watershed Processes. http://wwwbrr.cr.usgs.gov/projects/Burned_Watersheds/Rll_IntR.jpg. Devegetation. Hydrophobic Soils. ↓interception ↓ transpiration. ↑ runoff.

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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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