The Effect of Prairie Fires on the Magnetic Properties of Modern Soils at Konza Prairie, Kansas

Prairie fires have been proposed as a possible mechanism that influences the magnetic enhancement of modern and buried soils because they can create a partially reducing environment that may transform weakly magnetic minerals into strongly magnetic minerals in the upper soil horizons. We analyzed the magnetic properties of shallow loessic soils from Konza Prairie, Kansas to examine the possibility of magnetic enhancement due to prairie fires. Konza Prairie is a Long Term Ecological Research Site (LTER) and has a long record (20+ years) of controlled burns. This makes it an ideal location for isolating the role of repeated prairie fires on the magnetic properties of soils. We sampled 46 sites that have been subjected to fire treatments ranging from annual burns to burn frequencies a low as once every 20 years. Our analyses include measurements of magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), S-ratios, and coercivity distributions of IRM. Plotting several magnetic enhancement parameters against burn frequency showed that no evidence that repeated prairie fires cause magnetic enhancement in modern soils. Our results suggest that prairie fires do not burn hot enough to significantly alter the magnetic properties of soils and are an unlikely explanation for the magnetic enhancement of paleosols.