Natural and human disturbances greatly impact forest ecosystems. Our research investigates the interaction between historical logging and the occurrence of fire in the forest surrounding a northern Wisconsin lake. Charcoal accumulation rates in lake sediment samples from Circle Lily Lake were compared with historical records of logging and drought in northern Wisconsin forests. Historical records indicate extensive logging occurred in northern Wisconsin forests in the late 1800s and early 1900s. We compared historical fire events with historical logging activities, to investigate how human activities have impacted the occurrence of forest fires over time.
Results/Conclusions
Charcoal accumulation rates (CHAR (fragments cm2year-1)) and the number of fire episodes were compared between 40 year time periods: 1890-1929 (logging period), 1930-1969 (after logging period), and 1970-2009 (modern period). Average CHAR over the logging period were highest (0.5727), with lower average CHAR occurring in the period after logging (0.1614), and the lowest average CHAR occurring during the modern period (0.0594). Increased charcoal accumulation rates during logging suggest that the human disturbance of logging led to an increase in charcoal accumulation in Circle Lily Lake. Fire episodes were identified by peaks in CHAR that were significantly higher than charcoal background rates. Despite fire suppression legislation passed around the end of the logging period, four fire episodes occurred both during logging and the period after logging. The occurrence of fire episodes after logging corresponds to years of drought conditions in the area (1936, 1954, and 1968), suggesting dry conditions made the area prone to fire. Only one fire episode occurred during the modern period, suggesting a decrease in forest fire due to human suppression.