Impacts of Forest Fire on Boreal Lakes Discuss characteristics of boreal zone (aka taiga) Northern U.S (Minn), Canada (Quebec) conifer and mixed hardwood forests thin organic layer predominant geology- granite glacial kettle lakes Source: http://blog.e-democracy.org/posts/91 Tess Chadil

Impacts to Physical Watershed Processes http://wwwbrr.cr.usgs.gov/projects/Burned_Watersheds/Rll_IntR.jpg Devegetation Hydrophobic Soils ↓interception ↓ transpiration Hydrophobic soil formation- waxy organic plant material on forest floor is volatilized into gas gas penetrates into soil column gas cools, forms hydrophobic layer beneath the soil surface prevents infiltration ↑ runoff ↑ erosion ↑ sediment transport ↑ion and nutrient contributions to lakes Source: http://www.wrh.noaa.gov/wrh/02TAs/0212/figure23.gif

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 Atmospheric Hg deposited in precipitation and carried into lakes via runoff

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 Boreal Lakes are usually P limited Quebec study- Soluble reactive phosphorous increased almost 7x pre-burn levels

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 Only some lakes reported significant increases in pH In some cases pH permanently stabilized above pre burn levels

Aquatic Ecology Reduced algal species richness Increased Hg concentrations reported in fish Hg concentrations limited by “growth-dilution” effect Source: http://biology.mcgill.ca/grad/alison/photos/researchInterest1.jpg 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

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 Lakes recover slowly- on the order of decades Predominant vegetation conifer 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

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

Management Implications Climate change Increased incidence of fire Increased nutrient transport potential Fire Management Practices Fisheries value Need for further long-term studies Climate change forecast increased fires in Canadian boreal zones Warmer, wetter climate- higher accumulation of organic material Fire management- suppression vs. let it burn? thinning/prevention? Source: http://www.ec.gc.ca/INRE-NWRI/0CD66675-AD25-4B23-892C-5396F7876F65/ch8-forestfire%5B1%5D.jpg