EXAMINING THE EFFECTS OF 18TH-19TH CENTURY CHARCOAL PRODUCTION ON SOIL-WATER REPELLENCY IN NORTHWESTERN, CONNECTICUT

Burned and charred organic material within soils can affect water retention and infiltration, and therefore may be related to increased runoff, erosion, and flooding. While the effects of burned soils following wildfire events have been studied around the world, there has been less research on the effects of increased charcoal and burned organic material within soils due to anthropogenic land use changes. This study shows how remnants of charcoal in soil from 18th-19th century charcoal production throughout northwestern Connecticut alters infiltration rates and soil water repellency. Charcoal production during this time period was accomplished by making platforms on which mounds were constructed to pyrolyze cut trees into charcoal. These sites, which we call relict charcoal hearths (RCHs), can be found throughout the northeast region and to date over 20,000 have been located. Each RCH is ~8-16 m in diameter and typically consists of one or more soil layers that are very dark and exhibit large quantities of charcoal fragments and burned organic material. Soil samples consisted of 6.5 cm diameter, 5.5 cm thick rings, and were collected from both RCHs and sites adjacent to RCHs at multiple depths within individual soil pits. In total, we analyzed 127 soil samples, 92 of which had clear amounts of charcoal and burned organic material, while 35 soil samples analyzed did not. For each soil ring, we calculate the water-repellency index (R) by comparing two wetting liquids (water vs. ethanol) with differing soil-liquid contact angles following the methods of Young et al., 1997. Our results indicate that charcoal and burned organic matter present in the RCH samples alter properties of the soil and leads to a different soil-water repellency. The charcoal laden aggregates exhibit a higher mean R-index and greater range in R-index tending towards higher values. There also appears to be variation with depth. Overall, this study shows that land use that occurred over 125 years ago continues to have a lasting impact on soil properties today.