PALEOLIMNOLOGICAL RECONSTRUCTION OF DROUGHT CONDITIONS FROM MAX LAKE, VILAS COUNTY, WISCONSIN

The Wisconsin Department of Natural Resources in conjunction with the University of Wisconsin Stevens Point is using the sedimentary record from Max Lake in Vilas County, Wisconsin to establish a correlation between drought and changes in the pH of northern kettle lakes. A 536cm core collected from Max Lake in the spring of 2009 is being used to reconstruct Holocene changes in alkalinity, cycles of drought, and fire history. Previous experiments indicate that during times of drought lake pH rises as the relative contribution of precipitation decreases, and that of groundwater increases. During drought an increase in dissolved carbonate concentration leads to an increase in alkalinity that may be observed in sediment chemistry and diatom assemblages. Likewise, drought conditions create an environment prone to wildfires which should be represented by escalated charcoal counts. We use LOI to measure changes in sedimentary carbonates and charcoal isolation methods to infer past fire frequency. In addition to charcoal counts, charcoal morphology is used to signal vegetation type and suggests predominance of canopy or ground fires and their associated fire intensity; while charcoal size class is used to signify fire proximity. Initial findings indicate a pattern of increased charcoal abundance concurrent with periods of amplified carbonates in the upper part of the core demonstrating variations in climate within Max Lake. Independent analysis of diatom assemblages will be used to confirm these drought induced changes and infer pH.